A planet is an astronomical body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and – according to the International Astronomical Union but not all planetary scientists – has cleared its neighbouring region of planetesimals.
Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandth the mass of the Sun. Jupiter is the third-brightest natural object in the Earth's night sky after the Moon and Venus. It has been observed since pre-historic times and is named after the Roman god Jupiter, the king of the gods, because of its observed size.
Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It only has one-eighth the average density of Earth; however, with its larger volume, Saturn is over 95 times more massive. Saturn is named after the Roman god of wealth and agriculture; its astronomical symbol (♄) represents the god's sickle. The Romans named the seventh day of the week Saturday, Sāturni diēs no later than the 2nd century for the planet Saturn.
Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus, who, according to Greek mythology, was the great-grandfather of Ares (Mars), grandfather of Zeus (Jupiter) and father of Cronus (Saturn). It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. Uranus is similar in composition to Neptune, and both have bulk chemical compositions which differ from that of the larger gas giants Jupiter and Saturn. For this reason, scientists often classify Uranus and Neptune as "ice giants" to distinguish them from the other giant planets. Uranus's atmosphere is similar to Jupiter's and Saturn's in its primary composition of hydrogen and helium, but it contains more "ices" such as water, ammonia, and methane, along with traces of other hydrocarbons. It has the coldest planetary atmosphere in the Solar System, with a minimum temperature of 49 K, and has a complex, layered cloud structure with water thought to make up the lowest clouds and methane the uppermost layer of clouds. The interior of Uranus is mainly composed of ices and rock.
The Great Red Spot is a persistent high-pressure region in the atmosphere of Jupiter, producing an anticyclonic storm that is the largest in the Solar System. Located 22 degrees south of Jupiter's equator, it produces wind-speeds up to 432 km/h. Observations from 1665 to 1713 are believed to be of the same storm; if this is correct, it has existed for at least 356 years. It was next observed in September 1831, with 60 recorded observations between then and 1878 when continuous observations began.
David Clifford Jewitt is a British-American astronomer who studies the Solar System, especially its minor bodies. He is based at the University of California, Los Angeles, where he is a Member of the Institute for Geophysics and Planetary Physics, the Director of the Institute for Planets and Exoplanets, Professor of Astronomy in the Department of Physics and Astronomy and Professor of Astronomy in the Department of Earth, Planetary and Space Sciences. He is best known for being the first person to discover a body beyond Pluto and Charon in the Kuiper belt.
Harold (Hal) Masursky was an American astrogeologist.
Neptune has been directly explored by only one space probe, Voyager 2, in 1989. As of June 2021, there are no approved future missions to visit the Neptunian system. NASA, ESA, and independent academic groups have proposed future scientific missions to visit Neptune. Some mission plans are still active, while others have been abandoned or put on hold.
Heidi B. Hammel is a planetary astronomer who has extensively studied Neptune and Uranus. She was part of the team imaging Neptune from Voyager 2 in 1989. She led the team using the Hubble Space Telescope to view Shoemaker-Levy 9's impact with Jupiter in 1994. She has used the Hubble Space Telescope and the Keck Telescope to study Uranus and Neptune, discovering new information about dark spots, planetary storms and Uranus' rings. In 2002, she was selected as an interdisciplinary scientist for the James Webb Space Telescope.
Philip D. Nicholson is an Australian-born professor of astronomy at Cornell University in the Astronomy department specialising in Planetary Sciences. He has been editor-in-chief of the journal Icarus since 1998.
Harold James Reitsema is an American astronomer who was part of the teams that discovered Larissa, the fifth of Neptune's known moons, and Telesto, Saturn's thirteenth moon. Reitsema and his colleagues discovered the moons through ground-based telescopic observations. Using a coronagraphic imaging system with one of the first charge-coupled devices available for astronomical use, they first observed Telesto on April 8, 1980, just two months after being one of the first groups to observe Janus, also a moon of Saturn. Reitsema, as part of a different team of astronomers, observed Larissa on May 24, 1981, by watching the occultation of a star by the Neptune system.
