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Solar System Exploration
Beyond Our Solar System: Overview
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Annotated image of the Milky Way galaxy.
There are billions of stars and countless solar systems in our galaxy.

10 Need-to-Know Things About the Universe:

  1. Edwin Hubble discovered our universe is expanding. About 14 billion years ago, the universe was compressed into a single point in space.
    Link to Voyager 1 interstellar mission.
    Voyager 1: First to Interstellar Space
  2. There are believed to be at least a hundred billion galaxies in the universe. A galaxy is full of stars: Our sun is just one of at least a hundred billion stars in our own Milky Way galaxy, and each of those stars could have their own planetary system.
  3. About 68 percent of the universe is made of dark energy. Dark matter makes up about 27 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.
  4. We now know that our universe has a foamy structure. The galaxies that comprise the observable universe are concentrated in vast sheets and filaments surrounding enormous cosmic voids.
  5. The Milky Way galaxy is in the Local Group, a neighborhood of about 30 galaxies. Our nearest major neighboring galaxy is called Andromeda.
  6. More than 1,000 extrasolar planets (or exoplanets) planets have been confirmed. There are thousands of potential exoplanets await discovery confirmation.
  7. Other planetary systems could have the potential for life, but no signs have yet been found beyond Earth.
  8. Two-thirds of the galaxies within the Universe are similar to the Milky Way galaxy, in that they are spiral-shaped. The remaining third have elliptical shapes, and a few have unusual shapes like toothpicks or rings.
  9. The Hubble Space Telescope observed a tiny patch of sky (one-tenth the diameter of the moon) for 11.6 days and found approximately 10,000 galaxies of all sizes, shapes and colors.
  10. Black holes are not empty spaces in the Universe. A black hole is a great amount of matter packed into a very small area, which results in a gravitational field so strong that nothing -- not even light -- can escape.

Editor's Note: This page provides a brief overview of our Universe. For a comprehensive look at the Universe, visit NASA's Astrophysics Division.

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Homework? We can help. Link to beyond our solar system homework helper.
Just the Facts
Billions and billions: Even though we can't actually count the number of stars in our galaxy, we can estimate the number of stars in the galaxy at roughly 100,000,000,000.

Planet Hunt: Extrasolar planet hunters have found more than 450 planets orbiting more than 380 distant stars.
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Last Updated: 8 Apr 2014