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Mercury (planet)
Mercury is the innermost and smallest planet in the solar system, orbiting the Sun once every 88 days. It ranges in brightness from about −2.0 to 5.5 in apparent magnitude, but is not easily seen; its greatest angular separation from the Sun (greatest elongation) is only 28.3° (it can only be seen in twilight). Comparatively little is known about the planet: the only spacecraft to approach Mercury was Mariner 10 from 1974 to 1975, which mapped only 40 to 45 percent of the planet's surface.
Physically, Mercury is similar in appearance to the Moon as it is heavily cratered. It has no natural satellites and no substantial atmosphere. The planet has a large iron core which generates a magnetic field about 1 percent as strong as that of the Earth. Surface temperatures on Mercury range from about 90 to 700 K (-180 to 430°C) , with the subsolar point being the hottest and the bottoms of craters near the poles being the coldest.
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April 28, 2026
Apr. 27, 2026 A group of undergraduate students pulled off something remarkable: they built their own dark matter detector and used it to probe one of physics’ biggest mysteries. Working with limited resources but plenty of creativity, they designed a ...
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Latest Headlines
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Apr. 28, 2026 Curiosity has detected a surprising variety of organic molecules on Mars, including compounds tied to the chemistry of life. Some of these molecules may be billions of years old, preserved in ancient ...
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Apr. 25, 2026 In the chaotic first moments after the Big Bang, ripples in spacetime may have done more than just echo through the cosmos—they could have helped create dark matter itself. New research suggests ...
Apr. 24, 2026 Scientists are grappling with a cosmic mystery: why does the Universe behave differently on massive scales compared to our own solar system? While ...
Apr. 24, 2026 A mysterious cosmic explosion has astronomers buzzing, as a strange event may hint at an entirely new kind of stellar cataclysm. After detecting ripples in space-time, scientists spotted a ...
Apr. 22, 2026 Scientists have discovered unexpected water-ice clouds on a distant, Jupiter-like exoplanet, challenging current atmospheric models. By directly imaging Epsilon Indi Ab with the James Webb Space ...
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Apr. 19, 2026 Astronomers have long been puzzled by a cosmic mystery: planets orbiting two stars—like Star Wars’ Tatooine—are surprisingly rare, even though they should be common. New research suggests the ...
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