Posted on by Nancy Atkinson

Hubble Spies an Amazing Cosmic Spiral

An Extraordinary Celestial Spiral. Credit: ESA/NASA & R. Sahai

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The Hubble Space Telescope’s Advanced Camera for Surveys has captured a remarkable image of a spiral in space. No, not a spiral galaxy, (and not another Norway Spiral!) but the formation of an unusual pre-planetary nebula in one of the most perfect geometrical spirals ever seen. The nebula, called IRAS 23166+1655, is forming around the star LL Pegasi (also known as AFGL 3068) in the constellation of Pegasus.

The image shows what appears to be a thin spiral pattern of amazing precision winding around the star, which is itself hidden behind thick dust. Mark Morris from UCLA and an international team of astronomers say that material forming the spiral is moving outwards at a speed of about 50,000 km/hour and by combining this speed with the distance between layers, they calculate that the shells are each separated by about 800 years.

The spiral pattern suggests a regular periodic origin for the nebula’s shape, and astronomers believe that shape is forming because LL Pegasi is a binary star system. One star is losing material as it and the companion star are orbiting each other. The spacing between layers in the spiral is expected to directly reflect the orbital period of the binary, which is estimated to be also about 800 years.

A progression of quasi-concentric shells has been observed around a number of preplanetary nebulae, but this almost perfect spiral shape is unique.

Morris and his team say that the structure of the AFGL 3068 envelope raises the possibility that binary companions are responsible for quasi-concentric shells in most or all of the systems in which they have been observed, and the lack of symmetry in the shells seen elsewhere can perhaps be attributed to orbital eccentricity, to different projections of the orbital planes, and to unfavorable illumination geometries.

Additionally – and remarkably — this object may be illuminated by galactic light.

This image appears like something from the famous “Starry Night” painting by Vincent van Gogh, and reveals what can occur with stars that have masses about half that of the Sun up to about eight times that of the Sun. They do not explode as supernovae at the ends of their lives, but instead can create these striking and intricate features as their outer layers of gas are shed and drift into space. This object is just starting this process and the central star has yet to emerge from the cocoon of enveloping dust.

Abstract: A Binary-Induced Pinwheel Outflow from the Extreme Carbon Star, AFGL 3068

Source: ESA

Posted on by Nancy Atkinson

Supernova Spews Its Guts Across Space

Supernova 1987A and a glowing gas ring encircling the supernova remnant known as the "String of Pearls." Credit: NASA

The recently refurbished Hubble Space Telescope has taken a new look at Supernova 1987A and its famous “String of Pearls,” a glowing ring 6 trillion miles in diameter encircling the supernova remnant. The sharper and clearer images are allowing astronomers to see the “innards” of the star being ejected into space following the explosion, and comparing the new images with ones taken previously provides a unique glimpse of a young supernova remnant as it evolves. They found significant brightening of the object over time, and also evident is how the shock wave from the star’s explosion has expanded and rebounded.

Kevin France from the University of Colorado Boulder and colleagues compared the new Hubble data on the SN1987A taken in 2010 with older images, and observed the supernova in optical, ultraviolet and near-infrared light. They were able to look at the interplay between the stellar explosion and the ‘String of Pearls’ that encircles the supernova remnant. The gas ring — energized by X-rays — likely was spewed out about 20,000 years before the supernova exploded, and shock waves rushing out from the remnant have been brightening some 30 to 40 pearl-like “hot spots” in the ring — objects that likely will grow and merge together in the coming years to form a continuous, glowing circle.

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“The new observations allow us to accurately measure the velocity and composition of the ejected ‘star guts,’ which tell us about the deposition of energy and heavy elements into the host galaxy,” said France, lead author of the study which was published in Science. “The new observations not only tell us what elements are being recycled into the Large Magellanic Cloud, but how it changes its environment on human time scales.”

The significant brightening that was detected is consistent with some theoretical predictions about how supernovae interact with the galactic environment surrounding them. Discovered in 1987, Supernova 1987A is the closest exploding star to Earth to be detected since 1604 and is located in the nearby Large Magellanic Cloud, a dwarf galaxy adjacent to our own Milky Way Galaxy.

