Vega’s asteroid belts hint at hidden planets

This conceptual illustration depicts an asteroid belt around the bright star Vega. Evidence for the ring of debris comes from NASA and ESA space telescopes. Credit: NASA/JPL-Caltech

Look low in the northwestern sky at dusk in mid-January and you’ll spy a bright, sparkling star. That’s Vega, Lyra the Harp’s most luminous star and the fifth brightest in the sky … after the sun, of course. We’ve known since 1983 that Vega is surrounded by a dusty disk of debris, the first star discovered to have one. Warmed by the star, dust radiates a feeble heat that was detected by the NASA’s orbiting Infrared Astronomical Satellite (IRAS).

Look for Vega above the trees during the early evening. This map shows the sky facing northwest around 6:30 p.m. local time. Maps created with Stellarium

Earlier this week NASA announced evidence for two separate asteroid belts and potential planets around the star. Sound familiar? Our solar system has both an inner, warm asteroid belt located between Mars and Jupiter and a cold, outer belt of “ice”-teroids beyond Neptune. Using NASA’s Spitzer Space Telescope and the European Space Agency Herschel Space Telescope, both of which are optimized to detect infrared (heat) light, astronomers detected two bands of dust created and replenished by collisions of comets and rocky asteroids around Vega.

The amount of dust indicates that Vega’s belts have far more material than our own asteroid belts, no surprise given that our solar system is far older – about 5 billion years – and has had a much longer time to “clean house” through planet-asteroid interactions. Vega, a star with twice the sun’s mass and 36 times more luminous, is thought to be a youthful 600 million years old.

The Vega system, with its own set of asteroid-comet belts, is compared to our solar system in this illustration. The relative size of our system compared to Vega is illustrated by the small drawing in the middle. On the right, our solar system is scaled up four times. Both inner and outer belts have similar proportions. Credit: NASA/JPL-Caltech

Check out the layout of Vega’s belts. Back at home, the main asteroid belt is kept in place by the interplay of gravity between Jupiter and the inner planets, while the outer Kuiper Belt was fashioned by the giant outer planets. Although we can’t see them yet, there are almost certainly planets at play in maintaining Vega’s belts, too. Ain’t gravity fun?

Arcturus, auger of spring, comes up around midnight below the handle of the Big Dipper.

Last night while out checking on a supernova in a galaxy in Leo, a bright spark of ruby light caught my eye low in the northeastern sky. I almost didn’t recognize it, but a second later it hit me -  Arcturus. The time was midnight and already the sky offered this taste of spring.

Arcturus is a brilliant ruddy star that stands high in the south come May. Because of its prominence in late spring and early summer, it’s imbued with memories of warm nights and green grass. In January, Arcturus still slumbers below the eastern horizon until shortly before midnight. Seeing it poke between the trees warmed me up … just a little.

The sun at 10:30 a.m. CST Jan. 10, 2013 photographed by the Solar Dynamics Observatory. The pair of sunspots at left, region 1654, is big enough to see with the naked eye using a safe solar filter. This group harbors the potential for significant solar flares. Credit: NASA

Nicer yet was the sun, which burned away in a blue sky this morning. Lots of sunspot groups, including two large new spots that have recently rounded the sun’s eastern limb, have increased the chance for solar flares in the coming days.

I don’t know about you but I miss the aurora. The last one good show in northern Minnesota happened in November. Let’s hope we won’t have to wait much longer.

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About astrobob

My name is Bob King and I work at the Duluth News Tribune in Duluth, Minn. as a photographer and photo editor. I'm also an amateur astronomer and have been keen on the sky since age 11. My modest credentials include membership in the American Association of Variable Star Observers (AAVSO) where I'm a regular contributor, International Meteorite Collectors Assn. and Arrowhead Astronomical Society. I also teach community education astronomy classes at our local planetarium.

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