Cosmic clues.Last January, NASA's long-awaited Stardust star·dust n. 1. A dreamlike, romantic, or uncritical sense of well-being. 2. A cluster of stars too distant to be seen individually, resembling a dimly luminous cloud of dust. Not in scientific use. 3. capsule capsule In botany, a dry fruit that opens when ripe. It splits from top to bottom into separate segments known as valves, as in the iris, or forms pores at the top (e.g., poppy), or splits around the circumference, with the top falling off (e.g., pigweed and plantain). returned to Earth after traveling almost 3 billion miles in space. The spacecraft carried the first dust particles ever collected from a comet. Researchers are now studying the dust to discover what makes up comet Wild 2. This body of ice, rock, dust, and gas circles the sun. The comet is thought to have formed roughly 4.6 billion years ago, when the solar system solar system, the sun and the surrounding planets, natural satellites, dwarf planets, asteroids, meteoroids, and comets that are bound by its gravity. The sun is by far the most massive part of the solar system, containing almost 99.9% of the system's total mass. was just taking shape. "[We hope] to determine if comets Non-periodic comets are seen only once. They are usually on near-parabolic orbits that will not return to the vicinity of the Sun for thousands of years, if ever. Periodic comets usually have elongated elliptical orbits, and usually return to the vicinity of the Sun after a number are composed of materials formed inside the solar nebula--the spinning disk of gas and dust that formed the sun, Earth, and other planets," says Don Brownlee, an astronomer at the University of Washington. |
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