Astronomy

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Mercury, Venus, Mars, Jupiter and Saturn are the five planets that are visible without a telescope. These five planets were known to ancient astronomers long before the invention of telescopes. Some experts also include the Earth on the list of planets you can see with the naked eye.

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  • Why do stars pulsate?

    Q: Why do stars pulsate?

    A: Stars appear to pulsate and twinkle in the night sky due to the refraction of light through the Earth's atmosphere. When the light from a star enters the atmosphere, air molecules bounce and deflect the light rays, slightly altering the apparent position and intensity of the star.
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  • Are stars bigger than the sun?

    Q: Are stars bigger than the sun?

    A: Stars exist that are both bigger and smaller than the sun. The sun has a radius of 1.4 million kilometers and, relative to other stars, is an average size.
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  • What causes a lunar eclipse?

    Q: What causes a lunar eclipse?

    A: Lunar eclipses are caused when the moon travels through the Earth’s shadow. Complete lunar eclipses are rare, but partial lunar eclipses may occur up to four times per year.
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  • What is the sky made of?

    Q: What is the sky made of?

    A: Four layers of the earth's atmosphere containing various gases make up the composition of the sky. The layers of the atmosphere are divided into the troposphere, the stratosphere, the mesosphere and the thermosphere. The atmosphere's divisions occur according to temperature fluctuations.
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  • What is the purpose of the Hubble space telescope?

    Q: What is the purpose of the Hubble space telescope?

    A: The Hubble Space Telescope was created to capture detailed images or objects that are too far away to be viewed with conventional telescopes. The Hubble's instruments create images that are far superior to those of terrestrial observatories, which suffer from the effects of atmospheric distortion.
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  • What causes the Cassini division in Saturn's rings?

    Q: What causes the Cassini division in Saturn's rings?

    A: The Cassini Division, a gap in the rings of Saturn, is caused by gravitational pull from Saturn’s moon Mimas. The moon’s gravity affects the tiny particles that make up the rings, creating what looks like empty space. Other divisions in Saturn’s rings are the result of similar interactions with the planet’s moons.
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  • How did the constellation Orion get its name?

    Q: How did the constellation Orion get its name?

    A: Stargazers in ancient Greece observed the "pictures" formed by stars and named the Orion constellation after a mythological hunter. Many origin stories exist, but one popular version recounts Orion's quest to defeat a giant scorpion sent by Gaia, the goddess of Earth, according to the Windows to the Universe.
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  • What is the primary purpose of an astronomical telescope?

    Q: What is the primary purpose of an astronomical telescope?

    A: The astronomical telescope is a central apparatus used to study distant planets, stars and moons from the Earth. Astronomer Galileo Galilei famously used the earliest telescopes in 1610 to prove the heliocentric solar system theory put forth by Nicolaus Copernicus in the early 16th century.
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  • How many satellites does Jupiter have?

    Q: How many satellites does Jupiter have?

    A: In 2011, most experts came to agree that Jupiter has a total of 67 satellites. Its four largest moons are known as the Galilean satellites: Europa, lo, Callisto and Ganymede. Around 50 of its satellites are less than 6.2 miles in diameter.
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  • Who named the Milky Way?

    Q: Who named the Milky Way?

    A: Early Greek astronomers named the galaxy "Via Lactea" in reference to the pale band of light formed by stars along the galactic plane. The origin of the name, which translates as "Road of Milk," has been lost to time.
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  • What is the weather like on Uranus?

    Q: What is the weather like on Uranus?

    A: With an atmospheric temperature of -224 degrees Celsius and a surface temperature of -197 degrees Celsius, Uranus is a very cold planet with strong winds. It is the coldest planet in the solar system.
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  • How did the solar system form?

    Q: How did the solar system form?

    A: The formation of the solar system began with the creation of the sun after an exploding supernova caused spherical accumulation of dust particles and gas in a huge swirling cloud called nebula. Planets and other components of the solar system formed in the flat plane of the rotating disc of dust.
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  • What color is the Milky Way?

    Q: What color is the Milky Way?

    A: In 2012, a team of astronomers from the University of Pittsburgh announced that the Milky Way galaxy is aptly named thanks to its pure, milky white color, which the scientists described as resembling a fresh snowfall. The fact that Earth is located within the Milky Way galaxy has made the process of measuring the galaxy's color difficult; obstructions from things like dust and gas within the galaxy had previously made it hard for scientists to get a broad enough view of the Milky Way in order to determine its color.
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  • How many times bigger is the sun than the earth?

    Q: How many times bigger is the sun than the earth?

    A: According to NASA, the sun’s diameter is approximately 100 times larger than the diameter of the earth. The earth would have to be lined up 100 times in order to stretch across the face of the sun.
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  • What is the bright object in the western sky?

    Q: What is the bright object in the western sky?

    A: The planet Venus is the brightest object in the western sky. At its brightest, Venus is almost 10 times brighter than Jupiter, the sky's second brightest object.
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  • What are heavenly bodies in space?

    Q: What are heavenly bodies in space?

    A: Natural objects found outside of the Earth's atmosphere, such as planets, stars, moons, comets, meteors and asteroids, are some of the heavenly bodies in space. It is believed that there are other forms of heavenly bodies or objects in space that are yet to be discovered and explored.
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  • How do space craters get their names?

    Q: How do space craters get their names?

    A: The International Astronomical Union (IAU), an organization of astronomers, names the craters on planets and moons in the solar system by giving each planet a creative theme. For example, the moon’s craters are usually named for deceased explorers, scientists and scholars, while large craters on Venus are named for famous women in various professional fields.
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  • What happens to stars as they age?

    Q: What happens to stars as they age?

    A: Stars on the main sequence that are the same size as the Sun begin as yellow stars and turn into red giants as their hydrogen fuel runs out. Other stars shrink or explode, depending on their size.
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  • Did Sir Isaac Newton have any children?

    Q: Did Sir Isaac Newton have any children?

    A: Sir Isaac Newton never married and did not have any children. According to Biography.com, the English mathematician and physicist, who was known for his law of gravitation, died on March 31, 1727, at the age of 85.
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  • What is a burnt-out star called?

    Q: What is a burnt-out star called?

    A: A burnt-out star is called a white dwarf. A white dwarf results after a star’s nuclear fuel burns out, which causes it to collapse or implode. While it has a mass similar to that of the sun, its radius is similar to that of the Earth.
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  • Why are summer days long and winter days short?

    Q: Why are summer days long and winter days short?

    A: The Earth's tilt on its axis is what causes the change in the seasons and explains why summer days are longer than winter days. The Earth orbits in an ellipse around the Sun, and because of this, it draws closer to the Sun at some points than at others. It is the direction of the Earth's tilt in its axis that determines the length of days and nights.
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