Figure 1: Band of Light Comparison
This artist's concept illustrates what the night sky might look like from
a hypothetical alien planet in a star system with an asteroid belt 25
times as massive as the one in our own solar system (alien system above,
ours below; see Figure 1).
NASA's Spitzer Space Telescope found evidence for such a belt around the
nearby star called HD 69830, when its infrared eyes spotted dust,
presumably from asteroids banging together. The telescope did not find
any evidence for a planet in the system, but astronomers speculate one or
more may be present.
The movie begins at dusk on the imaginary world, when HD 69830, like our
Sun, has begun to set over the horizon. Time is sped up to show the onset
of night and the appearance of a brilliant band of light. This light comes from
dust in a massive asteroid belt, which scatters sunlight.
In our solar system, anybody observing the skies on a moonless night far
from city lights can see the sunlight that is scattered by dust in our
asteroid belt. Called zodiacal light and sometimes the "false dawn," this
light appears as a dim band stretching up from the horizon when the Sun is
about to rise or set. The light is faint enough that the disk of our Milky
Way galaxy remains the most prominent feature in the sky. (The Milky Way
disk is shown perpendicular to the zodiacal light in both pictures.)
In contrast, the zodiacal light in the HD 69830 system would be 1,000
times brighter than our own, outshining even the Milky Way.
