[meteorite-list] NASA, ESA Telescopes Find Evidence for Asteroid Belt Around Vega

[Ron Baalke]

Jan. 8, 2013

J.D. Harrington 
Headquarters, Washington                                
202-358-5241 
j.d.harrington at nasa.gov 

Whitney Clavin 
Jet Propulsion Laboratory, Pasadena, Calif. 
818-354-4673 
whitney.clavin at jpl.nasa.gov 

RELEASE: 13-006

NASA, ESA TELESCOPES FIND EVIDENCE FOR ASTEROID BELT AROUND VEGA

WASHINGTON -- Astronomers have discovered what appears to be a large 
asteroid belt around the star Vega, the second brightest star in 
northern night skies. The scientists used data from NASA's Spitzer 
Space Telescope and the European Space Agency's (ESA) Herschel Space 
Observatory, in which NASA plays an important role. 

The discovery of an asteroid belt-like band of debris around Vega 
makes the star similar to another observed star called Fomalhaut. The 
data are consistent with both stars having inner, warm belts and 
outer, cool belts separated by a gap. This architecture is similar to 
the asteroid and Kuiper belts in our own solar system. 

What is maintaining the gap between the warm and cool belts around 
Vega and Fomalhaut? The results strongly suggest the answer is 
multiple planets. Our solar system's asteroid belt, which lies 
between Mars and Jupiter, is maintained by the gravity of the 
terrestrial planets and the giant planets, and the outer Kuiper belt 
is sculpted by the giant planets. 

"Our findings echo recent results showing multiple-planet systems are 
common beyond our sun," said Kate Su, an astronomer at the Steward 
Observatory at the University of Arizona. Su presented the results 
Tuesday at the American Astronomical Society meeting in Long Beach, 
Calif., and is lead author of a paper on the findings accepted for 
publication in the Astrophysical Journal. 

Vega and Fomalhaut are similar in other ways. Both are about twice the 
mass of our sun and burn a hotter, bluer color in visible light. Both 
stars are relatively nearby at about 25 light-years away. The stars 
are thought to be around 400 million years old, but Vega could be 
closer to its 600 millionth birthday. Fomalhaut has a single 
candidate planet orbiting it, Fomalhaut b, which orbits at the inner 
edge of its cometary belt. 

The Herschel and Spitzer telescopes detected infrared light emitted by 
warm and cold dust in discrete bands around Vega and Fomalhaut, 
discovering the new asteroid belt around Vega and confirming the 
existence of the other belts around both stars. Comets and the 
collisions of rocky chunks replenish the dust in these bands. The 
inner belts in these systems cannot be seen in visible light because 
the glare of their stars outshines them. 

Both the inner and outer belts contain far more material than our own 
asteroid and Kuiper belts. The reason is twofold: the star systems 
are far younger than our own, which has had hundreds of millions more 
years to clean house, and the systems likely formed from an initially 
more massive cloud of gas and dust than our solar system. 

The gap between the inner and outer debris belts for Vega and 
Fomalhaut also proportionally corresponds to the distance between our 
sun's asteroid and Kuiper belts. This distance works out to a ratio 
of about 1:10, with the outer belt 10 times farther away from its 
host star than the inner belt. As for the large gap between the two 
belts, it is likely there are several undetected planets, 
Jupiter-sized or smaller, creating a dust-free zone between the two 
belts. A good comparison star system is HR 8799, which has four known 
planets that sweep up the space between two similar disks of debris. 

"Overall, the large gap between the warm and the cold belts is a 
signpost that points to multiple planets likely orbiting around Vega 
and Fomalhaut," said Su. 

If unseen planets do in fact orbit Vega and Fomalhaut, these bodies 
will not likely stay hidden. 

"Upcoming new facilities such as NASA's James Webb Space Telescope 
should be able to find the planets," said paper co-author Karl 
Stapelfeldt, chief of the Exoplanets and Stellar Astrophysics 
Laboratory at NASA's Goddard Space Flight Center in Greenbelt, Md. 

For NASA's Herschel website, visit: 

http://www.nasa.gov/herschel 

For ESA's Herschel website, visit: 

http://www.esa.int/SPECIALS/Herschel/index.html 

For more information about Spitzer, visit: 

http://www.nasa.gov/spitzer 
	
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