In addition to ejecting massive amounts of hydrogen, 1987A has spewed helium, oxygen, nitrogen and rarer heavy elements like sulfur, silicon and iron. Supernovae are responsible for a large fraction of biologically important elements, including oxygen, carbon and iron found in plants and animals on Earth today, France said. The iron in a person’s blood, for example, is believed to have been made by supernovae explosions.

The team compared STIS observations in January 2010 with Hubble observations made over the past 15 years on 1987A’s evolution. STIS has provided the team with detailed images of the exploding star, as well as spectrographic data — essentially wavelengths of light broken down into colors like a prism that produce unique fingerprints of gaseous matter. The results revealed temperatures, chemical composition, density and motion of 1987A and its surrounding environment, said France.

Since the supernova is roughly 163,000 light-years away, the explosion occurred in roughly 161,000 B.C., said France. One light year is about 6 trillion miles.

“To see a supernova go off in our backyard and to watch its evolution and interactions with the environment in human time scales is unprecedented,” he said. “The massive stars that produce explosions like Supernova 1987A are like rock stars — they live fast, flashy lives and die young.”

France said the energy input from supernovae regulates the physical state and the long-term evolution of galaxies like the Milky Way. Many astronomers believe a supernova explosion near our forming sun some 4 to 5 billion years ago is responsible for a significant fraction of radioactive elements in our solar system today, he said.

“In the big picture, we are seeing the effect a supernova can have in the surrounding galaxy, including how the energy deposited by these stellar explosions changes the dynamics and chemistry of the environment,” said France. “We can use this new data to understand how supernova processes regulate the evolution of galaxies.”

France and his team will be looking at Supernova 1987A again with Hubble’s Cosmic Origins Spectrograph, an instrument which scientists hope will help them better understand the “cosmic web” of of material permeating the cosmos and learn more about the conditions and evolution of the early universe.

Source: ScienceExpress

Posted on by Nancy Atkinson

Giant Ultraviolet Rings Found Around Ancient Galaxies

Astronomers have found unexpected rings and arcs of ultraviolet light around a selection of galaxies, four of which are shown here as viewed by NASA's and the European Space Agency's Hubble Space Telescope. Image credit: NASA/ESA /JPL-Caltech/STScI/UCLA

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Title this ‘Zombie Galaxies’ or ‘Night of the Living Galaxies.’ Astronomers have found mysterious, giant loops of ultraviolet light around old, massive galaxies, which were presumed to be “dead,” and these galaxies seem to have come back to life. Somehow these “over-the-hill galaxies” have been infused with fresh gas to form new stars that power these truly gargantuan rings, some of which could encircle several Milky Way galaxies.

The discovery of these rings implies that old bloated galaxies that were once devoid of star-making can be reignited with star birth, and that galaxy evolution does not proceed straight from the cradle to the grave.

“In a galaxy’s lifetime, it must make the transition from an active, star-forming galaxy to a quiescent galaxy that does not form stars,” said Samir Salim, lead author of a recent study and a research scientist in the department of astronomy at Indiana University, Bloomington. “But it is possible this process goes the other way, too, and that old galaxies can be rejuvenated.”

Using two orbiting observatories, NASA’s Galaxy Evolution Explorer and Hubble Space Telescope, the astronomers surveyed a vast region of the sky in ultraviolet light. GALEX picked out 30 elliptical and lens-shaped “early” galaxies with puzzlingly strong ultraviolet emissions but no signs of visible star formation, and Hubble was used to take a closer look.

What Hubble showed shocked the astronomers. Three-quarters of the galaxies were spanned by great, shining rings of ultraviolet light, with some ripples stretching 250,000 light-years. A few galaxies even had spiral-shaped ultraviolet features.

“We haven’t seen anything quite like these rings before,” said Michael Rich, co-author of the paper and a research astronomer at UCLA. “These beautiful and very unusual objects might be telling us something very important about the evolution of galaxies.”

But astronomers are unsure where the gas for this galactic resurrection came from and how it has created rings. One possibility is that a smaller galaxy merged with a big, old one, bringing in fresh gas to spawn hordes of new stars, and could in rare instances give rise to the ring structures as well.

