Universe

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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  • 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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  • 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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  • 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 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 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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  • 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 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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  • Q: Is the Universe Flat?

    A: As of 2014, the universe is believed to be flat, according to the inflationary theory. This theory has to do with the density of the universe and suggests that the universe must be flat as piece of paper.
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  • Q: What Are Edgar Cayce's Thoughts on Black Holes?

    A: The writings and revelations of Edgar Cayce may be mute on the topic of black holes specifically, but he does refer to what he terms "the outer darkness," a region devoid of light, love and life that some may encounter at the time of death. Cayce's description of the outer darkness, denser in its center than at its outer edges, resemble some characteristics of the present-day understanding of black holes.
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  • Q: What Are the Types of Black Holes?

    A: The universe contains three different categories of black holes: stellar, supermassive and miniature, which are further divided according to whether they are spinning. Non-spinning black holes are always spherical, while spinning black holes tend to be more oblate. The degree of equatorial bulge is determined only by the rotational velocity of the object.
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  • Q: What Is the Ultimate Fate of an Open Universe?

    A: Although the ultimate fate of the universe is a largely debated topic, according to the University of Tennessee, in an open universe the universe will continue to expand forever. This is due to insufficient mass to cause the expansion to stop.
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  • Q: What Are Some Facts About the Planet Sedna?

    A: Sedna is not a planet. It is more likely to be a dwarf planet that orbits very far away from the sun. Some astronomers, however, are reluctant to place it in that category because it is so far away that observing it is difficult.
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  • Science Lesson: How Old Is the Universe?

    Q: Science Lesson: How Old Is the Universe?

    A: The universe's exact age is unknown; researchers estimate that the universe is around 13.8 billion years old. Astronomers have two methods of determining the universe's age, according to the National Aeronautics and Space Administration (NASA).
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  • Q: How Big Is the Universe?

    A: As of 2013, the National Aeronautics and Space Administration determined, with a margin of error of only 0.4 percent, that the universe is infinite in size. The observable universe extends 92 billion light years in diameter. The exact size of the universe, or if there are multiples, is unknown.
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  • How Many Solar Systems Are There?

    Q: How Many Solar Systems Are There?

    A: The exact number of solar systems is not known. According to NASA, there are more than 100 billion galaxies within the universe. One of these galaxies is the Milky Way galaxy, where our solar system is located.
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  • Q: How Big Is Space?

    A: As far as humans can tell, space is infinite; it has no end or borders. Scientists believe that space will always seem infinite to humans for two reasons. First, our investigation of space has never found an edge (or any indications of an edge). Second, measurements show that space is expanding faster and faster, which pushes the edges of the universe ? if there are any ? ever farther out.
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  • Q: How Do Black Holes Form?

    A: Universe Today explains that black holes are the result of objects collapsing under the force of gravity until the acceleration needed to escape from them exceeds the speed of light. Any object can, in principle, become a black hole if it collapses to sufficient density. They can also be formed from two neutron stars colliding together. According to Universe Today, there are supermassive black holes in every galaxy.
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  • Q: Who Discovered the First Black Hole?

    A: In science, if something isn't directly observable it can't be "discovered." There is only indirect evidence of black holes. The existence of black holes has been a topic of speculation for hundreds of years, but John Wheeler is credited with coining the term, "black hole," in 1969.
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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: How Did the Milky Way Get Its Name?

    A: The Milky Way's name stems from the Greeks, who referred to the galaxy as galaxias kyklos, or milky circle. The Romans, who called it via lactea, or "the road of milk," altered the term from its original Greek origins.
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