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Substellar Object
A substellar object, sometimes called a substar, is an astronomical object the mass of which is smaller than the smallest mass at which hydrogen fusion can be sustained (approximately 0.08 solar masses). This definition includes brown dwarfs and former stars similar to EF Eridani B, and can also include objects of planetary mass, regardless of their formation mechanism and whether or not they are associated with a primary star. Assuming that a substellar object has a composition similar to the Sun's and at least the mass of Jupiter (approximately 10−3 solar masses), its radius will be comparable to that of Jupiter (approximately 0.1 solar radii) regardless of the mass of the substellar object (brown dwarfs are less than 75 Jupiter masses). This is because the center of such a substellar object at the top range of the mass (just below the hydrogen-burning limit) is quite degenerate, with a density of ≈103 g/cm3, but this degeneracy lessens with decreasing mass until, at the mas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomical Object
An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists in the observable universe. In astronomy, the terms ''object'' and ''body'' are often used interchangeably. However, an astronomical body or celestial body is a single, tightly bound, contiguous entity, while an astronomical or celestial ''object'' is a complex, less cohesively bound structure, which may consist of multiple bodies or even other objects with substructures. Examples of astronomical objects include planetary systems, star clusters, nebulae, and galaxies, while asteroids, moons, planets, and stars are astronomical bodies. A comet may be identified as both body and object: It is a ''body'' when referring to the frozen nucleus of ice and dust, and an ''object'' when describing the entire comet with its diffuse coma and tail. History Astronomical objects such as stars, planets, nebulae, asteroids and comets ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbit
In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as a planet, moon, asteroid, or Lagrange point. Normally, orbit refers to a regularly repeating trajectory, although it may also refer to a non-repeating trajectory. To a close approximation, planets and satellites follow elliptic orbits, with the center of mass being orbited at a focal point of the ellipse, as described by Kepler's laws of planetary motion. For most situations, orbital motion is adequately approximated by Newtonian mechanics, which explains gravity as a force obeying an inverse-square law. However, Albert Einstein's general theory of relativity, which accounts for gravity as due to curvature of spacetime, with orbits following geodesics, provides a more accurate calculation and understanding of the exact mechanics of orbi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Super-Jupiter
A super-Jupiter is a gas giant exoplanet that is more massive than the planet Jupiter. For example, companions at the planet–brown dwarf borderline have been called super-Jupiters, such as around the star Kappa Andromedae. By 2011 there were 180 known super-Jupiters, some hot, some cold. Even though they are more massive than Jupiter, they remain about the same size as Jupiter up to 80 Jupiter masses. This means that their surface gravity and density go up proportionally to their mass. The increased mass compresses the planet due to gravity, thus keeping it from being larger. In comparison, planets somewhat lighter than Jupiter can be larger, so-called "puffy planets" (gas giants with a large diameter but low density). An example of this may be the exoplanet HAT-P-1b with about half the mass of Jupiter but about 1.38 times larger diameter. CoRoT-3b, with a mass around 22 Jupiter masses, is predicted to have an average density of 26.4 g/cm3, greater than osmium (22.6 g/cm3), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jupiter Mass
Jupiter mass, also called Jovian mass, is the unit of mass equal to the total mass of the planet Jupiter. This value may refer to the mass of the planet alone, or the mass of the entire Jovian system to include the moons of Jupiter. Jupiter is by far the most massive planet in the Solar System. It is approximately 2.5 times as massive as all of the other planets in the Solar System combined. Jupiter mass is a common unit of mass in astronomy that is used to indicate the masses of other similarly-sized objects, including the outer planets, extrasolar planets, and brown dwarfs, as this unit provides a convenient scale for comparison. Current best estimates The current best known value for the mass of Jupiter can be expressed as : :M_\mathrm=(1.89813 \pm 0.00019)\times10^ \text, which is about as massive as the sun (is about ): :M_\mathrm=\frac M_ \approx (9.547919 \pm 0.000002) \times10^ M_. Jupiter is 318 times as massive as Earth: :M_\mathrm = 3.1782838 \times 10^2 M_\oplu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2010A&A
1 (one, unit, unity) is a number representing a single or the only entity. 1 is also a numerical digit and represents a single unit of counting or measurement. For example, a line segment of ''unit length'' is a line segment of length 1. In conventions of sign where zero is considered neither positive nor negative, 1 is the first and smallest positive integer. It is also sometimes considered the first of the infinite sequence of natural numbers, followed by 2, although by other definitions 1 is the second natural number, following 0. The fundamental mathematical property of 1 is to be a multiplicative identity, meaning that any number multiplied by 1 equals the same number. Most if not all properties of 1 can be deduced from this. In advanced mathematics, a multiplicative identity is often denoted 1, even if it is not a number. 1 is by convention not considered a prime number; this was not universally accepted until the mid-20th century. Additionally, 1 is the s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exoplanet
