galaxies Archives

February 7, 2009April 26, 2016 by Anne Minard

Next-Generation Telescope Gets Team

Artist's rendering of the Giant Magellan Telescope and support facilities at Las Campanas Observatory, Chile, high in the Andes Mountains. Photo by Todd Mason/Mason Productions

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Astronomy organizations in the United States, Australia and Korea have signed on to build the largest ground-based telescope in the world – unless another team gets there first. The Giant Magellan Telescope, or GMT, will have the resolving power of a single 24.5-meter (80-foot) primary mirror, which will make it three times more powerful than any of the Earth’s existing ground-based optical telescopes. Its domestic partners include the Carnegie Institution for Science, Harvard University, the Smithsonian Institution, Texas A & M University, the University of Arizona, and the University of Texas at Austin. Although the telescope has been in the works since 2003, the formal collaboration was announced Friday.

Charles Alcock, director of the Harvard-Smithsonian Center for Astrophysics, said the Giant Magellan Telescope is being designed to build on the legacy of a rash of smaller telescopes from the 1990s in California, Hawaii and Arizona. The existing telescopes have mirrors in the range of six to 10 meters (18 to 32 feet), and – while they’re making great headway in the nearby universe – they’re only able to make out the largest planets around other stars and the most luminous distant galaxies.

With a much larger primary mirror, the GMT will be able to detect much smaller and fainter objects in the sky, opening a window to the most distant, and therefore the oldest, stars and galaxies. Formed within the first billion years of the Big Bang, such objects reveal tantalizing insight into the universe’s infancy.

Earlier this year, a different consortium including the California Institute of Technology and the University of California, with Canadian and Japanese institutions, unveiled its own next-generation concept: the Thirty Meter Telescope. Whereas the GMT’s 24.5-meter primary mirror will come from a collection of eight smaller mirrors, the TMT will combine 492 segments to achieve the power of a single 30-meter (98-foot) mirror design.

In addition, the European Extremely Large Telescope is in the concept stage.

In terms of science, Alcock acknowledged that the two telescopes with US participation are headed toward redundancy. The main differences, he said, are in the engineering arena.

“They’ll probably both work,” he said. But Alcock thinks the GMT is most exciting from a technological point of view. Each of the GMT’s seven 8.4-meter primary segments will weigh 20 tons, and the telescope enclosure has a height of about 200 feet. The GMT partners aim to complete their detailed design within two years.

The TMT’s segmented concept builds on technology pioneered at the W.M. Keck Observatory in Hawaii, a past project of the Cal-Tech and University of California partnership.

Construction on the GMT is expected to begin in 2012 and completed in 2019, at Las Campanas Observatory in the Andes Mountains of Chile. The total cost is projected to be $700 million, with $130 million raised so far.

Artists concept of the Thirty Meter Telescope Observatory. Credit: TMT

Construction on the TMT could begin as early as 2011 with an estimated completion date of 2018. The telescope could go to Hawaii or Chile, and final site selection will be announced this summer. The total cost is estimated to be as high as $1 billion, with $300 million raised at last count.

Alcock said the next generation of telescopes is crucial for forward progress in 21st Century astronomy.

“The goal is to start discovering and characterizing planets that might harbor life,” he said. “It’s very clear that we’re going to need the next generation of telescopes to do that.”

And far from being a competition, the real race is to contribute to science, said Charles Blue, a TMT spokesman.

“All next generation observatories would really like to be up and running as soon as possible to meet the scientific demand,” he said.

In the shorter term, long distance space studies will get help from the James Webb Space Telescope, designed to replace the Hubble Space Telescope when it launches in 2013. And the Atacama Large Millimeter Array (ALMA), a large interferometer being completed in Chile, could join the fore by 2012.

