The number of confirmed extra-solar planets (or exoplanets) is approaching 1000, with examples having masses and orbital characteristics far beyond the range present in the solar system. Most of the planets detected so far are gas giant planets like Jupiter or Neptune, but this is due to an observational bias, as these large planets are easier to detect. Technological advances are pushing inexorably towards the detection of Earth-like planets around Sun-like stars. As of December 2011, NASA’s Kepler mission has discovered several Earth-like planets: two planets Kepler 22-e and Kepler 22-f are the smallest exoplanets known so far, although too close to their star to be in its habitable zone, and Kepler 22-b which is about 2.4 times the size of the Earth and located in the habitable zone. The discovery of planets outside our solar system brings an opportunity to learn about the formation and evolution of planets in general, and improves our understanding of the planets in our own solar system by putting them into a larger context. More information about Exoplanets research @ UCLA
Giant planets Jupiter, Saturn, Uranus and Neptune probably formed by nucleated instability (like raindrops around a condensation nucleus), in the earliest stages of the solar system formation. However, their formation process in not certain and many details remain unclear. They contain most of the mass in the solar system outside the sun, and their gravity determines the dynamics of interplanetary bodies, and may have set the architecture of the planetary orbits in an earlier, chaotic epoch.
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Ongoing laboratory research programs include the study of mineral physics and the response of planetary materials to high pressures; high resolution geochronology with applications to the origin of planetary crust, magma chamber development, cosmochemistry and more; studies of isotopic fractionation of matter incorporated into the nascent protoplanetary nebula; studies of meteorites (the Department houses one of the largest meteorite collections in the US); and laboratory simulations of rotating planet convection. In the Dept. Physics and Astronomy, the Infrared Laboratory develops instruments for use on telescopes, including the Keck 10 meter, the airborne NASA SOFIA Observatory and, in the future, the James Webb Space Telescope.
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Areas of interest include space plasma simulation, planetary plasma physics and space physics. Scientists conduct investigations of the solar wind and the magnetospheres, ionospheres and atmospheres of the planets.
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Astronomical observations (using telescopes on the ground and in space) provide an essential complement to observations taken in-situ from spacecraft. Whereas the latter provide highly detailed measurements of specific objects, astronomical investigations reveal the broad scientific context within which spacecraft data must be interpreted. Scientists at UCLA conduct a wide range of planetary astronomical investigations using facilities from the world’s largest optical telescopes (the 10-m Keck twins, jointly run by University of California and Caltech) and the largest radio dish (the 305-m diameter Arecibo) to smaller telescopes on the ground, the Hubble and Herschel telescopes in space and, soon, the SOFIA Stratospheric Observatory.
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Planetary satellites come in two flavors. The regular satellites generally have small inclinations and eccentricities and orbit within a few 10s of planetary radii of their planets. These properties are consistent with formation in circum-planetary disks and, to some extent, each satellite system (of the major planets) presents a miniature model of the circum-solar disk from which the planets condensed. The irregular satellites, by contrast, commonly possess large inclinations and eccentricities and have orbits sometimes measured in hundreds of planetary radii. These properties, particularly the fact that many irregular satellites orbit in a sense opposite to that of planetary rotation, suggest an origin by capture.
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Small bodies are believed to be the primordial building blocks of the planets. The principal reservoirs of the small bodies are the asteroids (main-belt and near-Earth), the comets, the Centaurs, the Kuiper belt objects and the comets of the Oort Cloud. Small bodies are especially important in planetary science for two reasons. First, most small bodies have escaped wholesale melting or other severe forms of thermal processing and thus preserve chemical compositions closer to the initial ones. [In fact, many small bodies (e.g. the comets) formed and remained so cold over cosmic time that they retain the volatile ices from which they formed]. Second, the small bodies are very numerous compared to the major planets. They make excellent dynamical tracers and allow detailed models of the origin and evolution of the solar system to be tested.
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UCLA scientists are engaged in several on-going space missions, notably the DIVINER infrared radiometer aboard NASA’s Lunar Reconnaissance Orbiter (PI: Paige), the DAWN mission to large asteroids Ceres and Vesta (PI: Russell) and the THEMIS mission to study magnetospheric interactions with the Earth (P.I Angelopoulos). Department scientists are also closely involved with the Juno mission to Jupiter, the Cassini mission presently orbiting Saturn, and with the study of Mercury via the Messenger spacecraft and of the solar wind from samples brought back by the Genesis spacecraft.
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The Terrestrial planets show a fantastic diversity in their physical properties, surface morphologies, thermal histories and other properties. Except on the Earth, with its highly active system of convectively driven plates, the role of cosmic impact is strong or dominant.
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Many of the mysteries of planetary science must be investigated theoretically (or numerically) due to the limited availability of data. Many of the mysteries of planetary science must be investigated theoretically (or numerically) due to the limited availability of data. For example, probing planetary interiors, following the evolution of planetary objects, and investigating various physical processes relevant to planetary science (e.g., interior dynamics, convection) can be done only theoretically. Using analytical equations, semi-analytical models and numerical simulations, we can gain a better understanding of observations and in addition establish predictions. More information about Theory research @ UCLA