Hubble Movies Show Supersonic Jets from Young Stars

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Ann
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Next APOD?

Post by Ann » Wed Aug 31, 2011 3:40 pm

The HST has photographed the jets and bow shocks of young stars. The next APOD?

Check it out here.

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orin stepanek
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signatures of star birth

Post by orin stepanek » Wed Aug 31, 2011 5:05 pm

http://hubblesite.org/newscenter/archiv ... 0/image/a/
ABOUT THIS IMAGE:

The glowing, clumpy streams of material shown in these NASA Hubble Space Telescope images are the signposts of star birth.

Ejected episodically by young stars like salvos from a cannon, the blobby material zips along at more than 440,000 miles (770,000 kilometers) an hour. Called Herbig-Haro or HH objects, these speedy outflows have a bumpy ride through space.

When fast-moving blobs "rear-end" slower gas, bow shocks (the blue features) arise as the material heats up. Bow shocks are glowing waves of matter similar to waves produced by the bow of a ship plowing through water. In HH 2, at lower right, several bow shocks (the compact blue and white features) can be seen where fast-moving clumps bunch up like cars in a traffic jam. In HH 34, at lower left, a grouping of merged bow shocks reveals regions that brighten and fade over time as the heated material cools, shown in red, where the shocks intersect.

In HH 47, at top, a long jet of material has burst out of a dark cloud of gas and dust that hides the newly forming star. The blue, fan-shaped region at left is the edge of a cavity illuminated by the fledgling star. A massive clump of jet material collides with upstream gas, creating the white bow-shaped shock wave at right.

These images are part of a series of time-lapse movies astronomers have made showing the outflows' motion over time. The movies were stitched together from images taken over a 14-year period by Hubble's Wide Field Planetary Camera 2. Hubble followed the jets over three epochs. Observations of HH 2 were made from 1994, 1997, and 2007; HH 34 from 1994, 1998, and 2007; and HH 47 from 1994, 1999, and 2008.

The outflows are roughly 1,350 light-years from Earth. HH 34 and HH 2 reside near the Orion Nebula, in the northern sky. HH 47 is located in the southern constellation Vela.

Object Names: HH 47, HH 34, HH 2

Credit: NASA, ESA, and P. Hartigan (Rice University)
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Hubble Movies Show Supersonic Jets from Young Stars

Post by bystander » Wed Aug 31, 2011 8:44 pm

Hubble Movies Provide Unprecedented View of Supersonic Jets from Young Stars
ESA Hubble European Information Center (HEIC) | 2011 Aug 31
Astronomers have combined two decades of Hubble observations to make unprecedented movies revealing never-before-seen details of the birth pangs of new stars. This sheds new light on how stars like the Sun form.

Stars aren’t shy about sending out birth announcements. They fire off energetic jets of glowing gas travelling at supersonic speeds in opposite directions through space.

Although astronomers have looked at still pictures of stellar jets for decades, now they can watch movies, thanks to the NASA/ESA Hubble Space Telescope.

An international team of scientists led by astronomer Patrick Hartigan of Rice University in Houston, USA, has collected enough high-resolution Hubble images over a 14-year period to stitch together time-lapse movies of young jets ejected from three stars.

The moving pictures offer a unique view of stellar phenomena that move and change over just a few years. Most astronomical processes change over timescales that are much longer than a human lifetime.

The movies reveal the motion of the speedy outflows as they tear through the interstellar environments. Never-before-seen details in the jets’ structure include knots of gas brightening and dimming and collisions between fast-moving and slow-moving material, creating glowing arrowhead features. These phenomena are providing clues about the final stages of a star’s birth, offering a peek at how the Sun behaved 4.5 billion years ago.

“For the first time we can actually observe how these jets interact with their surroundings by watching these time-lapse movies,” said Hartigan. “Those interactions tell us how young stars influence the environments out of which they form. With movies like these, we can now compare observations of jets with those produced by computer simulations and laboratory experiments to see which aspects of the interactions we understand and which we don’t understand.”

Hartigan’s team’s results appear in the 20 July 2011 issue of the Astrophysical Journal.

Jets are an active, short-lived phase of star formation, lasting only about 100 000 years. They are called Herbig-Haro (HH) objects, named after George Herbig and Guillermo Haro, who studied the outflows in the 1950s. Astronomers still don’t know what role jets play in the star formation process or exactly how the star unleashes them.

A star forms from a collapsing cloud of cold hydrogen gas. As the star grows, it gravitationally attracts more matter, creating a large spinning disc of gas and dust around it. Eventually, planets may arise within the disc as dust clumps together.

The disc material gradually spirals onto the star and escapes as high velocity jets along the star’s axis of spin. The speedy jets may initially be confined to narrow beams by the star’s powerful magnetic field. The jet phase stops when the disc runs out of material, usually a few million years after the star’s birth.