Sources: EurekAlert and interviews with Charles Alcock, Charles Blue

February 5, 2009December 24, 2015 by Nancy Atkinson

Deep Hubble View of Unusual “Fluffy” Galaxy – and Beyond

This deep image taken with the NASA/ESA Hubble Space Telescope shows the spiral galaxy NGC 4921 along with a spectacular backdrop of more distant galaxies. It was created from a total of 80 separate pictures taken with yellow and near-infrared filters. Credits: NASA, ESA and K. Cook (Lawrence Livermore National Laboratory, USA)

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The Coma Galaxy cluster is home to a rich collection of galaxies in the nearby Universe. NGC 4921 is one of the rare spirals in Coma, and a rather unusual one. It looks “fluffy,” with lots of swirling dust. Astronomers say this galaxy is an “anemic spiral” where a small amount of star formation is taking place, and so less light is coming from the galaxy’s arms, as is usually seen in a spiral galaxy. This is an image from the Hubble Space Telescope, and with Hubble’s sharp vision, you can see a few bright young blue stars. But what’s really amazing, besides seeing the incredible detail of NGC 4921, is looking beyond the big fluffy galaxy and seeing how Hubble was able to pick up a marvelous collection of remote galaxies of all shapes, sizes and colors. Many have the spotty and ragged appearance of galaxies from the early Universe. Click here to get a bigger, better view.

This image was created from data obtained by Hubble’s Advanced Camera for Surveys. The Coma galaxy cluster, is in the northern constellation of Coma Berenices. The cluster, also known as Abell 1656, is about 320 million light-years from Earth and contains more than 1000 members. The brightest galaxies, including NGC 4921, were discovered back in the late 18th century by William Herschel.

Annotated deep Hubble Space Telescope image of NGC 4921 indictating the locations of some of the more interesting features of the galaxy and its surroundings. Credits: NASA, ESA and K. Cook (Lawrence Livermore National Laboratory, USA)

The galaxies in rich clusters undergo many interactions and mergers that tend to gradually turn gas-rich spirals into elliptical systems without much active star formation. As a result, there are far more ellipticals and fewer spirals in the Coma Cluster than are found in quieter corners of the Universe.

The Hubble images used to make this picture were originally obtained by a team led by Kem Cook (Lawrence Livermore National Laboratory, California). The team used Hubble to search for Cepheid variable stars in NGC 4921 that could be used to measure the distance to the Coma cluster and hence the expansion rate of the Universe.

Unfortunately the failure of the Advanced Camera for Surveys in early 2007 meant that they had insufficient data to complete their original program, although they hope to continue after the servicing mission. Very deep imaging data like this, which is available to anyone from the Hubble archives, may also be used for other interesting scientific exploration of this galaxy and its surroundings.

A wide-field image of the region around the Coma galaxy cluster (Abell 1656) constructed from the images in the Digitized Sky Survey. NGC 4921 is the largest galaxy to the left, and slightly below, the pair of galaxies at the centre of the image. The field-of-view is approximately 2.7 x 2.85 degrees. Credits: NASA, ESA, and the Digitized Sky Survey 2. Acknowledgment: Davide De Martin (ESA/Hubble)

The top image was created from 50 separate exposures with a yellow filter and another 30 exposures with a near-infrared filter using the Wide Field Channel of the Advanced Camera for Surveys on Hubble. The total exposure times were approximately 17 hours and 10 hours respectively.

Source: ESA

January 28, 2009December 24, 2015 by Nancy Atkinson

A Disturbance in the Force in Centaurus A

Centaurus A. Credit: ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray)

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There are some interesting dynamics going on with Centaurus A, an elliptical galaxy about 13 million light-years away. This is a very active and luminous region of space and a great disturbance is going on as another spiral galaxy is trying to get in on the action by merging with Centaurus A. But astronomers now have new insight on what causing all the ruckus: a supermassive black hole at the core of Centaurus A. Jets and lobes emanating from the central black hole have been imaged at submillimeter wavelengths for the first time by using the 12-meter Atacama Pathfinder Experiment (APEX) telescope in Chile. By using a combination of visible and X-ray wavelengths, astronomers were able to produce this striking new image. Help me APEX, you are our only hope!

