Dead Galaxy? Don’t Think So.

University of Michigan astronomers examined old galaxies and were surprised to discover that they are still making new stars. The results provide insights into how galaxies evolve with time.

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There was a time when most astronomers concluded that elliptical galaxies were a lot like their globular clusters – full of similarly evolved and aged stars. But not anymore. Thanks to the resolving power of the Hubble Space Telescope, a team of researchers from the University of Michigan were able to peer into the heart of Messier 105 and pick out several young stars and clusters. Apparently, “The reports of my death have been greatly exaggerated…”

U-M research fellow Alyson Ford and astronomy professor Joel Bregman are scheduled to present their findings May 31 at a meeting of the Canadian Astronomical Society in London, Ontario. Using the Wide Field Camera 3 on the Hubble Space Telescope, they saw individual young stars and star clusters in four galaxies that are about 40 million light-years away. One light-year is about 5.9 trillion miles.

“Scientists thought these were dead galaxies that had finished making stars a long time ago,” Ford said. “But we’ve shown that they are still alive and are forming stars at a fairly low level.”

We’re all aware of differing galaxy structures, from grand design spirals to disturbed irregulars. However, perhaps one of the most common is the elliptical. Ranging in flat form to nearly spherical, these smooth customers can contain anywhere from hundreds of millions to over one trillion stars – and most of them are believed to be the offspring of galaxy collision. Most elliptical galaxies are composed of older, low-mass stars, with a sparse interstellar medium and minimal star formation activity. Making up somewhere between 10 to 15% of known galaxy population, they are surrounded by globular clusters and usually make their home at the center of galaxy clusters. But what elliptical galaxies aren’t known for is star formation.

“Astronomers previously studied star formation by looking at all of the light from an elliptical galaxy at once, because we usually can’t see individual stars. Our trick is to make sensitive ultraviolet images with the Hubble Space Telescope, which allows us to see individual stars.” said Ford. “”We were confused by some of the colors of objects in our images until we realized that they must be star clusters, so most of the star formation happens in associations.”

The eureka moment came when the team turned the Hubble towards a galaxy most of us have observed on a personal level – M105. Located 38 million light years away in the constellation of Leo and part of the M96 Galaxy Group, this rather ordinary looking elliptical galaxy is one of the brightest to observe. Although there wasn’t any reason to believe star formation was in progress, Ford and Bregman saw a few bright, very blue stars, resembling a single star 10 to 20 times the mass of the Sun. In addition, they also observed objects that aren’t blue enough to be single stars, but instead are clusters of many stars. When accounting for these clusters, stars are forming in Messier 105 at an average rate of one Sun every 10,000 years, Ford and Bregman concluded. “This is not just a burst of star formation but a continuous process,” Ford said.

New stars from a dead galaxy? Maybe it’s a zombie. And it’s not the first time the Hubble has looked its way, either. Investigations of the central region of M105 have revealed that this galaxy contains a massive central object of about 50 million solar masses – a supermassive black hole. Of course, this new evidence creates more questions than it answers and high among the ranks is the origin of the gas that forms the stars.

“We’re at the beginning of a new line of research, which is very exciting, but at times confusing,” Bregman said. “We hope to follow up this discovery with new observations that will really give us insight into the process of star formation in these ‘dead’ galaxies.”

Dead… But maybe not so dead, after all.

Original story source Physorg.com.

Hubble Finds “Oddball” Stars in Milky Way Hub

Astronomers using the Hubble Space Telescope to peer deep into the central bulge of our galaxy have found a population of rare and unusual stars. Dubbed “blue stragglers”, these stars seem to defy the aging process, appearing to be much younger than they should be considering where they are located. Previously known to exist within ancient globular clusters, blue stragglers have never been seen inside our galaxy’s core – until now.

The stars were discovered following a seven-day survey in 2006 called SWEEPS – the Sagittarius Window Eclipsing Extrasolar Planet Search – that used Hubble to search a section of the central portion of our Milky Way galaxy, looking for the presence of Jupiter-sized planets transiting their host stars. During the search, which examined 180,000 stars, Hubble spotted 42 blue stragglers.

Of the 42 it’s estimated that 18 to 37 of them are genuine.