An exoplanet is a planet located outside the Solar System. The first evidence of an exoplanet was noted as early as 1917, but was not recognized as such until 2016. No planet discovery has yet come from that evidence. However, the first scientific detection of an exoplanet began in 1988. Afterwards, the first confirmed detection came in 1992, with the discovery of several terrestrial-mass planets orbiting the pulsar PSR B1257+12. The first confirmation of an exoplanet orbiting a main-sequence star was made in 1995, when a giant planet was found in a four-day orbit around the nearby star 51 Pegasi. Some exoplanets have been imaged directly by telescopes, but the vast majority have been detected through indirect methods, such as the transit method and the radial-velocity method. As of 22 June 2021, there are 4,768 confirmed exoplanets in 3,527 planetary systems, with 783 systems having more than one planet. This is a list of the most notable discoveries.
David Morrison is an American astronomer, a senior scientist at the Solar System Exploration Research Virtual Institute, at NASA Ames Research Center in Mountain View, California. Morrison is the former director of the Carl Sagan Center for Study of Life in the Universe at the SETI Institute and of the NASA Lunar Science Institute. He is the past Director of Space at NASA Ames. Morrison is credited as a founder of the multi-disciplinary field of astrobiology. Morrison is best known for his work in risk assessment of near Earth objects such as asteroids and comets. Asteroid 2410 Morrison was named in his honor. Morrison is also known for his "Ask an Astrobiologist" series on NASA's website where he provides answers to questions submitted by the public. He has published 12 books and over 150 papers primarily on planetary science, astrobiology and near earth objects.
Tortugas Mountain Observatory (TMO) is an astronomical observatory owned and operated by New Mexico State University (NMSU). It is located on Tortugas Mountain, also known locally as 'A' Mountain, in southern New Mexico (USA), approximately 8 kilometers (5.0 mi) southeast of Las Cruces and 4 kilometers (2.5 mi) east of the NMSU campus. Founded in 1963 under the supervision of Clyde Tombaugh, the observatory focused on observing the planets. Much of the information captured at TMO is now available through the Planetary Data System's Atmospheres Node, which is managed by NMSU. The two-dome observatory building was completed in 1964, though observing began with one of the telescopes in 1963. A second building, with a larger single dome, was completed at the opposite end of the ridgeline of Tortugas Mountain in 1967. Regular use of TMO ceased in 1999 or 2000, but the observatory equipment was not dismantled. In 2008 it was used for the Lunar CRater Observing and Sensing Satellite project. In 2010, efforts to revive the observatory for use by the American Association of Variable Star Observers began. As of 10 June 2011, work on project was reported to be 60-75% done.
Mark Robert Showalter is a Senior Research Scientist at the SETI Institute. He is the discoverer of six moons and three planetary rings. He is the Principal Investigator of NASA's Planetary Data System Rings Node, a co-investigator on the Cassini–Huygens mission to Saturn, and works closely with the New Horizons mission to Pluto.
Henry B. Throop, is an American astronomer and planetary scientist who specializes in the dynamics of rings and dust in the outer solar system. Throop is a member of the science team for NASA's New Horizons mission to Pluto and the Kuiper Belt, and has been involved with NASA missions throughout the solar system. Throop lives in Washington, DC where he runs NASA's science programs in the outer solar system. He has done extensive education and outreach around the world, having spent nearly a decade as an astronomer living in South Africa, India, and Mexico. The asteroid 193736 Henrythroop is named after him.
Sarah Hörst is an associate professor of planetary sciences at Johns Hopkins University, who focuses on understanding planetary atmospheric hazes, in particular the atmosphere of Saturn's moon Titan.
Carrie Anderson is an American planetary scientist at NASA's Goddard Space Flight Center.
Amy Simon is an American planetary scientist at NASA's Goddard Space Flight Center, involved in several missions of the Solar System Exploration Program.
Melissa McGrath is an astronomer whose expertise is the atmosphere and magnetosphere of our Solar System planets and their moon. Her main interest has focused on imaging and spectroscopic studies of Jupiter’s Galilean moons. She is currently co-investigator on the ultraviolet spectrometer instrument on ESA JUICE mission to Ganymede, and co-investigator on two proposed instruments on the NASA Europa Clipper mission. McGrath is senior scientist at SETI Institute in Mountain View, California.
