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Young Star Caught Speeding (Forwarded)



 
 
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Old January 6th 04, 12:49 AM
Andrew Yee
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Default Young Star Caught Speeding (Forwarded)

Harvard-Smithsonian Center for Astrophysics
Cambridge, Massachusetts

For more information, contact:

David Aguilar, Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
Phone: 617-495-7462 Fax: 617-495-7468


Christine Lafon, Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
Phone: 617-495-7463, Fax: 617-495-7016


For Release: 12:30 p.m. EST, Monday, January 5, 2004

Release No.: 04-02

Young Star Caught Speeding

Atlanta, GA -- Astronomers Alyssa Goodman (Harvard-Smithsonian Center for
Astrophysics) and Hector Arce (Caltech) announced today at the 203rd
meeting of the American Astronomical Society that they have caught a
newly formed star in the act of speeding. PV Ceph, located about 1400
light years away in the constellation Cepheus, is whizzing through space
at a speed of 40,000 miles per hour -- some 40 times faster than a
speeding bullet. And like a bullet, it left an exit wound when it ripped
out of the star cluster where it formed.

These findings linking a speeding star to its birthplace provide direct
observational support of theoretical simulations predicting that
protostars can be tossed out of a young cluster. This is the first time
that such a fast-moving young star has been seen outside of a cluster or
binary system.

"PV Ceph was exiled from its home, thrown out before it even finished
forming. It crossed an ocean of empty space and now has found a new home
in another molecular cloud," said Goodman.

Their discovery has significant implications for calculations of star
formation efficiency -- how many stars of what sizes are likely to form
from a given molecular cloud. Modeling that process correctly is critical
to understanding how galaxies everywhere turn gas into stars.

PV Ceph Puzzle Pieces

"Figuring out the story of PV Ceph was like conducting a CSI
investigation. We had to piece together a jigsaw puzzle of clues to
assemble a picture of what happened to this star," said Arce.

The first clue came from examining the Herbig-Haro (HH) knots on either
side of PV Ceph. Those blobs of shocked gas were ejected from the young
star in opposite directions. The midpoint of the line connecting a pair
of these blobs hints at where the star was located when it ejected that
matter.

Three lines can be drawn between three pairs of HH knots near PV Ceph.
Each midpoint falls in a different location, marking the star's trail
like breadcrumbs and providing clear evidence that the star is moving
across the sky.

More remarkably, the star's path points straight back to the young star
cluster NGC 7023. In fact, it points to a dark rift in the nebulosity
where a line of gas has been swept clear.

"The chances of this alignment being random are literally astronomical,"
said Arce.

Delving deeper, Goodman and Arce examined their recent radio observations
of the dense interstellar gas near PV Ceph, and found that the star
appears to be leaving behind a trail of molecular gas pointing in the
same direction as that implied by the geometry of the HH knots.

"That trail of gas was left behind like a wake from a ship," said
Goodman.

A fourth clue involves the tilt apparent in the high-velocity molecular
jet now emanating from the star. That tilt again implies a speed of
40,000 miles per hour, completely independent of the other lines of
evidence.

Even the approximate 500,000-year age of PV Ceph matches the estimated
time for it to travel the huge 30 light-year distance from NGC 7023 to
its current location.

"Clearly, the preponderance of evidence points to NGC 7023 as the origin
of PV Ceph," concluded Goodman.

Open Questions

Still unanswered is the question of what PV Ceph was doing, and what gas
and/or disk it took along with it, in the time it was traveling through
the empty space between NGC 7023 and its current home. Goodman and Arce's
calculations show that the star may have been able to hold onto a
surrounding cocoon of material as large as 200 astronomical units. (An
astronomical unit is the average distance between the Earth and Sun.) A
cocoon of that size would encompass our solar system out beyond Pluto to
the Kuiper Belt.

"It's not impossible that planets are forming around PV Ceph right now
from that material," said Goodman.

Also unanswered is what this finding implies for theories of star
formation in molecular clouds.

"How do you conduct a census of a star cluster's true population when
some clusters are losing stars, some clusters are gaining stars, and some
clusters are unchanged? If these ejections are at all common, then
calculations of star formation efficiency become much more difficult,"
said Goodman.

Goodman and Arce recommend a focused campaign to measure the velocities
of young stars in search of other "speeders."

Their study of PV Ceph will be published in an upcoming issue of The
Astrophysical Journal.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for
Astrophysics is a joint collaboration between the Smithsonian
Astrophysical Observatory and the Harvard College Observatory. CfA
scientists, organized into six research divisions, study the origin,
evolution and ultimate fate of the universe.

Note to Editors:

An image to accompany this release is online at:
http://cfa-www.harvard.edu/press/pr0402image.html

A movie and additional information, including the AAS presentation,
are online at:
http://cfa-www.harvard.edu/~agoodman...s/aas04PVCeph/

 




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