Structure of the universe




When you look up at the night sky, much of what you see is pretty ancient "stuff." Although objects look very close together, they're actually vast distances apart! Here we see galaxies, stars and star groupings, and nebulae. But many more objects exist in our universe, such as planets, satellites, comets, gravitational fields, and forms of radiation.




MilKy Way Because Earth lies inside the spiral arms of the Milky Way, the few hundred billion stars of our home galaxy appear as a bright band of stars across the
night sky. Dark splotches among the stars are massive globs of interstellar dust and gas that block the light from stars behind them. The nearest star to us in the Milky Way is the Sun, a medium-size star.



Pleiades Star Cluster Glittering like jewels in the night sky, the Pleiades (PLEE-uh-deez) is a cluster of new stars over 400 light-years from Earth. Though only a few are visible to us, the cluster contains hundreds of stars. The bluish glow that seems to surround the stars is a cloud of interstellar gas and dust, which scatters blue light from the stars. Different people have called the cluster "Seven Sisters," "Bunch of Grapes," and "Sailing Stars."




Eta Carinae When supermassive star Eta Carinae (ay-tuh cuh-REE-nay) exploded about 150 years ago, it became the brightest object in the sky. Eta Carinae released as much light as a supernova, but it managed to survive as a star. Today the debris stretches over a distance equivalent to the diameter of our solar system. Its outer edges are moving away from the center at about 1.5 million miles per hour.