Astronomy Archives

December 10, 2009April 8, 2017 by Fraser Cain

What is Jupiter’s Great Red Spot?

One of the most prominent features in the Solar System is Jupiter’s Red Spot. This is a massive storm three times the size of the Earth that has been raging across the cloud tops of Jupiter since astronomers first looked at it with a telescope.

Known as the Great Red Spot, this is an anticyclonic (high pressure) storm that rotates around the planet at about 22°. Astronomers think that its darker red color comes from how it dredges up sulfur and ammonia particles from deeper down in Jupiter’s atmosphere. These chemicals start out dark and then lighten as they’re exposed to sunlight. Smaller storms on Jupiter are usually white, and then darken as they get larger. The recently formed Red Spot Jr. storm turned from white to red as it grew in size and intensity.

Astronomers aren’t sure if Jupiter’s Red Spot is temporary or permanent. It has been visible since astronomers started making detailed observations in the 1600s, and it’s still on Jupiter today. Some simulations have predicted that this a storm like this might be a permanent fixture on Jupiter. You can still see the Red Spot with a small telescope larger than about 15 cm (6 inches).

The edge of the Red Spot is turning at a speed of about 360 km/h (225 mph). The whole size of the spot is ranges from 24,000 km x 12,000 km to as wide as 40,000 km. You could fit two or three Earths inside the storm. The actual edge of the storm lifts up about 8 km above the surrounding cloud tops.

Astronomers have noticed that it’s been slowly shrinking over the last decade or so, losing about 15% of its total size. This might be a temporary situation, or Jupiter’s Red Spot might go on losing its size. If it continues, it should look almost round by 2040.

We’ve written many articles about Jupiter’s Red Spot for Universe Today. Here’s an article about Jupiter’s little red spot, and here’s an article about Jupiter’s red spot colliding together.

If you’d like more info on Jupiter, check out Hubblesite’s News Releases about Jupiter, and here’s a link to NASA’s Solar System Exploration Guide to Jupiter.

We’ve also recorded an episode of Astronomy Cast all about Jupiter. Listen here, Episode 56: Jupiter.

December 10, 2009December 24, 2015 by Jean Tate

Stellar Parallax

Progress in astrometic accuracy (Credit: ESA)

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Parallax is the apparent difference in the position (line of sight to) an object, when the object is viewed from different locations. So, when we observe that a star has apparently moved (not to be confused with it actually having moved – proper motion), when we look at it from two different locations on the Earth’s orbit around the Sun (i.e. on different dates), that’s stellar parallax! (And if the star does not seem to have moved? Well, its parallax is zero).

The furthest apart two locations on the Earth’s orbit can be is 2 au (two astronomical units), as when observations of an object are taken six months apart. By simple trigonometry (geometry), the distance to the object being observed is just the length of the baseline divided by the tangent of the parallax angle (the angular difference in the two lines of sight) … and since parallax angles are extremely small for stars (less than one arcsecond), the tangent of the angle is the same as the angle. This gives a natural unit of distance for stars, the parsec … which is the distance at which an object has a parallax of one arcsecond when viewed from a baseline of one au.

There was a pretty hot competition, among astronomers, to be the first to measure the parallax of a star (other than the Sun), back in the 1830s; the race was won by Friedrich Bessell (remember Bessell functions?), in 1838, with a measurement of the parallax of 61 Cygni (0.314 arcsecs, in case you were wondering; two other astronomers measured the parallax of different stars in the same year).

To date, the most accurate parallaxes (~1 milli-arcsec) are the 100,000 or so obtained by the ESA’s Hipparcos mission (which operated between 1989 and 1993; results published in 1997) … Hipparcos stands for High Precision Parallax Collecting Satellite, but is also a nod to the ancient Greek astronomer Hipparchus. The follow-up mission, Gaia (target launch date: 2012) will substantially improve on this (up to a billion stars, parallaxes as small as 20 micro-arcsec). Here’s a fun fact: Gaia will measure the gravitational deflection caused the Sun … across the whole sky (and detect that due to Mars, for stars near the line sight to it)!

