Planetary Systems

Planetary Systems includes topics such as Extrasolar and Solar planets and Planetology. A planetary system consists of the various non-stellar objects orbiting a star such as planets, moons, asteroids, meteoroids, comets, and cosmic dust. The Sun and its planetary system, which includes Earth, is known as the Solar System. Planetary systems are generally believed to form as part of the same process which results in star formation. Accepted theories today argue that a protoplanetary disk forms by gravitational collapse of a molecular cloud and then evolves into a planetary system by collisions and gravitational capture.


  • Let the Planet Hunt Begin Featured News Article Let the Planet Hunt Begin Let the Planet Hunt Begin

    NASA-JPL (May 13, 2009) – NASA's Kepler spacecraft has begun its search for other Earth-like worlds. The mission, which launched from Cape Canaveral, Fla., on March 6, will... More »

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NASA's Kepler Space Telescope Discovers Five Exoplanets Last Updated on 2010-01-05 00:00:00 PASADENA, CA (Jan. 4, 2010) – NASA's Kepler space telescope, designed to find Earth-size planets in the habitable zone of sun-like stars, has discovered its first five new exoplanets, or planets beyond our solar system. Kepler's high sensitivity to both small and large planets enabled the discovery of the exoplanets, named Kepler 4b, 5b, 6b, 7b and 8b. The discoveries were announced Monday, Jan. 4, by members of the Kepler science team during a news briefing at the American Astronomical Society meeting in Washington. "These observations contribute to our understanding of how planetary systems form and evolve from the gas and dust disks that give rise to both the stars and their planets," said William Borucki of NASA's Ames Research Center in Moffett Field, Calif. Borucki is the mission's science principal investigator. "The discoveries also show that our... More »
In All the Universe, Just 10 Percent of Solar Systems Are Like Ours Last Updated on 2010-01-05 00:00:00 WASHINGTON, DC (Jan. 5, 2010) – In their quest to find solar systems analogous to ours, astronomers have determined how common our solar system is. They’ve concluded that about 15 percent of stars in the galaxy host systems of planets like our own, with several gas giant planets in the outer part of the solar system. FIGURE CAPTION – The planets are shown in the correct order of distance from the Sun, the correct relative sizes, and the correct relative orbital distances. The sizes of the bodies are greatly exaggerated relative to the orbital distances. The faint rings of Jupiter, Uranus, and Neptune are not shown. Eris, Haumea, and Makemake do not appear in the illustration owing to their highly tilted orbits. The dwarf planet Ceres is not shown separately; it resides in the asteroid belt between Mars and Jupiter. (Credit: NASA) “Now we know our place in the... More »
Exoplanet: Atmosphere Last Updated on 2009-11-09 00:00:00 An "exoplanet" is an extra-solar planet, that is, a planet orbiting a star other than our own sun. Of the roughly 307 currently known extrasolar planets, about thirty of them transit their star (that is, their orbits take them in front of their star as seen from earth). Because an exoplanet is so faint as compared to its their respective sun, and usually also appear so close to it in the sky, its light is extremely difficult to measure. Astronomers trying to better understand all planets, including the earth, have, however, recently been able to measure useful limits to the reflected light of an exoplanet (see the SAO Science Weekly of 16 July 2008), and thereby to conclude, at least in this case, that its upper atmosphere probably does not contain clouds. SAO astronomer Joe Hora, together with five of his colleagues, has used the Infrared Array Camera (IRAC) on the... More »
Let the Planet Hunt Begin Last Updated on 2009-05-15 00:00:00 NASA-JPL (May 13, 2009) – NASA's Kepler spacecraft has begun its search for other Earth-like worlds. The mission, which launched from Cape Canaveral, Fla., on March 6, will spend the next three-and-a-half years staring at more than 100,000 stars for telltale signs of planets. Kepler has the unique ability to find planets as small as Earth that orbit sun-like stars at distances where temperatures are right for possible lakes and oceans. "Now the fun begins," said William Borucki, Kepler science principal investigator at NASA's Ames Research Center, Moffett Field, Calif. "We are all really excited to start sorting through the data and discovering the planets." Scientists and engineers have spent the last two months checking out and calibrating the Kepler spacecraft. Data have been collected to characterize the imaging performance as well as the noise level in the measurement... More »
Detecting Extrasolar Planets Last Updated on 2008-07-02 00:00:00 The first detection of extrasolar planets was announced in 1995 by two competing groups. One was headed by Geoff Marcy, then at San Francisco State University, the other by Michel Mayor at the Geneva Observatory. The same technique was used by both: measuring the back and forth motion of a star due to the “teeter-totter” like reaction induced by the orbiting of a massive planet. In the case of our own solar system, this motion would be predominantly due to Jupiter. Since the Sun outweighs Jupiter by more than a factor of 1000, the Sun’s back and forth motion is tiny: about the speed of a good runner. It is amazing that this can be precisely measured. To date well over 200 planets have been discovered using this technique, and in a few recent cases, as precision keeps improving, even multiple planets around a star can be extracted from the data. Scale diagram of planet/star ratio... More »