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.