Universe Today has several stories on, or featuring, stellar parallax; here are a few: New Stellar Neighbors Found, Chasing an Occultation, and Happy Birthday Johannes Kepler.

Distance in Space is an Astronomy Cast episode on this very topic!

References:
http://hyperphysics.phy-astr.gsu.edu/hbase/astro/para.html
http://starchild.gsfc.nasa.gov/docs/StarChild/questions/parallax.html

December 10, 2009December 24, 2015 by Brian Ventrudo

Half a Million Galaxies, Yours to Explore

This deep-field image from CFHT contains 500,000 galaxies.

Move over, Hubble Deep Field. The Canada-France-Hawaii Telescope has released a new deep-field image of as many as 500,000 galaxies out to a distance of 7 billion light years. And you can surf the entire image at high resolution with an interactive zoom feature at the CFHT website.

This new image is the result of the accumulation of several hundreds of hours of light integration over five years (2003-2008) with the CFHT using the 340 megapixel camera called MegaCam. This field and three more like it from other parts of the sky were systematically observed every three nights to detect faint supernovae going off in distant galaxies to study the effect of the mysterious dark energy responsible for the observed accelerating expansion of the universe.

Stacking these individual MegaCam images reveals a dense wallpaper of distant galaxies. An observing technique called “dithering” allows coverage of a larger field of view than that of the camera itself, leading to a sky coverage over 370 megapixels. Approximately half a million galaxies can be counted on the entire image.

As it covers a full square degree of sky (about 5 times greater than the size of the full moon), the entire image is impressive enough. But the ultra-high resolution of the image, along with a nifty interactive tool on the CFHT website, allows you to zoom in on tiny subsets of the image to see an astonishing assortment of galaxies out to a distance of 7 billion light years, about half-way to the edge of the observable universe. A few foreground stars of our own galaxy are visible. But almost everything else you see in this image is a distant galaxy.

You can access the image and the interactive viewer at the CFHT website.

Source: Canada-France-Hawaii Telescope

December 9, 2009December 24, 2015 by Nancy Atkinson

Extra Star Found in the Big Dipper

The handle of the Big Dipper just got stronger! Astronomers have found an additional star located in the Dipper’s gripper that is invisible to the unaided eye. Alcor, one of the stars that makes the bend in the Big Dipper’s handle has a smaller red dwarf companion orbiting it. Now known as “Alcor B,” the star was found with an innovative technique called “common parallactic motion,” and was found by members of Project 1640, an international collaborative team that gives a nod to the insight of Galileo Gallilei.

“We used a brand new technique for determining that an object orbits a nearby star, a technique that’s a nice nod to Galileo,” says Ben R. Oppenheimer, Curator at the Museum of Natural History. “Galileo showed tremendous foresight. Four hundred years ago, he realized that if Copernicus was right—that the Earth orbits the Sun—they could show it by observing the ‘parallactic motion’ of the nearest stars. Incredibly, Galileo tried to use Alcor to see it but didn’t have the necessary precision.”

If Galileo had been able to see change over time in Alcor’s position, he would have had conclusive evidence that Copernicus was right. Parallactic motion is the way nearby stars appear to move in an annual, repeatable pattern relative to much more distant stars, simply because the observer on Earth is circling the Sun and sees these stars from different places over the year.

The collaborative team that found the star includes astronomers from the American Museum of Natural History, the University of Cambridge’s Institute of Astronomy, the California Institute of Technology, and NASA’s Jet Propulsion Laboratory.

Alcor is a relatively young star twice the mass of the Sun. Stars this massive are relatively rare, short-lived, and bright. Alcor and its cousins in the Big Dipper formed from the same cloud of matter about 500 million years ago, something unusual for a constellation since most of these patterns in the sky are composed of unrelated stars. Alcor shares a position in the Big Dipper constellation with another star, Mizar. In fact, both stars were used as a common test of eyesight—being able to distinguish “the rider from the horse”—among ancient people. One of Galileo’s colleagues observed that Mizar itself is actually a double, the first binary star system resolved by a telescope. Many years later, the two components Mizar A and B were themselves determined each to be tightly orbiting binaries, altogether forming a quadruple system.