An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, initially detected in 1988, was confirmed in 2003. There are many methods of detecting exoplanets. Transit photometry and Doppler spectroscopy have found the most, but these methods suffer from a clear observational bias favoring the detection of planets near the star; thus, 85% of the exoplanets detected are inside the tidal locking zone. In several cases, multiple planets have been observed around a star. About 1 in 5 Sun-like starsFor the purpose of this 1 in 5 statistic, "Sun-like" means G-type star. Data for Sun-like stars was not available so this statistic is an extrapolation from data about K-type stars. have an "Earth-sized"For the purpose of this 1 in 5 statistic, Earth-sized means 1–2 Earth radii. planet in the habitable zone. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wide Field Infrared Images Of Gliese 229 B
WIDE or Wide may refer to: *Wide (cricket) *Wide and narrow data, terms used to describe two different presentations for tabular data *WIDE Project, Widely Integrated Distributed Environment *Wide-angle Infinity Display Equipment *WIDE-LP, a radio station (99.1 FM) licensed to Madison, Wisconsin *Women in Development Europe; see * wide (tennis), meaning beyond the sidelines People with the name Wide *Ernst Wide (1888–1950), a Swedish Olympic long-distance runner *Edvin Wide (1896–1996), a Swedish Olympic long-distance runner *Samuel Wide (1861–1918), a Swedish archaeologist See also * * * *Widen *Width (other) {{Disambiguation, callsign ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Super Earth
A super-Earth is an extrasolar planet with a mass higher than Earth's, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17 times Earth's, respectively. The term "super-Earth" refers only to the mass of the planet, and so does not imply anything about the surface conditions or habitability. The alternative term "gas dwarfs" may be more accurate for those at the higher end of the mass scale, although "mini-Neptunes" is a more common term. Definition In general, super-Earths are defined by their masses, and the term does not imply temperatures, compositions, orbital properties, habitability, or environments. While sources generally agree on an upper bound of 10 Earth masses (~69% of the mass of Uranus, which is the Solar System's giant planet with the least mass), the lower bound varies from 1 or 1.9 to 5, with various other definitions appearing in the popular media. The term "super-Earth" is also used by astronomers to re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mini-Neptune
A Mini-Neptune (sometimes known as a gas dwarf or transitional planet) is a planet less massive than Neptune but resembling Neptune in that it has a thick hydrogen–helium atmosphere, probably with deep layers of ice, rock or liquid oceans (made of water, ammonia, a mixture of both, or heavier volatiles). A gas dwarf is a gas planet with a rocky core that has accumulated a thick envelope of hydrogen, helium, and other volatiles, having, as a result, a total radius between 1.7 and 3.9 Earth radii (). The term is used in a three-tier, metallicity-based classification regime for short-period exoplanets, which also includes the rocky, terrestrial-like planets with less than and planets greater than , namely ice giants and gas giants. Properties Theoretical studies of such planets are loosely based on knowledge about Uranus and Neptune. Without a thick atmosphere, it would be classified as an ocean planet instead. An estimated dividing line between a rocky planet and a gaseous pla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Terrestrial Planet Finder
The Terrestrial Planet Finder (TPF) was a proposed project by NASA to construct a system of space telescopes for detecting extrasolar terrestrial planets. TPF was postponed several times and finally cancelled in 2011. There were two telescope systems under consideration, the TPF-I, which had several small telescopes, and TPF-C, which used one large telescope. History In May 2002, NASA chose two TPF mission architecture concepts for further study and technology development. Each would use a different means to achieve the same goal—to block the light from a parent star in order to see its much smaller, dimmer planets. The technological challenge of imaging planets near their much brighter star has been likened to finding a firefly near the beam of a distant searchlight. Additional goals of the mission would include the characterization of the surfaces and atmospheres of newfound planets, and looking for the chemical signatures of life. The two planned architectures were: *In ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
William Duncan MacMillan
William Duncan MacMillan (July 24, 1871 – November 14, 1948) was an American mathematician and astronomer on the faculty of the University of Chicago. He published research on the applications of classical mechanics to astronomy, and is noted for pioneering speculations on physical cosmology. For the latter, Helge Kragh noted, "the cosmological model proposed by MacMillan was designed to lend support to a cosmic optimism, which he felt was threatened by the world view of modern physics." Biography He was born in La Crosse, Wisconsin, to D. D. MacMillan, who was in the lumber business, and Mary Jane McCrea. His brother, John H. MacMillan, headed the Cargill Corporation from 1909 to 1936. MacMillan graduated from La Crosse High School in 1888. In 1889, he attended Lake Forest College, then entered the University of Virginia. Later in 1898, he earned an A.B. degree from Fort Worth University, which was then a Methodist university in Texas. He performed his graduate work at the Un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gas Giant
A gas giant is a giant planet composed mainly of hydrogen and helium. Gas giants are also called failed stars because they contain the same basic elements as a star. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" was originally synonymous with "giant planet". However, in the 1990s, it became known that Uranus and Neptune are really a distinct class of giant planets, being composed mainly of heavier volatile substances (which are referred to as "ices"). For this reason, Uranus and Neptune are now often classified in the separate category of ice giants. Jupiter and Saturn consist mostly of hydrogen and helium, with heavier elements making up between 3 and 13 percent of their mass.The Interior of Jupiter, Guillot et al., in ''Jupiter: The Planet, Satellites and Magnetosphere'', Bagenal et al., editors, Cambridge University Press, 2004 They are thought to consist of an outer layer of compressed molecular hydrogen surrounding a layer of liquid metallic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
