Spitzer and Hershel Space Telescopes Detect Debris Belt(s) Around Vega

Artist's conception of the Asteroid Belt around Vega

This is an artist’s rendering of the debris belt around the star Vega. Image Credit: NASA/JPL-Caltech

Scientists working with data from both NASA’s Spitzer Space Telescope and the ESA’s Herschel Space Observatory have confirmed the detection of an asteroid-belt-like debris belt around the nearby star Vega.

Vega is the second brightest star in the Northern Celestial Hemisphere, after Arcturus. It’s the brightest star in the constellation Lyra (the Harp) and is of the spectral type A0V. It is about twice the mass of the Sun, twice its radius, and 40 times its brightness.

Many stars have been discovered with discs of debris or dust, so it might seem at first blush that this is not a significant discovery. In fact, evidence of dust was detected around Vega itself by the Infrared Astronomical Satellite. And again in 2005, Spitzer found evidence for a debris disk.

Artist's rendering of how Vega's debris belt persists

This is an artist’s conception of how the dust disk around Vega is sustained by collisions by larger objects. Otherwise, the dust would be pushed into space by the intense radiation pressure. Image Credit: NASA/JPL-Caltech

The significance of the find is not merely that there is non-stellar matter around Vega, but that there are two discreet belts of material around Vega. The inner belt is very warm and seems similar to the Solar System’s own asteroid belt, and the outer, colder belt seems like our Kuiper Belt. Both belts are much, much heavier than their Solar System equivalents, however.

But why are they separated? Even if they started out in discreet bands, the chaotic orbital dynamics of the larger debris in those belts would tend to spread the dust and debris out evenly with respect to distance from the star. Closer in, of course, the dust would fall into the star, but midway between the belts there seems to be no obvious reason for the lack of dust.

But the scientists contend that the separation of the belts is itself evidence for other objects in orbit around Vega: planets. They take the Solar System analogy further; just as the four outer gas giants Jupiter, Saturn, Uranus, and Neptune clear away stray objects from their orbital neighborhoods, several planetary objects around Vega must be clearing the debris between the two discreet bands of debris.

Diagram of the belts around Vega and the Sun

This diagram shows the relative sizes and locations of the debris belts around Vega and our own Sun. Image Credit: NASA/JPL-Caltech

No current telescope is large enough to confirm the existence of planets around Vega—close by though it is—but NASA’s James Webb Space Telescope should be able to detect them if they exist.

So, until the JWST is finished, launched, and begins observing, scientists will have to make do studying the patterns in the dust of the Vega system if they want to know more.

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