A Galaxy With a Big “S” on Its Chest

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Can galaxy NGC 157 leap tall buildings in a single bound, stop a speeding bullet or bend steel in it’s bare hands? This relatively mild-mannered galaxy has a central sweep of stars that resembles a giant “S”, almost just like the comic book hero Superman’s symbol. The image was taken by the HAWK-I (High-Acuity Wide-field K-band Imager) on the Very Large Telescope in Chile. HAWK-I looks in infrared light, allowing us to peer through the gas and dust that normally obscures our view and see parts of NCG 157 that otherwise is hidden from our optical view.

Looking at this and other galaxies like it, astronomers can learn about star formation, as the same processes that are coalescing material and creating stars in NGC 157 also took place around 4.5 billion years ago in the Milky Way to form our own star, the Sun.

NGC 157 is faint — about magnitude 11, but can be seen bigger amateur telescopes. It is located within the constellation of Cetus (the Sea Monster).

For those interested in observing this object, see this post on WikiSky.

And just in case you don’t get the Superman references:

Source: ESO

Hidden Companion Responsible for Surprising Disk Around Strange Supergiant Star

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For several years, astronomers have been trying to get a good look at a peculiar supergiant star that is surrounded by a disk of gas and dust. The star, HD 62623, is one of the very few known supergiant stars to have such a disk. These disks are generally only associated with smaller, young stars, as supergiants have strong stellar winds that would blow away any surrounding plasma and debris. Now, using long-baseline stellar interferometry with the “Amber” instrument at ESO’s Very Large Telescope interferometer, a team of astronomers were able to capture, for the first time, a 3-D view of this strange star and its surrounding environment, which revealed a hidden secret: a companion star is likely responsible for the surrounding disk.

“Thanks to our interferometric observations with Amber we could synthetize a 3-D image of HD 62623 as seen through a virtual 130 m-diameter telescope”, says Florentin Millour, leading author of the study, from Observatoire de la Côte d’Azur. “The resolution is an order of magnitude higher compared with the world’s largest optical telescopes of 8-10 m diameter.”

HD 62623 is an exotic, hot, supergiant star. Supergiants are the most massive stars out there, ranging between 10 to 70 solar masses, and can range in brightness from 30,000 to hundreds of thousands of times the output of our Sun. They have very short lifespans, living from 30 million down to just a few hundred thousand years. Supergiants seem to always detonate as Type II supernovae at the end of their lives.

“Our new 3D image locates the dust-forming region around HD 62623 very precisely, and it provides evidence for the rotation of the gas around the central star,” said co-author Anthony Meilland from Max Planck Institute for Radio Astronomy. “This rotation is found to be Keplerian, the same way the Solar system planets rotate around the Sun.”

The companion star, although not seen directly because its light couldn’t be resolved among the brightness of HD62623, was detected by a central cavity between the gas disk and HD 62623. The companion is thought to be approximately the mass of our Sun, and its presence would explain the exotic characteristics of HD 62623, which has many similar characteristics to a monster among the old stars within our Galaxy, Eta Carinae.

HD 62623 is located in the constellation Cygnus near another bright supergiant, Deneb of the summer triangle. Deneb however, like most other supergiants, has no surrounding disk.

Four domes of the 1.8 m Auxiliary Telescopes (AT), utilized for the Very Large Telescope Interferometer (VLTI). ESO, Cerro Paranal, Chile. Image: F. Millour, OCA, Nice, France.

The images obtained with the Amber instrument combines spatial and velocity information, showing not only the shape of the close environment of HD 62623, but also its kinematics or motion. Up to now, the necessary kinematics information was missing in such images.

The astronomers were able to “disentangle” the dust and gas emission in the HD 62623 circumstellar disc, and measure the dusty disc inner rim. They also constrained the inclination angle and the position angle of the major-axis of the disc.

The new 3D imaging technique used by the team is equivalent to integral-field spectroscopy, but gives access to a 15 times larger angular resolution or capacity to detect fine details in the images. “With these new capacities, the VLTI will be able to provide a better comprehension of many sky targets, too small to be resolved by the largest telescopes,” said Millour. “We could aim at young stellar disks or jets, or even the central regions of active galaxies.”