What makes blue stragglers such an unusual find? For one thing, stars in the galactic hub should appear much older and cooler… aging Sun-like stars and old red dwarfs. Scientists believe that the central bulge of the Milky Way stopped making new stars billions of years ago. So what’s with these hot, blue, youthful-looking “oddballs”? The answer may lie in their formation.

Artist's concept of a blue straggler pair. NASA, ESA, and G. Bacon (STScI)

A blue straggler may start out as a smaller member of a binary pair of stars. Over time the larger star ages and gets even bigger, feeding material onto the smaller one. This fuels fusion in the smaller star which then grows hotter, making it shine brighter and bluer – thus appearing similar to a young star.

However they were formed, just finding the blue stragglers was no simple task. The stars’ orbits around the galactic core had to be determined through a confusing mix of foreground stars within a very small observation area. The region of the sky Hubble studied was no larger than the width of a fingernail held at arm’s length! Still, within that small area Hubble could see over 250,000 stars. Incredible.

“Only the superb image quality and stability of Hubble allowed us to make this measurement in such a crowded field.”

– Lead author Will Clarkson, Indiana University in Bloomington and the University of California in Los Angeles

The discovery of these rare stars will help astronomers better understand star formation in the Milky Way’s hub and thus the evolution of our galaxy as a whole.

Read more on the Hubble News Center.

Image credit: NASAESA, W. Clarkson (Indiana University and UCLA), and K. Sahu (STScI)

Hubble Hunts Down Star Formation in Canes Venatici

Hubble's view of NGC 4214, Canes Venatici (The Hunting Dogs). Credit: NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration

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Lots of activity taking place inside NGC 4214, and Hubble has peered inside this dwarf galaxy to see stars in all stages of their evolution, as well as gas clouds with huge cavities blown out by stellar winds. Wow! Also visible are bright stellar clusters and complex patterns of glowing hydrogen, some forming a candy-cane-like structure in the upper right of this optical and near-infrared image. NGC 4214 is located in the constellation of Canes Venatici (The Hunting Dogs), about 10 million light-years away. Hubble scientists say this galaxy is an ideal laboratory to research the triggers of star formation and evolution.


Observations of this dwarf galaxy have also revealed clusters of much older red supergiant stars. Additional older stars can be seen dotted all across the galaxy. The variety of stars at different stages in their evolution indicates that the recent and ongoing starburst periods are not the first, and the galaxy’s abundant supply of hydrogen means that star formation will continue into the future.

This color image was taken using the Wide Field Camera 3 in December 2009. See the HubbleSite for a larger view of this colorful galaxy.

Two Views of a Lopsided Galaxy

This picture of the Meathook Galaxy (NGC 2442) was taken by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at La Silla, Chile. Credit: ESO

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From an ESO press release:

The Meathook Galaxy, or NGC 2442, has a dramatically lopsided shape. One spiral arm is tightly folded in on itself and host to a recent supernova, while the other, dotted with recent star formation, extends far out from the nucleus. The MPG/ESO 2.2-metre telescope and the NASA/ESA Hubble Space Telescope have captured two contrasting views of this asymmetric spiral galaxy.

The Meathook Galaxy, or NGC 2442, in the southern constellation of Volans (The Flying Fish), is easily recognised for its asymmetric spiral arms. The galaxy’s lopsided appearance is thought to be due to gravitational interactions with another galaxy at some point in its history — though astronomers have not so far been able to positively identify the culprit.

This broad view, taken by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at La Silla, Chile, very clearly shows the double hook shape that gives the galaxy its nickname. This image also captures several other galaxies close to NGC 2442 as well as many more remote galaxies that form a rich backdrop. Although the Wide Field Imager, on the ground, cannot approach the sharpness of images from Hubble in space, it can cover a much bigger section of sky in a single exposure. The two tools often provide complementary information to astronomers.

