Posted on

Messier 69 – the NGC 6637 Globular Cluster

Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at the globular cluster known as Messier 69.

In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects he initially mistook for comets. In time, he would come to compile a list of approximately 100 of these objects, hoping to prevent other astronomers from making the same mistake. This list – known as the Messier Catalog – would go on to become one of the most influential catalogs of Deep Sky Objects.

One of these objects is known as Messier 69 (NGC 6637), a globular cluster located in the constellation Sagittarius. Located about about 29,700 light-years away from Earth, this cluster lies close to Messier 70 (both of which were discovered Charles Messier on August 31st, 1780). Both objects lie close to the galactic center, and M69 is one of the most metal-rich globular clusters known.

Description:

At about 29,700 light years from Earth, this 61 light year diameter ball of stars is one of the faintest of the Messier objects and very close to our galactic center. It was formed quite early in our galactic history and is one of the most metal rich of all globular clusters. As Robert Zinn and Pierre DeMarque of Yale University’s Department of Astronomy wrote in a 1996 study:

“We have observed the metal-rich globular clusters NGC 6624 and NGC 6637 (M69) using the planetary camera of the WFPC2 on the Hubble Space Telescope (HST). Observations of the Ca II triplet lines in giant stars in these clusters show that NGC 6624 and NGC 6637 have metallicities on the Zinn and West scale of [Fe/H] = -0.63 ± 0.09 and -0.65 ± 0.09, only slightly more metal rich than 47 Tuc [Fe/H] = -0.71 ± 0.07. For clusters of identical (or nearly so) metallicity, one can make a direct comparison of the color-magnitude diagrams to derive the relative ages of the clusters. The positions of NGC 6624 and NGC 6637 in the Galaxy suggest that they belong to the bulge population of globular clusters. The only other bulge clusters that have been dated so far are the more metal rich clusters NGC 6528 and NGC 6553, which also appear to be very old. Consequently, the age-metallicity relation of the bulge may be very steep. The close similarity of the ages and metallicities of NGC 6624 and NGC 6637 to the thick-disk globular clusters 47 Tuc and NGC 6352 indicates that the age-metallicity relations of these populations intersect. We briefly discuss the possibility that these populations had a common origin.”

This dazzling image shows the globular cluster Messier 69, as viewed through the NASA/ESA Hubble Space Telescope. Credit: NASA/ESA/HST

One very odd thing about M69 is its lack of variable stars. Harlow Shapley didn’t find any and the number of known variable stars debatable, with a few of them being Mira-type variable stars with periods of about 200 days. As J.D. Gregorsok (et al) indicated in a 2003 study:

“We present time-series VI photometry of the metal-rich globular cluster NGC 6637. Our color-magnitude diagrams show a predominantly red-clump horizontal branch morphology with hints of a blue horizontal branch extension as seen in NGC 6388 and NGC 6441. We discovered at least four new long-period variable stars in addition to recovering the nine variable stars already discovered. We discuss the cluster membership probabilities of the variables, and present their light curves.”

Are studies like this important? You bet. Because neighboring globular cluster M70 is so close in distance, there’s a distinct chance the two might be physical neighbors. Only through studies can we understand if they truly formed together or not. As A. Rosenberg (et al) explained in a 2000 study:

“Among the many tools we have to investigate the properties of a stellar population, the color-magnitude diagrams (CMD) are the most powerful ones, as they allow to recover for each individual star its evolutionary phase, giving precious information on the age of the entire stellar system, its chemical content, and its distance. This information allows us to locate the system in the space, giving a base for the distance scale, study the formation histories of the Galaxy, and test our knowledge of stellar evolution models.”

The Messier 69 globular cluster, as imaged by the Hubble Space Telescope. Credit: NASA/ESA/Hubble Space Telescope

History of Observation:

M69 was discovered by Charles Messier and added to his catalog on August 31, 1780, the same night he found M70. In his notes he states: “Nebula without star, in Sagittarius, below his left arm and near the arc; near it is a star of 9th magnitude; its light is very faint, one can only see it under good weather, and the least light employed to illuminate the micrometer wires makes it disappear: its position has been determined from Epsilon Sagittarii: this nebula has been observed by M. de La Caille, and reported in his Catalog; it resembles the nucleus of a small Comet. (diam 2′)”.

While Messier was mistaken about LaCaille’s position, there was no mistaking the observations of Sir William Herschel who first resolved this globular cluster – from a very northern position! “1784, 20 feet telescope. Very bright, pretty large, easily resolvable, or rather an already resolved cluster of minute stars. It is a miniature of the 53d of the Connoissance [M53].” His son John would go on to add it to the General Catalog and describe it as a “blaze of stars”, while Messier’s error would continue on for many years as a debate on LaCaille’s position.

But you know where to find it!

Locating Messier 69:

Because the constellation of Sagittarius is so low for the northern hemisphere, it is best to wait until it is at culmination (its highest point) before trying for this small globular cluster. Begin by identifying the familiar teapot asterism and draw a mental line between its southernmost stars – Zeta and Epsilon. About one third the distant between Epsilon and Zeta, you will see a conspicuous pair of stars that will show easily in your binoculars or telescope finderscope. M69 is less than a degree north of the northernmost of this pair.

The location of Messier 69 in the Sagittarius constellation. Credit: IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)

In binoculars, M69 will appear almost stellar and very faint – like a hairy star that won’t quite resolve. To a small telescope it will appear cometary and begin resolution in apertures around 8″. It requires dark, transparent skies and is not well suited to moonlight or urban lighting situations.

And here are the quick facts on this Messier Object to help you get started:

Object Name: Messier 69
Alternative Designations: M69, NGC 6637
Object Type: Class V Globular Cluster
Constellation: Sagittarius
Right Ascension: 18 : 31.4 (h:m)
Declination: -32 : 21 (deg:m)
Distance: 29.7 (kly)
Visual Brightness: 7.6 (mag)
Apparent Dimension: 9.8 (arc min)

We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects,  M1 – The Crab Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons.

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources:

Posted on

Messier 67 – the King Cobra Open Star Cluster

Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at the big snake – the King Cobra Cluster (aka. Messier 67).

In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects he initially mistook for comets. In time, he would come to compile a list of approximately 100 of these objects, hoping to prevent other astronomers from making the same mistake. This list – known as the Messier Catalog – would go on to become one of the most influential catalogs of Deep Sky Objects.

One of these objects is the open star cluster known as Messier 67, aka. the King Cobra Cluster. Located in the Cancer Constellation, and with age estimates ranging from 3.2 and 5 billion years, this cluster is one of the oldest clusters known. And at a distance of roughly 2610 and 2930 (800 – 900 pc) from Earth, it is the closest of any of the older open star clusters.

Description:

At 3.2 billion years, Messier 67 is billed as one of the oldest star clusters known and the oldest of all the Messier clusters. Containing perhaps 500 stars, and about 100 stars similar to our own Sun, this cloud contains no main sequence stars bluer than spectral type F, since the brighter stars of that age have already left the main sequence – no matter how it may appear! Among its 150 white dwarf stars, there’s only about 30 blue stragglers…

Messier 67 (aka. the King Cobra Cluster), one of the oldest known open star clusters. . Credit & Copyright: Processing – Noel Carboni, Imaging – Greg Parker/NASA

As Xiao-Bin Zhan (et al) indicated in a 2005 study:

“We present results of a time-series CCD photometry of two blue stragglers in the open cluster M67 that are also oscillating variables, S1280 and S1284. The observations obtained on 11 nights confirmed the Delta Scuti-like variability of the two stars. Four and five main pulsating frequencies are detected for S1280 and S1284, respectively, through a power spectral analysis. A preliminary mode identification indicates that the two stars are both in radial oscillation. Based on the nature of oscillation, the physical parameters of the two stars are determined, and their evolutionary status discussed.”

As you look at this old open cluster, realize that it’s a great study field for stellar evolution. As Jarrod R. Hurley (et al) explained in their 2005 study:

“The old open cluster M67 is an ideal testbed for current cluster evolution models because of its dynamically evolved structure and rich stellar populations that show clear signs of interaction between stellar, binary and cluster evolution. Here we present the first truly direct N-body model for M67, evolved from zero age to 4 Gyr taking full account of cluster dynamics as well as stellar and binary evolution. Our preferred model starts with 12000 single stars and 12000 binaries placed in a Galactic tidal field at 8.0 kpc from the Galactic Centre. Our choices for the initial conditions and for the primordial binary population are explained in detail. At 4 Gyr, the age of M67, the total mass has reduced by 90% as a result of mass loss and stellar escapes. The mass and half-mass radius of luminous stars in the cluster are a good match to observations although the model is more centrally concentrated than observations indicate. The stellar mass and luminosity functions are significantly flattened by preferential escape of low-mass stars. We find that M67 is dynamically old enough that information about the initial mass function is lost, both from the current luminosity function and from the current mass fraction in white dwarfs. The model contains 20 blue stragglers at 4 Gyr which is slightly less than the 28 observed in M67. Nine are in binaries. The blue stragglers were formed by a variety of means and we find formation paths for the whole variety observed in M67. Both the primordial binary population and the dynamical cluster environment play an essential role in shaping the population. A substantial population of short-period primordial binaries (with periods less than a few days) is needed to explain the observed number of blue stragglers in M67.”

