Bessel discovered Sirius' unseen companion star long before technology allowed us to see Sirius B and even longer before quantum mechanics explained the nature of white dwarfs.

A dusty snowball orbiting the Sun, trailing gas and dust as it melts—a poetic and highly accurate way to describe a comet. Find out how these solar snowballs take their places around the Sun.

Imagine gravity so strong that even light is contained by its force. When a country parson first described black holes in 1783, the concept was so ahead of its time that it was mostly ignored.

A meteorite that escaped from Mars 16 million years ago was found recently in Antarctica. Does it, or doesn't it, hold evidence that proves the existence of life on the red planet?

Update your image of astronomers. Today they spend most of their time peering into computer screens rather than through the eyepiece of a telescope. Learn what this new vantage point has gained them.

At this distance in time and space, can we prove that the universe was created with a single explosion? See how scientists have detected a faint remnant glow that supports the Big Bang theory.

Today, we accept the notion that enormous rocks exist within our solar system and that some of them fall to Earth. A little over 200 years ago, though, this idea garnered skepticism and ridicule.

When a Catholic priest—cosmologist first proposed that the universe began as a "primeval atom," it seemed preposterous. Yet, within a few years, his theory had helped revolutionize cosmology.

What are the stars made of? At 25, Cecilia Payne answered this fundamental question in her Ph.D. thesis. Her pioneering work also made it possible to read a star's surface temperature.

While studying one of Jupiter's moons, Ole Roemer happened upon the first good estimate of the speed of light. Before his 1676 discovery, scientists assumed that light could not be measured.