Universe

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Depending on the size of the star before it explodes as a supernova, the core of the star either shrinks back into a tiny neutron star or becomes a black hole. If the star is only a few times bigger than the sun, the core becomes a tiny neutron star. If the star is much bigger than the sun, the chances of it becoming a black hole are much greater.

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  • Who discovered the planet Saturn?

    Q: Who discovered the planet Saturn?

    A: It is impossible to determine who discovered Saturn, as it is one of five planets that are visible without the aid of instruments. Saturn has been widely observed by people for thousands of years, although its unique and complex system of rings are only visible using a telescope.
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  • Why do some stars appear brighter than others?

    Q: Why do some stars appear brighter than others?

    A: The apparent brightness of a star viewed from Earth varies based both on the type of star and its distance from the planet. The apparent magnitude differs from a star's absolute magnitude, which describes its brightness from a set distance, rather than the varying distances of stars seen from Earth. The lower the apparent magnitude, the brighter the star is as seen from Earth.
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  • What are some facts about the Aurora Borealis?

    Q: What are some facts about the Aurora Borealis?

    A: Aurora Borealis occurs when materials from the surface of the Sun collide with the atmosphere of the Earth. Experts make predictions about the occurrence of Aurora Borealis based on events taking place on the Sun and the speed of matter being thrown from the Sun's surface. Aurora Borealis is visible in portions of the Northern Hemisphere, including Canada, Scandinavia, North America, Siberia and Northern Europe.
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  • What is the temperature of a black hole?

    Q: What is the temperature of a black hole?

    A: According to NASA, the temperature of a black hole with the mass of the sun is only one ten-millionth of a degree over absolute zero. Scientists determine this by measuring the temperature of the radiation that comes from a black hole.
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  • Why did people once believe that Earth was the center of the Universe?

    Q: Why did people once believe that Earth was the center of the Universe?

    A: The belief of early astronomers that the Earth was the center of the universe stemmed from limited astronomical tools and geocentric attitudes. The Ptolemaic Model, developed around 100 A.D., presented the Earth-centered solar system in which most early Roman astronomers believed.
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  • Do the planets travel around the sun in a path called an orbit?

    Q: Do the planets travel around the sun in a path called an orbit?

    A: Planets travel around the sun in paths called orbits. Each planet has its own orbit around the sun, and one orbit around the sun is called a year. All planets travel in the same direction around the sun.
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  • How many modern constellations are there?

    Q: How many modern constellations are there?

    A: As of 2014, there are 41 modern constellations, which are constellations added to the catalogue after 1600. Four of them, Carina, Puppis, Pyxis and Vela are derived from Argo, a constellation catalogued by Ptolemy.
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  • What happens after a supernova?

    Q: What happens after a supernova?

    A: Depending on the size of the star before it explodes as a supernova, the core of the star either shrinks back into a tiny neutron star or becomes a black hole. If the star is only a few times bigger than the sun, the core becomes a tiny neutron star. If the star is much bigger than the sun, the chances of it becoming a black hole are much greater.
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  • Q: What makes up the universe?

    A: The universe is made up of ordinary matter, dark matter and dark energy. Only 4.6 percent of the universe is made from ordinary atoms, the other 95.4 percent is composed of matter that humans cannot see.
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  • Q: How far is the edge of space from Earth?

    A: The edge of space is generally recognized internationally to be at the Kármán Line, which is 62 miles from the surface of Earth. While the exact boundary of space is open to interpretation, this is the definition recognized by the Federation Aeronautique Internationale and National Aeronautics and Space Administration.
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  • Q: What are some world facts?

    A: Observed from space, the United States is the brightest country on the brightest planet in the Solar System because Earth's water makes it the brightest planet and the United States is abundant in artificial lighting, especially at night. Russia is the largest country in the world, Vatican City is the smallest country, and 39 million Vatican Cities could fit inside Russia. In 2011, the global population topped 7 billion people and is expected to reach 10.5 billion by 2050.
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  • Q: What is Ptolemy's universe theory?

    A: Greek philosopher Claudius Ptolemy believed that the sun, planets and stars all revolved around the Earth. This belief gave way to the ancient Greek theory of a geocentric or Ptolemaic model of the universe. "Geocentric" refers to the belief that the Earth is the center of the universe.
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  • How many solar systems are there in the universe?

    Q: How many solar systems are there in the universe?

    A: There are billions of stars, and no one knows how many solar systems there are. The Earth's galaxy, the Milky Way, is so large that it would take an object 100,000 years to cross it traveling at the speed of light.
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  • Q: Why is outer space dark?

    A: Outer space appears dark at night for multiple reasons, the most simple being that the nearest light source, the sun, is blocked by the earth, creating darkness. Outside Earth's atmosphere, outer space appears dark instead of blue because the sun's light is not refracted by atmospheric gases.
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  • Q: Did the idea of a heliocentric view of the solar system originate with Copernicus?

    A: The ancient Greek astronomer and mathematician known as Aristarchus of Samos was the first person to propose a heliocentric view of the solar system. He lived circa 310 B.C. to 230 B.C. and stated that the Earth, like other planets, orbited the sun, which he regarded as the universe's center.
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  • Q: How far does space go?

    A: From Earth's surface, outer space begins at the somewhat-arbitrary Karman Line, or 100 km up, according to the Space website. From there, the observable universe stretches out without reaching any perceptible boundary.
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  • What does NASA say about galactic alignment?

    Q: What does NASA say about galactic alignment?

    A: According to NASA, the sun aligns with the center of the Milky Way galaxy as compared to the Earth every December when the sun enters Sagittarius. Doomsday predictions about the winter solstice of December 2012 revolved around the alignment of the sun, Earth and the galactic center. The sun and moon tug on the planet more than the galactic center, so galactic alignment does not alter the Earth whatsoever.
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  • Q: Where is Nibiru located?

    A: No one is sure of the location of Nibiru or whether it actually exists. Nibiru has never been seen, and there is no scientific or astronomical evidence of its existence as of 2015. Sometimes referred to as Planet X, Nibiru is an alleged planetary mass beyond Neptune.
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  • Q: How does gravity hold the universe together?

    A: Gravity holds the universe together by keeping the large bodies that make up the universe together. It keeps the Earth in orbit around the sun, the sun in orbit around the center of the Milky Way and the Milky Way bound to other nearby galaxies known as the Local Group.
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  • Q: What percentage of the universe have scientists been able to map?

    A: Scientists estimate that they have mapped 0.42 percent of the observable night time sky as of 2015, but they have no way of determining what percentage of the entire universe the observable portion comprises. They hope to map 12.5 percent of the observable portion by 2018.
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  • Q: Does the universe end?

    A: Scientists believe the Universe is infinitely large and does not end. However, only part of the Universe is visible from Earth. The Observable Universe is a sphere around the Earth, and anything beyond this sphere cannot be observed from Earth because of continuing expansion over a long period of time.
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