Planets

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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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  • How did Neptune get its name?

    Q: How did Neptune get its name?

    A: Neptune was given its name by its discoverer, Urbain Le Verrier. Honoring the tradition of naming planets after Roman gods, Le Verrier chose Neptune, who was the Roman sea god. He chose this name because of the blue colors that dominate the planet.
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  • What are the names of Mercury's moons?

    Q: What are the names of Mercury's moons?

    A: There are no names for Mercury's moons because the planet does not have any moons. The only other planet that has no moons is Venus.
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  • Could people live on Saturn?

    Q: Could people live on Saturn?

    A: Saturn would provide a hostile environment for most of the life found on Earth, according to Fraser Cain of Universe Today. It could not be inhabited by humans without extensive protection.
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  • Does Mars have clouds?

    Q: Does Mars have clouds?

    A: Mars indeed does have water ice clouds, similar to Earth's cirrus clouds, both high in the atmosphere and often forming as icy fog just above the ground surface. The Viking orbiter was able to capture sunrise pictures during which an icy fog was rising from within Martian craters.
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  • What is the atmosphere like on Mars?

    Q: What is the atmosphere like on Mars?

    A: According to Space.com, the atmosphere on Mars is around 100 times thinner compared to that of the Earth's and is composed of about 95 percent carbon dioxide. However, the Martian atmosphere is still thick enough to sustain weather, winds and clouds.
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  • What are some cool facts about Mars?

    Q: What are some cool facts about Mars?

    A: Mars, the fourth planet from the sun, has interested people for thousands of years, according to BBC News. However, whereas the people of ancient Greece and Rome found Mars fascinating for its red color, people today are more interested in finding water on the planet.
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  • Can Mars sustain life?

    Q: Can Mars sustain life?

    A: According to NASA, 7 billion years ago, Mars may have been an excellent place for microbes to live, but currently it cannot support life because the air is too thin and is comprised mainly of carbon dioxide. After drilling into the rocks on Mars, scientists discovered the key ingredients of life, including sulfur, nitrogen, hydrogen, oxygen and carbon.
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  • What is the composition of Mars' atmosphere?

    Q: What is the composition of Mars' atmosphere?

    A: The composition of Mars' atmosphere is 95.32 percent carbon dioxide, 2.7 percent nitrogen, 1.6 percent oxygen and 0.08 percent carbon monoxide. The remaining 0.3 percent is made up of various trace elements.
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  • Why is Earth important?

    Q: Why is Earth important?

    A: As the only known planet that is habitable for human beings, the Earth’s importance is self-evident. Every living organism known to science obtains all of its resources from Earth, and has very few other options available. Without the Earth, humans would be doomed to extinction, unless they were able to adapt to another planet's conditions before the Earth disappeared.
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  • How many light years away is Mars?

    Q: How many light years away is Mars?

    A: Mars is considerably less than 1 light-year away from Earth. According to Cornell University, Mars orbits the Sun at an average distance of 1.5 times the Earth's mean orbital distance. At the two planets' closest approach, the distance between them shrinks to 0.5 astral units, which equals 75 million kilometers.
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  • Where is Mars located?

    Q: Where is Mars located?

    A: Mars is the fourth planet from the sun. Its average distance from the sun is 141,633,120 miles, approximately 1.5 times that of Earth.
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  • How long does it take the earth to rotate on its axis?

    Q: How long does it take the earth to rotate on its axis?

    A: A complete rotation of the earth on its axis takes approximately 23 hours, 56 minutes and four seconds with respect to the background stars. However, the sun returns to the same place in the sky (correcting for seasonal differences) every 24 hours. The reason for this difference is that the journey of the sun back to the same spot is a solar day, while the period of rotation is known as the sidereal day.
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  • How long does it take Saturn to rotate on its axis?

    Q: How long does it take Saturn to rotate on its axis?

    A: Historically, scientists believed that it takes Saturn 10.656 hours to rotate on its axis or about 10 hours and 39 minutes. More recently, astronomers received satellite messages indicating that the length of Saturn's day is closer to 10 hours and 45 minutes.
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  • What planet in our solar system is closest in size to Earth?

    Q: What planet in our solar system is closest in size to Earth?

    A: Venus is, by far, the closest match to the Earth in size. Venus has a measured diameter that is just about 95 percent that of the Earth and a planetary mass equal to 81.5 percent of the Earth's.
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  • How many satellites does Mercury have?

    Q: How many satellites does Mercury have?

    A: The planet Mercury does not have any known moons (natural satellites) as of 2014. There has been one known artificial satellite orbiting Mercury, known as Messenger.
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  • How many satellites does Mars have?

    Q: How many satellites does Mars have?

    A: Mars has two very small satellites orbiting it, Phobos and Deimos. Scientists believe that both moons are actually asteroids captured via Mars's gravitational field. Made of dark rock that includes a great deal of carbon, both satellites have many craters due to collisions with debris.
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  • What is the Earth's motion that causes day and night?

    Q: What is the Earth's motion that causes day and night?

    A: The spinning and rotating movement of the earth along its vertical axis causes the difference between day and night. The differences between light and darkness on the earth's surface are caused primarily by the earth’s rotation along a vertical axis. This constant spinning motion accounts for hourly changes in light and produces long-term changes in daylight hours through the seasons.
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  • How much would a 100-pound person weigh on Saturn?

    Q: How much would a 100-pound person weigh on Saturn?

    A: A person weighing 100 pounds on Earth would weigh 107 pounds near the poles of Saturn and 91 pounds near Saturn's equator. This difference is due to centrifugal force offsetting some of the pull of gravity along the equator as the planet spins on its axis.
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  • What is the difference between a moon and a planet?

    Q: What is the difference between a moon and a planet?

    A: NASA states that for an astronomical body to be considered a moon, that object must orbit a planet. For a planet to be classified as such, it must meet certain strict criteria set by the International Astronomical Union.
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  • What probes have been sent to Saturn?

    Q: What probes have been sent to Saturn?

    A: As of June 2014, there have been a total of four probes to visit the planet Saturn. Since the Pioneer 11 spacecraft first visited Saturn in 1979, much has been learned about the ringed planet.
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  • How many Earths can fit into Jupiter?

    Q: How many Earths can fit into Jupiter?

    A: According to NASA, about 1000 Earths can fit inside Jupiter. The massive fifth planet is large enough to hold all the planets in the solar system easily.
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