Astronomy Picture of the Day

Explanation: 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 seem 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.