What are these two bands in the sky?
The more commonly seen band is on the left and is the central band of our
Milky Way galaxy.
Our
Sun orbits in the disk of
this spiral galaxy
so that from inside, it
appears as a band
of comparable brightness all the way
around the sky.
The less commonly seen band, on the right, is
zodiacal light -- sunlight reflected from dust
orbiting the Sun in our
Solar System.
Zodiacal light is
brightest near the Sun and so is best
seen just before sunrise or just after sunset.
On some evenings, this ribbon of zodiacal light can
appear quite prominent.
It was
discovered only in this century
that zodiacal dust was mostly expelled by comets that have passed
near Jupiter.
The
featured image was captured about a year ago from the
Atacama Desert in
Chile.