Hartigan and his colleagues used Hubble’s Wide Field Planetary Camera 2 to study jets HH 1, HH 2, HH 34, HH 46, and HH 47. HH 1-HH 2 and HH 46-HH 47 are pairs of jets emanating in opposite directions from single stars. Hubble followed the jets over three epochs: HH 1 and HH 2 in 1994, 1997, and 2007; HH 34 in 1994, 1998, and 2007; and HH 46 and HH 47 in 1994, 1999, and 2008. The jets are roughly ten times the width of the Solar System and zip along at more than 700 000 kilometres per hour.

All of the outflows are roughly 1350 light-years from Earth. HH 34, HH 1, and HH 2 reside near the Orion Nebula, in the northern sky. HH 46 and HH 47 are in the southern constellation of Vela (The Sails).

Computer software has woven together these observations, taken over many years, and generated movies that show continuous motion. The movies support previous observations which revealed that the twin jets are not ejected in a steady stream, like water flowing from a garden hose. Instead, they are launched sporadically in clumps. The beaded-jet structure might be like a “ticker tape”, recording episodes when material fell onto the star.

The movies show that the clumpy gas in the jets is moving at different speeds like traffic on a motorway. When fast-moving blobs collide with gas in the slow lane, bow shocks arise as the material heats up. Bow shocks are glowing waves of material similar to waves produced by the bow of a ship ploughing through water. In HH 2, for example, several bow shocks can be seen where several fast-moving clumps have bunched up like cars in a traffic jam. In another jet, HH 34, a grouping of merged bow shocks reveals regions that brighten and fade over time as the heated material cools where the shocks intersect.

In other areas of the jets, bow shocks form from encounters with the surrounding dense gas cloud. In HH 1 a bow shock appears at the top of the jet as it grazes the edge of a dense gas cloud. New glowing knots of material also appear. These knots may represent gas from the cloud being swept up by the jet, just as a swift-flowing river pulls along mud from the shoreline.

The movies also provide evidence that the inherent clumpy nature of the jets begins near the newborn stars. In HH 34 Hartigan traced a glowing knot to within about 14 billion kilometres of the star.

“Taken together, our results paint a picture of jets as remarkably diverse objects that undergo highly structured interactions between material within the outflow and between the jet and the surrounding gas,” Hartigan explained. “This contrasts with the bulk of the existing simulations which depict jets as smooth systems.”

The details revealed by Hubble were so complex that Hartigan consulted with experts in fluid dynamics from Los Alamos National Laboratory in New Mexico, the UK Atomic Weapons Establishment, and General Atomics in San Diego, California, as well as computer specialists from the University of Rochester in New York. Motivated by the Hubble results, Hartigan’s team is now conducting laboratory experiments at the Omega Laser facility in New York to understand how supersonic jets interact with their environment.

“Our collaboration has exploited not just large laser facilities such as Omega, but also computer simulations that were developed for research into nuclear fusion,” explains Paula Rosen of the UK Atomic Weapons Establishment, a co-author of the research. “Using these experimental methods has enabled us to identify aspects of the physics that the astronomers overlooked — it is exciting to know that what we do in the laboratory here on Earth can shed light on complex phenomena in stellar jets over a thousand light-years away. In future, even larger lasers, like the National Ignition Facility at the Lawrence Livermore National Laboratory in California, will be able explore the nuclear processes that take place within stars.”

Hubble Movies Provide Unprecedented View of Supersonic Jets from Young Stars
NASA Space Telescope Science Institute (STScI) | 2011 Aug 31
New movies created from years of still images collected by NASA’s Hubble Space Telescope provide new details about the stellar birthing process, showing energetic jets of glowing gas ejected from young stars in unprecedented detail.

The jets are a byproduct of gas accretion around newly forming stars and shoot off at supersonic speeds of about 100 miles per second in opposite directions through space.

These phenomena are providing clues about the final stages of a star’s birth, offering a peek at how our Sun came into existence 4.5 billion years ago.

Hubble’s unique sharpness allows astronomers to see changes in the jets over just a few years’ time. Most astronomical processes change over timescales that are much longer than a human lifetime.

A team of scientists led by astronomer Patrick Hartigan of Rice University in Houston, Texas, collected enough high-resolution Hubble images over a 14-year period to stitch together time-lapse movies of the jets ejected from three young stars.

Never-before-seen details in the jets’ structure include knots of gas brightening and dimming over time and collisions between fast-moving and slow-moving material, creating glowing arrowhead features. The twin jets are not ejected in a steady stream, like water flowing from a garden hose. Instead, they are launched sporadically in clumps. The beaded-jet structure might be like a “ticker tape,” recording how material episodically fell onto the star.

“For the first time we can actually observe how these jets interact with their surroundings by watching these time-lapse movies,” said Hartigan. “Those interactions tell us how young stars influence the environments out of which they form. With movies like these, we can now compare observations of the jets with those produced by computer simulations and laboratory experiments to see what aspects of the interactions we understand and what parts we don’t understand.”

