Andrew Yee[_1_]
January 9th 07, 12:07 AM
National Radio Astronomy Observatory
P.O. Box O
Socorro, NM 87801
http://www.nrao.edu
Contact:
Dave Finley, Public Information Officer
(505) 835-7302
EMBARGOED For Release: 2:00 p.m., PST, Monday, January 8, 2007
VLBA Helps Build New Picture of Star-Forming Regions
New, high-precision distance measurements by the National Science
Foundation's Very Long Baseline Array (VLBA) radio telescope are providing a
major advance for astronomers trying to understand how stars form. "A large
improvement in measuring the distance to a young, still-forming star means a
large improvement in measuring characteristics such as its mass and
intrinsic brightness," said Laurent Loinard, of the National University of
Mexico (UNAM). Loinard, Amy Mioduszewski of the National Radio Astronomy
Observatory, UNAM graduate student Rosa Torres and UNAM professor Luis
Rodriguez presented their findings to the American Astronomical Society's
meeting in Seattle, Washington.
"Most of what we know about the processes of star formation has come from
studying young stars in a few, relatively nearby regions," Loinard said.
"However, estimates of the distance to these regions have been imprecise.
That imprecision has limited the ability of real-world observations to
improve theoretical models for star formation," he added.
The new VLBA distance measurements are great improvements over earlier
estimates. For example, earlier work placed a famous young stellar system in
the constellation Taurus between 423 and 489 light-years from Earth. The new
VLBA measurements narrow the range to 418-422 light-years. "Our observations
brought the error in this measurement down from 66 light-years to four,"
Mioduszewski said.
The new VLBA observations also refined the distance estimate to another
star-forming region in the constellation Ophiuchus.
The new results are part of a long-term project led by Loinard and
Mioduszewski to make precise distance measurements to individual young stars
within well-studied regions of prolific star formation. They do this by
measuring the tiny apparent shift of the star's position against the
background sky caused by Earth's rotation around the Sun. This method,
called trigonometric parallax, produces a direct, unambiguous measurement of
the star's distance.
"The VLBA is the only instrument in the world that can do this on these
objects," Loinard explained. This is because the visible light from young
stars is dimmed by the cloud of gas and dust from which they are being
formed. In addition, young stars also are often surrounded by material that
obscures their visible light. This means that even the Hipparcos satellite,
which measured distances of more than 100,000 stars, was handicapped when it
came to young stars. However, processes occurring in the magnetic fields of
newly-formed stars often produce bright radio emission that the VLBA can
detect readily.
The VLBA, a system of 10 radio-telescope antennas stretching from Hawaii to
the Caribbean, provides the best ability to see fine detail, called
resolving power, of any astronomical tool in the world. The VLBA can
routinely produce images hundreds of times more detailed than those produced
by the Hubble Space Telescope. The VLBA's tremendous resolving power is what
permits the astronomers to make the precise distance determinations.
The scientific payoff is great. The improved distance measurements allow
better determinations of the young stars' physical characteristics. By
measuring distances to multiple stars in a star-forming region, the
astronomers can build a three-dimensional picture of the region. Observing
the stars over a period of years will allow the scientists to determine
their speeds and motions.
"All this new information about the stars and the environment in which they
are formed will greatly improve our ability to understand such regions and
the processes that turn clouds of gas and dust into stars," said
Mioduszewski.
The results the astronomers announced in Seattle are just the beginning of
their project, they said. They intend to use the VLBA to study additional
star-forming regions in addition to more stars within the regions already
studied.
"By carefully building up well-measured, three-dimensional pictures of
several star-forming regions, as well as learning about the motions of stars
within those regions, we expect that we'll find some surprises that revise
our understanding of the all-important process of star formation," Loinard
said.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation, operated under cooperative agreement by Associated
Universities, Inc.