But the researchers have their doubts about this origin scenario. “To create a density shock wave that forms rings like those we’ve seen, a small galaxy has to hit a larger galaxy pretty much straight in the center,” said Salim. “You have to have a dead-on collision, and that’s very uncommon.”

Another option that the astronomers like better is that the rejuvenating spark could have come from a gradual sopping-up of the gas in the so-called intergalactic medium, the thin soup of material between galaxies. This external gas could generate these rings, especially in the presence of bar-like structures that span some galaxies’ centers.

Ultimately, more observations will be needed to show how these galaxies began growing younger and lit up with humongous halos. Salim and Rich plan to search for more evidence of bars, as well as faint structures that might be the remnants of stellar blooms that occurred in the galaxies’ pasts. Rather like recurring seasons, it may be that galaxies stirred from winter can breed stars again and then bask in another vibrant, ultraviolet-soaked summer.

The study detailing the findings appeared in the April 21 issue of the Astrophysical Journal.

Source: JPL

Posted on by Ryan Anderson

Hubble Confirms Comet-like Tail on Vaporizing Planet

Next time you hear someone complaining that it’s too hot outside, you can make them feel better by pointing out that at least their planet isn’t so hot it is vaporizing into space. Unless of course you happen to be speaking to someone from the gaseous extrasolar planet HD 209458b.

New observations from the Hubble Cosmic Origins Spectrograph (COS) confirm suspicions from 2003 that the planet HD 209458b is behaving like a Jupiter-sized comet, losing its atmosphere in a huge plume due to the powerful solar wind of its too-close star.

HD 209458b is a “hot Jupiter”: a gas giant that orbits extremely close to its star. It whips around its star in 3.5 days, making even speedy little Mercury with its 88 day orbit around the sun look like a slacker.

Astronomers have managed to learn a lot about HD 209458b because it is a transiting planet. That means that its orbit is aligned just right, so from our point of view it blocks some of the light from its star. When that happens, it gives hints at the planet’s size, and gives a much better constraint on the mass. HD 209458b is a little more than two thirds the mass of Jupiter, but heat from its star has puffed it up to two and a half times Jupiter’s diameter.

In the case of HD 209458b, during transits some of the star’s light passes through the planet’s escaping, 2,000-degree-Fahrenheit atmosphere, allowing scientists to tell what it is made of and how fast it is being lost to space.

“We found gas escaping at high velocities, with a large amount of this gas flowing toward us at 22,000 miles per hour,” said astronomer Jeffrey Linsky of the University of Colorado in Boulder, leader of the COS study. “This large gas flow is likely gas swept up by the stellar wind to form the comet-like tail trailing the planet.”

The escaping planetary gases absorbed starlight at wavelengths characteristic of heavier elements like carbon and silicon, suggesting that the star’s intense heat is driving circulation deep in HD 209458b’s atmosphere, dredging up material that would otherwise remain far beneath lighter elements like hydrogen.

Even though its atmosphere is constantly streaming away into space, HD 209458b won’t be disappearing anytime soon. At the measured rate of loss, the planet would last about a trillion years, far longer than the lifetime of its host star.

So, be thankful that even on hot summer days, your planet is in no danger of being vaporized by its star. And if you do happen to be speaking to someone from HD 209458b, you can reassure them that their planet will still be there when they return home. Well, most of it, anyway.

Oh, and remind them to stock up on sunscreen.

Posted on by Nancy Atkinson

Hubble, Bubble, Toil and Star Formation

A colorful star-forming region in NGC 2467. Credit: NASA, ESA and Orsola De Marco (Macquarie University)

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OK, that headline doesn’t rhyme, but this incredible new Hubble image looks like a witch’s cauldron of an exotic cosmic brew. It billows with huge clouds of gas and dust and is sprinkled with Eye of Newt, um…er, bright blue hot young stars. These dust clouds in NGC 2467 look like a murky, shadowy liquid, but they are actually star forming regions made mostly of hydrogen, perfect for bubbling up newborn stars. And your little dog, too.