In March, members of Project 1640 attached their coronagraph and adaptive optics to the 200-inch Hale Telescope at the Palomar Observatory in California and pointed to Alcor. “Right away I spotted a faint point of light next to the star,” says Neil Zimmerman, a graduate student at Columbia University who is doing his PhD dissertation at the Museum. “No one had reported this object before, and it was very close to Alcor, so we realized it was probably an unknown companion star.”

The team retuned a few months later and found the star had the same motion as Alcor, proving it was a companion star.

Alcor and its smaller companion Alcor B are both about 80 light-years away and orbit each other every 90 years or more. The team was also able to determine Alcor B is a common type of M-dwarf star or red dwarf that is about 250 times the mass of Jupiter, or roughly a quarter of the mass of our Sun. The companion is much smaller and cooler than Alcor A.

“Red dwarfs are not commonly reported around the brighter higher mass type of star that Alcor is, but we have a hunch that they are actually fairly common,” says Oppenheimer. “This discovery shows that even the brightest and most familiar stars in the sky hold secrets we have yet to reveal.”

The team plans to use parallactic motion again in the future. “We hope to use the same technique to check that other objects we find like exoplanets are truly bound to their host stars,” says Zimmerman. “In fact, we anticipate other research groups hunting for exoplanets will also use this technique to speed up the discovery process.”

Source: EurekAlert

December 9, 2009December 24, 2015 by Nicholos Wethington

Very First Image of a Very Hot Star

No, this article is not about Johnny Depp or Angelina Jolie. They may be hot stars, but in comparison to the star at the center of the Bug Nebula, pictured left, they’ve got nothin’. The first image of the star at the center of the Bug Nebula (NGC 6302) has been taken by a team of astronomers at the Jodrell Bank Centre for Astrophysics, using the newly refurbished Hubble Space Telescope. This star, one of the hottest in the galaxy, has a temperature of about 200,000 Kelvin – 33 times hotter than the Sun – and is at the center of one of the most beautiful planetary nebula in the galaxy.

The star at the heart of the Bug Nebula, which lies about 3500 light-years away from Earth in the constellation Scorpius, is what gives the two lobes of the formation their glow. Its extreme temperature of at least 200,000 K (and possibly up to 400,000 K) ionizes the gas in the nebula, which is itself composed of ejecta from the star as it shed its corona during the later stages of its life. The star has gone through its red giant phase and is now a late-stage white dwarf.

As a comparison to how hot the star powering the luminosity of the Bug Nebula is, our Sun’s hottest temperature is 5,800 Kelvin which is about 5,500 degrees Celsius and almost 10,000 degrees Fahrenheit. The mass of the star is calculated to be 0.64 solar masses, though it was many times heavier than the Sun before it ejected much of its matter into the nebula.

The astronomers were lucky to have been able to image the star at this point in its life, as the light it is emitting is fading at about 1% a year. Professor Albert Zijlstra of the University of Manchester said in an email interview, “The star seems to be in a phase where nuclear burning has ceased very recently (within the past 100-1000 yr). It is radiating its left-over surface heat away, and that goes quickly. At some time heat from interior will take over, and as that is a much larger heat reservoir, the star will fade much more slowly from that point.”

This does not mean, however, that the ionized gas in the nebula will fade out quite as quickly, Zijlstra said. ‘The nebula is ionized by ultra-violet photons from the star. The ionized elements recombine with electrons, before being re-ionized. Normally, there is a good balance between ionizations and recombinations. In NGC 6302, if the star is fading rapidly, it is possible that the time scale for recombinations is longer than the time over which the star fades. The nebula would ‘remember’ a more luminous star, and be ionized to a higher degree than the star could currently support. It is like living off your savings.”

