"The Secret of the Ninth Planet The Secret of the Ninth Planet is a science-fiction novel written by Donald A. Wollheim and first published in the United States in 1959 by the John C. Winston Co. Wollheim takes his heroes on a grand tour of the solar system as that team struggles to prevent an alien force from blowing up the sun. This is the last of three juvenile novels that Wollheim wrote for Winston, the other two being ""The Secret of Saturn's Rings"" and ""The Secret of the Martian Moons"". This is one of the thirty-five juvenile novels that"
"2 Pallas Pallas (minor-planet designation: 2 Pallas) is the second asteroid to have been discovered (after Ceres), and is one of the largest asteroids in the Solar System. With an estimated 7% of the mass of the asteroid belt, it is the third-most-massive asteroid, being 10–30% less massive than Vesta. It is in diameter, somewhat smaller than 4 Vesta. It is likely a remnant protoplanet. When Pallas was discovered by the German astronomer Heinrich Wilhelm Matthäus Olbers on 28 March 1802, it was counted as a planet, as were other asteroids in the early 19th century. The discovery of many"
"the Sun: Jupiter is the largest, at 318 Earth masses, whereas Mercury is the smallest, at 0.055 Earth masses. The planets of the Solar System can be divided into categories based on their composition: An exoplanet (extrasolar planet) is a planet outside the Solar System. In early 1992, radio astronomers Aleksander Wolszczan and Dale Frail announced the discovery of two planets orbiting the pulsar PSR 1257+12. This discovery was confirmed, and is generally considered to be the first definitive detection of exoplanets. These pulsar planets are believed to have formed from the unusual remnants of the supernova that produced the"
"define the term ""planet"" formally in 2006, during their 26th General Assembly. That definition excluded Pluto and reclassified it as a dwarf planet. Pluto is the largest and second-most-massive known dwarf planet in the Solar System, and the ninth-largest and tenth-most-massive known object directly orbiting the Sun. It is the largest known trans-Neptunian object by volume but is less massive than Eris. Like other Kuiper belt objects, Pluto is primarily made of ice and rock and is relatively small—about one-sixth the mass of the Moon and one-third its volume. It has a moderately eccentric and inclined orbit during which it"
"Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a giant planet with a mass one-thousandth that of the Sun, but two-and-a-half times that of all the other planets in the Solar System combined. Jupiter and Saturn are gas giants; the other two giant planets, Uranus and Neptune, are ice giants. Jupiter has been known to astronomers since antiquity. It is named after the Roman god Jupiter. When viewed from Earth, Jupiter can reach an apparent magnitude of −2.94, bright enough for its reflected light to cast shadows, and making it"
"Neptune Neptune is the eighth and farthest known planet from the Sun in the Solar System. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times the mass of Earth and slightly larger than Neptune. Neptune orbits the Sun once every 164.8 years at an average distance of . It is named after the Roman god of the sea and has the astronomical symbol ♆, a stylised version of the"
"astronomers led by Anne-Marie Lagrange from Grenoble, France. The planet, named Beta Pictoris b, is about seven times as massive as Jupiter, the largest planet in the Solar System. It orbits the star at some ten Astronomical Units (AU), which is ten times the distance between the Earth and the Sun and the same distance as planet Saturn orbits the Sun. In 2016 there were predictions published that the Beta Pictoris b Hill Sphere (or gravitational sphere of influence), or perhaps the planet itself, would be passing in front of its star as seen from the Earth. The detailed observation"
"moon Triton to be investigated around 2029. The proposed ""New Horizons 2"" mission (which was later scrapped) might also have done a close flyby of the Neptunian system. Neptune Neptune is the eighth and farthest known planet from the Sun in the Solar System. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times the mass of Earth and slightly larger than Neptune. Neptune orbits the Sun once every 164.8"
