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Ultra-short Period Planets
An ultra-short period (USP) planet is a type of exoplanet with an orbital period of less than one Earth day. At this short distance, tidal interactions lead to relatively rapid orbital and spin evolution. Therefore when there is a USP planet around a mature main-sequence star it is most likely that the planet has a circular orbit and is tidally locked. There are not many USP planets with sizes exceeding 2 Earth radii. About one out of 200 Sun-like stars ( G dwarfs) has an ultra-short-period planet. There is a strong dependence of the occurrence rate on the mass of the host star. The occurrence rate falls from (1.1 ± 0.4)% for M dwarfs to (0.15 ± 0.05)% for F dwarfs. Mostly the USP planets seem consistent with an Earth-like composition of 70% rock and 30% iron, but K2-229b has a higher density suggesting a more massive iron core. WASP-47e and 55 Cnc e have a lower density and are compatible with pure rock, or a rocky-iron body surrounded by a layer of water (or other volatil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
KIC 12557548
Kepler-1520 (initially published as KIC 12557548) is a K-type main-sequence star located in the constellation Cygnus (constellation), Cygnus. The star is particularly important, as measurements taken by the ''Kepler (spacecraft), Kepler'' spacecraft indicate that the variations in the star's light curve cover a range from about 0.2% to 1.3% of the star's light being blocked. This indicates that there may be a rapidly disintegrating planet, a prediction not yet conclusively confirmed, in orbit around the star, losing mass at a rate of 1 Earth mass every billion years. The planet itself is about 0.1 Earth masses, or just twice the mass of Mercury, and is expected to disintegrate in about 100-200 million years. The planet orbits its star in just 15.7 hours, at a distance only two stellar diameters away from the star's surface, and has an estimated effective temperature of about 2255 K. The orbital period of the planet is one of the shortest ever detected in the history of the ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hot Jupiter
Hot Jupiters (sometimes called hot Saturns) are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter (i.e. Jupiter analogue, Jupiter analogues) but that have very short orbital periods (). The close proximity to their stars and high surface-atmosphere temperatures resulted in their informal name "hot Jupiters". Hot Jupiters are the easiest extrasolar planets to detect via the radial velocity, radial-velocity method, because the oscillations they induce in their parent stars' motion are relatively large and rapid compared to those of other known types of planets. One of the best-known hot Jupiters is . Discovered in 1995, it was the first extrasolar planet found orbiting a Sun-like star. has an orbital period of about four days. General characteristics Though there is diversity among hot Jupiters, they do share some common properties. * Their defining characteristics are their large masses and short orbital periods, spanning 0.36–11.8 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steam
Steam is water vapor, often mixed with air or an aerosol of liquid water droplets. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporization. Saturated or superheated steam is invisible; however, wet steam, a visible mist or aerosol of water droplets, is often referred to as "steam". When liquid water becomes steam, it increases in volume by 1,700 times at standard temperature and pressure; this change in volume can be converted into work (physics), mechanical work by steam engines such as reciprocating engine, reciprocating piston type engines and steam turbines, which are a sub-group of steam engines. Piston type steam engines played a central role in the Industrial Revolution and modern steam turbines are used to generate more than 80% of the world's electricity. If liquid water comes in contact with a very hot surface or depressurizes quickly below its vapor pressure, vapour pressure, it can create a steam exp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Water
Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a solvent). It is vital for all known forms of life, despite not providing food energy or organic micronutrients. Its chemical formula, , indicates that each of its molecules contains one oxygen and two hydrogen atoms, connected by covalent bonds. The hydrogen atoms are attached to the oxygen atom at an angle of 104.45°. In liquid form, is also called "water" at standard temperature and pressure. Because Earth's environment is relatively close to water's triple point, water exists on Earth as a solid, a liquid, and a gas. It forms precipitation in the form of rain and aerosols in the form of fog. Clouds consist of suspended droplets of water and ice, its solid state. When finely divided, crystalline ice ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TOI-561
TOI-561 is an old, metal-poor, Sun-like star, known to have multiple small planets. It is an orange dwarf, estimated to be 10.5 billion years old, and about 79% the mass and 85% the radius of Sol, Earth's sun. It is located in the constellation Sextans, near the border with Leo. In January 2021, a team led by Lauren Weiss of the University of Hawaii at Manoa announced that, using data from NASA's Transiting Exoplanet Survey Satellite, they had found a Super-Earth in a very close orbit, as well as two outer Sub-Neptunes. The innermost planet, TOI-561 b, orbits in under one Earth day. Another team led by Gaia Lacedelli of the University of Padua independently announced the discovery in a paper published in December 2020. However, the two papers disagree on the structure of the system. While the innermost two planets were confirmed from data by both papers, Weiss proposes only a single third planet in a 16.3-day orbit, while Lacedelli argues that the system instead contains ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planetary System