This close-up Hubble view of the Meathook Galaxy (NGC 2442) focuses on the more compact of its two asymmetric spiral arms as well as the central regions. The spiral arm was the location of a supernova that exploded in 1999. These observations were made in 2006 in order to study the aftermath of this supernova. Ground-based data from MPG/ESO 2.2-metre telescope were used to fill out parts of the edges of this image. Credit: NASA/ESA and ESO

A close-up image from the NASA/ESA Hubble Space Telescope (eso1115b) focuses on the galaxy’s nucleus and the more compact of its two spiral arms. In 1999, a massive star at the end of its life exploded in this arm in a supernova. By comparing older ground-based observations, previous Hubble images made in 2001, and these shots taken in late 2006, astronomers have been able to study in detail what happened to the star in its dying moments. By the time of this image the supernova itself had faded and is not visible.

ESO’s observations also highlight the other end of the life cycle of stars from Hubble. Dotted across much of the galaxy, and particularly in the longer of the two spiral arms, are patches of pink and red. This colour comes from hydrogen gas in star-forming regions: as the powerful radiation of new-born stars excites the gas in the clouds they formed from, it glows a bright shade of red.

The interaction with another galaxy that gave the Meathook Galaxy its unusual asymmetric shape is also likely to have been the trigger of this recent episode of star formation. The same tidal forces that deformed the galaxy disrupted clouds of gas and triggered their gravitational collapse.

Hit and Run Asteroid Caused Scheila’s Comet-like Behavior

Faint dust plumes bookend asteroid (596) Scheila, which is overexposed in this composite. Visible and ultraviolet images from Swift's UVOT (circled) are merged with a Digital Sky Survey image of the same region. The UVOT images were acquired on Dec. 15, 2010, when the asteroid was about 232 million miles from Earth. Credit: NASA/Swift/DSS/D. Bodewits (UMD)

Asteroid or comet? That was the question astronomers were asking after an asteroid named Scheila had unexpectedly brightened, and seemingly sprouted a tail and coma. But follow-up observations by the Swift satellite and the Hubble Space Telescope show that these changes likely occurred after Scheila was struck by a much smaller asteroid.

“Collisions between asteroids create rock fragments, from fine dust to huge boulders, that impact planets and their moons,” said Dennis Bodewits, an astronomer at the University of Maryland in College Park and lead author of the Swift study. “Yet this is the first time we’ve been able to catch one just weeks after the smash-up, long before the evidence fades away.”

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On Dec. 11, 2010, images from the University of Arizona’s Catalina Sky Survey, a project of NASA’s Near Earth Object Observations Program, revealed the Scheila to be twice as bright as expected and immersed in a faint comet-like glow. Looking through the survey’s archived images, astronomers inferred the outburst began between Nov. 11 and Dec. 3.

Three days after the outburst was announced, Swift’s Ultraviolet/Optical Telescope (UVOT) captured multiple images and a spectrum of the asteroid. Ultraviolet sunlight breaks up the gas molecules surrounding comets; water, for example, is transformed into hydroxyl (OH) and hydrogen (H). But none of the emissions most commonly identified in comets — such as hydroxyl or cyanogen (CN) — showed up in the UVOT spectrum. The absence of gas around Scheila led the Swift team to reject the idea that Scheila was actually a comet and that exposed ice accounted for the brightening.

Hubble observed the asteroid’s fading dust cloud on Dec. 27, 2010, and Jan. 4, 2011. Images show the asteroid was flanked in the north by a bright dust plume and in the south by a fainter one. The dual plumes formed as small dust particles excavated by the impact were pushed away from the asteroid by sunlight.

The science teams from the two space observatories found the observations were best explained by a collision with a small asteroid impacting Scheila’s surface at an angle of less than 30 degrees, leaving a crater 1,000 feet across. Laboratory experiments show a more direct strike probably wouldn’t have produced two distinct dust plumes. The researchers estimated the crash ejected more than 660,000 tons of dust–equivalent to nearly twice the mass of the Empire State Building.

The Hubble Space Telescope imaged (596) Scheila on Dec. 27, 2010, when the asteroid was about 218 million miles away. Scheila is overexposed in this image to reveal the faint dust features. The asteroid is surrounded by a C-shaped cloud of particles and displays a linear dust tail in this visible-light picture acquired by Hubble's Wide Field Camera 3. Because Hubble tracked the asteroid during the exposure, the star images are trailed. Credit: NASA/ESA/D. Jewitt (UCLA)

“The Hubble data are most simply explained by the impact, at 11,000 mph, of a previously unknown asteroid about 100 feet in diameter,” said Hubble team leader David Jewitt at the University of California in Los Angeles. Hubble did not see any discrete collision fragments, unlike its 2009 observations of P/2010 A2, the first identified asteroid collision.