NGC 2467 lies in the southern constellation of Puppis, approximately 13,000 light-years from Earth.

The picture was created from images taken with the Wide Field Channel of the Advanced Camera for Surveys through three different filters (F550M, F660N and F658N, shown in blue, green and red respectively). These data were taken in 2004 but just released today.

This region looks somewhat like the Orion Nebula and the hot young stars that recently formed among this bubbling brew are emitting fierce ultraviolet radiation that is causing the whole scene to glow while also sculpting the environment and gradually eroding the gas clouds. Studies have shown that most of the radiation comes from the single hot and brilliant massive star just above the center of the image. Its fierce radiation has cleared the surrounding region and some of the next generation of stars are forming in the denser regions around the edge.

Source: ESA Hubble

Posted on by Nancy Atkinson

Hubble Captures Beautiful Baby Stars

Hubble view of the huge star formation region N11 in the Large Magellanic Cloud. Credit: NASA, ESA and Jesús Maíz Apellániz (Instituto de Astrofísica de Andalucía, Spain).

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Within the Large Magellenic Cloud is one of the most active star forming regions in our nearby Universe. This new Hubble image highlights N11 – also known as the Bean Nebula — a beautiful region of energetic star formation. The billowing pink clouds that look like cotton candy and bright bubbles of glowing gasses and are telltale signs that stars are being created. Click the image for a larger, hi-res version.

Beans, bubbles and candy aren’t the only terrestrial shapes to be found in this spectacular image from the Hubble Space Telescope.

If you zoom into upper left (click this link for a zoom video) you’ll find a rose: The Rose Nebula LHA 120-N 11A. Its rose-like petals of gas and dust are illuminated from within, thanks to the radiation from the massive hot stars at its centre. N11A is relatively compact and dense and is the site of the most recent burst of star development in the region.

If you live in the southern hemisphere, both the Large Magellanic Cloud and its small companion, the Small Magellanic Cloud, are easily seen with the unaided eye. That’s a sight I would someday love to see!

For more videos and images of this region, see this ESA Hubble page.

Posted on by Nancy Atkinson

Hubble Delves into Two Recent Jupiter Mysteries

Detailed observations made by the NASA/ESA Hubble Space Telescope have led researchers to believe that the flash of light seen on Jupiter on 3 June was a meteor. Credit: NASA, ESA, M. H. Wong (University of California, Berkeley, USA), H. B. Hammel (Space Science Institute, Boulder, Colorado, USA), A. A. Simon-Miller (Goddard Space Flight Center, Greenbelt, Maryland, USA) and the Jupiter Impact Science Team.

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Jupiter has a few mysteries these days. Between an equatorial belt that has gone missing and an impact that didn’t leave a mark, astronomers decided they needed to put the Hubble Space Telescope on the case. New and detailed observations from the venerable space telescope have provided some insights into these two recent puzzling events.

At 22:31 (CEST) on June 3, 2010 Australian amateur astronomer Anthony Wesley saw a two-second-long flash of light on the disc of Jupiter, captured from a live video feed from his telescope. In the Philippines, amateur astronomer Chris Go confirmed that he had simultaneously recorded the transitory event on video. Wesley was also the discoverer of the now world-famous July 2009 impact.

Astronomers around the world suspected that something significant must have hit the giant planet to unleash a flash of energy bright enough to be seen here on Earth, about 770 million kilometers away. But they didn’t know how just how big it was or how deeply it had penetrated into the atmosphere. Over the past two weeks there have been ongoing searches for the “black-eye” pattern of a deep direct hit like those left by former impactors.

Astronomers turned Hubble’s Wide Field Camera 3 aboard the NASA/ESA Hubble Space Telescope on June 7, and found no sign of debris above Jupiter’s cloud tops. This means that the object didn’t descend beneath the clouds and explode as a fireball. If it had, then dark sooty blast debris would have been ejected and would have rained down onto the clouds.

Instead the flash is thought to have come from a giant meteor burning up high above Jupiter’s cloud tops, which did not plunge deep enough into the atmosphere to explode and leave behind any telltale cloud of debris, as seen in previous Jupiter collisions.