Centaurus A (NGC 5128) is one of our closest galactic neighbors, and is located in the southern constellation of Centaurus. The supermassive black hole is the source of the force: strong radio and X-ray emissions. Visible in the image is a dust ring encircling the giant galaxy, and the fast-moving radio jets ejected from the galaxy center. In submillimeter light, the heat glow from the central dust disc can be seen and also the emission from the central radio source.

APEX was also able to discern – for the first time in the submillimeter – the inner radio lobes north and south of the disc. Measurements of this emission, which occurs when fast-moving electrons spiral around the lines of a magnetic field, reveal that the material in the jet is travelling at approximately half the speed of light. In the X-ray emission, we see the jets emerging from the centre of Centaurus A and, to the lower right of the galaxy, the glow where the expanding lobe collides with the surrounding gas, creating a shockwave.

Zoom 13 Million Light-years to See Heart of Active Galaxy

Galaxy NGC 253 is shown here as observed with the WFI instrument, while the insert shows a close-up of the central parts as observed with the NACO instrument on ESO's Very Large Telescope and the ACS on the NASA/ESA Hubble Space Telescope. Credit: ESO

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Using data from the Very Large Telescope’s powerful near-infrared eyes, astronomers have created a movie that takes you across 13 million light-years to galaxy NGC 253, an active galaxy filled with young, massive and dusty stellar nurseries. “We now think that these are probably very active nurseries that contain many stars bursting from their dusty cocoons,” says Jose Antonio Acosta-Pulido, a member of the team from Instituto de Astrofísica de Canarias in Spain. NGC 253 is known as a starburst galaxy, after its very intense star formation activity. Each bright region could contain as many as one hundred thousand young, massive stars. And in the center of this galaxy appears a strikingly familiar sight: a virtual twin of our own Milky Way’s supermassive black hole.

Watch the movie. (For different viewing options, click here).

The astronomers used NACO, a sharp-eyed adaptive optics instrument on the VLT to study the fine detail in NGC 253, one of the brightest and dustiest spiral galaxies in the sky. Adaptive Optics (AO) corrects for the blurring effect introduced by the Earth’s atmosphere. This turbulence causes the stars to twinkle in a way that delights poets, but frustrates astronomers, since it smears out the images. With AO in action the telescope can produce images that are as sharp as is theoretically possible, as if the telescope were in space.

NACO revealed features in the galaxy that were only 11 light-years across. “Our observations provide us with so much spatially resolved detail that we can, for the first time, compare them with the finest radio maps for this galaxy — maps that have existed for more than a decade,” says Juan Antonio Fernández-Ontiveros, the lead author of the paper reporting the results.

Close-up of the central regions of the starburst galaxy NGC 253. Credit: ESO

Astronomers identified 37 distinct bright regions packed into a tiny region at the core of the galaxy, comprising just one percent of the galaxy’s total size. This is three times more than seen previously. The astronomers combined their NACO images with data from the infrared instrument on VLT, the VISIR, as well as with images from the NASA/ESA Hubble Space Telescope and radio observations made by the Very Large Array and the Very Large Baseline Interferometer. Combining these observations, taken in different wavelength regimes, provided a clue to the nature of these regions.

In looking at all the data together, astronomers concluded that the center of NGC 253 hosts a scaled-up version of Sagittarius A*, the bright radio source that lies at the core of the Milky Way and which we know harbors a massive black hole. “We have thus discovered what could be a twin of our Galaxy’s Centre,” says co-author Almudena Prieto.

Source: ESO

January 7, 2009December 24, 2015 by Nancy Atkinson

Which Comes First: Galaxy or Black Hole?

Enlarge VLA image (right) of gas in young galaxy seen as it was when the Universe was only 870 million years old. Image: NRAO/AUI/NSF, SDSS

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Do galaxies form first and then a black hole springs up in the center, or possibly, do galaxies form around an already existing black hole? That’s the cosmic chicken-and-the-egg problem astronomers have been trying to figure out. The answer? “It looks like the black holes form before the host galaxy, and somehow grow a galaxy around them. The evidence is piling up,” said Chris Carilli, of the National Radio Astronomy Observatory (NRAO), speaking at today’s press conference at the American Astronomical Society’s meeting. By observing with the Very Large Array radio telescope and the Plateau de Bure Interferometer in France at sub-kiloparsec resolution, the researchers have been “weighing” the earliest galaxies, ones that formed within a billion years of the Big Bang.