There have been many attempts at imaging this star, but the brightness of the nebula combined with the dust obscuring the star made imaging difficult. Only with the new Wide-Field Camera 3, installed on the Hubble earlier this year, were the astronomers able to make out the star buried in the heart of the Bug Nebula.

Zijlstra said of the Hubble’s capabilities, “It is a combination of sensitivity and available filters. The nebula is very bright, and it is difficult to detect the faint star against the very bright nebular background. To get the best sensitivity, you need high resolution (which dilutes the nebulae light while concentrating the stellar light – this requires HST), good sensitivity and ideally, a filter which excludes the brightest emission lines (H alpha, [O III]). We detected the star with two different filters which select fainter emission lines, which reduces the glare from the nebula. The extinction through the dust in the nebula is also very high, which makes the star even fainter especially in the blue.”

Further observations of the star are definitely in order, including molecular and dust spectroscopy, but Zijlstra said his team does not have any observations of the star planned as of now. The results of the imaging and calculations detailing the properties of the star will be published in The Astrophysical Journal, but a pre-print article is available on Arxiv.

A zoom animation of some of the images put together is also available on the Jodrell Bank Centre for Astrophysics site right here.

Source: Jodrell Bank press release, email interview with Albert Zijlstra

December 9, 2009December 24, 2015 by Fraser Cain

Earth’s Mass

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The Earth’s mass is 5.9736 x 10²⁴ kg. That’s a big number, so let’s write it out in full: 5,973,600,000,000,000,000,000,000 kg. You could also say the Earth’s mass is 5.9 sextillion tonnes. Phew, that’s a lot of mass.

That sounds like a lot, and it is, but the Earth has a fraction of the mass of some other objects in the Solar System. The Sun has 333,000 times more mass than the Earth. And Jupiter has 318 times more mass. But then there are some less massive objects too. Mars has only 11% the mass of the Earth.

Because of its high mass for its size, Earth actually has the highest density of all the planets in the Solar System. The density of Earth is 5.52 grams per cubic centimeter. The high density comes from the Earth’s metallic core, which is surrounded by the rocky mantle. Less dense planets, like Jupiter, are just made up of gases like hydrogen.

We’ve written several articles about the mass of planets in the Solar System. Here’s an article about the mass of Mercury, and here’s an article about the mass of the Sun.

If you’d like more information on the Earth mass, check out NASA’s Solar System Exploration Guide on Earth. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about the Earth. Listen here, Episode 51: Earth.

December 7, 2009December 24, 2015 by Jon Voisey

Dating a Cluster – A New Trick

The hundreds of thousands of stars orbiting inside the globular cluster M13 (HST/NASA)

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Finding the ages of things in astronomy is hard. While it is undoubted that the properties of objects change as they age, the difficulty lies in that the initial parameters are often so varied that, for most cases, finding reliable ages is challenging. There’s some tricks to do it though. One of the best ones, taught conceptually in introductory astronomy courses, is to use the “main sequence turn-off” of a cluster. Of course, applying any of these methods is easier said than done, but a new method may help alleviate some of the challenges and allow for smaller errors.

The largest difficulty in the main sequence turn-off method lies in the inherent scatter caused by numerous sources that must be accounted for. Stars that lie along the same line of sight as the cluster being observed can add extraneous data points. Any interstellar reddening caused by gas may make stars appear more red than they should be. Close binary stars that cannot be spatially resolved appear brighter than they should be as an individual star. The amount of heavy elements in the star will also effect the fitting of the model. All of these factors and more contribute to an uncertainty in any calculation that requires an accurate Hertzsprung-Russell Diagram. Tricks to correct for some of these factors exist. Others cannot (yet) be accounted for.

Thanks to all these problems, fitting the data can often be challenging. Finding the point where the cluster “peels away” from the main sequence is difficult, so one of the tricks is to look for other points that should have significant numbers of stars to provide extra reference points for fitting. Examples of this include the horizontal branch and the red clump.

