NASA's Spitzer Space Telescope recently captured these images of the star
Vega, located 25 light years away in the constellation Lyra. Spitzer was
able to detect the heat radiation from the cloud of dust around the star
and found that the debris disc is much larger than previously thought.
This side by side comparison, taken by Spitzer's multiband imaging
photometer, shows the warm infrared glows from dust particles orbiting
the star at wavelengths of 24 microns (figure 2 in blue) and 70 microns
(figure 3 in red).
Both images show a very large, circular and smooth debris disc. The disc
radius extends to at least 815 astronomical units. (One astronomical unit
is the distance from Earth to the Sun, which is 150-million kilometers or
93-million miles).
Scientists compared the surface brightness of the disc in the infrared
wavelengths to determine the temperature distribution of the disc and
then infer the corresponding particle size in the disc. Most of the
particles in the disc are only a few microns in size, or 100 times
smaller than a grain of Earth sand.
These fine dust particles originate from collisions of embryonic planets
near the star at a radius of approximately 90 astronomical units, and are
then blown away by Vega's intense radiation. The mass and short lifetime
of these small particles indicate that the disc detected by Spitzer is
the aftermath of a large and relatively recent collision, involving
bodies perhaps as big as the planet Pluto.
The images are 3 arcminutes on each side. North is oriented upward and
east is to the left.