Previous studies of galaxies and their central black holes in the nearby Universe revealed an intriguing connection between the masses of the black holes and of the central “bulges” of stars and gas in the galaxies. The ratio of the black hole and the bulge mass is nearly the same for a wide range of galactic sizes and ages. For central black holes from a few million to many billions of times the mass of our Sun, the black hole’s mass is about one one-thousandth of the mass of the surrounding galactic bulge.

“This constant ratio indicates that the black hole and the bulge affect each others’ growth in some sort of interactive relationship,” said Dominik Riechers, of Caltech. “The big question has been whether one grows before the other or if they grow together, maintaining their mass ratio throughout the entire process.”

“We finally have been able to measure black-hole and bulge masses in several galaxies seen as they were in the first billion years after the Big Bang, and the evidence suggests that the constant ratio seen nearby may not hold in the early Universe. The black holes in these young galaxies are much more massive compared to the bulges than those seen in the nearby Universe,” said Fabian Walter of the Max-Planck Institute for Radioastronomy (MPIfR) in Germany.

“The implication is that the black holes started growing first.”

The next challenge is to figure out how the black hole and the bulge affect each others’ growth. “We don’t know what mechanism is at work here, and why, at some point in the process, the ‘standard’ ratio between the masses is established,” Riechers said.

New telescopes now under construction will be key tools for unraveling this mystery, Carilli explained. “The Expanded Very Large Array (EVLA) and the Atacama Large Millimeter/submillimeter Array (ALMA) will give us dramatic improvements in sensitivity and the resolving power to image the gas in these galaxies on the small scales required to make detailed studies of their dynamics,” he said.

“To understand how the Universe got to be the way it is today, we must understand how the first stars and galaxies were formed when the Universe was young. With the new observatories we’ll have in the next few years, we’ll have the opportunity to learn important details from the era when the Universe was only a toddler compared to today’s adult,” Carilli said.

Carilli, Riechers and Walter worked with Frank Bertoldi of Bonn University; Karl Menten of MPIfR; and Pierre Cox and Roberto Neri of the Insitute for Millimeter Radio Astronomy (IRAM) in France.

Source: NRAO, AAS Press Conference

January 6, 2009December 24, 2015 by Nancy Atkinson

With No Smoke or Mirrors, Spacecraft Hunts for Active Galaxies with Central Black Holes

Swift's Hard X-ray Survey offers the first unbiased census of active galactic nuclei in decades. Dense clouds of dust and gas, illustrated here, can obscure less energetic radiation from an active galaxy's central black hole. High-energy X-rays, however, easily pass through. Credit: ESA/NASA/AVO/Paolo Padovani

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NASA’s Swift spacecraft is designed to hunt for gamma-ray bursts. But in the time between these almost-daily cosmic explosions, Swift’s Burst Alert Telescope (BAT) scans the sky, performing an ongoing X-ray survey. Some of the first results of that survey were shared at the American Astronomical Society meeting in Long Beach, California. The BAT is revealing differences between nearby active galaxies and those located about halfway across the universe. Understanding these differences will help clarify the relationship between a galaxy and its central black hole. But unlike most telescopes, the BAT observations are not done with mirrors, optics or direct focusing. Instead, images are made by analyzing the shadows cast by 52,000 randomly placed lead tiles on 32,000 hard X-ray detectors. And BAT is becoming a workhorse: The survey is now the largest and most sensitive census of the high-energy X-ray sky.

“There’s a lot we don’t know about the workings of supermassive black holes,” says Richard Mushotzky of NASA’s Goddard Space Flight Center in Greenbelt, Md. Astronomers think the intense emission from the centers, or nuclei, of active galaxies arises near a central black hole containing more than a million times the sun’s mass. “Some of these feeding black holes are the most luminous objects in the universe. Yet we don’t know why the massive black hole in our own galaxy and similar objects are so dim.”