The new technique, developed by a large team of international astronomers, uses “a well defined knee located along the lower main sequence” which they refer to as the Main Sequence Knee (MSK). This “knee” appears in H-R diagrams of the clusters taken in the near-infrared and is largely independent of the age of the cluster. As such, it provides a stable reference point to improve corrections for the general main sequence turn-off method. Additionally, since this system uses infrared wavelengths, it is less prone to contamination between gas and dust.

To test this new method, the group selected a globular cluster (NGC 3201) as a test case. When their method was applied, they found that their derived age for the cluster was consistent with ages derived by other methods.

However, the new method is not without difficulties of its own. Since the knee is at the faint end of the main sequence, this requires that exposure times for target clusters be sufficiently long to bring out such faint stars. Fortunately, with new telescopes like the the James Webb Space Telescope, these faint stars should be in reach.

December 7, 2009December 24, 2015 by Nicholos Wethington

Red Giant Brightness Variations Still Mysterious

As the get older, Sun-like stars become red giants. 30-50 percent of these red giants exhibit a strange variability in their brightness that has so far eluded explanation. Image Credit: ESO/S. Steinhofel

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Like everything else in the Universe, stars get old. As they become older, stars like our own Sun “puff up”, becoming red giants for a period before finally settling down into white dwarfs. During this late period of their stellar lives, about 30% of low-mass red giants exhibit a curious variability in their brightness that remains unexplained to this day. A new survey of these types of red giants rules out most of the current explanations put forth, making it necessary to find a new theory for their behavior.

Red giants are a stage in the later part of a Sun-like star’s life when most of the fuel powering nuclear fusion in the core of the star is exhausted. The resulting lack of light pressure pushing out against the force of gravity causes the star to collapse in on itself. When this collapse occurs, though, it heats up a shell of hydrogen around the core enough to reignite fusion, resulting in an increase in nuclear fusion that causes the star to become bigger due to the increased light pressure. This can result in the star becoming 1,000 to 10,000 times more luminous.

Variability in the light output of red giants is natural -they swell up and shrink down in a consistent pattern, resulting in brighter and dimmer light outputs. There is, however, a difference in the brightness of roughly a third to one half of these stars that happens over longer time periods, to the tune of up to five years.

Called the Long Secondary Period (LSP), the changing brightness of the star happens over longer timescales than the shorter period pulsation. It is this long-term variation in brightness that remains unexplained.

A new detailed study of 58 variable red giants in the Large Magellanic cloud by Peter Wood and Christine Nicholls, both of the Research School of Astronomy and Astrophysics at the Australian National University, shows that the proposed explanations of this mysterious variability fall short of the measured properties of the stars. Nicholls and Wood used the FLAMES/GIRAFFE spectrograph on ESO’s Very Large Telescope, and combined the information with data from other telescopes like the Spitzer Space Telescope.

There are two leading explanations of the phenomenon: the presence of a companion object to the red giants that orbit in such a way to change their brightness, or the presence of a circumstellar dust cloud that somehow blocks the light coming from the star in our direction on a periodic scale.

A binary companion to the stars would change their orbit in such a way that they would approach and recede from the vantage point of the Earth, and if the companion passed in front of the star it would also dim the light streaming from the red giant. In the case of a binary companion, the spectra of the brightness change among all of these stars is relatively similar, meaning that for this explanation to work, all of the red giants exhibiting the LSP variation would have to have a companion of a similar size, approximately 0.09 times the mass of the Sun. This scenario would be extremely unlikely, given the large number of stars that show this brightness variation.

The effect of a circumstellar dust cloud could be a possible explanation. A cloud of circumstellar dust that obscures the light from the star once per orbit would dim its light enough to explain the phenomenon. The presence of such a dust cloud would be revealed by an excess of light coming from the star in the mid-infrared spectrum. The dust would absorb light from the star, and re-emit it in the form of light in the mid-infrared region of the spectrum.