A planetary system is a set of gravity, gravitationally bound non-stellar Astronomical object, bodies in or out of orbit around a star or star system. Generally speaking, systems with one or more planets constitute a planetary system, although such systems may also consist of bodies such as dwarf planets, asteroids, natural satellites, meteoroids, comets, planetesimals and circumstellar disks. For example, the Sun together with the planetary system revolving around it, including Earth, form the Solar System. The term exoplanetary system is sometimes used in reference to other planetary systems. Planetary systems are, by convention, named for their host, or parent star, as is the case in our Solar Planetary System, named for its hosting, star, "Sol". Debris disk, Debris disks are known to be common while other objects are more difficult to observe. Of particular interest to astrobiology is the habitable zone of planetary systems where planets could have surface liquid water, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Accretion (astrophysics)
In astrophysics, accretion is the accumulation of particles into a massive object by gravity, gravitationally attracting more matter, typically gaseous matter, into an accretion disk. Most astronomical objects, such as galaxy, galaxies, stars, and planets, are formed by accretion processes. Overview The accretion model that Earth and the other terrestrial planets formed from meteoric material was proposed in 1944 by Otto Schmidt, followed by the ''protoplanet theory'' of William McCrea (astronomer), William McCrea (1960) and finally the ''capture theory'' of Michael Woolfson. For details of Kant's position, see In 1978, Andrew Prentice resurrected the initial Laplacian ideas about planet formation and developed the ''modern Laplacian theory''. None of these models proved completely successful, and many of the proposed theories were descriptive. The 1944 accretion model by Otto Schmidt was further developed in a quantitative way in 1969 by Viktor Safronov. He calculated, in deta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The TESS-Keck Survey
The TESS-Keck Survey or TKS is an exoplanet search project that uses the Keck I and the Automated Planet Finder (APF) to conduct ground-based follow-up of planet candidates discovered by the Transiting Exoplanet Survey Satellite Transiting Exoplanet Survey Satellite (TESS) is a space telescope for NASA's Explorer program, designed to search for exoplanets using the transit method in an area 400 times larger than that covered by the Kepler mission. It was launched on .... The TKS aims to measure the mass for about 100 exoplanets and has been awarded some of the largest time allocations in the histories of Keck I and APF. The program has four main science themes: # the bulk compositions of small planets # dynamical temperatures and system architectures # a larger, more refined sample for future atmospheric studies # planets orbiting evolved stars List of discoveries Follow-up works by TKS studied the already discovered planets TOI-1726 c and WASP-107b. References ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gas Dwarf
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, they would be classified as an ocean planet instead. An estimated dividing line between a rocky planet and a gaseous pl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metallicity
In astronomy, metallicity is the Abundance of the chemical elements, abundance of Chemical element, elements present in an object that are heavier than hydrogen and helium. Most of the normal currently detectable (i.e. non-Dark matter, dark) matter in the universe is either hydrogen or helium, and astronomers use the word ''metals'' as convenient shorthand for ''all elements except hydrogen and helium''. This word-use is distinct from the conventional chemical or physical definition of a metal as an electrically conducting element. Stars and nebulae with relatively high abundances of heavier elements are called ''metal-rich'' when discussing metallicity, even though many of those elements are called ''Nonmetal (chemistry), nonmetals'' in chemistry. Metals in early spectroscopy In 1802, William Hyde WollastonMelvyn C. UsselmanWilliam Hyde WollastonEncyclopædia Britannica, retrieved 31 March 2013 noted the appearance of a number of dark features in the solar spectrum. In 1814, Jo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exoplanetology
This page describes exoplanet orbital and physical parameters. Orbital parameters Most known extrasolar planet candidates have been discovered using indirect methods and therefore only some of their physical and orbital parameters can be determined. For example, out of the six independent orbital element, parameters that define an orbit, the radial-velocity method can determine four: semi-major axis, orbital eccentricity, eccentricity, longitude of periastron, and time of periastron. Two parameters remain unknown: inclination and longitude of the ascending node. Distance from star and orbital period There are exoplanets that are much closer to their parent star than any planet in the Solar System is to the Sun, and there are also exoplanets that are much further from their star. Mercury (planet), Mercury, the closest planet to the Sun at 0.4 astronomical units (AU), takes 88 days for an orbit, but the smallest known orbits of exoplanets have orbital periods of only a few ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
55 Cnc E
55 Cancri e (abbreviated 55 Cnc e), formally named Janssen , is an exoplanet orbiting a Sun-like host star, 55 Cancri A. The mass of the exoplanet is about eight Earth masses and its diameter is about twice that of the Earth. 55 Cancri e was discovered on 30 August 2004, thus making it the first super-Earth discovered around a main sequence star, predating Gliese 876 d by a year. It is the innermost planet in its planetary system, taking less than 18 hours to complete an orbit. However, until the 2010 observations and recalculations, this planet had been thought to take about 2.8 days to orbit the star. Due to its proximity to its star, 55 Cancri e is extremely hot, with temperatures on the day side exceeding 3,000 Kelvin. The planet's thermal emission is observed to be variable, possibly as a result of volcanic activity. It has been proposed that 55 Cancri e could be a carbon planet. The atmosphere of 55 Cancri e has been extensively studied, with varying results. Initial stu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