Scheila is approximately 113 km (70 miles) across and orbits the sun every five years.

“The dust cloud around Scheila could be 10,000 times as massive as the one ejected from comet 9P/Tempel 1 during NASA’s UMD-led Deep Impact mission,” said co-author Michael Kelley, also at the University of Maryland. “Collisions allow us to peek inside comets and asteroids. Ejecta kicked up by Deep Impact contained lots of ice, and the absence of ice in Scheila’s interior shows that it’s entirely unlike comets.”

The studies will appear in the May 20 edition of The Astrophysical Journal Letters.

Source: NASA Goddard

Hubble Captures Ancient Beauty: M5

A new Hubble image of the Messier 5 cluster. Credit: ESA/Hubble & NASA

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This is just plain pretty. You’re looking at some of the oldest stars in the Universe. This new Hubble image of the globular cluster Messier 5 shows this giant huddle of stars, which is one of the oldest clusters in the Milky Way. Astronomers say the majority of M5’s stars formed more than 12 billion years ago. But there are some new and blue stars among the mix, adding some vitality and color to this ancient bunch.

Stars in globular clusters form in the same stellar nursery and grow old together. The most massive stars age quickly, exhausting their fuel supply in less than a million years, and end their lives in spectacular supernovae explosions. This process should have left the ancient cluster Messier 5 with only old, low-mass stars, which, as they have aged and cooled, have become red giants, while the oldest stars have evolved even further into blue horizontal branch stars.

Yet astronomers have spotted many young, blue stars in this cluster, hiding among the much more luminous ancient stars. Astronomers think that these laggard youngsters, called blue stragglers, were created either by stellar collisions or by the transfer of mass between binary stars. Such events are easy to imagine in densely populated globular clusters, in which up to a few million stars are tightly packed together.

Messier 5 lies at a distance of about 25 000 light-years in the constellation of Serpens (The Snake). This image was taken with Wide Field Channel of Hubble’s Advanced Camera for Surveys.

Source: ESA’s Hubble website.

A New Spin on Galactic Evolution

Spiral galaxy arms may carry stars along with them, suggests new study

 

There’s a new concept in the works regarding the evolution of galactic arms and how they move across the structure of spiral galaxies. Robert Grand, a postgraduate student at University College London’s Mullard Space Science Laboratory, used new computer modeling to suggest that these signature features of spiral galaxies – including our own Milky Way – evolve in different ways than previously thought.

The currently accepted theory is as spiral galaxies rotate, the “arms” are actually transient structures that move across the flattened disc of stars surrounding the galactic bulge, yet don’t directly affect the movement of the individual stars themselves. This would work in much the same way as a “wave” goes across a crowd at a stadium event. The wave moves, but the individual people do not move along with it – rather, they stay seated after it has passed.

However when Grand researched this suggested motion using computer models of galaxies, he and his colleagues found that this was not what tended to happen. Instead the stars actually moved along with the arms, rather than maintaining their positions.

Also it was observed in these models that the arms themselves are not permanent features, but rather break up and reform over the course of 80 to 100 million years. Grand suggests that this may be due to the powerful gravitational shear forces generated by the spinning of the galaxy.

“We simulated the evolution of spiral arms for a galaxy with five million stars over a period of 6 billion years. We found that stars are able to migrate much more efficiently than anyone previously thought. The stars are trapped and move along the arm by their gravitational influence, but we think that eventually the arm breaks up due to the shear forces.”

– Robert Grand

Snapshots of face-on view of a simulated disc galaxy.

The computer models also showed that the stars along the leading edge of the arms tended to move inwards toward the galactic center while the stars lining the trailing ends were carried to the outer edge of the galaxy.

Since it takes hundreds of millions of years for a spiral galaxy to complete even just one single rotation, observing their evolution and morphology is impossible to do in real time. Researchers like Grand and his simulations are key to our eventual understanding of how these islands of stars formed and continue to shape themselves into the vast, varied structures we see today.

