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The Planet Uranus
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Our Solar System
The Planet Mercury
The planet Mercury is the smallest planet in our solar system, and the one that is closest to the sun. This proximity to the sun has made it difficult to study the planet. The closest look that we have ever had was in 1974 and 1975 when the unmanned Mariner 10 was sent to map the surface of Mercury. Only about 40% to 45% of the surface was actually mapped.
Mercury resembles our moon in appearance as it is heavily cratered. There is an atmosphere of sorts on Mercury but not one that would sustain life as we know it. The atmosphere is very unstable and is made up of hydrogen, helium, oxygen, sodium, calcium and potassium.
Records of studies made of Mercury date back to 300 BC. The name "Mercury" was given to the planet by the Romans after the god Mercurius. Chinese, Korean, Japanese, and Vietnamese cultures refer to Mercury as the water star based on the Five Elements. Other cultures have called the planet by other names. The Babylonians, for example, called the planet Nabu or Nebu after the messenger to the Gods in their mythology.
The temperature on Mercury varies. The average temperature is 179° C, but the extremes are a low of -183 °C to a high of 427° C. Sunlight on Mercury is six and a half times stronger than it is on Earth.
There is evidence that water does exist on Mercury despite the extreme temperature variations. The bottoms of some of the deepest craters near the poles are never exposed to direct sunlight. Temperatures in these areas remain far lower than the global average, so it is possible for ice to exist. |
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The Planet Saturn
Our Sun's Twin
Jorge Melendez of the Australian National University, and Ivan Ramirez of the University of Texas at Austin, are both astronomers from Peru. Using the Harlan J. Smith Telescope at McDonald Observatory located atop Mount Locke and Mount Fowlkes in the Davis Mountains of West Texas, they discovered the best candidate as a twin to our sun that has been found to date in November 2007. The findings by Melendez and Ramirez suggest that our sun's chemical composition is not unique, as some previously thought.
The star found by the Peruvian astronomers is in the constellation Draco, which is over 200 light years away from our solar system. HIP 56948, the star in question is more like our sun than any yet seen. The star may be a billion years older than the sun.
There have been three other possible twins to our sun located, but there is a major difference in the amount of lithium they contained. These stars -- 18 Scorpius, HD 98618, and HIP 100963 -- have all been contenders, but they all contain several times more lithium than our sun. This difference has led astronomers to believe that our sun was possibly unique because of its low amount of lithium. Now, it seems, maybe our sun is not so unique after all.
The search for solar twins to our sun is important because astronomers use our sun as a baseline for a variety of astronomical studies, and studying our own sun is very difficult because it is too close and too bright.
The discovery of HIP 56948 by Melendez and Ramirez lays to rest the belief that our sun is somehow completely unique and that the uniqueness is what allowed life to spring up and thrive and raises the possibility (no, probability) that life exists in other places in the universe. Maybe we aren't alone.
Related Topics: Our Sun's Twin,
The Planet Neptune, Deep Sky Objects
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