Galaxies Fade
On the human time scale, the Milky Way galaxy is eternal. The starry Milky Way shined down on the first […]
The Local Group
These galaxies move through space as a single unit, bound together by their mutual gravitational pull. The number of galaxies
The Milky Way
In summer, in a clear place with dark night skies, an irregular glowing band arcs high overhead. The ancients likened
Galaxy Formation
Observations by Hubble Space Telescope and ground-based instruments show that the first galaxies took shape as little as one billion
Types of Galaxies
The most beautiful galaxies are called spirals. The Milky Way is a spiral, and so is the Andromeda galaxy (M31).
Galaxies: Cities of Stars
Astronomer Edwin Hubble was studying an object in the autumn constellation Andromeda known as the Andromeda Nebula. Viewed through a
Finding Earth-Like Planets
How do astronomers find planets outside our solar system? The most successful search method used to date is called the
Signs of Life
The discovery of many giant planets orbiting other stars shows us that planets — at least Jupiter-like planets — probably
Exoplanets
Are we alone in the universe? This question has captured the imaginations of scientists, theologians, and philosophers for millennia. And
Black Holes
If the Sun were compressed to a diameter of just four miles (6 km), its escape velocity would equal the