Observations of LSP stars show the mid-infrared signature that’s a telltale sign of dust, but the correlation between the two doesn’t mean that the dust is causing the brightness variation. It could be that the dust is a byproduct of ejected mass from the star itself, the underlying cause of which could be associated with the change in brightness.

Whatever the cause of the oscillation of brightness in these red giants may be, it does make them eject mass in large clumps or in the form of an expanding disc. Obviously, further observations will be necessary to track down the reason for this phenomenon.

The results of the observations made by Nicholls and Wood have been published in The Astrophysical Journal. Two articles describing their findings are available on Arxiv, here and here.

Source: ESO, Arxiv papers

December 7, 2009December 24, 2015 by Abby Cessna

Tallest Mountains

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There are many tall mountains around the world as well as on other worlds. Mount Everest is the highest mountain in the world at 8,848 meters. Mauna Kea is the tallest mountain in the world. The tallest mountain is measured from base to top while the highest mountain is measured from sea level to the top. Everest is located in the Himalayan mountain range in Nepal and near Tibet. Mauna Kea is located in Hawaii and is 10,200 meters from base to tip. From sea level though, it is only about 4,205 meters tall. Mauna Kea is an extinct shield volcano.

These are not the only tall mountains though. K2 is in the Karakoram mountain range on the border of Pakistan and China. It is 8,612 meters tall and is generally considered the second tallest mountain in the world. The Himalayans are home to many tall mountains besides Mount Everest. This includes Mount Kangchenjunga at 8,586 meters and Mount Lhotse I at 8,501 meters.

Most of the world’s tallest mountains are located in Asia; however, there are a number of tall mountains that are located on other continents. The seven tallest mountains in different continents are known as the Seven Summits. Climbing all seven mountains is a mountaineering challenge that was started in the 1980’s.The first of these is Mount Everest. Another summit is Aconcagua, which is a mountain in Argentina in South America. At approximately 6,962 meters, it is the tallest mountain in the Americas. North America’s tallest mountain is Mount McKinley at 6,194 meters. Mount Kilimanjaro can be found in Tanzania in the continent of Africa and is 5,895 meters tall. The large summit of Mount Kilimanjaro is covered with an ice cap that is receding and according to scientists will eventually be gone. Mount Elbrus, the tallest mountain in Europe at 5,642 meters, can be found in Russia. Vinson Massif is Antarctica’s tallest mountain at 4,897 meters. It is also very large being 21 kilometers long and 13 kilometers wide. Australia-Oceania’s largest mountain can be found in Indonesia. At 4,884 meters, it is Puncak Jaya, which is also known as the Carstensz Pyramid.

The tallest mountain that we know of is not even on Earth. It is located on Mars and is known as Olympus Mon. A shield volcano, Olympus Mon is 27,000 meters tall. Mars is not the only other planet with tall mountains though. Venus’ Maxwell Montes is 11,000 meters tall. Satellites also have tall mountains including our Moon, which has Mons Huygens at 4,700 meters tall. The moon Io has a mountain, Boösaule Montes, which is approximately 17,000 meters tall.

Universe Today has articles on tallest mountain and tallest mountain in the Solar System.

For more information, you should take a look at what are the world’s tallest mountains and highest mountains.

Astronomy Cast has an episode on Earth you will find interesting.

Sources:
http://en.wikipedia.org/wiki/List_of_highest_mountains

December 4, 2009December 24, 2015 by Tammy Plotner

Weekend SkyWatcher’s Forecast – December 5-7, 2009

Greetings, fellow SkyWatchers! Are you ready for an mmm mmm good weekend? Well, the “m” stands for Messier and we’re off to study three of the late year’s finest… and a Herschel object as well! Don’t feel like taking out the telescope? Then don’t worry, because all of our weekend studies are easily done with even small binoculars! When ever you’re ready, I’ll see you in the dark…

Friday, December 4, 2009 – On this date in 1978, the Pioneer Venus Orbiter became the first spacecraft to orbit Venus. And, in 1996, the Mars Pathfinder mission was launched.