"candidate sites had little or no possibility of being the results of the proposed impacts. More recent discoveries include the following: Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a giant planet with a mass one-thousandth that of the Sun, but two-and-a-half times that of all the other planets in the Solar System combined. Jupiter and Saturn are gas giants; the other two giant planets, Uranus and Neptune, are ice giants. Jupiter has been known to astronomers since antiquity. It is named after the Roman god Jupiter. When viewed from"
"HR 8799 e </math></ref> HR 8799 e is a large exoplanet, orbiting the star HR 8799, which lies 129 lightyears from Earth. This gas giant is between 5 and 10 times the mass of Jupiter, the largest planet in the Solar System. Due to their young age and high temperature all four discovered planets in the HR 8799 system are large, compared to all gas giants in the Solar System. HR 8799 e is the fourth planet orbiting HR 8799 in order of discovery. It is a young, hot and massive gas giant, and is fairly close to its star,"
"Saturn 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 about nine times that of Earth. It has only one-eighth the average density of Earth, but with its larger volume Saturn is over 95 times more massive. Saturn is named after the Roman god of agriculture; its astronomical symbol (♄) represents the god's sickle. Saturn's interior is probably composed of a core of iron–nickel and rock (silicon and oxygen compounds). This core is surrounded by a deep layer of metallic hydrogen, an intermediate"
"the second most massive and third largest terrestrial planet ever discovered, behind Kepler-277c in radius and PSR J1719-1438 b in both radius and mass. Due to its proximity to its host star, Kepler-277b is quite hot with an equilibrium temperature of about , hot enough to melt certain metals. Kepler-277b orbits close to its host star, with one orbit lasting 17.324 days. Its semi-major axis, or average distance from the parent object, is about 0.136 AU. For comparison, the planet Mercury in our Solar System takes 88 days to orbit at a distance of 0.38 AU. At this distance, Kepler-277b"
"Eris (dwarf planet) Eris (minor-planet designation 136199 Eris) is the most massive and second-largest (by volume) dwarf planet in the known Solar System. Eris was discovered in January 2005 by a Palomar Observatory-based team led by Mike Brown, and its discovery was verified later that year. In September 2006 it was named after Eris, the Greek goddess of strife and discord. Eris is the ninth most massive object directly orbiting the Sun, and the 16th most massive overall, because seven moons are more massive than all known dwarf planets. It is also the largest which has not yet been visited"
"naked eye. The binary system is known to host three planets, all larger than Earth with no solid surface. The innermost planet, Kepler-47b, is a gas giant and resides close to its parent stars and therefore is inhospitable to life. It is thought to be smaller than Kepler-47c and is roughly three times the radius of Earth. The second planet, Kepler-47c, is also a gas giant and the outermost planet. It is situated within the habitable zone and its radius is 4 times the Earth's. Although it is assumed Kepler-47c is not capable of harboring life, it is marginally larger"
"a Subgiant star. Kepler-277c Kepler-277c (also known by its Kepler Objects of Interest designation KOI-1215.02) is the third most massive and second-largest rocky planet ever discovered, with a mass about 64 times that of Earth. Discovered in 2014 by the Kepler Space Telescope, Kepler-277c is a Neptune-sized exoplanet with a very high mass and density for an object of its radius, suggesting a composition made mainly of rock with some amounts of water. Along with its sister planet, Kepler-277b, the planet's mass was determined using transit-timing variations (TTVs). Kepler-277c was detected using the transit method and TTVs, allowing for both"
"years, as opposed to the similarly sized Great Red Spot of Jupiter, which has persisted for centuries. Of all known giant planets in the Solar System, Neptune emits the most internal heat per unit of absorbed sunlight, a ratio of approximately 2.6. Saturn, the next-highest emitter, only has a ratio of about 1.8. Uranus emits the least heat, one-tenth as much as Neptune. It is suspected that this may be related to its extreme 98˚ axial tilt. This causes its seasonal patterns to be very different from those of any other planet in the Solar System. There are still no"