“This research has many potential implications for future observational astronomy, like the European Space Agency’s next corner stone mission, Gaia, which MSSL is also heavily involved in.  As well as helping us understand the evolution of our own galaxy, it may have applications for regions of star formation.”

– Robert Grand

The results were presented at the Royal Astronomical Society’s National Astronomy Meeting in Wales on April 20. Read the press release on the Royal Astronomical Society’s website here.

Top image: M81, a spiral galaxy similar to our own Milky Way, is one of the brightest galaxies that can be seen from Earth. The spiral arms wind all the way down into the nucleus and are made up of young, bluish, hot stars formed in the past few million years, while the central bulge contains older, redder stars. Credit: NASAESA, and The Hubble Heritage Team (STScI/AURA)

Hubble Comes of Age With Dramatic New Image

In celebration of the 21st anniversary of the Hubble Space Telescope’s deployment into space, astronomers pointed Hubble at Arp 273. Credit: NASA, ESA and the Hubble Heritage Team (STScI/AURA

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Hubble has now turned 21, and unlike human young adults, we don’t have to worry about it staying up all night carousing at orbital drinking establishments. Instead the space telescope celebrates by doing what is has done best the past two decades, taking a marvelous image. This dramatic look at Arp 273 shows the very photogenic group of interacting galaxies that glow bright with intense star formation, perhaps triggered by a little carousing the two galaxies are doing with each other as they approach and interact.

Arp 273 lies in the constellation Andromeda and is roughly 300 million light-years away from Earth. The image shows a tenuous tidal bridge of material between the two galaxies that are actually separated by tens of thousands of light-years from each other. But still, the gravitational pull between the two is causing distortions: visible in the larger of the spiral galaxies, known as UGC 1810, is a distorted disc. The swathe of blue stars across the top is the combined light from clusters of intensely bright and hot young stars.

These massive stars glow fiercely in ultraviolet light. A series of uncommon spiral patterns in the large galaxy are a telltale sign of interaction, say the Hubble astronomers. The large, outer arm appears partially as a ring, a feature that is seen when interacting galaxies actually pass through one another, so astronomers believe the smaller companion actually dived deeply, but off-center, through UGC 1810.

The smaller, nearly edge-on companion below is known as UGC 1813. It also shows distinct signs of intense star formation at its nucleus.

The larger galaxy has a mass that is about five times that of the smaller galaxy. In unequal pairs such as this, the relatively rapid passage of a companion galaxy produces the lopsided or asymmetric structure in the main spiral. Also in such encounters, the starburst activity typically begins earlier in the minor galaxy than in the major galaxy. These effects could be due to the fact that the smaller galaxies have consumed less of the gas present in their nucleus, from which new stars are born.

The image was taken on December 17, 2010, with Hubble’s Wide Field Camera 3 (WFC3).

Happy Birthday Hubble! (and many more…)

See more information on this image at ESA’s Hubble website, or NASA’s HubbleSite

A Twisted Sister Galaxy

Galaxy ESO 510-G13. Credit: NASA/ESA and The Hubble Heritage Team STScI/AURA

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This is an older image from Hubble but I came across it today and wanted to share it. It shows an unusual edge-on galaxy, that has been twisted by a recent collision with a nearby galaxy, and is in the process of being swallowed up. This could be a spiral sister to our own Milky Way, as the dust and arms of normal spiral galaxies appear flat when viewed edge-on. And the twisting effect could be an example of what could happen to our galaxy in about 3 billion years when it begins to collide with the Andromeda galaxy.


As the gravitational forces distort the structures of the galaxies as their stars, gas, and dust merge together, it also sparks star formation. In the outer regions of ESO 510-G13, especially on the right-hand side of the image, the twisted disk contains not only dark dust, but also bright clouds of new, blue stars.
Eventually, in millions of years, all the matter will coalesce and the activity and disturbances will die out, and ESO 510-G13 will become a normal-looking single galaxy.

This galaxy was first observed by ESO’s ground based telescopes, and Hubble’s Wide Field Planetary Camera 2 (WFPC2) observed ESO 510-G13 in April 2001.

See more about the image at the HubbleSite.

At Shuttle Program’s Twilight, Tears and Cheers as Triumphs and Tragedies are Remembered

NASA Administrator Charles Bolden gets choked up during the 30th anniversary of the shuttle program.

