Posted on by Jason Major

A Four Cluster Pile-Up

Abell 2744, a.k.a. "Pandora's Cluster"

[/caption]

Abell 2744, shown above in a composite of images from the Hubble Space Telescope, the ESO’s Very Large Telescope and NASA’s Chandra X-ray  Observatory, is one of the most complex and dramatic collisions ever seen between galaxy clusters.

X-ray image of Abell 2744

Dubbed “Pandora’s Cluster”, this is a region 5.9 million light-years across located 3.5 billion light-years away. Many different kinds of structures are found here, shown in the image as different colors. Data from Chandra are colored red, showing gas with temperatures in the millions of degrees. Dark matter is shown in blue based on data from Hubble, the European Southern Observatory’s VLT array and Japan’s Subaru telescope. Finally the optical images showing the individual galaxies have been added.

Even though there are many bright galaxies visible in the image, most of the mass in Pandora’s Cluster comes from the vast areas of dark matter and extremely hot gas. Researchers made the normally invisible dark matter “visible” by identifying its gravitational effects on light from distant galaxies. By carefully measuring the distortions in the light a map of the dark matter’s mass could be created.

Galaxy clusters are the largest known gravitationally-bound structures in the Universe, and Abell 2744 is where at least four clusters have collided together. The vast collision seems to have separated the gas from the dark matter and the galaxies themselves, creating strange effects which have never been seen together before. By studying the history of events like this astronomers hope to learn more about how dark matter behaves and how the different structures that make up the Universe interact with each other.

Check out this HD video tour of Pandora’s Cluster from the team at Chandra:

Read more on the Chandra web site or in the NASA news release.

Image credit: X-ray: NASA/CXC/ITA/INAF/J.Merten et al, Lensing: NASA/STScI; NAOJ/Subaru; ESO/VLT, Optical: NASA/STScI/R.Dupke.

___________________

Jason Major is a graphic designer, photo enthusiast and space blogger. Visit his website Lights in the Dark and follow him on Twitter @JPMajor or on Facebook for the most up-to-date astronomy awesomeness!

 

Posted on by Nancy Atkinson

Hubble’s Stunning New View of Centaurus A

[/caption]

From a HubbleSite press release:

Resembling looming rain clouds on a stormy day, dark lanes of dust crisscross the giant elliptical galaxy Centaurus A. Hubble’s panchromatic vision, stretching from ultraviolet through near-infrared wavelengths, reveals the vibrant glow of young, blue star clusters and a glimpse into regions normally obscured by the dust.

The warped shape of Centaurus A’s disk of gas and dust is evidence for a past collision and merger with another galaxy. The resulting shockwaves cause hydrogen gas clouds to compress, triggering a firestorm of new star formation. These are visible in the red patches in this Hubble close-up.

At a distance of just over 11 million light-years, Centaurus A contains the closest active galactic nucleus to Earth. The center is home for a supermassive black hole that ejects jets of high-speed gas into space, but neither the supermassive or the jets are visible in this image.

This image was taken in July 2010 with Hubble’s Wide Field Camera 3.

Posted on by Jason Major

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: NASA, ESA, W. Clarkson (Indiana University and UCLA), and K. Sahu (STScI)

Posted on by Nancy Atkinson

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

[/caption]

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.

Posted on by Nancy Atkinson

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

[/caption]

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.

Posted on by Nancy Atkinson

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.”

[/caption]

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

Posted on by Nancy Atkinson

Hubble Captures Ancient Beauty: M5

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

[/caption]

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.

Posted on by Nancy Atkinson

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

[/caption]

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

Posted on by Nancy Atkinson

A Twisted Sister Galaxy

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

[/caption]

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.

Posted on by Nancy Atkinson

Space Telescopes Observe Unprecedented Explosion

mages from Swift's Ultraviolet/Optical (white, purple) and X-ray telescopes (yellow and red) were combined in this view of GRB 110328A. The blast was detected only in X-rays, which were collected over a 3.4-hour period on March 28. Credit: NASA/Swift/Stefan Immler

[/caption]

From a NASA press release:

NASA’s Swift, Hubble Space Telescope and Chandra X-ray Observatory have teamed up to study one of the most puzzling cosmic blasts yet observed. More than a week later, high-energy radiation continues to brighten and fade from its location.

Astronomers say they have never seen anything this bright, long-lasting and variable before. Usually, gamma-ray bursts mark the destruction of a massive star, but flaring emission from these events never lasts more than a few hours.

Although research is ongoing, astronomers say that the unusual blast likely arose when a star wandered too close to its galaxy’s central black hole. Intense tidal forces tore the star apart, and the infalling gas continues to stream toward the hole. According to this model, the spinning black hole formed an outflowing jet along its rotational axis. A powerful blast of X- and gamma rays is seen if this jet is pointed in our direction.

On March 28, Swift’s Burst Alert Telescope discovered the source in the constellation Draco when it erupted with the first in a series of powerful X-ray blasts. The satellite determined a position for the explosion, now cataloged as gamma-ray burst (GRB) 110328A, and informed astronomers worldwide.

This is a visible-light image of GRB 110328A's host galaxy (arrow) taken on April 4 by the Hubble Space Telescope's Wide Field Camera 3. The galaxy is 3.8 billion light-years away. Credit: NASA/ESA/A. Fruchter (STScI)

As dozens of telescopes turned to study the spot, astronomers quickly noticed that a small, distant galaxy appeared very near the Swift position. A deep image taken by Hubble on April 4 pinpoints the source of the explosion at the center of this galaxy, which lies 3.8 billion light-years away.

That same day, astronomers used NASA’s Chandra X-ray Observatory to make a four-hour-long exposure of the puzzling source. The image, which locates the object 10 times more precisely than Swift can, shows that it lies at the center of the galaxy Hubble imaged.

“We know of objects in our own galaxy that can produce repeated bursts, but they are thousands to millions of times less powerful than the bursts we are seeing now. This is truly extraordinary,” said Andrew Fruchter at the Space Telescope Science Institute in Baltimore.

NASA's Chandra X-ray Observatory completed this four-hour exposure of GRB 110328A on April 4. The center of the X-ray source corresponds to the very center of the host galaxy imaged by Hubble (red cross). Credit: NASA/CXC/ Warwick/A. Levan

“We have been eagerly awaiting the Hubble observation,” said Neil Gehrels, the lead scientist for Swift at NASA’s Goddard Space Flight Center in Greenbelt, Md. “The fact that the explosion occurred in the center of a galaxy tells us it is most likely associated with a massive black hole. This solves a key question about the mysterious event.”

Most galaxies, including our own, contain central black holes with millions of times the sun’s mass; those in the largest galaxies can be a thousand times larger. The disrupted star probably succumbed to a black hole less massive than the Milky Way’s, which has a mass four million times that of our sun

Astronomers previously have detected stars disrupted by supermassive black holes, but none have shown the X-ray brightness and variability seen in GRB 110328A. The source has repeatedly flared. Since April 3, for example, it has brightened by more than five times.

Scientists think that the X-rays may be coming from matter moving near the speed of light in a particle jet that forms as the star’s gas falls toward the black hole.

“The best explanation at the moment is that we happen to be looking down the barrel of this jet,” said Andrew Levan at the University of Warwick in the United Kingdom, who led the Chandra observations. “When we look straight down these jets, a brightness boost lets us view details we might otherwise miss.”

This brightness increase, which is called relativistic beaming, occurs when matter moving close to the speed of light is viewed nearly head on.

Astronomers plan additional Hubble observations to see if the galaxy’s core changes brightness.

For more information see this NASA press release.