Read the team’s paper: “Imaging the spinning gas and dust in the disc around the supergiant A[e] star HD62623,” Florentin Millour, Anthony Meilland, Olivier Chesneau, Philippe Stee, Samer Kanaan, Romain Petrov, Denis Mourard, Stefan Kraus, 2011, Astronomy & Astrophysics, Vol. 526, A107.

Source: Max Planck Institute for Astronomy

HAWK-I Hunts Down Spiral Galaxies in Stunning Detail

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Just like its ornithological namesake, the HAWK-I imager on the Very Large Telescope uses its piercing eyesight to hunt down its prey. But the High-Acuity Wide-field K-band Imager draws on its infrared vision to provide new insights into the spiral structures of galaxies. Today, ESO released six stunning new images of bright galaxies, showing exquisite detail with a clarity that is only possible by observing in the infrared.
Usually, dust in the arms of spiral galaxies blocks out much of the detail from our view, but observing in infrared light, much of the obscuring dust becomes transparent to its detectors. Compared to another VLT infrared camera called ISAAC, HAWK-I has sixteen times as many pixels to cover a much larger area of sky in one shot and, by using newer technology than ISAAC, it has a greater sensitivity to faint infrared radiation.

The six galaxies are part of a study of spiral structure led by Preben Grosbøl at ESO. Because HAWK-I can study galaxies stripped bare of the confusing effects of dust and glowing gas it is ideal for studying the vast numbers of stars that make up spiral arms, as well as helping astronomers to understand the complex and subtle ways in which the stars in these systems form into such perfect spiral patterns.

NGC 5247. Credit: ESO

The first image shows NGC 5247, a spiral galaxy dominated by two huge arms, located 60–70 million light-years away. The galaxy lies face-on towards Earth, thus providing an excellent view of its pinwheel structure. It lies in the zodiacal constellation of Virgo (the Maiden).

Messier 100, also known as NGC 4321. Credit: ESO

The galaxy in the second image is Messier 100, also known as NGC 4321, which lies about 55 million light-years from Earth in the Virgo Cluster of galaxies. It is an example of a “grand design” spiral galaxy — a class of galaxies with very prominent and well-defined spiral arms.

NGC 1300. Credit: ESO

The third image is of NGC 1300, a spiral galaxy with arms extending from the ends of a spectacularly prominent central bar. It is considered a prototypical example of barred spiral galaxies and lies at a distance of about 65 million light-years, in the constellation of Eridanus (the River).

NGC 4030. Credit: ESO

The spiral galaxy in the fourth image, NGC 4030, lies about 75 million light-years from Earth, in the constellation of Virgo.

NGC 2997. Credit: ESO

The fifth image, NGC 2997, is a spiral galaxy roughly 30 million light-years away in the constellation of Antlia. NGC 2997 is the brightest member of a group of galaxies of the same name in the Local Supercluster of galaxies. Our own Local Group, of which the Milky Way is a member, is itself also part of the Local Supercluster.

NGC 1232. Credit: ESO

Last but not least, NGC 1232 is a beautiful galaxy some 65 million light-years away in the constellation of Eridanus (the River). The galaxy is classified as an intermediate spiral galaxy — somewhere between a barred and an unbarred spiral galaxy.

Source: ESO

Galaxy Growth Not Always Result of Violent Collisions

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Until recently, it was thought the galactic equivalent of a motorway pile-up was the only way galaxies got bigger. But startling new evidence from a European team of astronomers suggests that violent galactic collisions are not the only way that galaxies evolve and grow, and instead there seems to be something else happening that has affected the majority of galaxies — a kinder, gentler action which is not quite so disruptive.

For some years, astronomers have struggled to understand why the mass of galaxies seems to have increased dramatically just a few billion years after the Big Bang. We know from observation that galaxies collide but this is an incredibly violent activity and one that is not particularly common.

