Tiny Particles, So Far Away
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 disk 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 (on the left in blue) and 70 microns (on the right in red).
Both images show a very large, circular and smooth debris disk. The disk 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 disk in the infrared wavelengths to determine the temperature distribution of the disk and then refer the corresponding particle size in the disk. Most of the particles in the disk 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 disk 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.