“The cloud tops and the impact site would have appeared dark in the ultraviolet and visible images due to debris from an explosion,” said team member Heidi Hammel of the Space Science Institute in Boulder, Colorado. “We can see no feature that has those distinguishing characteristics in the known vicinity of the impact, suggesting there was no major explosion and no ‘fireball’.”

Dark smudges marred Jupiter’s atmosphere when a series of fragments of Comet Shoemaker-Levy 9 hit Jupiter in July 1994, and a similar dark area formed in July 2009 when a suspected asteroid slammed into Jupiter. The latest intruder is estimated to be only a fraction of the size of these previous impactors and is thought to have been a meteor.

So, Wesley and Go were fortunate to have spotted the flash.

“Observations of these impacts provide a window on the past — onto the processes that shaped our Solar System in its early history,” said team member Leigh Fletcher of the University of Oxford, UK. “Comparing the two collisions — from 2009 and 2010 — will hopefully yield insights into the types of impact processes in the outer Solar System, and the physical and chemical response of Jupiter’s atmosphere to these amazing events.”

These Hubble images of Jupiter taken 11 months apart show the Southern Equatorial Belt has disappeared. Credit: NASA, ESA, M. H. Wong (University of California, Berkeley, USA), H. B. Hammel (Space Science Institute, Boulder, Colorado, USA), A. A. Simon-Miller (Goddard Space Flight Center, Greenbelt, Maryland, USA) and the Jupiter Impact Science Team.

Since Hubble was now trained on Jupiter, astronomers used the opportunity to get a close-up look at changes in Jupiter’s atmosphere following the disappearance of the dark cloud feature known as the Southern Equatorial Belt several months ago.

In the Hubble view, a slightly higher altitude layer of white ammonia ice crystal clouds appears to obscure the deeper, darker belt clouds. “Weather forecast for Jupiter’s Southern Equatorial Belt: cloudy with a chance of ammonia,” Hammel said.

The team predicts that these ammonia clouds should clear out in a few months, as they have done in the past. The clearing of the ammonia cloud layer should begin with a number of dark spots like those seen by Hubble along the boundary of the south tropical zone.

“The Hubble images tell us these spots are holes resulting from localized downdrafts. We often see these types of holes when a change is about to occur,” said Amy Simon-Miller from Goddard Space Flight Center. .

“The Southern Equatorial Belt last faded in the early 1970s. We haven’t been able to study this phenomenon at this level of detail before,” Simon-Miller added. “The changes of the last few years are adding to an extraordinary database on dramatic cloud changes on Jupiter.”

Source: ESA’s Hubble website

Posted on by Nancy Atkinson

Life-size Wooden Spacecraft Sculptures

"My Voyager" by artist Peter Hennessey

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If you think about it, spacecraft are kind of ethereal in that once they are launched into space, we don’t ever see them again. Australian artist Peter Hennessey has created life-size wooden sculptures of several different spacecraft, giving people the chance to see and touch these objects that are immediately recognizable but which we will never actually experience. Hennessey says he wanted to “reverse the virtualization of physical things” by creating life-size reproductions of the spacecraft such as the Voyager space probe, Apollo Lunar Rover, the Hubble Space Telescope, and more. From Hennessey’s website: “By ‘re-enacting’ space traveling, scientific and military objects in plywood, galvanized steel and canvas, the artist creates ‘stand-ins’ that allow the viewer to contemplate their physical, symbolic and historical resonances as well as the political processes that they represent.”

I just think they are really cool, and I’d love to see them – Hubble has to be huge! See below.


'My Hubble (the universe turned in on itself)' by artist Peter Hennessey.

“My Hubble (the universe turned in on itself) is now on display in Sydney Australia as part of “Biennale of sydney 2010.” This life size ‘re-enactment’ of the Hubble Space Telescope was constructed “with the aim of giving the viewer a physical experience of the object.” It is constructed from lasercut plywood and steel and simultaneously enacts the scale and detail
of the original. This is an interactive sculpture: visitors are encouraged to play with, modify and create their own mini universes on the ground, which are then reflected by the telescope into the heavens.