Tonight we’ll launch toward a bright open cluster known by many names: Herschel VII.32, Melotte 12, Collinder 23, and NGC 752. You’ll find it three finger-widths south (RA 01 57 41 Dec +37 47 06) of Gamma Andromedae.

Under dark skies, this 5.7-magnitude open cluster can just be spotted with the unaided eye, is revealed in the smallest of binoculars, and can be completely resolved with a telescope. Chances are NGC 752 was discovered by Hodierna over 350 years ago, but it was not cataloged until Sir William gave it a designation in 1786. But give credit where credit is due, for it was Caroline Herschel who observed it on September 28, 1783! Containing literally scores of stars, galactic cluster NGC752 could be well over a billion years old and is strung out in chains and knots in an X pattern over a rich field. Take a close look at the southern edge for orange star 56; although this is a true binary star, the companion you see is merely optical. Enjoy this unsung symphony of stars tonight!

Saturday, December 5, 2009 – No one is certain, but it is believed that Werner Heisenberg was born on this date in 1901! Heisenberg was a physicist and philosopher who discovered a way to formulate quantum mechanics in terms of matrices. His uncertainty principle won him the Nobel Prize for Physics in 1932.

Is it gone yet? Nope. The Moon will rise a little later this evening, but we’re going to run ahead of it tonight and enjoy some studies in Auriga! Looking roughly like a pentagon in shape, Capella is the brightest of these stars. Due south of Capella is the second brightest star, El Nath. By aiming binoculars at El Nath, go north about one-third the distance between the two and enjoy all the stars! You will note two very conspicuous clusters of stars in this area, and so did Le Gentil in 1749.

Binoculars will reveal the pair in the same field, as will telescopes using lowest power. The dimmest of these is M38 (RA 05 28 43 Dec +35 51 18), and it will appear vaguely cruciform in shape. At roughly 4,200 light-years away, the 100 or so fainter members will require larger aperture to resolve.

About 2.5 degrees to the southeast (RA 05 36 12 Dec +34 08 24) you will see the much brighter M36. More easily resolved in binoculars and small scopes, this ‘‘jewel box’’ galactic cluster is quite young and about 100 light-years closer!

Sunday, December 6, 2009 – Today we note the 1848 birth on this date of Johann Palisa. He discovered 122 asteroids with a 600 refractor, and all were visual observations. Check out some asteroids for yourself over the next few days as they approach easily noted objects. You’ll still find the asteroid Psyche close to Jupiter!

The Moon will be along shortly, but we still have time to set our sights about halfway between Theta Aurigae and El Nath. Our study object will be the open cluster M37 (RA 05 52 19 Dec+32 33 12).

Apparently discovered by Messier himself in 1764, this galactic cluster will appear almost nebula-like to binoculars and very small telescopes, but comes to perfect resolution with larger instruments. About 4,700 light-years away and spanning a massive 25 light-years, M37 is often billed as the finest of the three Aurigan open clusters for bigger scopes. Offering beautiful resolvability, this one contains around 150 members down to magnitude 12 and has a total population in excess of 500.

What makes it unique? As you view, you will note the presence of several red giants. For the most part, open clusters are composed of stars that are all about the same age (usually young), but the brightest star in M37 appears orange in color and not blue! So what exactly is going on here? Apparently, some of these big, bright stars have evolved much faster, consuming their fuel at an incredible rate. Other stars in this cluster are still quite young on a cosmic scale, yet they all left the ‘‘nursery’’ at the same time! In theory, this allows us to judge the relative age of open clusters. For example, M36 is around 30 million years old and M38 about 40, but the presence of the red giants in M37 puts its estimated age at 150 million years!

Enjoy the weekend and keep a look out for stray members of the Geminid meteor shower!

This week’s awesome images are (in order of appearance): NGC 752, M38 and M36 (credit—Palomar Observatory, courtesy of Caltech), Johann Palisa (historical image) and M37 (credit—NOAO/AURA/NSF). We thank you so much!