Jets are an active, short-lived phase of star formation, lasting only about 100,000 years. Astronomers don’t know precisely what role jets play in the star-formation process or exactly how the star unleashes them. The jets appear to work in concert with magnetic fields. This helps bleed excess angular momentum from infalling material that is swirling rapidly. Once the material slows down it feeds the growing protostar, allowing it to fully condense into a mature star.

Hartigan and his colleagues used the Wide Field Planetary Camera 2 to study the jets, called Herbig-Haro (HH) objects, named in honor of George Herbig and Guillermo Haro, who studied the outflows in the 1950s. Hubble followed HH 1, HH 2, HH 34, HH 46, and HH 47 over three epochs, 1994, 1998, and 2008.

The team used computer software that wove together the observations to generate movies showing continuous motion.

“Taken together, our results paint a picture of jets as remarkably diverse objects that undergo highly structured interactions both within the material in the outflow and between the jet and the surrounding gas,” Hartigan explained. “This contrasts with the bulk of the existing simulations, many of which depict jets as smooth systems.”

Hartigan’s team’s results appeared in the July 20, 2011 issue of The Astrophysical Journal.

HubbleSite Video: New Details Emerge About the Birth of Young Stars

Hubble movies reveal solar-system-sized traffic jams
Rice University | Jeff Fitlow | 2011 Aug 31
Giant jets spewing from newborn stars revealed in telescope's images
Click to play embedded YouTube video.

When it comes to big-budget action movies, Rice University astronomer Patrick Hartigan prefers Hubble to Hollywood.

Using Hubble Space Telescope images collected over 14 years, Hartigan has created time-lapse movies that offer astronomers their first glimpse of the dynamic behavior of stellar jets, huge torrents of gas and particles that spew from the poles of newborn stars.

An analysis of the movies that was published in The Astrophysical Journal is forcing astronomers to rethink some of the processes that occur during the latter stages of star birth. And in an effort to learn even more, Hartigan and colleagues are using powerful lasers to recreate a small-scale version of the solar-system-sized jets in a lab in upstate New York.

"The Hubble's given us spectacular images," said Hartigan, professor of physics and astronomy at Rice. "In the nebulae where stars are born, for instance, we can see beautiful filaments and detailed structure. We know these images are frozen snapshots in time, but we would need to watch for hundreds of thousands of years to see how things actually play out."

Hartigan said stellar jets are different because they move very quickly. Stellar jets blast out into space from the poles of newly formed stars at about 600,000 miles an hour. Astronomers first noticed them about 50 years ago, and they believe the sun probably had stellar jets when it formed about 4.5 billion years ago.

Hartigan began using Hubble to collect still frames of stellar jets in 1994. The jets emerge from each pole of a young star, and Hartigan used Hubble to revisit the jets from three stars in 1994, 1998 and 2008. All three stars are about 1,350 light years from Earth. Two are near the Orion Nebula, and the third is in the southern sky in the constellation Vela.

By lacing the images together and using a computer to fill in what occurred between still frames, Hartigan and his collaborators created time-lapse movies. The movies clearly showed something that wasn't obvious in any of the still images; clouds of dust and gas within the jets move at different speeds.

"The bulk motion of the jet is about 300 kilometers per second," Hartigan said. "That's really fast, but it's kind of like watching a stock car race; if all the cars are going the same speed, it's fairly boring. The interesting stuff happens when things are jumbling around, blowing past one another or slamming into slower moving parts and causing shockwaves."

Understanding what happens in those huge collisions is another challenge. The phenomena didn't look like anything that Hartigan and his astronomer colleagues had seen. But when he showed them to colleagues who were familiar with the physics of nuclear explosions, they immediately saw patterns in the shockwaves that looked familiar.

"The fluid dynamicists immediately picked up on an aspect of the physics that astronomers typically overlook, and that led to a different interpretation for some of the features we were seeing," Hartigan explained. "The scientists from each discipline bring their own unique perspectives to the project, and having that range of expertise has proved invaluable for learning about this critical phase of stellar evolution."

Motivated by the results from Hubble, Hartigan and colleagues are conducting experiments at the Omega Laser Facility in Rochester, New York, to recreate small-scale versions of the solar-system-sized features captured in the movies.

"It's one more tool we have to better understand the underlying physics," Hartigan said.

In addition to Hartigan, the research team includes Adam Frank of the University of Rochester; John Foster and Paula Rosen of the Atomic Weapons Establishment in Aldermaston, U.K.; Bernie Wilde, Rob Coker and Melissa Douglas of Los Alamos National Laboratory in New Mexico; and Brent Blue and Freddy Hansen of General Atomics in San Diego, Calif.

The research is funded by NASA and the National Nuclear Security Administration.

Herbig-Haro Jet Movies from HST

Fluid Dynamics of Stellar Jets in Real Time: Third Epoch HST Images of HH 1, HH 34, and HH 47 - P. Hartigan et al
Hubble Captures Stars Unleashing Supersonic Jets
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