A new study using the Very Large Telescope (VLT) at the European Southern Observatory (ESO), by a team led by Giovanni Cresci, looked for evidence that galaxies might be accreting material from the hydrogen and helium gas that filled the early Universe and permeates the space between the galaxies. We know that they are surrounded by halos of unseen material but Cresci’s team wanted to see if there was any evidence of material being sucked into the galaxy from the surrounding environment.

Their study focused on a group of distant galaxies which would represent those in the early Universe, about 2 billion years after the big bang, to see if they could detect any evidence of this gas accretion.

Using the SINFONI (Spectrograph for Integral Field Observation in the Near Infrared) attached to the VLT, Cresci and his team mapped the distribution of elements within the target galaxies. Their findings showed that instead of heavier elements being concentrated around the core as we find in today’s galaxies, the core was surprisingly abundant of the lighter elements hydrogen and helium. This can only be as a result of accretion of lighter elements from the surrounding area boosting the rate of star formation in the core. The accretion process itself relies on cool gas being transferred directly into the core of the galaxy.

“The primordial gas in the halo of galaxies, especially at great distances, is mostly shock heated and therefore very hot,” Cresci told Universe Today. “To be accreted it has to be cooled and this is not an efficient process. Recent theoretical models have shown that narrow streams of cold gas can form, and that they are able to penetrate the hot gas and to provide fresh gas to the centre of the galaxy. Unlike more destructive and violent mergers between galaxies, the streams are likely to keep the rotating disk configuration intact, although turbulent.”

This new discovery means astronomers have perhaps found an answer to a long standing question but with the major consequence of needing to rewrite our current theories of the evolution of the Universe.

Source: ESO, email exchange with Cresci

Mark Thompson is a writer and the astronomy presenter on the BBC One Show. See his website, The People’s Astronomer, and you can follow him on Twitter, @PeoplesAstro

Dramatic Moonset — Amazing Sight on Cerro Paranal

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Need a new desktop image? Usually the Very Large Telescope on Cerro Paranal in Chile provides us with stunning views of the cosmos. This image, however, is a gorgeous view of the observatory itself. As the Moon was setting after a long night of observing, ESO staff member Gordon Gillet welcomed the new day by capturing this stunning image from 14 km away. This image is not a montage or computer-generated (such as the infamous ‘Moon and Sun over the North Pole‘ urban legend)

The ESO website explains:

The Moon appears large because it is seen close to the horizon and our perception is deceived by the proximity of references on the ground. In order to get this spectacular close view, a 500-mm lens was necessary. The very long focal length reduces the depth of field making the objects in focus appear as if they were at the same distance. This effect, combined with the extraordinary quality of this picture, gives the impression that the Moon lies on the VLT platform, just behind the telescopes, even though it is in fact about 30,000 times further away.

Interestingly, Gillet took the image from the road leading to the nearby Cerro Armazones, the peak recently chosen by the ESO Council as the preferred location for the planned 42-meter European Extremely Large Telescope (E-ELT), which should be open for business by 2018.

Source: ESO

Hail to His Spiralness, M83

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ESO released a beautiful image today of M83, a classic spiral galaxy. The image was taken by the HAWK-I instrument on ESO’s Very Large Telescope (VLT) at the Paranal Observatory in Chile. The picture shows the galaxy in infrared light and the combination of the huge mirror of the VLT, the large field of view and great sensitivity of the HAWK –I and the superb observing conditions at ESO’s Paranal Observatory makes this one of the sharpest and most detailed pictures of Messier 83 ever taken from the ground. M83 is perhaps a mirror to how our own Milky Way galaxy looks, could we step outside and take a look.

Messier 83 is located about 15 million light-years away in the constellation of Hydra. It is famous for its many supernovae: over the last century, six supernovae have been observed in Messier 83 — a record number that is matched by only one other galaxy. Even without supernovae, Messier 83 is one of the brightest nearby galaxies, visible using just binoculars.

Check out this article by our resident astronomer Tammy Plotner to find out how you can spot M83 in the night sky.