According to the Design Bloom website, when creating his work Hennessey looked at 7 different images of the Hubble, and rather than using 3D software to model individual parts as one might expect, he used adobe illustrator. Building the telescope took about 3 months – in which 6 weeks were dedicated to laser cutting individual parts and building them into sections and the rest of the time was dedicated to assembling it.

'My Lunar Rover' by artist Peter Hennessey.

With ‘My Moon Landing’ Hennessey’s wanted to explore the “physicality, presences and symbolic power of the inaccessible objects that derive from the space race.”

Hennessey has even built a wooden replica of mission control.

Check out all his unique sculptures on his website.

Hat tip to Rachel Hobson!

Posted on by Nancy Atkinson

New Hubble Images Zoom In on Asteroid Impact on Jupiter

These NASA Hubble Space Telescope snapshots reveal an impact scar on Jupiter fading from view over several months between July 2009 and November 2009. Credit: NASA, ESA, M. H. Wong (University of California, Berkeley), H. B. Hammel (Space Science Institute, Boulder, Colo.), I. de Pater (University of California, Berkeley), and the Jupiter Impact Team

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When amateur astronomer Anthony Wesley from Australia saw a dark spot the size of the Pacific Ocean appear on Jupiter through his telescope on July 19, 2009, this started a flurry of astronomic activity, with other telescopes quickly slewing to take a look. It didn’t take long for other astronomers to confirm Jupiter had been hit by an object, either an asteroid or a comet. Of course, the world’s most famous telescope, Hubble, zeroed in on this unexpected activity on Jupiter, and luckily, the telescope had been recently updated with a new Wide Field Camera 3 and newly repaired Advanced Camera for Surveys. Astronomers have now released a series of images from Hubble which may show for the first time the immediate aftermath of an asteroid striking another planet.

Astronomers have witnessed this kind of cosmic event before, but from a comet. Similar scars had been left behind during the course of a week in July 1994, when more than 20 pieces of Comet P/Shoemaker-Levy 9 (SL9) plunged into Jupiter’s atmosphere. The 2009 impact occurred during the same week, 15 years later.

But comparing Hubble images of both collisions, astronomers say the culprit was likely an asteroid about 1,600 feet (500 meters) wide.

Jupiter, Hubble WFC3: July 23, 2009
Source: Hubblesite.org

“This solitary event caught us by surprise, and we can only see the aftermath of the impact, but fortunately we do have the 1994 Hubble observations that captured the full range of impact phenomena, including the nature of the objects from pre-impact observations” says astronomer Heidi Hammel of the Space Science Institute in Boulder, Colo., leader of the Jupiter impact study.

The analysis revealed key differences between the two collisions (in 1994 and 2009), providing clues to the 2009 event. Astronomers saw a distinct halo around the 1994 impact sites in Hubble ultraviolet (UV) images, evidence of fine dust arising from a comet-fragment strike. The UV images also showed a strong contrast between impact-generated debris and Jupiter’s clouds.

Hubble ultraviolet images of the 2009 impact showed no halo and also revealed that the site’s contrast faded rapidly. Both clues suggest a lack of lightweight particles, providing circumstantial evidence for an impact by a solid asteroid rather than a dusty comet.

The elongated shape of the recent asteroid impact site also differs from the 1994 strike, indicating that the 2009 object descended from a shallower angle than the SL9 fragments. The 2009 body also came from a different direction than the SL9 pieces.

HST WFC3 Image of Jupiter: July 23, 2009
Source: Hubblesite.org

Team member Agustin Sanchez-Lavega of the University of the Basque Country in Bilbao, Spain, and colleagues performed an analysis of possible orbits that the 2009 impacting body could have taken to collide with Jupiter. Their work indicates the object probably came from the Hilda family of bodies, a secondary asteroid belt consisting of more than 1,100 asteroids orbiting near Jupiter.

The 2009 strike was equal to a few thousand standard nuclear bombs exploding, comparable to the blasts from the medium-sized fragments of SL9. The largest of those fragments created explosions that were many times more powerful than the world’s entire nuclear arsenal blowing up at once.