"show evidence of Methane and Acetylene but no Ammonia or Carbon Dioxide. There is currently no explanation why this planet shows strong methane absorption, but the other 3 planets in this system do not, despite all 4 planets having similar atmospheric temperatures. HR 8799 e </math></ref> HR 8799 e is a large exoplanet, orbiting the star HR 8799, which lies 129 lightyears from Earth. This gas giant is between 5 and 10 times the mass of Jupiter, the largest planet in the Solar System. Due to their young age and high temperature all four discovered planets in the HR 8799"
"larger, and Jupiter's is the strongest in the Solar System (so strong in fact that it poses a serious health risk to future manned missions to its moons). The magnetic fields of the other giant planets are roughly similar in strength to that of Earth, but their magnetic moments are significantly larger. The magnetic fields of Uranus and Neptune are strongly tilted relative the rotational axis and displaced from the centre of the planet. In 2004, a team of astronomers in Hawaii observed an extrasolar planet around the star HD 179949, which appeared to be creating a sunspot on the"
"known to a precision of one part in ten-thousand. The solar mass is quite a large unit on the scale of the Solar System: 1.9884(2) kg. The largest planet, Jupiter, is 0.09% the mass of the Sun, while the Earth is about three millionths (0.0003%) of the mass of the Sun. Various different conventions are used in the literature to overcome this problem: for example, inverting the ratio so that one quotes the planetary mass in the 'number of planets' it would take to make up one Sun. Here, we have chosen to list all planetary masses in 'microSuns' –"
"10199 Chariklo 10199 Chariklo ( or ; ; provisional designation ) is the largest confirmed centaur (minor planet of the outer Solar System). It orbits the Sun between Saturn and Uranus, grazing the orbit of Uranus. On 26 March 2014, astronomers announced the discovery of two rings (nicknamed Oiapoque and Chuí) around Chariklo by observing a stellar occultation, making it the first minor planet known to have rings. Chariklo was discovered by James V. Scotti of the Spacewatch program on February 15, 1997. Chariklo is named after the nymph Chariclo (""""), the wife of Chiron and the daughter of Apollo."
"and observed since it was discovered, it is unlikely that there are any large moons orbiting Pallas. Pallas has not been visited by spacecraft and there are no plans for exploration of Pallas by spacecraft. A flyby after the ""Dawn"" probe's visits to 4 Vesta and 1 Ceres was discussed but was not possible. 2 Pallas Pallas (minor-planet designation: 2 Pallas) is the second asteroid to have been discovered (after Ceres), and is one of the largest asteroids in the Solar System. With an estimated 7% of the mass of the asteroid belt, it is the third-most-massive asteroid, being 10–30%"
"cloud tops. This was the probe's first solo planetary flyby, since ""Voyager 1"" ended its tour of the outer planets at Saturn's moon Titan. Uranus is the third-largest planet in the Solar System. It orbits the Sun at a distance of about and completes one orbit every 84 years. The length of a day on Uranus as measured by ""Voyager 2"" is 17 hours and 14 minutes. Uranus is distinguished by the fact that it is tipped on its side. Its unusual position is thought to be the result of a collision with a planet-sized body early in the Solar"
"alcohol 2003 Sedna 2003 Psamathe 2003 Mab 2003 Perdita 2003 Cupid 2004 Orcus 2005 Makemake 2005 Eris Eris, formal designation 136199 Eris, is the largest-known dwarf planet in the Solar System and the ninth-largest body known to orbit the Sun directly. It is approximately 2,500 kilometres in diameter and 27% more massive than the dwarf planet Pluto. Eris was discovered in 2005 at W. M. Keck Observatory by American astronomer Michael E. Brown. 2005 Dysnomia Dysnomia, officially (136199) Eris I Dysnomia, is the only known moon of the dwarf planet Eris. In conjunction of finding Eris, American astronomer Michael E."