“The BAT sees about half of the entire sky every day,” Mushotzky said. “Now we have cumulative exposures for most of the sky that exceed 10 weeks.”

Galaxies that are actively forming stars have a distinctly bluish color (“new and blue”), while those not doing so appear quite red (“red and dead”). Nearly a decade ago, surveys with NASA’s Chandra X-Ray Observatory and ESA’s XMM-Newton showed that active galaxies some 7 billion light-years away were mostly massive “red and dead” galaxies in normal environments.

The BAT survey looks much closer to home, within about 600 million light-years. There, the colors of active galaxies fall midway between blue and red. Most are spiral and irregular galaxies of normal mass, and more than 30 percent are colliding. “This is roughly in line with theories that mergers shake up a galaxy and ‘feed the beast’ by allowing fresh gas to fall toward the black hole,” Mushotzky says.

Until the BAT survey, astronomers could never be sure they were seeing most of the active galactic nuclei. An active galaxy’s core is often obscured by thick clouds of dust and gas that block ultraviolet, optical and low-energy (“soft”) X-ray light. Dust near the central black hole may be visible in the infrared, but so are the galaxy’s star-formation regions. And seeing the black hole’s radiation through dust it has heated gives us a view that is one step removed from the central engine. “We’re often looking through a lot of junk,” Mushotzky says.

But “hard” X-rays — those with energies between 14,000 and 195,000 electron volts — can penetrate the galactic junk and allow a clear view. Dental X-rays work in this energy range.

Astronomers think that all big galaxies have a massive central black hole, but less than 10 percent of these are active today. Active galaxies are thought to be responsible for about 20 percent of all energy radiated over the life of the universe, and are thought to have had a strong influence on the way structure evolved in the cosmos.

The Swift spacecraft was launched in 2004.

Source: NASA

January 5, 2009December 24, 2015 by Nancy Atkinson

Hubble, Spitzer Collaborate for Stunning Panorama of Galactic Center

Galactic center in unprecedented detail.Credit for Hubble image: NASA, ESA, and Q.D. Wang (University of Massachusetts, Amherst)

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Two of the biggest space telescopes have combined forces to create a HUGE panorama of the center of the Milky Way galaxy. This sweeping, composite color panorama is the sharpest infrared picture ever made of the Galactic core. Revealed in the image are a new population of massive stars and new details of complex structures in the hot gas and dust swirling around, created by solar winds and supernova explosions. The image shows an area about 300 light-years across. Click here for options in seeing this image in small, medium or super-sized extra large resolution! Click here for a stunning movie showing the location and more detail of this image in visible light. Astronomers at the American Astronomical Society meeting pointed out the actual galactic center is in the large white region near the lower right side of the image. If you need something to keep you occupied for awhile, try counting the number of stars in this image!

More about this image…

This image provides insight into how massive stars form and influence their environment in the often violent nuclear regions of other galaxies. This view combines the sharp imaging of the Hubble Space Telescope’s Near Infrared Camera and Multi-Object Spectrometer (NICMOS) with color imagery from a previous Spitzer Space Telescope survey done with its Infrared Astronomy Camera (IRAC). The Galactic core is obscured in visible light by intervening dust clouds, but infrared light penetrates the dust. The spatial resolution of NICMOS corresponds to 0.025 light-years at the distance of the galactic core of 26,000 light-years. Hubble reveals details in objects as small as 20 times the size of our own solar system. The NICMOS images were taken between February 22 and June 5, 2008.

Source: HubbleSite

December 17, 2008December 24, 2015 by Nancy Atkinson

Water ‘Way Out There

Detection of the earliest and most distant water. CREDIT: Milde Science Communication, STScI, CFHT, J.-C. Cuillandre, Coelum.