History of Observation:

According to Johann Elert Bode, M67 was originally discovered by Johann Gottfried Koehler before the year 1779, but his telescope was so primitive that little more than the light could be made out. According to historical records his listed it as his object nineteen, describing it as, “A rather conspicuous nebula in elongated figure, near Alpha of Cancer.”

Charles Messier independently rediscovered M67, resolved it into stars, and cataloged it on April 6, 1780: “Cluster of small stars with nebulosity, below the southern claw of Cancer.” It was observed again by Caroline Herschel, and many times by Sir William, ending up getting its General Catalog designation for John Herschel. Of all the folks in history who described it… Dreyer said it best when he said it was a “Remarkable; cluster; very bright; very large; extremely rich.”

Locating Messier 67:

Finding M67 is easy in both binoculars and a telescope once you’ve identified the upside down Y shape of the constellation of Cancer. Simply take aim at the easternmost star in the Y, and you’ll find this delightful open cluster about a finger width to the west.

The location Messier 67 in the Cancer constellation. Credit: IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)

In binoculars and very small telescopes you’ll spy a rich concentration that will appear almost galaxy-like, while larger apertures will fully resolve this cloud of stellar points. M67 is well suited to urban skies and moderate moonlit conditions.

Enjoy the magnificent M67 yourself!

And here are the quick facts on this Messier Object to help you get started:

Object Name: Messier 67
Alternative Designations: M67, NGC 2682
Object Type: Open Galactic Star Cluster
Constellation: Cancer
Right Ascension: 08 : 50.4 (h:m)
Declination: +11 : 49 (deg:m)
Distance: 2.7 (kly)
Visual Brightness: 6.1 (mag)
Apparent Dimension: 30.0 (arc min)

We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects,  M1 – The Crab Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons.

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources:

Posted on

Messier 66 – the NGC 3627 Intermediate Spiral Galaxy

Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at the intermediate spiral galaxy known as Messier 66.

In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects he initially mistook for comets. In time, he would come to compile a list of approximately 100 of these objects, hoping to prevent other astronomers from making the same mistake. This list – known as the Messier Catalog – would go on to become one of the most influential catalogs of Deep Sky Objects.

One of these objects is the intermediate elliptical galaxy known as Messier 66 (NGC 3627). Located about 36 million light-years from Earth in the direction of the Leo constellation, this galaxy measures 95,000 light-years in diameter. It is also the brightest and largest member of the Leo Triplet of galaxies and is well-known for its bright star clusters, dust lanes, and associated supernovae.

Description:

Enjoying life some 35 million light years from the Milky Way, the group known as the “Leo Trio” is home to bright galaxy Messier 66 – the easternmost of the two M objects. In the telescope or binoculars, you’ll find this barred spiral galaxy far more visible and much easier to see details within its knotted arms and bulging core.

Hubble image of the intermediate spiral galaxy Messier 66. Credits: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration/Davide De Martin/Robert Gendler

Because of interaction with its neighboring galaxies, M66 shows signs of a extremely high central mass concentration as well as a resolved noncorotating clump of H I material apparently removed from one of the spiral arms. Even one of its spiral arms got it noted in Halton Arp’s collection of Peculiar Galaxies! So exactly what did it collide with?As   Xiaolei Zhang (et al) indicated in a 1993 study:

“The combined CO and H I data provide new information, both on the history of the past encounter of NGC 3627 with its companion galaxy NGC 3628 and on the subsequent dynamical evolution of NGC 3627 as a result of this tidal interaction. In particular, the morphological and kinematic information indicates that the gravitational torque experienced by NGC 3627 during the close encounter triggered a sequence of dynamical processes, including the formation of prominent spiral structures, the central concentration of both the stellar and gas mass, the formation of two widely separated and outwardly located inner Lindblad resonances, and the formation of a gaseous bar inside the inner resonance. These processes in coordination allow the continuous and efficient radial mass accretion across the entire galactic disk. The observational result in the current work provides a detailed picture of a nearby interacting galaxy which is very likely in the process of evolving into a nuclear active galaxy. It also suggests one of the possible mechanisms for the formation of successive instabilities in postinteraction galaxies, which could very efficiently channel the interstellar medium into the center of the galaxy to fuel nuclear starburst and Seyfert activities.”

Ah, yes! Star forming regions… And what better way to look deeper than through the eyes of the Spitzer Space Telescope? As R. Kennicutt (University of Arizona) and the SINGS Team observed:

“M66’s blue core and bar-like structure illustrates a concentration of older stars. While the bar seems devoid of star formation, the bar ends are bright red and actively forming stars. A barred spiral offers an exquisite laboratory for star formation because it contains many different environments with varying levels of star-formation activity, e.g., nucleus, rings, bar, the bar ends and spiral arms. The SINGS image is a four-channel false-color composite, where blue indicates emission at 3.6 microns, green corresponds to 4.5 microns, and red to 5.8 and 8.0 microns. The contribution from starlight (measured at 3.6 microns) in this picture has been subtracted from the 5.8 and 8 micron images to enhance the visibility of the dust features.”

Colour composite image of the spiral galaxy M66 (or NGC 3627) obtained with the FORS1 and FORS2 multi-mode instruments (at VLT MELIPAL and YEPUN, respectively). Credit: ESO

Messier 66 has also been deeply studied for evidence of forming super star clusters, too. As David Meier indicated:

“Super star clusters are thought to be precursors of globular clusters and are some of the most extreme star formation regions in the universe. They tend to occur in actively starbursting galaxies or near the cores of less active galaxies. Radio super star clusters cannot be seen in optical light because of extreme extinction, but they shine brightly in infrared and radio observations. We can be certain that there are many massive O stars in these regions because massive stars are required to provide the UV radiation that ionizes the gas and creates a thermally bright HII regions. Not many natal SSCs are currently known, so detection is an important science goal in its own right. In particular, very few SSCs are known in galactic disks. We need more detections to be able to make statistical statements about SSCs and fill in the mass range of forming star clusters. With more detections, we will be able to investigate the effects of other environments (e.g. bars, bubbles, and galactic interaction) on SSCs, which could potentially be followed up in the far future with the Square Kilometer Array to discover their effects on individual forming massive stars.”

But there’s still more. Try magnetic properties in M66’s spiral patterns. As M. Soida (et al) indicated in their 2001 study:

“By observing the interacting galaxy NGC 3627 in radio polarization we try to answer the question; to which degree does the magnetic field follow the galactic gas flow. We obtained total power and polarized intensity maps at 8.46 GHz and 4.85 GHz using the VLA in its compact D-configuration. In order to overcome the zero-spacing problems, the interferometric data were combined with single-dish measurements obtained with the Effelsberg 100-m radio telescope. The observed magnetic field structure in NGC 3627 suggests that two field components are superposed. One component smoothly fills the interarm space and shows up also in the outermost disk regions, the other component follows a symmetric S-shaped structure. In the western disk the latter component is well aligned with an optical dust lane, following a bend which is possibly caused by external interactions. However, in the SE disk the magnetic field crosses a heavy dust lane segment, apparently being insensitive to strong density-wave effects. We suggest that the magnetic field is decoupled from the gas by high turbulent diffusion, in agreement with the large Hi line width in this region. We discuss in detail the possible influence of compression effects and non-axisymmetric gas flows on the general magnetic field asymmetries in NGC 3627. On the basis of the Faraday rotation distribution we also suggest the existence of a large ionized halo around this galaxy.”

History of Observation:

Both M65 and M66 were discovered on the same night – March 1, 1780 – by Charles Messier, who described M66 as, “Nebula discovered in Leo; its light is very faint and it is very close to the preceding: They both appear in the same field in the refractor. The comet of 1773 and 1774 has passed between these two nebulae on November 1 to 2, 1773. M. Messier didn’t see them at that time, no doubt, because of the light of the comet.”

Both galaxies would be observed and cataloged by the Herschel family and further expounded upon by Admiral Smyth:

“A large elongated nebula, with a bright nucleus, on the Lion’s haunch, trending np [north preceding, NW] and sf [south following, SE]; this beautiful specimen of perspective lies just 3deg south-east of Theta Leonis. It is preceded at about 73s by another of a similar shape, which is Messier’s No. 65, and both are in the field at the same time, under a moderate power, together with several stars. They were pointed out by Mechain to Messier in 1780, and they appeared faint and hazy to him. The above is their appearance in my instrument.

