Astrophotography from Boulder, Colorado
The universe is mostly empty space, populated by scattered galaxies. The galaxies presented here range from 2 to 500 million light years distant.
Nebulae are clouds of gas - mainly hydrogen, with traces of common elements such as oxygen, sulfur and nitrogen. They are the birthplace of future generations of stars.
Most stars are members of a cluster for at least part of their lives. Clusters vary from sparse young open clusters to dense ancient globular clusters.
The solar system includes planets, moons, comets, and the Sun itself.