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A long time ago in a galaxy far, far away there was water. Astronomers have found tell-tale signatures of water molecules in a galaxy more than 11 billion light years from Earth. Using the giant, 100-meter-diameter radio telescope in Effelsberg, Germany, along with the Very Large Array (VLA) in New Mexico, scientists detected the most distant water yet seen in the Universe. Previously, the most distant water had been seen in a galaxy less than 7 billion light-years from Earth. Since it is so far away, we’re actually seeing it as it was long ago; as when the Universe was one-sixth the age it is now. The astronomers were able to take advantage of two types of natural “amplification” to detect the water in this galaxy. The galaxy, dubbed MG J0414+0534 has a quasar — a supermassive black hole powering bright emission — at its core. In the region near the core, the water molecules are acting as masers, the radio equivalent of lasers, to amplify radio waves at a specific frequency. Additionally, another galaxy was used as a gravitational lens to magnify the radio signals used to detect the water molecules.

The astronomers say their discovery indicates that such giant water masers were more common in the early Universe than they are today. At the galaxy’s great distance, even the strengthening of the radio waves done by the masers would not by itself have made them strong enough to detect with the radio telescopes.

With the help of gravitational lensing from another galaxy, nearly 8 billion light-years away, located directly in the line of sight from MG J0414+0534 to Earth, the foreground galaxy’s gravity served as a lens to further brighten the more-distant galaxy and make the emission from the water molecules visible to the radio telescopes.

The astronomers first detected the water signal with the Effelsberg telescope. They then turned to the VLA’s sharper imaging capability to confirm that it was indeed coming from the distant galaxy. The gravitational lens produces not one, but four images of MG J0414+0534 as seen from Earth. Using the VLA, the scientists found the specific frequency attributable to the water masers in the two brightest of the four lensed images.

The radio frequency emitted by the water molecules was Doppler shifted by the expansion of the Universe from 22.2 GHz to 6.1 GHz.

“We were only able to discover this distant water with the help of the gravitational lens,” said Violette Impellizzeri, an astronomer with the Max-Planck Institute for Radioastronomy (MPIfR) in Bonn, Germany. “This cosmic telescope reduced the amount of time needed to detect the water by a factor of about 1,000,” she added.

Water masers have been found in numerous galaxies at closer distances. Typically, they are thought to arise in disks of molecules closely orbiting a supermassive black hole at the galaxy’s core. The amplified radio emission is more often observed when the orbiting disk is seen nearly edge-on. However, the astronomers said MG J0414+0534 is oriented with the disk almost face-on as seen from Earth.

“This may mean that the water molecules in the masers we’re seeing are not in the disk, but in the superfast jets of material being ejected by the gravitational power of the black hole,” explained John McKean, also of MPIfR.

The team’s paper will be published in the Dec. 18 edition of Nature.

Source: NRAO

December 10, 2008December 24, 2015 by Ian O'Neill

Beyond Any Reasonable Doubt: A Supermassive Black Hole Lives in Centre of Our Galaxy

The stars in the centre of our galaxy. Our supermassive black hole IS in there, somewhere... (ESO)

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One the one hand, this might not be surprising news, but on the other, the implications are startling. A supermassive black hole (called Sagittarius A*) lives at the centre of the Milky Way. This is the conclusion of a 16 year observation campaign of a region right in the centre of our galaxy where 28 stars have been tracked, orbiting a common, invisible point.

Usually these stars would be obscured by the gas and dust in that region, but the European Southern Observatory (ESO) in Chile has used its infrared telescopes to peer deep into the black hole’s lair. Judging by the orbital trajectories of these 28 stars, astronomers have not only been able to pinpoint the black hole’s location, they have also deduced its mass…

It has been long recognised that supermassive black holes probably occupy the centres of most galaxies, from dwarf galaxies to thin galactic disks to large spiral galaxies; the majority of galaxies appear to have them. But actually seeing a black hole is no easy task; astronomers depend on observing the effect a supermassive black hole has on the surrounding gas, dust and stars rather than seeing the object itself (after all, by definition, a black hole is black).

In 1992, astronomers using the ESO’s 3.5-metre New Technology Telescope in Chile turned their attentions on our very own galactic core to begin an unprecedented observation campaign. Since 2002, the 8.2-metre Very Large Telescope (VLT) was also put to use. 16 years later, with over 50 nights of total observation time, the results are in.