IMAGE CAPTION:
[http://www.nrao.edu/pr/2007/starfmparallax/Parallax-Illustration.jpg
(153KB)]
Trigonometric Parallax method determines distance to star by measuring its
slight shift in apparent position as seen from opposite ends of Earth's
orbit. CREDIT: Bill Saxton, NRAO/AUI/NSF
OTHER IMAGES & ANIMATION:
* Animation of apparant motion on sky of young star T Tauri S (MPEG, 891KB)
http://www.nrao.edu/pr/2007/starfmparallax/parallax.mpeg
* Still Frame from above animation (14KB)
http://www.nrao.edu/pr/2007/starfmparallax/moviestill.jpg
* B&W Plot of T Tauri S Parallax motion (51KB)
http://www.nrao.edu/pr/2007/starfmparallax/parallax.plot.jpg
P.O. Box O
Socorro, NM 87801
http://www.nrao.edu
Contact:
Dave Finley, Public Information Officer
(505) 835-7302
EMBARGOED For Release: 2:00 p.m., PST, Monday, January 8, 2007
VLBA Helps Build New Picture of Star-Forming Regions
New, high-precision distance measurements by the National Science
Foundation's Very Long Baseline Array (VLBA) radio telescope are providing a
major advance for astronomers trying to understand how stars form. "A large
improvement in measuring the distance to a young, still-forming star means a
large improvement in measuring characteristics such as its mass and
intrinsic brightness," said Laurent Loinard, of the National University of
Mexico (UNAM). Loinard, Amy Mioduszewski of the National Radio Astronomy
Observatory, UNAM graduate student Rosa Torres and UNAM professor Luis
Rodriguez presented their findings to the American Astronomical Society's
meeting in Seattle, Washington.
"Most of what we know about the processes of star formation has come from
studying young stars in a few, relatively nearby regions," Loinard said.
"However, estimates of the distance to these regions have been imprecise.
That imprecision has limited the ability of real-world observations to
improve theoretical models for star formation," he added.
The new VLBA distance measurements are great improvements over earlier
estimates. For example, earlier work placed a famous young stellar system in
the constellation Taurus between 423 and 489 light-years from Earth. The new
VLBA measurements narrow the range to 418-422 light-years. "Our observations
brought the error in this measurement down from 66 light-years to four,"
Mioduszewski said.
The new VLBA observations also refined the distance estimate to another
star-forming region in the constellation Ophiuchus.
The new results are part of a long-term project led by Loinard and
Mioduszewski to make precise distance measurements to individual young stars
within well-studied regions of prolific star formation. They do this by
measuring the tiny apparent shift of the star's position against the
background sky caused by Earth's rotation around the Sun. This method,
called trigonometric parallax, produces a direct, unambiguous measurement of
the star's distance.
"The VLBA is the only instrument in the world that can do this on these
objects," Loinard explained. This is because the visible light from young
stars is dimmed by the cloud of gas and dust from which they are being
formed. In addition, young stars also are often surrounded by material that
obscures their visible light. This means that even the Hipparcos satellite,
which measured distances of more than 100,000 stars, was handicapped when it
came to young stars. However, processes occurring in the magnetic fields of
newly-formed stars often produce bright radio emission that the VLBA can
detect readily.
The VLBA, a system of 10 radio-telescope antennas stretching from Hawaii to
the Caribbean, provides the best ability to see fine detail, called
resolving power, of any astronomical tool in the world. The VLBA can
routinely produce images hundreds of times more detailed than those produced
by the Hubble Space Telescope. The VLBA's tremendous resolving power is what
permits the astronomers to make the precise distance determinations.
The scientific payoff is great. The improved distance measurements allow
better determinations of the young stars' physical characteristics. By
measuring distances to multiple stars in a star-forming region, the
astronomers can build a three-dimensional picture of the region. Observing
the stars over a period of years will allow the scientists to determine
their speeds and motions.
"All this new information about the stars and the environment in which they
are formed will greatly improve our ability to understand such regions and
the processes that turn clouds of gas and dust into stars," said
Mioduszewski.
The results the astronomers announced in Seattle are just the beginning of
their project, they said. They intend to use the VLBA to study additional
star-forming regions in addition to more stars within the regions already
studied.
"By carefully building up well-measured, three-dimensional pictures of
several star-forming regions, as well as learning about the motions of stars
within those regions, we expect that we'll find some surprises that revise
our understanding of the all-important process of star formation," Loinard
said.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation, operated under cooperative agreement by Associated
Universities, Inc.
IMAGE CAPTION:
[http://www.nrao.edu/pr/2007/starfmparallax/Parallax-Illustration.jpg
(153KB)]
Trigonometric Parallax method determines distance to star by measuring its
slight shift in apparent position as seen from opposite ends of Earth's
orbit. CREDIT: Bill Saxton, NRAO/AUI/NSF
OTHER IMAGES & ANIMATION:
* Animation of apparant motion on sky of young star T Tauri S (MPEG, 891KB)
http://www.nrao.edu/pr/2007/starfmparallax/parallax.mpeg
* Still Frame from above animation (14KB)
http://www.nrao.edu/pr/2007/starfmparallax/moviestill.jpg
* B&W Plot of T Tauri S Parallax motion (51KB)
http://www.nrao.edu/pr/2007/starfmparallax/parallax.plot.jpg