“These inconceivably vast creations are followed, exactly on the same parallel, ar Delta AR=174s, by another elliptical nebula of even a more stupendous character as to apparent dimensions. It was discovered by H. [John Herschel], in sweeping, and is No. 875 in his Catalogue of 1830 [actually, probably an erroneous position for re-observed M66]. The two preceding of these singular objects were examined by Sir William Herschel, and his son [JH] also; and the latter says, “The general form of elongated nebulae is elliptic, and their condensation towards the centre is almost invariably such as would arise from the superposition of luminous elliptic strata, increasing in density towards the centre. In many cases the increase of density is obviously attended with a diminution of ellipticity, or a nearer approach to the globular form in the central than in the exterior strata.” He then supposes the general constitution of those nebulae to be that of oblate spheroidal masses of every degree of flatness from the sphere to the disk, and of every variety in respect of the law of their density, and ellipticity towards the centre. This must appear startling and paradoxical to those who imagine that the forms of these systems are maintained by forces identical with those which determine the form of a fluid mass in rotation; because, if the nebulae be only clusters of discrete stars, as in the greater number of cases there is every reason to believe them to be, no pressure can propagate through them. Consequently, since no general rotation of such a system as one mass can be supposed, Sir John suggests a scheme which he shows is not, under certain conditions, inconsistent with the law of gravitation. “It must rather be conceived,” he tells us, ” as a quiescent form, comprising within its limits an indefinite magnitude of individual constituents, which, for aught we can tell, may be moving one among the other, each animated by its own inherent projectile force, and deflected into an orbit more or less complicated, by the influence of that law of internal gravitation which may result from the compounded attractions of all its parts.”

Messier 66 location. Credit: IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)

Locating Messier 66:

Even though you might think by its apparent visual magnitude that M66 wouldn’t be visible in small binoculars, you’d be wrong. Surprisingly enough, thanks to its large size and high surface brightness, this particular galaxy is very easy to spot directly between Iota and Theta Leonis. In even 5X30 binoculars under good conditions you’ll easy see both it and M65 as two distinct gray ovals.

A small telescope will begin to bring out structure in both of these bright and wonderful galaxies, but to get a hint at the “Trio” you’ll need at least 6″ in aperture and a good dark night. If you don’t spot them right away in binoculars, don’t be disappointed – this means you probably don’t have good sky conditions and try again on a more transparent night. The pair is well suited to modestly moonlit nights with larger telescopes.

May you equally be attracted to this galactic pair!

And here are the quick facts on M66 to help you get started:

Object Name: Messier 66
Alternative Designations: M66, NGC 3627, (a member of the) Leo Trio, Leo Triplet
Object Type: Type Sb Spiral Galaxy
Constellation: Leo
Right Ascension: 11 : 20.2 (h:m)
Declination: +12 : 59 (deg:m)
Distance: 35000 (kly)
Visual Brightness: 8.9 (mag)
Apparent Dimension: 8×2.5 (arc min)

We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects,  M1 – The Crab Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons.

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources:

Posted on

Messier 63 – the Sunflower Galaxy

Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at the “Sunflower Galaxy”, otherwise known as Messier 63.

In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects he initially mistook for comets. In time, he would come to compile a list of approximately 100 of these objects, hoping to prevent other astronomers from making the same mistake. This list – known as the Messier Catalog – would go on to become one of the most influential catalogs of Deep Sky Objects.

One of these objects is the spiral galaxy known as Messier 63 – aka. the Sunflower Galaxy. Located in the Canes Venatici constellation, this galaxy is located roughly 37 million light-years from Earth and has an active nucleus. Messier 63 is part of the M51 Group, a group of galaxies that also includes Messier 51 (the ‘Whirlpool Galaxy’), and can be easily spotted using binoculars and small telescopes.

Description:

Messier 63 is what is known as a a flocculent spiral galaxy, consisting of a central disc surrounded by many short spiral arm segments – one not connected by a central bar structure. Drifting along in space some 37,000 light years from our own galaxy, we known it interacts gravitationally with M51 (the Whirlpool Galaxy) and we also know that its outer regions are rotating so quickly that if it weren’t for dark matter – it would rip itself apart.

Infrared image of the Sunflower Galaxy (Messier 63) taken by the Spitzer Space Telescope. Credit: NASA/JPL-Caltech/SINGS Team

As Michele D. Thornley and Lee G. Mundy, of the Maryland University Department of Astronomy, indicated in a 1997 study:

“The morphology and inematics described by VLA observations of H I emission and FCRAO and Berkeley-Illinois-Maryland Association (BIMA) Array observations of CO emission provide evidence for the presence of low-amplitude density waves in NGC 5055. The distribution of CO and H I emission suggests enhanced gas surface densities along the NIR spiral arms, and structures similar to the giant molecular associations found in the grand design spirals M51 and M100 are detected. An analysis of H I and H? velocity fields shows the kinematic signature of streaming motions similar in magnitude to those of M100 in both tracers. The lesser degree of organization along the spiral arms of NGC 5055 may be due to the lower overall gas surface density, which in the arms of NGC 5055 is a factor of 2 lower than in M100 and a factor of 6 lower than in M51; an analysis of gravitational instability shows the gas in the arms is only marginally unstable and the interarm gas is marginally stable. The limited extent of the spiral arm pattern is consistent with an isolated density wave with a relatively high pattern speed.”

There very well could be a massive object hidden within. As Sebastien Blais-Ouellette of the Universite de Montreal said in a 1998 study:

“In a global kinematical study of NGC 5055 using high resolution Fabry-Perot, intriguing spectral line profiles have been observed in the center of the galaxy. These profiles seem to indicate a rapidly rotating disk with a radius near 365 pc and tilted 50 deg with respect to the major axis of the galaxy. In the hypothesis of a massive dark object, a naive keplerian estimate gives a mass around 10^7.2 to 10^7.5 M.”

Infrared image of the M63 galaxy made by Médéric Boquien, using data retrieved on the SINGS project public archives of the Spitzer Space Telescope. Credit: NASA/JPL-Caltech

But that’s not all they’ve found either… How about a lopsided, chemically unbalanced nucleus! As V.L. Afanasiev (et al) pointed out in their 2002 study:

“We have found a resolved chemically distinct core in NGC 5055, with the magnesium-enhanced region shifted by 2″.5 (100 pc) to the south-west from a photometric center, toward a kinematically identified circumnuclear stellar disk. Mean ages of stellar populations in the true nucleus, defined as the photometric center, and in the magnesium-enhanced substructure are coincident and equal to 3-4 Gyr being younger by several Gyr with respect to the bulge stellar population.”

Yep. It might be beautiful, but it’s warped. As G. Battaglia of the Kapteyn Astronomical Institute indicated in a 2005 study:

“NGC 5055 shows remarkable overall regularity and symmetry. A mild lopsidedness is noticeable, however, both in the distribution and kinematics of the gas. The tilted ring analysis of the velocity field led us to adopt different values for the kinematical centre and for the systemic velocity for the inner and the outer parts of the system. This has produced a remarkable result: the kinematical and geometrical asymmetries disappear, both at the same time. These results point at two different dynamical regimes: an inner region dominated by the stellar disk and an outer one, dominated by a dark matter halo offset with respect to the disk.”

Sunflower Galaxy (Messier 63). Credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona

History of Observation:

Messier Object 63 was the very first discovery by Charles Messier’s friend and assistant Pierre Mechain, who turned it up on June 14, 1779. While Mechain himself did not write the notes, Messier did:

“Nebula discovered by M. Mechain in Canes Venatici. M. Messier searched for it; it is faint, it has nearly the same light as the nebula reported under no. 59: it contains no star, and the slightest illumination of the micrometer wires makes it disappear: it is close to a star of 8th magnitude, which precedes the nebula on the hour wire. M. Messier has reported its position on the Chart of the path of the Comet of 1779.”

Messier 63 would go on to be observed and resolved by Sir William Herschel and cataloged by his son John. It would be descriptively narrated by Admiral Symth and exclaimed over by many astronomers – one of the best of which was Lord Rosse: “Spiral? Darkness south flowing nucleus.” Of all the descriptions, perhaps the best belongs to Curtis, who first photographed it with the Crossley Reflector at Lick Observatory: “Has an almost stellar nucleus. The whorls are narrow, very compactly arranged, and show numerous almost stellar condensations.”

Locating Messier 63:

The beautiful Sunflower Galaxy is among one of the easiest of the Messier objects to find. It’s located almost precisely between Cor Caroli (Alpha Canes Venetici) and Eta Ursa Majoris. With the slightest of optical aid, stars 19, 20 and 23 CnV will show easily in finderscope or binoculars and M63 will be positioned right around two degrees away towards Eta UM.