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CAPE CANAVERAL – With the shuttle program’s end less than three months away, NASA took time to honor the program that has been the focal point of the agency’s manned space flight efforts for the past thirty years. At 1 p.m., NASA’s Administrator, Charles Bolden, along with Kennedy Space Center Director Robert Cabana, astronaut Janet Kavandi, shuttle Endeavour’s Vehicle Manager Mike Parrish and STS-1 Pilot Robert Crippen spoke to NASA employees and members of the media regarding the programs long history and its many achievements.

However, the most important announcement of the day was where the remaining shuttles will go when the program draws to a close. It was announced that the space shuttle Enterprise, a test article of the shuttle design, will move from its current home at the Smithsonian’s National Air and Space Museum Steven F. Udvar-Hazy Center in Virginia to the Intrepid Sea, Air & Space Museum in New York. The Udvar-Hazy Center will be home for Discovery, which finished its last mission in March. Endeavour, which is being readied for its final flight at the end of this month, will go to the California Science Center in Los Angeles. Atlantis, which is currently scheduled to fly the last shuttle mission in June, will go to the Kennedy Space Center Visitor Complex in Florida.

From left-to-right: Former astronaut and KSC Director Robert Crippen, former astronaut and current NASA Administrator Charles Bolden, astronaut Janet Kavandi, former astronaut and current KSC Director Bob Cabana and shuttle Endeavour's Vehicle Manager Mike Parrish. Behind them is shuttle Atlantis, which will remain at Kennedy Space Center in Florida. Photo Credit: Jason Rhian

Although Bolden and Cabana are former astronauts, they were joined by one of the two men that flew the very first shuttle mission, STS-1 – Robert Crippen. This mission is viewed as one of the most risky test flights in history. If something had gone wrong during the first mission’s launch, Crippen and Commander John Young would have had to eject from Columbia – through the vehicle’s fiery plume. However, everything worked according to plan and Columbia landed at Edwards Air Force Base in California two days later.

The weight of the day’s events had an obvious impact on Bolden and Crippen, both of whom were visibly emotional during the presentation. Crippen’s comments detailed the feelings of many in that this is a bitter-sweet anniversary. Those in attendance supported the four-time shuttle veteran with loud applause when it was announced that Atlantis would remain at Kennedy Space Center.

Former NASA astronaut and current Kennedy Space Center Director Robert Cabana gestures toward shuttle Atlantis which will remain in Florida at the Kennedy Space Center Visitor Complex. Photo Credit: Jason Rhian

“Stay focused, “said Bolden during his comments, referring to the gap in manned space flight that is about to take place. “It’s been a rough day.”

There was also a guest appearance from the current members of the International Space Station who called in from on orbit. They apologized for not being able to attend – before they acknowledged it was thanks to the hard work of those present that they couldn’t be there. Astronauts Cady Coleman, Ron Garan were joined by ESA astronaut Paolo Nespoli as well as cosmonauts Dmitry Kondratyev, Andrey Borisenko and Alexander Samokutyaev. The station’s crew spoke about how the shuttle program made this international effort possible.

The crew of the International Space Station conduct a long-distance phone call to attendees at the 30th Anniversary event of the shuttle program. Photo Credit: Jason Rhian

On April 12, 1981, the space shuttle Columbia roared into orbit on the first mission of the shuttle program. The first crew only had two astronauts on board, Apollo veteran John Young and rookie astronaut Robert Crippen. The first flight of the shuttle program took place 20 years to the day that the first human rode fire into orbit – Yuri Gagarin.

There are currently only two shuttle flights remaining, Endeavour is slated to conduct its 25th and final mission, STS-134, at the end of this month and Atlantis will launch the final mission on June 28. Once this mission is over, NASA will have to rely on Russia for access to the International Space Station until small, commercial firms; those supported under President Obama’s new plans for NASA can produce a launch system to fill the void.

“I would have been happy to get any of the orbiters here at KSC,” said Robert Crippen when interviewed. “Getting Atlantis makes this a very good day.”

The space shuttle Atlantis was on display, with commemorative banners from each of the orbiters. Atlantis will reside at Kennedy Space Center after her final flight this June. Photo Credit: Jason Rhian