Source: ESO

Runaway Star Needs Its Own Reality Docu-Drama

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In an astronomical version of “Biggest Loser” meets “Survivor,” a heavy weight star has been kicked out of its stellar nursery. This huge runaway star is rushing away from its birthplace at more than 402,336 kilometers per hour (250,000 miles an hour), and it likely was ejected by a group of even larger sibling stars. The future outlook for this tough-luck star seemingly doesn’t improve: Paul Crowther of the University of Sheffield, a member of the team who made the observations of 30 Dor #016, said the wayward star will continue to streak across space and will eventually end its life in a titanic supernova explosion, likely leaving behind a remnant black hole. There’s a new reality series in there somewhere!


The star on the run is found 375 light-years from its suspected home, a giant star cluster called R136 in 30 Doradus, also called the Tarantula Nebula, about roughly 170,000 light-years from Earth. R136 contains several stars topping 100 solar masses each. 30 Dor #016 is 90 times more massive than our Sun.

Astronomers say runaway stars can be made in a couple of ways: a star may encounter one or two heavier siblings in a massive, dense cluster and get booted out through a stellar game of pinball. Or, a star may get a ‘kick’ from a supernova explosion in a binary system, with the more massive star exploding first.

“It is generally accepted, however, that R136 is sufficiently young, 1 million to 2 million years old, that the cluster’s most massive stars have not yet exploded as supernovae,” says COS team member Danny Lennon of the Space Telescope Science Institute. “This implies that the star must have been ejected through dynamical interaction.”

30 Dor with 30 Dor #16 in the inset. Image credits: : NASA, ESA, J. Walsh (ST-ECF), and ESO

The renegade star may not be the only runaway in the region. Two other extremely hot, massive stars have been spotted beyond the edges of 30 Doradus. Astronomers suspect that these stars, too, may have been ejected from their home. They plan to analyze the stars in detail to determine whether 30 Doradus might be unleashing a barrage of massive stellar runaways into the surrounding neighborhood.

The observations came from a team-effort using Hubble’s newly installed Cosmic Origins Spectrograph (COS) to take an image of the region in 2009, an optical image of the star taken by the Wide Field Planetary Camera 2 in 1995, and another spectroscopic study from the European Southern Observatory’s Very Large Telescope (VLT) at the Paranal Observatory. It was first observed in 2006 when a team led by Ian Howarth of University College London spotted it with the Anglo-Australian Telescope at Siding Spring Observatory.

COS’s ultraviolet spectroscopic observations showed that the wayward star is unleashing a fury of charged particles in one of the most powerful stellar winds known, a clear sign that it is extremely massive, perhaps as much as 90 times heavier than the Sun. The star, therefore, also must be very young, about 1 million to 2 million years old, because extremely massive stars live only a few million years.

The VLT observations revealed that the star’s velocity is constant and not a result of orbital motion in a binary system. Its velocity corresponds to an unusual motion relative to the star’s surroundings, evidence that it is a runaway star.

The study also confirmed that the light from the runaway is from a single massive star rather than the combined light of two lower-mass stars. In addition, the observation established that the star is about 10 times hotter than the Sun, a temperature that is consistent with a high-mass object.

“These results are of great interest because such dynamical processes in very dense, massive clusters have been predicted theoretically for some time, but this is the first direct observation of the process in such a region,” says Nolan Walborn of the Space Telescope Science Institute in Baltimore and a member of the COS team that observed the misfit star. “Less massive runaway stars from the much smaller Orion Nebula Cluster were first found over half a century ago, but this is the first potential confirmation of more recent predictions applying to the most massive young clusters.”

The research team, led by Chris Evans of the Royal Observatory Edinburgh, published the study’s results May 5 in the online edition of The Astrophysical Journal Letters.

Science paper by Evans, et al. 2010

Source: HubbleSite

Astronomers Find 90% More Universe!