The location of Messier 63 in the Canes Venatici constellation. Credit: IAU/Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)

While this spiral galaxy has a nice overall brightness, it’s going to be very faint for binoculars, only showing as the tiniest contrast change in smaller models. However, even a modest telescope will easily see a faint oval shape with a concentrated nucleus. The more aperture you apply, the more details you will see. As size approaches 8″ and larger, expect to see spiral structure!

Power up… And look for the spiral in the Sunflower!

Object Name: Messier 63
Alternative Designations: M63, NGC 5055, Sunflower Galaxy
Object Type: Type Sb Spiral Galaxy
Constellation: Canes Venatici
Right Ascension: 13 : 15.8 (h:m)
Declination: +42 : 02 (deg:m)
Distance: 37000 (kly)
Visual Brightness: 8.6 (mag)
Apparent Dimension: 10×6 (arc min)

We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects,  M1 – The Crab Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons.

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources:

Posted on

Messier 62 – the NGC 6266 Globular Cluster

Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at the globular cluster known as Messier 62.

In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects he initially mistook for comets. In time, he would come to compile a list of approximately 100 of these objects, hoping to prevent other astronomers from making the same mistake. This list – known as the Messier Catalog – would go on to become one of the most influential catalogs of Deep Sky Objects.

One of these objects is the globular cluster known as Messier 62, which spans about 100 light-years in diameter and is approximately 22,200 light years from Earth. Located in the southern constellation of Ophiuchus, this cluster is easy to find because of its proximity to Antares – the brightest star in Scorpius constellation – and is easily viewed suing binoculars and small telescopes.

Description:

Positioned about 22,500 light years away from Earth, this glorious gravitationally bound ball of stars could span as much as 100 light years of space. Captured within its confines are 89 known variable stars – most of them RR Lyrae types. M62 has a very dense core… One which may have experienced core collapse during its long history. An ordinary globular cluster? Not hardly. It’s one that holds some optical surprises.

The globular cluster Messier 62 in the constellation Ophiuchus. Credit: Wikipedia Commons/Hewholooks

As G. Cocozza (et al) indicated in their 2008 study:

“We report on the optical identification of the companion to the eclipsing millisecond pulsar PSR J1701-3006B in the globular cluster NGC 6266. A relatively bright star with an anomalous red color and an optical variability (~0.2 mag) that nicely correlates with the orbital period of the pulsar (~0.144 days) has been found nearly coincident with the pulsar nominal position. This star is also found to lie within the error box position of an X-ray source detected by Chandra observations, thus supporting the hypothesis that some interaction is occurring between the pulsar wind and the gas streaming off the companion. Although the shape of the optical light curve is suggestive of a tidally deformed star which has nearly completely filled its Roche lobe, the luminosity (~1.9 Lsolar) and the surface temperature (~6000 K) of the star, deduced from the observed magnitude and colors, would imply a stellar radius significantly larger than the Roche lobe radius.”

Is it possible that this is the smoking gun for intermediate mass black holes in globular clusters? Julio Chaname seems to think so. As he explained in his 2009 study:

“The existence of intermediate-mass black holes [IMBHs] in star clusters has been predicted by a variety of theoretical arguments and, more recently, by several large, realistic sets of collisional N-body simulations. Establishing their presence or absence at the centers of globular clusters would profoundly impact our understanding of problems ranging from the formation and long-term dynamical evolution of stellar systems, to the nature of the seeds and the growth mechanisms of the supermassive black holes {BHs} that inhabit the centers of most large, luminous galaxies. Observationally, the unambiguous signature of a massive central BH would be the discovery of central, unresolved X-ray or radio emission that is not consistent with more common stellar-mass accreting objects or pulsars. Yet, due to the largely uncertain details of accretion modeling, a precise mass determination of a central BH must necessarily come from stellar dynamics. This goal has not been achieved to date at the centers of Galactic globular clusters because of lack of adequate data as well as the use of too simplified methods of analysis. This situation can be overcome today through the combination of HST proper-motion measurements and state-of-the-art dynamical models specifically designed to take full advantage of this type of dataset. In this project, we will use two HST orbits to obtain another epoch of observations of NGC 6266. This cluster has photometric and structural properties that are consistent with current theoretical expectations for a cluster harboring an IMBH. Even more importantly, it is the only Galactic globular cluster for which there exists a detection of radio emission coincident with the cluster’s core, and with a flux density that appears to rule out a stellar or binary origin. The goal of our project is to obtain proper motion measurements to either confirm an IMBH in this cluster and measure its mass, or to set limits to its mass and existence.”

The Messier 62 globular cluster, as imaged by the Hubble Space Telescope. Credit: NASA, ESA

History of Observation:

While Charles Messier first discovered this globular cluster on June 7, 1771 – he didn’t accurately record its position until June 4, 1779.

“”Very beautiful nebula, discovered in Scorpio, it resembles a little Comet, the center is brilliant and surrounded by a faint glow. Its position determined, by comparing it with the star Tau of Scorpius. M. Messier had already seen this nebula on June 7, 1771, without having determined the position where it is close to. Seen again on March 22, 1781.”

Sir William Herschel would resolve it two years after Messier cataloged it, but it was Admiral Smyth who gave it a little more historic significance when he writes in his notes:

“A fine large resolvable nebula, at the root of the creature’s [Scorpion’s] tail, and in the preceding part of the Galaxy [Milky Way band]. It is an aggregated mass of small stars running up to a blaze in the centre, which renders the differentiating comparatively easy and satisfactory; and in this instance it was referred to its neighbor, 26 Ophiuchi, which is 5deg distant to the north: and it lies only about 7deg from Antares, on the south-east. This was registered in 1779, and Messier described it as “a very pretty nebula, resembling a little comet, the centre bright, and surrounded by a faint light.” Sir William Herschel, who first resolved it, pronounced it a miniature of Messier’s No. 3, and adds, “By the 20-foot telescope, which at the time of these observations was of the Newtonian construction, the profundity of this cluster is of the 734th order.” To my annoyance, it was started as a comet a few years ago, by a gentleman who ought to have known better.”

Locating Messier 62:

M62 is easily located about 5 degrees (3 finger widths) southeast of Antares – but because it is small, it can easily be overlooked in binoculars. Take your time, because it is only just a little more than an average binocular field away from an easy marker star and bright enough to be seen even with smaller instruments under not so good skies.

The locations of Messier 62 in the Ophiuchus constellation. Credit: IAU/Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)

In the finderscope of a telescope, begin with Antares in the center and shift southwest. At 5X magnification, it will show as a faint haze. In a small telescope, you may get some resolution – but expect this globular cluster to appear more comet-like. Larger telescopes can expect a wonderful explosion of stars!

Enjoy your observations! And as always, here are the quick facts on this Messier Object to help you get started:

Object Name: Messier 62
Alternative Designations: M62, NGC 6266
Object Type: Class IV Globular Cluster
Constellation: Ophiuchus
Right Ascension: 17 : 01.2 (h:m)
Declination: -30 : 07 (deg:m)
Distance: 22.5 (kly)
Visual Brightness: 6.5 (mag)
Apparent Dimension: 15.0 (arc min)

We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects,  M1 – The Crab Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons.

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources:

Posted on

Messier 61- the NGC 4303 Barred Spiral Galaxy

Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at the barred spiral galaxy known as Messier 61.

In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects he initially mistook for comets. In time, he would come to compile a list of approximately 100 of these objects, hoping to prevent other astronomers from making the same mistake. This list – known as the Messier Catalog – would go on to become one of the most influential catalogs of Deep Sky Objects.

One of these objects is the intermediate barred spiral galaxy known as Messier 61. As one of the larger galaxies located in the Virgo Cluster, this galaxy is roughly 52.5 million light years from Earth and contains some spectacular supernovae. It also has an Active Galactic Nucleus (AGN), meaning it has a Supermassive Black Hole (SMBH) at its center, and shows evidence of considerable star formation.

What You Are Looking At:

Spanning about 100,000 light years across and about the same size as our own Milky Way Galaxy, this grand old spiral is one of the largest in the Virgo Cluster… and one of the most active in terms of starbursts and supernovae. According to Luis Colina (et al) indicated in a 1997 study:

“A high-resolution Hubble Space Telescope WFPC2 F218W UV image of the barred spiral NGC 4303 (classified as a LINER-type active galactic nucleus [AGN]) reveals for the first time the existence of a nuclear spiral structure of massive star-forming regions all the way down to the UV-bright unresolved core of an active galaxy. The spiral structure, as traced by the UV-bright star-forming regions, has an outer radius of 225 pc and widens as the distance from the core increases. The UV luminosity of NGC 4303 is dominated by the massive star-forming regions, and the unresolved LINER-type core contributes only 16% of the integrated UV luminosity. The nature of the UV-bright LINER-type core—stellar cluster or pure AGN—is still unknown.”

