ASTRONOMY TERMS

Astronomy terms are used to describe the various phenomena in space. In this section you can learn what every astronomy term means and how it helps us to better understand the cosmos.
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Millennium

Millennium, in a common Christian belief, the period of 1,000 years before the Last Judgment, during which time Christ and the saints will reign on earth.

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  • What existed before the big bang?

    What existed before the big bang?

    So much of our cosmological history starts with the much-discussed big bang, but what led up to that cataclysmic moment? And did time even exist back then? See more »

  • What if we were next to a black hole?

    What if we were next to a black hole?

    When a star dies, it becomes a black hole. Once something passes through the it's gone for good, never to be seen or heard from again. If we lived next to a black hole, would it suck us in too? See more »

  • Aurora Borealis

    Aurora Borealis

    Aurora Borealis, or Northern Lights, a glow in the night sky in the regions near the north magnetic pole. See more »

  • Corona Info

    Corona Info

    Corona, the outer portion of the sun's atmosphere. Normally, the corona is visible only during a total solar eclipse, when it appears as an irregular whitish halo around the darkened sphere of the sun. See more »

  • Horizon

    Horizon

    The horizon is the visible boundary between earth and sky. Learn more about how the horizon works. See more »

  • How does gravity assist with interplanetary satellites?

    How does gravity assist with interplanetary satellites?

    When satellites go off to places like Jupiter or Saturn (or even out of the solar system), they follow crazy orbits. They will often loop around a planet to get a "gravity assist" or "gravity boost." How does that work? I know the Galileo probe looped around Earth twice to get a boost, and the Pioneer and Voyager probes used Jupiter. See more »

  • How many teaspoons are there in a cubic light year?

    How many teaspoons are there in a cubic light year?

    Have you ever really thought about the scale of the universe? A good starting point is the teaspoon. See more »

  • If you were to move all of the matter in the universe into one corner, how much space would it take up?

    If you were to move all of the matter in the universe into one corner, how much space would it take up?

    If you took all of the matter in the universe and you pushed it all into one corner, how much space would it take up? I am trying to understand how much of the universe is 'empty.' See more »

  • Pulsar

    Pulsar

    Pulsar, a celestial body that emits radio signals in short, very evenly spaced bursts, or pulses. See more »

  • What is a light year?

    What is a light year?

    A light year is a way of measuring distance. That doesn't make much sense because "light year" contains the word "year," which is normally a unit of time. Even so, light years measure distance. See more »

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