Galaxies shaped round, like a ball, or oval, like an egg and vary greatly in size. Contain billions of stars, but have little gas and dust between the stars, so stars or no longer forming. Only old stars.
Galaxies with a bulge in the middle and arms spiraling outward, like a pinwheel. Spiral arms contain many bright, young stars as well as gas and dust. Very few stars are forming in the bulge.
Galaxies with no regular shape. Typically smaller than other galaxies.Generally, have many bright, young stars and lots of gas and dust to form new stars.
eclipsing binary star
A binary star system in which one star periodically blocks the light from the other star,at regular intervals.
A huge group of single stars, star systems, star clusters, dust and gas bound together by gravity.
A mysterious force that appears to be causing the expansion of the universe to accelerate.
Matter that does not give off electromagnetic radiation, but is quite abundant in the universe (up to 90% of matter).
A distant star that moves back an forth may indicate what?
That a planet or secondary star may exist near the star, even though we can't see it.
How did our solar system first begin to form?
Five billion years ago a huge cloud of dust and gas called the solar nebula collapsed.