The Virgo Cluster Galaxies. Credit & Copyright: Rogelio Bernal Andreo

Another fascinating aspect is Colina’s team has also identified a Super Star Cluster (SSC) withing Messier 61 as well. As Colina indicated in a 2002 study:

“These new HST/STIS results unambiguously show the presence of a compact SSC in the nucleus of a low-luminosity AGN, which is also its dominant ionizing source. We hypothesize that at least some LLAGNs in spirals could be understood as the result of the combined ionizing radiation emitted by an evolving SSC (i.e., determined by the mass and age) and a black hole accreting with low radiative efficiency (i.e., radiating at low sub-Eddington luminosities) coexisting in the inner few parsecs region. Complementary multifrequency studies give the first hints of the very complex structure of the central 10 pc of NGC 4303, where a young SSC apparently coexists with a low-efficiency accreting black hole and with an intermediate/old compact star cluster and where, in addition, an evolved starburst could also be present. If structures such as those detected in NGC 4303 are common in the nuclei of spirals, the modeling of the different stellar components and their contribution to the dynamical mass has to be established accurately before deriving any firm conclusion about the mass of central black holes of few to several million solar masses.”

Of course, studies don’t just stop there. As D. Tschoke (et al) indicated in a 2000 study:

“The late-type galaxy NGC 4303 (M61) is one of the most intensively studied barred galaxies in the Virgo Cluster. Its prominent enhanced star formation throughout large areas of the disk can be nicely studied due to its low inclination of about 27 degr. We present observations of NGC 4303 with the ROSAT PSPC and HRI in the soft X-ray (0.1-2.4 keV). The bulk of the X-ray emission is located at the nuclear region. It contributes more than 80% to the total observed soft X-ray flux. The extension of the central X-ray source and the L_X/L_Halpha ratio point to a low luminous AGN (LINER) with a circumnuclear star-forming region. Several separate disk sources can be distinguished with the HRI, coinciding spatially with some of the most luminous HII regions outside the nucleus of NGC 4303. The total star formation rate amounts to 1-2 Msun/yr. The X-ray structure follows the distribution of star formation with enhancement at the bar-typical patterns. The best spectral fit consists of a power-law component (AGN and HMXBs) and a thermal plasma component of hot gas from supernova remnants and superbubbles. The total 0.1-2.4 keV luminosity of NGC 4303 amounts to 5×10^40 erg/s, consistent with comparable galaxies, like e.g. NGC 4569.”

 

Hubble picture is the sharpest ever image of the core of spiral galaxy Messier 61. Taken using the High Resolution Channel of Hubble’s Advanced Camera for Surveys. Credit: ESA/NASA/HST

When it comes right down to it, it’s all about that star-forming ring. Said Eva Schinnerer (eta al) in a 2002 study:

“The UV continuum traces a complete ring that is heavily extincted north of the nucleus. Such a ring forms in hydrodynamic models of double bars, but the models cannot account for the UV emission observed on the leading side of the inner bar. Comparison with other starburst ring galaxies where the molecular gas emission and the star-forming clusters form a ring or tightly wound spiral structure suggests that the starburst ring in NGC 4303 is in an early stage of formation.”

How will today’s technologies continue to study the magnificent M61? Just take a look at what MOS can do! The very efficient multi-object-slit observing technique with the multi-mode instrument FORS1 has been demonstrated on the Virgo cluster galaxy NGC 4303 . Nineteen moveable slits at the instrument focal plane are positioned so that the faint light from several H II regions in this galaxy can pass into the spectrograph, while the much stronger “background” light (from the nearby areas in the galaxy and, to a large extent, from the Earth”s upper atmosphere) is blocked by the mask.

History of Observation:

M61 was discovered by Barnabus Oriani on May 5, 1779 when following the comet of that year. Said he, “Very pale and looking exactly like the comet.” As for our hero, Messier, he had also seen it on the same night – but thought it was the comet! Because Charles Messier was a good astronomer, he returned nightly to observe movement and it only took him a few days to realize his mistake and to admit it in his own notes:

“May 11, 1779. 61. 12h 10m 44s (182d 41′ 05″) +5d 42′ 05″ – Nebula, very faint & difficult to perceive. M. Messier mistook this nebula for the Comet of 1779, on the 5th, 6th and 11th of May; on the 11th he recognized that this was not the Comet, but a nebula which was located on its path and in the same point of the sky.”

Supernova SN2008in in the spiral galaxy Messier 61. Credit: Hewholooks/ Wikipedia Commons

Sir William and Sir John Herschel would also later return to M61 to assign it their own catalog numbers, both resolving certain portions of this wonderful galaxy – but neither truly beginning to understand what they were seeing. That took Admiral Smyth, who recorded in his notes:

“A large pale-white nebula, between the Virgo’s shoulders. This is a well defined object, but so feeble as to excite surprise that Messier detected it with his 3 1/2 foot telescope in 1779. Under the best action of my instrument it blazes towards the middle; but in H. [John Herschel]’s reflector it is faintly seen to be bicentral [an illusion caused by the bar], the nuclei 90″ apart, and lying sp [south preceding, SW] and nf [north following, NE]. It is preceded by four telescopic stars, and followed by another. Differentiated with the following object [17 Virginis], from which it bears about south by west, and is within a degree’s distance. This object is an outlier of a vast mass of discrete but neighboring nebulae, the spherical forms of which are indicative of compression.”

Locating Messier 61:

Locating Messier 61 is the Virgo Galaxy fields is relatively easily because it is so large and bright compared to any others in the area. Begin your hunt by identifying Beta and Delta Virginis. Between this pair you will see finderscope or binocular visible stars 17 and 16 Virginis. You destination is between this pair of stars. While M61 is binocular possible, it would require astronomical binoculars of approximately 80mm aperture and dark skies – although with excellent sky conditions the nucleus can be glimpsed with apertures as small as 60mm.

This star chart for M61 represents the view from mid-northern latitudes for the given month and time. Credits: NASA/Stellarium

In a small aperture telescope, M61 will appear as a very faint oval with a bright central region. As size increases, so do details and resolution. At 6-8″ in size, the nucleus becomes very clear and beginnings of spiral arms start to resolve. In the 10-12″ range, spiral structure becomes clear and some mottling texture becomes clear.

Enjoy your observations!

And here are the quick facts on Messier 61 to help you get started:

Object Name: Messier 61
Alternative Designations: M61, NGC 4303
Object Type: Type SABbc Spiral Galaxy
Constellation: Virgo
Right Ascension: 12 : 21.9 (h:m)
Declination: +04 : 28 (deg:m)
Distance: 60000 (kly)
Visual Brightness: 9.7 (mag)
Apparent Dimension: 6×5.5 (arc min)

We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects,  M1 – The Crab Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons.

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources:

Posted on

Messier 60 – the NGC 4649 Galaxy

Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at the elliptical galaxy known as Messier 60.

In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects he initially mistook for comets. In time, he would come to compile a list of approximately 100 of these objects, hoping to prevent other astronomers from making the same mistake. This list – known as the Messier Catalog – would go on to become one of the most influential catalogs of Deep Sky Objects.

One of the notable objects in this catalog is Messier 60, an elliptical galaxy located approximately 55 million light-years away in the Virgo constellation. Measuring some 60,000 light years across, this galaxy is only about half as large as the Milky Way. However, it still manages to pack in an estimated 400 billion stars which, depending on which estimates you go by, is between four times and the same amount as our own.

What You Are Looking At:

Located about 60 million light years away and spanning about 120 million light years of space, M60 is the third brightest elliptical in the Virgo group and and is the dominant member of a subcluster of four galaxies, which is the closest-known isolated compact group of galaxies. In larger telescopes, you’ll see another nearby galaxy – NGC 4647 – which might first be taken for a interactor, but may very well lay at a different distance since there is no tidal evidence so far found.

Messier 60. Credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona

As L.M. Young (et al.) explained in their 2006 study:

“We present matched-resolution maps of H I and CO emission in the Virgo Cluster spiral NGC 4647. The galaxy shows a mild kinematic disturbance in which one side of the rotation curve flattens but the other side continues to rise. This kinematic asymmetry is coupled with a dramatic asymmetry in the molecular gas distribution but not in the atomic gas. An analysis of the gas column densities and the interstellar pressure suggests that the H2/H I surface density ratio on the east side of the galaxy is 3 times higher than expected from the hydrostatic pressure contributed by the mass of the stellar disk. We discuss the probable effects of ram pressure, gravitational interactions, and asymmetric potentials on the interstellar medium and suggest it is likely that a m = 1 perturbation in the gravitational potential could be responsible for all of the galaxy’s features. Kinematic disturbances of the type seen here are common, but the curious thing about NGC 4647 is that the molecular distribution appears more disturbed than the H I distribution. Thus, it is the combination of the two gas phases that provides such interesting insight into the galaxy’s history and into models of the interstellar medium.”

