From Infogalactic: the planetary knowledge core
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The Space Portal
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Space (or outer space) describes the vast empty regions between and around planets and stars. The study of these, and other, astronomical objects is called astronomy, one of the oldest sciences. It is often said that space exploration began with the launch of Sputnik 1, the first man-made object to orbit the Earth. Then, in an almost unbelievable feat of human achievement, in 1969 Neil Armstrong and Buzz Aldrin travelled to the Moon and set foot on the surface during the Apollo 11 mission. Recently, it has become clear that the possibility of space colonization may no longer be exclusively reserved for science-fiction stories, and many controversial issues surrounding space have come to light, including commercial spaceflight, space laws and space weapons.
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 Mercury is the innermost planet in the Solar System. It is also the smallest, and its orbit is the most eccentric (that is, the least perfectly circular) of the eight planets. It orbits the Sun once in about 88 Earth days, completing three rotations about its axis for every two orbits. The planet is named after the Roman god Mercury, the messenger to the gods. Mercury's surface is heavily cratered and similar in appearance to Earth's Moon, indicating that it has been geologically inactive for billions of years. Due to its near lack of an atmosphere to retain heat, Mercury's surface experiences the steepest temperature gradient of all the planets, ranging from a very cold 100 K at night to a very hot 700 K during the day. Mercury's axis has the smallest tilt of any of the Solar System's planets, meaning that there are no seasons on its surface. Mercury and Venus can each make appearances in Earth's sky both as a morning star and an evening star (because they are closer to the Sun than the Earth), and at times Mercury can technically be regarded as a very bright object when viewed from Earth; however, its proximity in the sky to the Sun makes it more difficult to see than Venus.
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A TRACE image of sunspots on the surface, or photosphere, of the sun from September 2002, is taken in the far ultraviolet on a relatively quiet day for solar activity. However, the image still shows a large sunspot group visible as a bright area near the horizon. Although sunspots are relatively cool regions on the surface of the sun, the bright glowing gas flowing around the sunspots have a temperature of over one million °C (1.8 million °F). The high temperatures are thought to be related to the rapidly changing magnetic field loops that channel solar plasma.
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