The recent impact underscores the important work performed by amateur astronomers. “This event beautifully illustrates how amateur and professional astronomers can work together,” said Hammel.

The Jupiter bombardments reveal that the solar system is a rambunctious place, where unpredictable events may occur more frequently than first thought. Jupiter impacts were expected to occur every few hundred to few thousand years. Although there are surveys to catalogue asteroids, many small bodies may still go unnoticed and show up anytime to wreak havoc.

The study by Hammel’s team appeared in the June 1 issue of The Astrophysical Journal Letters.

Science Paper by: Hammel et al. (PDF document)

Source: HubbleSite

Posted on by Nancy Atkinson

Hubble Captures Surprisingly Restless Stars on the Move

NGC 3603 and its massive compact central star cluster was taken with the Advanced Camera for Surveys (ACS) on the NASA/ESA Hubble Space Telescope. The region that was studied in detail to detect the motion of stars within the cluster is shown as a box. Credit: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration

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Using the Hubble Space Telescope, astronomers from the Max Planck Institute for Astronomy made two observations ten years apart of the giant nebula NGC 3603 and found a surprising amount of movement and unrest in one of the most massive young star clusters in the Milky Way. The comparison images reveal several hundred stars continued to move for about 1 million years after the star cluster’s formation, with stellar motion not having “settled down” as expected. This new finding is at odds with current models of how such clusters evolve, and may force astronomers to rethink how star clusters form and develop.

While ordinary star clusters disperse over time as the different stars go their own separate ways, it was thought that very massive and compact clusters were different, and that they formed massive aggregations of stars known as globular clusters, whose tightly-packed stars remain gravitationally bound to each other for billions of years.

Conventional thinking was that stars with lower mass should move faster, and those with higher mass should move more slowly. But a team led by Wolfgang Brander, making high precision observations, found the stars in NGC 3603 are still moving at rates that are independent of their mass.

They found that all of the stars move at about the same average speed of 4.5 km/s (corresponding to a change in apparent position of a mere 140 micro-arc seconds per year). The average speed does not appear to vary with mass at all.

The team observed more than 800 stars and were able to obtain sufficiently precise speed measurements for 234 cluster stars of different masses and surface temperatures.

Partial view of the giant nebula (HII region) NGC 3603 with its central, 1 million year old compact starburst cluster. False-color image based on observations with the Wide Field/Planetary Camera 2 of the Hubble Space Telescope. The dominant green color signalizes light emitted as ionized hydrogen regains its missing electron ('recombination line H-alpha'). The field of view is about 160 arc seconds on each side. The image shape is due to the detector placement of the Wide Field/Planetary Camera. Credit: NASA/ESA/Wolfgang Brandner (MPIA), Boyke Rochau (MPIA) and Andrea Stolte (University of Cologne)

“Once our analysis was completed, we reached a precision of 27 millionths of an arc second per year,” said Boyke Rochau, the paper’s lead author. “Imagine you are in Bremen, observing an object that is located in Vienna. Now the object moves sideways by the breadth of a human hair. That’s a change in apparent position of about 27 millionths of an arc second.”

Apparently – and surprisingly – this very massive star cluster has not yet settled down. Instead, the stars’ velocities still reflect conditions from the time the cluster was formed, approximately one million years ago.

“For the first time, we have been able to measure precise stellar motions in such a compact young star cluster. This is key information for astronomers trying to understand how such clusters are formed, and how they evolve,” said team member Andrea Stolte from the University of Cologne.

Vexingly, the question of whether or not the massive young cluster in NGC 3603 will become a globular cluster remains open. Given the new results, it all depends on the speeds of the low-mass stars, which were too faint to allow for precise speed measurements with the Hubble Space Telescope. “To find out whether or not our star cluster will disperse, we will need to wait for the next generation of telescopes, such as the James Webb Space Telescope (JWST) or ESO’s European Extremely Large Telescope (E-ELT),” said Brandner.

The results have been published in the Letters section of the Astrophysical Journal. Read the paper here.

Sources: Max Planck Institute for Astronomy, Hubble ESA