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Astronomers have long known that many surveys of distant galaxies miss 90% of their targets, but they didn’t know why. Now, astronomers have determined that a large fraction of galaxies whose light took 10 billion years to reach us have gone undiscovered. This was found with an extremely deep survey using two of the four giant 8.2-meter telescopes that make up ESO’s Very Large Telescope (VLT) and a unique custom-built filter. The survey also helped uncover some of the faintest galaxies ever found at this early stage of the Universe.

Astronomers frequently use the strong, characteristic “fingerprint” of light emitted by hydrogen known as the Lyman-alpha line, to probe the amount of stars formed in the very distant Universe Yet there have long been suspicions that many distant galaxies go unnoticed in these surveys. A new VLT survey demonstrates for the first time that this is exactly what is happening. Most of the Lyman-alpha light is trapped within the galaxy that emits it, and 90% of galaxies do not show up in Lyman-alpha surveys.

“Astronomers always knew they were missing some fraction of the galaxies in Lyman-alpha surveys,” explains Matthew Hayes, the lead author of the paper, published this week in Nature, “but for the first time we now have a measurement. The number of missed galaxies is substantial.”

To figure out how much of the total luminosity was missed, Hayes and his team used the FORS camera at the VLT and a custom-built narrowband filter to measure this Lyman-alpha light, following the methodology of standard Lyman-alpha surveys. Then, using the new HAWK-I camera, attached to another VLT Unit Telescope, they surveyed the same area of space for light emitted at a different wavelength, also by glowing hydrogen, and known as the H-alpha line. They specifically looked at galaxies whose light has been traveling for 10 billion years (redshift 2.2), in a well-studied area of the sky, known as the GOODS-South field.

“This is the first time we have observed a patch of the sky so deeply in light coming from hydrogen at these two very specific wavelengths, and this proved crucial,” said team member Goran Ostlin. The survey was extremely deep, and uncovered some of the faintest galaxies known at this early epoch in the life of the Universe. The astronomers could thereby conclude that traditional surveys done using Lyman-alpha only see a tiny part of the total light that is produced, since most of the Lyman-alpha photons are destroyed by interaction with the interstellar clouds of gas and dust. This effect is dramatically more significant for Lyman-alpha than for H-alpha light. As a result, many galaxies, a proportion as high as 90%, go unseen by these surveys. “If there are ten galaxies seen, there could be a hundred there,” Hayes said.

Different observational methods, targeting the light emitted at different wavelengths, will always lead to a view of the Universe that is only partially complete. The results of this survey issue a stark warning for cosmologists, as the strong Lyman-alpha signature becomes increasingly relied upon in examining the very first galaxies to form in the history of the Universe. “Now that we know how much light we’ve been missing, we can start to create far more accurate representations of the cosmos, understanding better how quickly stars have formed at different times in the life of the Universe,” said co-author Miguel Mas-Hesse.

The breakthrough was made possible thanks to the unique camera used. HAWK-I, which saw first light in 2007, is a state-of-the-art instrument. “There are only a few other cameras with a wider field of view than HAWK-I, and they are on telescopes less than half the size of the VLT. So only VLT/HAWK-I, really, is capable of efficiently finding galaxies this faint at these distances,” said team member Daniel Schaerer.

Read the team’s paper.

Source: ESO

Pretty Picture of the Week: NGC 3603

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This magnificent image of the giant stellar nursery surrounding NGC 3603 was taken by the Very Large Telescope at Cerro Paranal, Chile. This nebula is a starburst region, a huge star-making factory where stars form frantically from the nebula’s billowing clouds of gas and dust. It is located 22,000 light-years away from the Sun, and is the closest region of this kind known in our galaxy. Thousands of stars inhabit this region, with most having masses similar to that of our sun. But other stars are some of the most spectacular and massive stars around. In fact, one star, NGC 3603 A1, is the most massive star ever “weighed.” Several blue supergiant stars crowd into a volume of less than a cubic light-year, along with three so-called Wolf-Rayet stars — extremely bright and massive stars that will do the supernova gig relatively soon. The Bad Astronomer tells it way better than I, so go check out his gigantisized blog post.


Source: ESO