"Kepler-277b Kepler-277b (also known by its Kepler Objects of Interest designation KOI-1215.01) is the second most massive and third-largest rocky planet ever discovered, with a mass close to that of Saturn. Discovered in 2014 by the Kepler Space Telescope, Kepler-277b is a sub-Neptune sized exoplanet with a very high mass and density for an object of its radius, suggesting a composition made mainly of rock and iron. Along with its sister planet, Kepler-277c, the planet's mass was determined using transit-timing variations (TTVs). Kepler-277b was detected using the transit method and TTVs, allowing for both its mass and radius to be"
"heights. Venus Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. It has the longest rotation period (243 days) of any planet in the Solar System and rotates in the opposite direction to most other planets (meaning the Sun would rise in the west and set in the east). It does not have any natural satellites. It is named after the Roman goddess of love and beauty. It is the second-brightest natural object in the night sky after the Moon, reaching an apparent magnitude of −4.6 – bright enough to cast shadows at night and,"
"reported. Another Super-Earth, K2-155d, is discovered. In July 2018, the discovery of 40 Eridani b was announced. At 16 light-years it is the closest super-Earth known, and its star is the second-brightest hosting a super-Earth. The Solar System contains no known super-Earths, because Earth is the largest terrestrial planet in the Solar System, and all larger planets both have at least 14 times the mass of Earth and thick gaseous atmospheres without well-defined rocky or watery surfaces; that is, they are either gas giants or ice giants, not terrestrial planets. In January 2016, the existence of a hypothetical super-Earth-mass ninth"
"Venus Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. It has the longest rotation period (243 days) of any planet in the Solar System and rotates in the opposite direction to most other planets (meaning the Sun would rise in the west and set in the east). It does not have any natural satellites. It is named after the Roman goddess of love and beauty. It is the second-brightest natural object in the night sky after the Moon, reaching an apparent magnitude of −4.6 – bright enough to cast shadows at night and, rarely,"
"source for chemical abundance, despite their rareness (only five have been recovered on Earth). The planets of the Solar System are divided into two groups: the four inner planets are the terrestrial planets (Mercury, Venus, Earth and Mars), with relatively small sizes and rocky surfaces. The four outer planets are the giant planets, which are dominated by hydrogen and helium and have lower mean densities. These can be further subdivided into the gas giants (Jupiter and Saturn) and the ice giants (Uranus and Neptune) that have large icy cores. Most of our direct information on the composition of the giant"
"The scientific paper describing the discovery was published in The Astrophysical Journal in 2003. A second massive gas giant planet was later discovered in an approximately 32 year orbit. HD 30177 HD 30177 is an 8th magnitude star located approximately 172 light-years (53 parsecs) away in the constellation Dorado. The star is a yellow dwarf, a type of yellow star that fuses hydrogen in its core. Since if this star is a late G-type, it is cooler and less massive than the Sun, but larger in radius. It is 1.8 times older than our Sun. This star system contains two"
"Since the dawn of the Space Age, close observation by space probes has found that Earth and the other planets share characteristics such as volcanism, hurricanes, tectonics, and even hydrology. Planets are generally divided into two main types: large low-density giant planets, and smaller rocky terrestrials. There are eight planets in the Solar System. In order of increasing distance from the Sun, they are the four terrestrials, Mercury, Venus, Earth, and Mars, then the four giant planets, Jupiter, Saturn, Uranus, and Neptune. Six of the planets are orbited by one or more natural satellites. Several thousands of planets around other"
"coastal borders of Brazil. A request for formal names will be submitted to the IAU at a later date. It has been speculated that 2060 Chiron may have a similar pair of rings. 10199 Chariklo 10199 Chariklo ( or ; ; provisional designation ) is the largest confirmed centaur (minor planet of the outer Solar System). It orbits the Sun between Saturn and Uranus, grazing the orbit of Uranus. On 26 March 2014, astronomers announced the discovery of two rings (nicknamed Oiapoque and Chuí) around Chariklo by observing a stellar occultation, making it the first minor planet known to have"
"Iapetus (moon) Iapetus (; ), or occasionally Japetus , is the third-largest natural satellite of Saturn, eleventh-largest in the Solar System, and the largest body in the Solar System known not to be in hydrostatic equilibrium. Iapetus is best known for its dramatic ""two-tone"" coloration. Discoveries by the ""Cassini"" mission in 2007 revealed several other unusual features, such as a massive equatorial ridge running three-quarters of the way around the moon. Iapetus was discovered by Giovanni Domenico Cassini, an Italian astronomer, in October 1671. He had discovered it on the western side of Saturn and tried viewing it on the"
"April 18, 2013. Kepler-62d Kepler-62d (also known by its Kepler Object of Interest designation ""KOI-701.01"") is the third innermost and the largest exoplanet discovered orbiting the star Kepler-62, with a size roughly twice the diameter of Earth. It was found using the transit method, in which the dimming that a planet causes as it crosses in front of its star is measured. Its stellar flux is 15 ± 2 times Earth's. Due to its closer orbit to its star, it is a super-Venus or, if it has a volatile composition, a hot Neptune, with an estimated equilibrium temperature of ,"