By tracking individual stars orbiting a common point, ESO researchers have derived the best empirical evidence yet for the existence of a 4 million solar mass black hole. All the stars are moving rapidly, one star even completed a full orbit within those 16 years, allowing astronomers to indirectly study the mysterious beast driving our galaxy.

“The centre of the Galaxy is a unique laboratory where we can study the fundamental processes of strong gravity, stellar dynamics and star formation that are of great relevance to all other galactic nuclei, with a level of detail that will never be possible beyond our Galaxy,” explains Reinhard Genzel, team leader of this research at the Max-Planck-Institute for Extraterrestrial Physics in Garching near Munich, Germany.

“Undoubtedly the most spectacular aspect of our 16-year study, is that it has delivered what is now considered to be the best empirical evidence that super-massive black holes do really exist,” Genzel continues. “The stellar orbits in the galactic centre show that the central mass concentration of four million solar masses must be a black hole, beyond any reasonable doubt.”

Apart from being the most detailed study of Sagittarius A*’s neighbourhood (the techniques used in this study are six-times more precise than any study before it), the ESO astronomers also deduced the most precise measurement of the distance from the galactic centre to the Solar System; our supermassive black hole lies a safe 27,000 light years away.

A lot of information was gleaned about the individual stars too. “The stars in the innermost region are in random orbits, like a swarm of bees,” says Stefan Gillessen, first author of the paper published in The Astrophysical Journal. “However, further out, six of the 28 stars orbit the black hole in a disc. In this respect the new study has also confirmed explicitly earlier work in which the disc had been found, but only in a statistical sense. Ordered motion outside the central light-month, randomly oriented orbits inside – that’s how the dynamics of the young stars in the Galactic Centre are best described.”

Quite simply, the object influencing these stars must be a supermassive black hole, there is no other explanation out there. Does this mean black holes have an even firmer standing as a cosmological “fact” rather than “theory”? It would appear so…

Sources: ESO, BBC

November 20, 2008December 24, 2015 by Nancy Atkinson

“Loner” Galaxy is Actually in the ‘Hood

NCG 1569. Image Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA), and A. Aloisi (STScI/ESA)

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Astronomers have long wondered why a small, nearby, isolated galaxy is pumping out new stars faster than any galaxy in our local neighborhood. Usually, galaxies need some sort of gravitational interaction with other galaxies to trigger star formation, and galaxy NGC 1569 appeared to be a loner, far away from other galaxies, but churning out new stars like crazy. Now, a new look at the galaxy with the Hubble Space Telescope shows the galaxy is farther away than originally thought, which places NCG 1569 in the middle of a group of about 10 galaxies. Gravitational interactions among the group’s galaxies may be compressing gas in NGC 1569 and igniting the star-birthing frenzy.

“Now the starburst activity seen in NGC 1569 makes sense, because the galaxy is probably interacting with other galaxies in the group,” said the study’s leader, Alessandra Aloisi of the Space Telescope Science Institute in Baltimore, Md., and the European Space Agency. “Those interactions are probably fueling the star birth.”

The farther distance not only means that the galaxy is intrinsically brighter, but also that it is producing stars two times faster than first thought. The galaxy is forming stars at a rate more than 100 times higher than the rate in the Milky Way. This high star-formation rate has been almost continuous for the past 100 million years.

Discovered by William Herschel in 1788, NGC 1569 is home to three of the most massive star clusters ever discovered in the local universe. Each cluster contains more than a million stars.

“This is a prime example of the type of massive starbursts that drive the evolution of galaxies in the distant and young universe,” said team member Roeland van der Marel of the Space Telescope Science Institute. “Starburst galaxies can only be studied in detail in the nearby universe, where they are much rarer. Hubble observations of our galactic neighborhood, including this study, are helping astronomers put together a complete picture of the galaxies in our local universe. Put the puzzle pieces in the right place, as for NGC 1569, and the picture makes much more sense.”

And besides all that, it’s just a pretty picture, too!

Source: HubbleSite