Astronomer Takes A New Spin On Vega; One Of Brightest Stars IsRapidly Rotating (Forwarded)

Stony Brook University
Stony Brook, New York

For further information, please contact:

Deane Peterson, Tel: +1 631 632 8223
Patrick Calabria, Tel: +1 631 632 6310 FAX: +1 631 632 6313

April 12, 2006

Astronomer Takes A New Spin On Vega; One Of Brightest Stars Is Rapidly
Rotating

Stony Brook Researcher Confirms Theory

STONY BROOK, N.Y. -- Vega, the second brightest star in the northern sky,
is a 'standard' that has been used to calibrate astronomical observations
from the ultraviolet through to the infrared, and it is the main star
against which models of stellar atmospheres are compared. But problems
with its use as a standard led to the suggestion that it is rapidly
rotating -- a theory that has now been confirmed by a Stony Brook
University researcher.

Deane Peterson, an Associate Professor of Astronomy at Stony Brook, and
colleagues now confirm that Vega, the 5th brightest star overall in the
universe, is rotating so fast that if it sped up by just 10 per cent it
would spin to pieces, according to research published in this week's
edition of the scientific journal Nature. Vega is flattened significantly
by the rotation, which means that the temperature at the star's surface
varies hugely, being over 2,400 degrees Celsius hotter at the poles
(around 10,000 degrees Celsius) than at the equator, because the equator
is farther from the energy-generating center.

This behavior hasn't been obvious previously because it was obscured by
Vega's orientation: its polar axis points more or less straight at the
Earth. The new results imply that both Vega's elemental composition and
its age may be rather different to what has been inferred until now. In
addition, Peterson said the star is "brighter than it should be" and puts
out more energy in the infrared than it should.

"The large impact of this particular result is because Vega is the primary
standard for a lot of different things in Astronomy," Peterson said. "Vega
is observed more than any star except the Sun, mostly in the role of
comparison. This won't change that role, but will affect how people think
about the objects they compare to Vega. The changes will generally be
subtle, but the use of Vega in this role is so pervasive that these
results will ripple through most of the discipline."

The research was conducted at the U.S. Naval Observatory's Flagstaff
Station in Flagstaff, Arizona, the USNO's dark-sky site for optical and
near-infrared astronomy. The U.S. Naval Observatory is one of the oldest
scientific agencies in the country. Established in 1830 as the Depot of
Charts and Instruments, its primary mission was to care for the U.S.
Navy's chronometers, charts and other navigational equipment. Today, the
U.S. Naval Observatory is the preeminent authority in the areas of Precise
Time and Astrometry, and distributes Earth Orientation parameters and
astronomical date other required for accurate for accurate navigation and
fundamental astronomy.