Although a search for young optical pulsars turned up negative after a recent supernova event, astronomer’s did discover something rather exciting… a supermassive black hole! As Philip J. Humphrey (et al) indicated in their 2008 study:

“We present a Chandra study of the hot ISM in the giant elliptical galaxy NGC4649. In common with other group-centred ellipticals, its temperature profile rises with radius in the outer parts of the galaxy. Under the assumption of hydrostatic equilibrium, we demonstrate that the central temperature spike arises due to the gravitational influence of a quiescent central super-massive black hole. This is the first direct measurement of MBH based on studies of hydrostatic X-ray emitting gas, which are sensitive to the most massive black holes, and is a crucial validation of both mass-determination techniques. This agreement clearly demonstrates the gas must be close to hydrostatic, even in the very centre of the galaxy, which is consistent with the lack of morphological disturbances in the X-ray image. NGC4649 is now one of only a handful of galaxies for which MBH has been measured by more than one method.”

History of Observation:

Both M59 and neighboring M60 were discovered on April 11, 1779 by Johann Gottfried Koehler who wrote: “Two very small nebulae, hardly visible in a 3-foot telescope: The one above the other.” It was independently found one day later by Barnabus Oriani, who missed M59, and four days later, on April 15, 1779, by Charles Messier, who also found nearby M58. In his notes Messier writes:

“Nebula in Virgo, a little more distinct than the two preceding [M58 and M59], on the same parallel as Epsilon [Virginis], which has served for its [position] determination. M. Messier reported it on the Chart of the Comet of 1779. He discovered these three nebulae while observing this Comet which passed very close to them. The latter passed so near on April 13 and 14 that the one and the other were both in the same field of the refractor, and he could not see it; it was not until the 15th, while looking for the Comet, that he perceived the nebula. These three nebulae don’t appear to contain any star.”

William Herschel would later perceive it as a double nebula and so would son John, calling it “A very fine and curious object.” However, it was Admiral Smyth who must have finally had a clear viewing night a took a look at what was all around!

“The hypothesis of Sir John Herschel, upon double nebulae, is new and attracting. They may be stellar systems each revolving round the other: each a universe, according to ancient notions. But as these revolutionary principles of those vast and distant firmamental clusters connot for ages yet be established, the mind lingers in admiration, rather than comprehension of such mysterious collocations. Meantime our clear duty is, so industriously to collect facts, that much of what is now unintelligible, may become plain to our successors, and a portion of the grand mechanism now beyond our conception, revealed. ‘How much,’ exclaims Sir John Herschel, ‘how much is escaping us! How unworthy is it in them who call themselves philosophers, to let these great phenomena of nature, these slow but majestic manifestations of power and the glory of God, glide unnoticed, and drop out of memory beyond the reach of recovery, because we will not take the pains to note them in their unobstrusive and furtive passage, because we see them in their every-day dress, and mark no sudden change, and conclude that all is dead, because we will not look for signs of life; and that all is uninteresting, because we are not impressed and dazzled.’ ….. ‘To say, indeed, that every individual star in the Milky Way, to the amount of eight or ten millions, is to have its place determined, and its motion watched, would be extravagant; but at least let samples be taken, at least let monographs of parts be made with powerful telescopes and refined instruments, that we may know what is going on in that abyss of stars, where at present imagination wanders without a guide!” Such is the enthusiastic call of one, whose father cleared the road by which we are introduced to the grandest phenomena of the stellar universe.'”

Locating Messier 58:

M59 is a telescopic only object and requires patience to find. Because the Virgo Galaxy field contains so many galaxies which can easily be mis-identified, it is sometimes easier to “hop” from one galaxy to the next! In this case, we need to start by locating bright Vindemiatrix (Epsilon Virginis) almost due east of Denebola.

Let’s starhop four and a half degrees west and a shade north of Epsilon to locate one of the largest elliptical galaxies presently known – M60. At a little brighter than magnitude 9, this galaxy could be spotted with binoculars, but stick with your telescope. In the same low power field (depending on aperture size) you may also note faint NGC 4647 which only appears to be interacting with M60.

In a smaller telescope, do not expect to see much. What will appear at low power is a tiny egg-shaped patch of contrast change with a brighter center. As aperture increases, a sharper nucleus will begin to appear as you move into the 4-6″ size range at dark sky locations, but elliptical galaxies do not show details. As with all galaxies, dark skies are a must!

Enjoy your own observations of the Virgo galaxy fields….

The location of Messier 60 in the Virgo constellation. Credit: IAU

And here are the quick facts on this Messier Object to help you get started:

Object Name: Messier 60
Alternative Designations: M60, NGC 4649
Object Type: E2 Galaxy
Constellation: Virgo
Right Ascension: 12 : 43.7 (h:m)
Declination: +11 : 33 (deg:m)
Distance: 60000 (kly)
Visual Brightness: 8.8 (mag)
Apparent Dimension: 7×6 (arc min)

We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects,  M1 – The Crab Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons.

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources:

Posted on

Messier 59 – the NGC 4621 Elliptical Galaxy

Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at the spiral galaxy known as Messier 59.

In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects he initially mistook for comets. In time, he would come to compile a list of approximately 100 of these objects, hoping to prevent other astronomers from making the same mistake. This list – known as the Messier Catalog – would go on to become one of the most influential catalogs of Deep Sky Objects.

One of these objects is the elliptical galaxy known as Messier 59 (aka. NGC 4621). This galaxy is located approximately 60 million light-years from Earth in the direction of the southern Virgo constellation. Sitting just a few degrees away Messier 60, and bordered at a distance by Messier 58, this galaxy is visible using smaller instruments, but is best observed using a larger telescope.

Atlas image of Messier 59 obtained by the Two micron All Sky Survey (2MASS). Credit: 2MASS/NASA/UMass

Description:

Located about 60 million light years away and spanning about 90 million light years of space, but what exactly is its type? Says Takao Mizuno (et al) in their 1996 study:

“We decomposed two-dimensionally an elliptical galaxy, NGC 4621, which shows deviations from the brightness distribution law. We have found that its brightness distribution can be reproduced by three components possessing constant ellipticities of the residuals in the circular region of radius. The component obeying the aw has 62% of the total light, and, hence, is the main body of this elliptical galaxy.” So it might not be the biggest or the brightest of the group, but it is home to nearly 2000 globular clusters. This isn’t news when it comes to this galaxy type, but what is news is how they rotate… the wrong way!

“We present adaptive optics assisted OASIS integral field spectrography of the S0 galaxy NGC 4621. Two-dimensional stellar kinematical maps (mean velocity and dispersion) reveal the presence of a 60 pc diameter counter-rotating core (CRC), the smallest observed to date.” says Fabien Wernli (et al), “The OASIS data also suggests that the kinematic center of the CRC is slightly offset from the center of the outer isophotes. This seems to be confirmed by archival HST/STIS data. We also present the HST/WFPC2 V-I colour map, which exhibits a central elongated red structure, also slightly off-centered in the same direction as the kinematic centre. Although the stellar velocities are reasonably fitted, including the region of the counter-rotating core, significant discrepancies between the model and the observations demonstrate the need for a more general model.”

What could account for such unusual behavior? Try a quiet black hole! As J. M. Wrobel (et al) indicated in their 2008 study:

“The nearby elliptical galaxies NGC 4621 and NGC 4697 each host a supermassive black hole. Analysis of archival Chandra data and new NRAO Very Large Array data shows that each galaxy contains a low-luminosity active galactic nucleus (LLAGN), identified as a faint, hard X-ray source that is astrometrically coincident with a faint 8.5-GHz source. The black holes energizing these LLAGNs have Eddington ratios placing them in the so-called quiescent regime. The emission from these quiescent black holes is radio-loud, suggesting the presence of a radio outflow. Also, application of the radio-X-ray-mass relation from Yuan & Cui for quiescent black holes predicts the observed radio luminosities to within a factor of a few. Significantly, that relation invokes X-ray emission from the outflow rather than from an accretion flow. The faint, but detectable, emission from these two massive black holes is therefore consistent with being outflow-dominated.”

The M59 spiral galaxy. Credit: NOAO

History of Observation:

Both M59 and neighboring M60 were discovered on April 11, 1779 by Johann Gottfried Koehler who wrote: “Two very small nebulae, hardly visible in a 3-foot telescope: The one above the other.” Charles Messier would independently recover it four days later and state in his notes:

“Nebula in Virgo and in the neighborhood of the preceding [M58], on the parallel of epsilon [Virginis], which has served for its [position] determination: it is of the same light as the above, equally faint. M. Messier reported it on the Chart of the Comet of 1779.”

