Facts about the Universe
Our sun is one of at least 100 billion stars, just in the Milky Way. Scientists calculate that there are at least 100 billion galaxies in the observable universe, each one brimming with stars. There are more stars than grains of sand on all of Earth’s beaches combined. In 1995, the first planet beyond our solar system was discovered. Now, thousands of planets orbiting sun-like stars, also known as exoplanets, have been found.
The Milky Way is a huge city of stars, so big that even at the speed of light (which is fast!), it would take 100,000 years to travel across it.
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Roughly 70 percent of the universe is made of dark energy. Dark matter makes up about 25 percent. The rest — everything on Earth, everything ever observed with all of our instruments, all normal matter — adds up to less than 5 percent of the universe.
If the sun were as tall as a typical front door, Earth would be the size of a nickel.
The sun accounts for almost all of the mass in our solar system, leaving 0.2 percent for all the planets and everything else.
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Edwin Hubble discovered that the universe is expanding and that at one point in time (14 billion years ago) the universe was all collected in just one point of space
Four American spacecraft are headed out of our solar system to what scientists call interstellar space. Voyager 1 is the farthest out — more than 11 billion miles from our sun. It was the first man-made object to leave our solar system. Voyager 2 is speeding along at more than 39,000 mph, but will take more than 296,000 years to pass Sirius, the brightest star in our night sky.