Massive Asteroid Belts Discovered Around Vega
Vega is famous for being the fifth-brightest star in global skies, but it may soon also become famous for sporting two asteroid belts and, by extension, an entire system of exoplanets.
This discovery was made by astronomers using data from NASA’s Spitzer Space Telescope and ESA’s Herschel Space Observatory — both orbital telescopes that observe the Universe in infrared light.
During observations of Vega, that is located 25 light-years away in the constellation Lyra, it became apparent that the star plays host to a warm inner belt of asteroids and an outer, cool belt ten-times further out from the star, separated by a gap. This may sound familiar — our solar system possesses an inner belt of asteroids (the Asteroid Belt that can be found between the orbits of Mars and Jupiter) and, ten-times further away, an outer belt of asteroids and cometary nuclei (the Kuiper Belt beyond the orbit of Neptune). This conforming 1:10 ratio is very interesting to astronomers.
Although there are similarities between Vega and the solar system, there are a couple of key differences. First, the Vega system is 4-times the size of the solar system and the star itself is twice the mass of our sun. Second, the star is only a fraction of the age of or sun — approximately 600 million years old (as compared with the sun’s age of over 4 billion years) — and therefore burns hotter and brighter.
The young Vega system is, by its nature, thick with dust and debris from the recent frenzy of star formation. The solar system on the other hand is much older and has had time to “settle”; dust has coalesced to form larger chunks of debris (asteroids, comets, planets). But the gap between the two asteroid belts is possibly the most fascinating discovery — that could be a zone where young planets roam.
“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, Tucson. Su, lead author of a paper accepted for publication in the Astrophysical Journal, announced her findings at the American Astronomical Society meeting in Long Beach, Calif. on Tuesday.
Spitzer and Herchel were able to see the two belts of rocky debris from the dust they produce — asteroids bump, grind and collide, kicking up dust. The radiation from the star then heated the dust, which, in turn, glows in infrared light.
This is a similar situation to the famous star Fomalhaut that is approximately the same mass as Vega, but a little younger. Fomalhaut also possesses a beautiful ring of dusty debris — generated by swarms of comets and asteroids. However, astronomers have identified a large world (Fomalhaut b) orbiting between the star system’s two dusty belts. Astronomers have yet to identify any exoplanets within the Vega system — even though the gap between belts suggests they’re lurking in there.
“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.
They may be invisible right now, but astronomers will be keen to use NASA’s next-generation space telescope — the James Webb Space Telescope (launching in 2018) — to tease out the weak infrared signal of the hypothetical system of planets swarming around these two stars.
Image credit: NASA/JPL-Caltech