While both William and John Herschel would also observe it, it sometimes confounds me that they didn’t seem to notice all the other galaxies around it! Fortunately for historic record, Admiral Smyth did:

“A fine field is exhibited under the eye-piece, which magnifies 93 times, just as this object [M60 with NGC 4647] enters, because the bright little nebula 59 M. is quitting the np [north preceding, NW] verge, and another small one is seen in the upper part, H. 1402 [NGC 4638]: in fact, four nebulae at once.”

Locating Messier 58:

M59 is a telescope-only object and requires patience to find. Because the Virgo Galaxy field contains so many galaxies which can easily be misidentified, it is sometimes easier to “hop” from one galaxy to the next. In this case, we need to start by locating bright Vindemiatrix (Epsilon Virginis) almost due east of Denebola. Then starhop four and a half degrees west and a shade north of Epsilon to locate one of the largest elliptical galaxies presently known – M60.

The location of M59, which sits between M58 and M60 in the direction of the Virgo constellation. Credit: IAU

At a little brighter than magnitude 9, this galaxy could be spotted with binoculars, but stick with your telescope. In the same low power field (depending on aperture size) you may also note faint NGC 4647 which only appears to be interacting with M60. Also in the field to the west (the direction of drift) is the Messier we’re looking for, bright cored elliptical galaxy M59.

In a smaller telescope, do not expect to see much. What will appear at low power is a tiny egg-shaped patch of contrast change with a brighter center. As aperture increases, a sharper nucleus will begin to appear as you move into the 4-6″ size range at dark sky locations, but elliptical galaxies do not show details. As with all galaxies, dark skies are a must!

Enjoy your journey around the Virgo Galaxy Field!

Object Name: Messier 59
Alternative Designations: M59, NGC 4621
Object Type: E5 Galaxy
Constellation: Virgo
Right Ascension: 12 : 42.0 (h:m)
Declination: +11 : 39 (deg:m)
Distance: 60000 (kly)
Visual Brightness: 9.6 (mag)
Apparent Dimension: 5×3.5 (arc min)

We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects,  M1 – The Crab Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons.

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources:

Posted on

Messier 58 – the NGC 4579 Barred Spiral Galaxy

Welcome back to Messier Monday! Today, we continue in our tribute to our dear friend, Tammy Plotner, by looking at the barred spiral galaxy, Messier 58.

In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects in the night sky. In time, he would come to compile a list of approximately 100 of these objects, with the purpose of making sure that astronomers did not mistake them for comets. However, this list – known as the Messier Catalog – would go on to serve a more important function, becoming one of the first catalogs of Deep Sky Objects.

One of these objects is the intermediate barred spiral galaxy known as Messier 58, which is located approximately 68 million light years away in the Virgo constellation. In addition to being one of just four barred spiral galaxies in the Messier Catalog, it is also one of the brightest galaxies in the Virgo Supercluster. Due to its proximity in the sky to other objects in the Virgo Galaxy Field, it can be seen only with the help of a telescope or a pair of large binoculars.

Description:

This beautiful old barred spiral galaxy located approximately 68 million light-years from Earth. Although it might appear pretty plain, it has some great things going for it… namely an active galactic nucleus. As Marcella Contini indicated in a 2004 study:

“We have modelled the low-luminosity active galactic nuclei (AGN) NGC 4579 by explaining both the continuum and the line spectra observed with different apertures. It was found that the nuclear emission is dominated by an AGN such that the flux from the active centre (AC) is relatively low compared with that of the narrow emission-line region (NLR) of Seyfert galaxies. However, the contribution of a young starburst cannot be neglected, as well as that of shock-dominated clouds with velocities of 100, 300 and 500kms-1. A small contribution from an older starburst with an age of 4.5 Myr, probably located in the external nuclear region, is also found. HII regions appear in the extended regions, where radiation and shock-dominated clouds prevail.

“The continuum SED of NGC 4579 is characterized by the strong flux from an old stellar population. Emissions in the radio range show synchrotron radiation from the base of the jet outflowing from the accretion disc within 0.1 pc from the active centre. Radio emission within intermediate distances is explained by the bremsstrahlung from gas downstream of low-velocity shocks reached by a relatively low radiation flux from the AC. In extended regions the radio emission is synchrotron radiation created by the Fermi mechanism at the shock front. The shocks are created by collision of clouds with the jet. All types of emissions observed at different radius from the centre can be reconciled with the presence of the jet.”

The Messier 58 barred spiral galaxy. Credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona

Yet where is this gas traveling to and why? According to 2014 study by S. Garcia-Burillo (et al):

“We created a complete gravity torque map of the disk of the LINER/Seyfert 1.9 galaxy NGC 4579. We quantify the efficiency of angular momentum transport and search for signatures of secular evolution in the fueling process from r ~ 15 kpc down to the inner r ~ 50 pc around the active galactic nucleus (AGN). The derived gravity torque budget in NGC 4579 shows that inward gas flow is occurring on different spatial scales in the disk. In the outer disk, the decoupling of the spiral allows the gas to efficiently populate the UHR region, and thus produce net gas inflow on intermediate scales. The co rotation barrier seems to be overcome by secular evolution processes. The gas in the inner disk is efficiently funneled by gravity torques down to r ~ 300 pc. Closer to the AGN, gas feels negative torques due to the combined action of the large-scale bar and the inner oval. The two m=2 modes act in concert to produce net gas inflow down to r ~ 50 pc, providing clear smoking gun evidence of inward gas transport on short dynamical timescales.”

What causes inward transport of gases? Why, a massive gravity pull of course. And what could be more gravitational attractive than a black hole! As Eliot Quataert (et al) indicated in their 1999 study:

“M81 and NGC 4579 are two of the few low-luminosity active galactic nuclei which have an estimated mass for the central black hole, detected hard X-ray emission, and detected optical/UV emission. In contrast to the canonical “big blue bump,” both have optical/UV spectra which decrease with increasing frequency in a plot. Barring significant reddening by dust and/or large errors in the black hole mass estimates, the optical/UV spectra of these systems require that the inner edge of a geometrically thin, optically thick, accretion disk lies at roughly 100 Schwarzschild radii. The observed X-ray radiation can be explained by an optically thin, two temperature, advection-dominated accretion flow at smaller radii.”

Galaxy NGC 4579 was captured by the Spitzer Infrared Nearby Galaxy Survey (SINGS) Legacy Project using the Spitzer Space Telescope’s Infrared Array Camera (IRAC). In this image, the red structures are areas where gas and dust are thought to be forming new stars, while the blue light comes from mature stars. This SINGS image is a four-channel, false-color composite, where blue indicates emission at 3.6 microns, green corresponds to 4.5 microns, and red to 5.8 and 8.0 microns. The contribution from starlight (measured at 3.6 microns) in this picture has been subtracted from the 5.8 and 8 micron images to enhance the visibility of the dust features.

Messier 58 (NGC 4579), as imaged by the Spitzer Infrared Nearby Galaxy Survey (SINGS) Legacy Project using the Spitzer Space Telescope’s Infrared Array Camera (IRAC). Credit: NASA/JPL-Caltech/R. Kennicutt (University of Arizona) and the SINGS Team

History of Observation:

When Charles Messier discovered this one on April 15, 1779, I’m sure he didn’t know he was looking back into time when he wrote:

“Very faint nebula discovered in Virgo, almost on the same parallel as Epsilon, 3rd mag. The slightest light for illuminating the micrometer wires makes it disappear. M. Messier reported it on the chart of the Comet of 1779, which is located in the volume of the Academy for the same year.”

Messier 58 may not have been a comet, but it certainly was another distant cousin of our own Milky Way!

Locating Messier 58:

Finding M58 requires a telescope or large binoculars, and lots of patience. Because the Virgo Galaxy field contains so many galaxies which can easily be misidentified, it is sometimes easier to “hop” from one galaxy to the next! In this case, we need to start by locating bright Vindemiatrix (Epsilon Virginis) almost due east of Denebola. Let’s hop four and a half degrees west and a shade north of Epsilon to locate one of the largest elliptical galaxies presently known – M60.

At a little brighter than magnitude 9, this galaxy could be spotted with binoculars, but stick with your telescope. In the same low power field (depending on aperture size) you may also note faint NGC 4647 which only appears to be interacting with M60. Also in the field to the west (the direction of drift) is our next Messier, bright cored elliptical M59. Now we will need to continue about an average eyepiece field of view, or a degree further west of this group to bring you to our “galactic twin”, fainter M58.

The location of M58, in the direction of the Virgo constellation. Credit: IAU

In a smaller telescope, do not expect to see much. What will appear at low power is a tiny egg-shaped patch of contrast change. As aperture increases, so does detail and a bright nucleus will begin to appear as you move into the 4-6″ size range and dark sky locations. As with all galaxies, dark skies are a must!

