Part of Hall of the Universe.

Stars AMNH/D. Finnin

The human eye can see about 6,000 stars in the night sky. Photographs reveal millions more in every direction. All of these stars reside in our Milky Way galaxy. But they are just a tiny fraction of the several hundred billion stars in our galaxy alone. Counting all the stars in all the galaxies, there are perhaps a hundred billion billion stars in the observable universe.

In This Section

Exhibit What is a Star? An ordinary star is a massive sphere of luminous gas, mainly hydrogen and helium. Exhibit Starlight The stars are so far away that, even with the best telescopes, they generally appear as just points of light. Exhibit Lives of Stars Stars are born, live out their lives, and die. Their appearance changes dramatically along the way. Exhibit Low-Mass Stars Low-mass stars are the longest lived of the energy-producing objects in the universe. Exhibit Intermediate-Mass Stars Stars of intermediate mass have lifetimes that range between 50 million and 20 billion years. Exhibit High-Mass Stars High-mass stars are very luminous and short lived. Exhibit Very High-Mass Stars In any batch of newly formed stars, the most massive ones are the rarest and shortest lived. Exhibit Organizing the Stars Astronomers sort stars by placing them on a diagram according to their luminosity and surface temperature. Exhibit Recycling the Stars The material of stars is recycled over billions of years. Exhibit Stellar Communities Telescopes reveal that about half the stars we see are actually double or multiple star systems. Exhibit Formation and Evolution of Stars The stars in the sky seem permanent and unchanging because it takes millions of billions of years for their lives to unfold. Exhibit A Spectacular Stellar Finale A supernova is the explosion of an entire star. Exhibit Our Star-The Sun Our Sun is an ordinary star, just one among hundreds of billions of stars in the Milky Way Galaxy.