And here are the quick facts on this object to help you get started:

Object Name: Messier 58
Alternative Designations: M58, NGC 4579
Object Type: SBc Galaxy
Constellation: Virgo
Right Ascension: 12 : 37.7 (h:m)
Declination: +11 : 49 (deg:m)
Distance: 60000 (kly)
Visual Brightness: 9.7 (mag)
Apparent Dimension: 5.5×4.5 (arc min)

We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects,  M1 – The Crab Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons.

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources:

Posted on

Messier 57 – The Ring Nebula

Welcome back to Messier Monday! We continue our tribute to our dear friend, Tammy Plotner, by looking at the the Big Ring itself, the planetary nebula known as Messier 57. Enjoy!

In the 18th century, while searching the night sky for comets, French astronomer Charles Messier kept noting the presence of fixed, diffuse objects in the night sky. In time, he would come to compile a list of approximately 100 of these objects, with the purpose of making sure that astronomers did not mistake them for comets. However, this list – known as the Messier Catalog – would go on to serve a more important function.

One of these objects is known as Messier 57, a planetary nebula that is also known as the Ring Nebula. This object is located about 2,300 light years from Earth in the direction of the Lyra constellation. Because of its proximity to Vega, the brightest star in Lyra and one of the stars that form the Summer Triangle, the nebula is relatively easy to find using binoculars or a small telescope.

What You Are Looking At:

Here you see the remainders of a sun-like star… At one time in its life, it may have had twice the mass of Sol, but now all that’s left is a white dwarf that burns over 100,000 degrees kelvin. Surrounding it is an envelope about 2 to 3 light years in size of what once was its outer layers – blown away in a cylindrical shape some 6000 to 8000 years ago. Like looking down the barrel of a smoking gun, we’re looking back in time at the end of a Mira-like star’s evolutionary phase.

It’s called a planetary nebula, because once upon a time before telescopes could resolve them, they appeared almost planet-like. But, as for M57, the central star itself is no larger than a terrestrial planet! The tiny white dwarf star, although it could be as much as 2300 light years away, has an intrinsic brightness of about 50 to 100 times that of our Sun.

One of the most beautiful features of M57 is the structure in the ring itself, sometimes called braiding – but scientifically known as “knots” in the gaseous structure. As C.R. O’Dell (et al) indicated in their 2003 study:

“We have studied the closest bright planetary nebulae with the Hubble Space Telescope’s WFPC2 in order to characterize the dense knots already known to exist in NGC 7293. We find knots in all of the objects, arguing that knots are common, simply not always observed because of distance. The knots appear to form early in the life cycle of the nebula, probably being formed by an instability mechanism operating at the nebula’s ionization front. As the front passes through the knots they are exposed to the photoionizing radiation field of the central star, causing them to be modified in their appearance. This would then explain as evolution the difference of appearance like the lacy filaments seen only in extinction in IC 4406 on the one extreme and the highly symmetric “cometary” knots seen in NGC 7293. The intermediate form knots seen in NGC 2392, NGC 6720, and NGC 6853 would then represent intermediate phases of this evolution.”

However, examining things like planetaries nebulae in different wavelengths of light can tell us so much more about them. Behold the beauty when see through the Spitzer Space Telescope! As M.M. Roth explained in a 2007 study:

“Emission nebulae like H II regions, Planetary Nebulae, Novae, Herbig Haro objects etc. are found as extended objects in the Milky Way, but also as point sources in other galaxies, where they are sometimes observable out to very large distances due to the high contrast provided by some prominent emission lines. It is shown how 3D spectroscopy can be used as a powerful tool for observations of both large resolved emission nebulae and distant extragalactic objects, with special emphasis on faint detection limits.”

History of Observation:

This deep space object was first discovered in early January 1779 by Antoine Darquier who wrote in his notes:

“This nebula, to my knowledge, has not yet been noticed by any astronomer. One can only see it with a very good telescope, it is not resembling any of those [nebula] already known; it has the apparent dimension of Jupiter, is perfectly round and sharply limited; its dull glow resembles the dark part of the Moon before the first and after the last quarter. Meanwhile, the center appears a bit less pale than the remaining part of its surface.”

Although Darquier did not post a date, it is believed his observation preceded Messier’s independent recovery made on January 31, 1779 when he states that Darquier picked it up before him:

“A cluster of light between Gamma and Beta Lyrae, discovered when looking for the Comet of 1779, which has passed it very close: it seems that this patch of light, which is round, must be composed of very small stars: with the best telescopes it is impossible to distinguish them; there stays only a suspicion that they are there. M. Messier reported this patch of light on the Chart of the Comet of 1779. M. Darquier, at Toulouse, discovered it when observing the same comet, and he reports: ‘Nebula between gamma and beta Lyrae; it is very dull, but perfectly outlined; it is as large as Jupiter and resembles a planet which is fading’.”

A few years later, Sir William Herschel would also observe Messier Object 57 with his superior telescope and in his private notes he writes:

“Among the curiosities of the heavens should be placed a nebula, that has a regular, concentric, dark spot in the middle, and is probably a Ring of stars. It is of an oval shape, the shorter axis being to the longer as about 83 to 100; so that, if the stars form a circle, its inclination to a line drawn from the sun to the center of this nebula must be about 56 degrees. The light is of the resolvable kind [i.e., mottled], and in the northern side three very faint stars may be seen, as also one or two in the southern part. The vertices of the longer axis seem less bright and not so well defined as the rest. There are several small stars very bear, but none seems to belong to it.”

Admiral Smyth would go on in later years to add his own detailed observations to history’s records:

“This annular nebula, between Beta and Gamma on the cross-piece of the Lyre, forms the apex of a triangle which it makes with two stars of the 9th magnitude; and its form is that of an elliptic ring, the major axis of which trends sp to nf [SW to NE]. This wonderful object seems to have been noted by Darquier, in 1779; but neither he nor his contemporaries, Messier and Méchain, discerned its real form, seeing in this aureola of glory only “a mass of light in the form of a planetary disc, very dingy in colour.”

“Sir W. Herschel called it a perforated resolvable nebula, and justly ranked it among the curiosities of the heavens. He considered the vertices of the longer axis less bright and not so well defined as the rest; and he afterwards added: ‘By the observations of the 20-feet telescope, the profundity of the stars, of which it probably consists, must be of a higher than the 900th order, perhaps 950.'”

“This is a vast view of the ample and inconceivable dimensions of the spaces of the Universe; and if the oft-cited cannon-ball, flying with the uniform velocity of 500 miles an hour, would require millions of years to reach Sirius, what an incomprehensible time it would require to pass so overwhelming an interval as 950 times the distance! And yet, could we arrive there, by all analogy, no boundary would meet the eye, but thousands and ten thousands of other remote and crowded systems would still bewilder the imagination.

“In my refractor this nebula has a most singular appearance, the central vacuity being black, so as to countenance the trite remark of its having a hole through it. Under favourable circumstances, when the instrument obeys the smooth motion of the equatorial clock, it offers the curious phenomenon of a solid ring of light in the profundity of space. The annexed sketch affords a notion of it. Sir John Herschel, however, with the superior light of his instrument, found that the interior is far from absolutely dark. “It is filled,’ he says, ‘with a feeble but very evident nebulous light, which I do not remember to have been noticed by former observers.'”

Since Sir John’s observation, the powerful telescope of Lord Rosse has been directed to this subject, and under powers 600, 800, and 1000, it displayed very evident symptoms of resolvability at its minor axis. The fainter nebulous matter which fills it, was found to be irregularly distributed, having several stripes or wisps in it, and the regularity of the outline was broken by appendages branching into space, of which prolongations the brightest was in the direction of the major axis.

Locating Messier 57:

M57 is a breeze to locate because it is positioned between Beta and Gamma Lyrae (the westernmost pair of the lyre’s stars), at about one-third the distance from Beta to Gamma. While it is easily seen in binoculars, it is a little difficult to identify because of its small size, so binoculars must be very steady to distinguish it from the surrounding star field.

In even a small telescope at minimum power, you’ll quickly notice a very small, but perfect ring structure which takes very well to magnification. Despite low visual brightness, M57 actually takes well to urban lighting conditions and can even be spied during fairly well moonlit nights. Larger aperture telescopes will easily see braiding in the nebula structure and often glimpse the central star. May you also see the many faces of the “Ring”!

The location of Messier 57 in the Lyra Constellation. Credit: IAU and Sky & Telescope magazine (Roger Sinnott & Rick Fienberg)

And here are the quick facts on Messier 57 to help you get started:

Object Name: Messier 57
Alternative Designations: M57, NGC 6720, the “Ring Nebula”
Object Type: Planetary Nebula
Constellation: Lyra
Right Ascension: 18 : 53.6 (h:m)
Declination: +33 : 02 (deg:m)
Distance: 2.3 (kly)
Visual Brightness: 8.8 (mag)
Apparent Dimension: 1.4×1.0 (arc min)

We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects,  M1 – The Crab Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons.

Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

Sources: