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HD 17156
HD 17156, named Nushagak by the IAU, is a yellow subgiant star approximately 255 light-years away in the constellation of Cassiopeia. The apparent magnitude is 8.17, which means it is not visible to the naked eye but can be seen with good binoculars. A search for a binary companion star using adaptive optics at the MMT Observatory was negative. The star is more massive and larger than the Sun while Its absolute magnitude of 3.70 and spectral type of G0, show that it is both hotter and more luminous. Based on asteroseismic density constraints and stellar isochrones, it was found that the age is 3.37 billion years making it about two thirds as old as the Sun. Spectral observations show that the star is metal-rich. An extrasolar planet, HD 17156 b, was discovered with the radial velocity method in 2007, and subsequently was observed to transit the star. At the time it was the transiting planet with the longest period. Name The star was given the name Nushagak by the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cassiopeia (constellation)
Cassiopeia () is a constellation in the northern sky named after the vain queen Cassiopeia, mother of Andromeda, in Greek mythology, who boasted about her unrivaled beauty. Cassiopeia was one of the 48 constellations listed by the 2nd-century Greek astronomer Ptolemy, and it remains one of the 88 modern constellations today. It is easily recognizable due to its distinctive ' W' shape, formed by five bright stars. Cassiopeia is located in the northern sky and from latitudes above 34°N it is visible year-round. In the (sub)tropics it can be seen at its clearest from September to early November, and at low southern, tropical, latitudes of less than 25°S it can be seen, seasonally, low in the North. At magnitude 2.2, Alpha Cassiopeiae, or Schedar, is generally the brightest star in Cassiopeia, though it is occasionally outshone by the variable Gamma Cassiopeiae, which has reached magnitude 1.6. The constellation hosts some of the most luminous stars known, including the yel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Absolute Magnitude
Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse logarithmic astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent magnitude that the object would have if it were viewed from a distance of exactly , without extinction (or dimming) of its light due to absorption by interstellar matter and cosmic dust. By hypothetically placing all objects at a standard reference distance from the observer, their luminosities can be directly compared among each other on a magnitude scale. As with all astronomical magnitudes, the absolute magnitude can be specified for different wavelength ranges corresponding to specified filter bands or passbands; for stars a commonly quoted absolute magnitude is the absolute visual magnitude, which uses the visual (V) band of the spectrum (in the UBV photometric system). Absolute magnitudes are denoted by a capital M, with a subscript representing the filter band used for mea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Stars With Extrasolar Planets
From the total of stars known to have exoplanets (as of ), there are a total of known multiplanetary systems, or stars with at least two confirmed planets, beyond the Solar System. This list includes systems with at least three confirmed planets, or with two confirmed planets where additional candidates have been proposed. The stars with the most confirmed planets are Sol (the Solar System's star, also referred to as the Sun) and Kepler-90 with 8 confirmed planets each, followed by TRAPPIST-1 with 7 planets. The multiplanetary systems are listed below according to the star's distance from Earth. Proxima Centauri, the closest star to the Solar System, has three planets ( b, c and d). The nearest system with four or more confirmed planets is Tau Ceti, with four known. The farthest confirmed multiplanetary system is OGLE-2012-BLG-0026L, at 13,300 ly away. The table below contains information about the coordinates, spectral and physical properties, and number of confirmed (un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transit Method
Any planet is an extremely faint light source compared to its parent star. For example, a star like the Sun is about a billion times as bright as the reflected light from any of the planets orbiting it. In addition to the intrinsic difficulty of detecting such a faint light source, the light from the parent star causes a glare that washes it out. For those reasons, very few of the exoplanets reported have been observed directly, with even fewer being resolved from their host star. Instead, astronomers have generally had to resort to indirect methods to detect extrasolar planets. As of 2016, several different indirect methods have yielded success. Established detection methods The following methods have at least once proved successful for discovering a new planet or detecting an already discovered planet: Radial velocity A star with a planet will move in its own small orbit in response to the planet's gravity. This leads to variations in the speed with which the star mov ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radial Velocity Method
Doppler spectroscopy (also known as the radial-velocity method, or colloquially, the wobble method) is an indirect method for finding extrasolar planets and brown dwarfs from radial-velocity measurements via observation of Doppler shifts in the spectrum of the planet's parent star. 1,018 extrasolar planets (about 19.5% of the total) have been discovered using Doppler spectroscopy, as of November 2022. History Otto Struve proposed in 1952 the use of powerful spectrographs to detect distant planets. He described how a very large planet, as large as Jupiter, for example, would cause its parent star to wobble slightly as the two objects orbit around their center of mass. He predicted that the small Doppler shifts to the light emitted by the star, caused by its continuously varying radial velocity, would be detectable by the most sensitive spectrographs as tiny redshifts and blueshifts in the star's emission. However, the technology of the time produced radial-velocity ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mulchatna River
The Mulchatna River ( Dena'ina: Vałts'atnaq') is a tributary of the Nushagak River in the U.S. state of Alaska. Beginning at Turquoise Lake, it flows generally southwest to meet the larger river northeast of Dillingham. The Mulchatna's mouth is slightly south (downstream) of the village of Koliganek on the Nushagak, which continues southwest to Nushagak Bay, an arm of Bristol Bay. The upper of the river, which flow through Lake Clark National Park and Preserve, became part of the National Wild and Scenic River System in 1980. Aside from scattered cabins, the Mulchatna River is undeveloped. However, there is a proposal to build a large copper/gold mine, the Pebble Mine, in the watershed of one of the Mulchatna tributaries, the Koktuli River. Recreation The Mulchatna River and one of its tributaries, the Chilikadrotna River, are popular Southwest Alaska destinations for floatfishing. Other Mulchatna tributaries, including the Stuyahok and Koktuli rivers, are also popular ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nushagak River
The Nushagak River ( esu, Iilgayaq) is a river in southwest Alaska, United States. It begins in the Alaska Range and flows southwest to Nushagak Bay, an inlet of Bristol Bay, east of Dillingham, Alaska. The Mulchatna River is a major tributary. Other navigable tributaries include the Nuyakuk River and the King Salmon River. Jet-boats are commonly used to access these tributaries and the upper Nushagak. The Wood River, Iowithla River and the Kokwok River are smaller tributaries. The villages of Portage Creek, Ekwok, Koliganek and New Stuyahok are on the river. The town of Dillingham (Pop. 2,466) is on Nushagak Bay. The Nushagak River is downstream of the proposed Pebble Mine, whose tailings storage lake would sit at the headwaters of the Koktuli River, one of the Nushagak's tributaries. Villages on the Nushagak are among the major opponents of the proposal. Five species of Pacific salmon ( Chinook, coho, sockeye, chum, and pink) spawn in the river or its tribu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NameExoWorlds
NameExoWorlds (also known as IAU NameExoWorlds) is the name of various projects managed by the International Astronomical Union (I.A.U.) to encourage names to be submitted for astronomical objects, which would later be considered for official adoption by the organization. History The first such project (NameExoWorlds I), in 2015, regarded the naming of stars and exoplanets. 573,242 votes were submitted by members by the time the contest closed on October 31, 2015, and the names of 31 exoplanets and 14 stars were selected from these. Many of the names chosen were based on world history, mythology and literature. In June 2019, another such project (NameExoWorlds II), in celebration of the organization's hundredth anniversary, in a project officially called IAU100 NameExoWorlds, welcomed countries of the world to submit names for exoplanets and their host stars. A star with an exoplanet was assigned to each country, and members of the public submitted names for them. In August 2 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomical Transit
In astronomy, a transit (or astronomical transit) is a phenomenon when a celestial body passes directly between a larger body and the observer. As viewed from a particular vantage point, the transiting body appears to move across the face of the larger body, covering a small portion of it. The word "transit" refers to cases where the nearer object appears smaller than the more distant object. Cases where the nearer object appears larger and completely hides the more distant object are known as ''occultations''. However, the probability of seeing a transiting planet is low because it is dependent on the alignment of the three objects in a nearly perfectly straight line. Many parameters of a planet and its parent star can be determined based on the transit. In the Solar System One example of a transit involves the motion of a planet between a terrestrial observer and the Sun. This can happen only with inferior planets, namely Mercury and Venus (see transit of Mercury ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HD 17156 B
HD 17156 b, named Mulchatna by the IAU, is an extrasolar planet approximately 255 light-years away in the constellation of Cassiopeia. The planet was discovered orbiting the yellow subgiant star HD 17156 in April 2007. The planet is classified as a relatively cool hot Jupiter planet slightly smaller than Jupiter but slightly larger than Saturn. This highly-eccentric three-week orbit takes it approximately 0.0523 AU of the star at periastron before swinging out to approximately 0.2665 AU at apastron. Its eccentricity is about the same as 16 Cygni Bb, a so-called "eccentric Jupiter". Until 2009, HD 17156 b was the transiting planet with the longest orbital period. Discovery The planet was discovered on April 14, 2007, by a team using the radial velocity method on the Keck and Subaru telescopes. The team made an initial negative, transit search, but they were only able to cover 25% of the search space. This left the possibility of a transit open. After the possibility of a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extrasolar Planet
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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metallicity
In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a convenient short term 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 solid. Stars and nebulae with relatively high abundances of heavier elements are called "metal-rich" in astrophysical terms, even though many of those elements are nonmetals in chemistry. The presence of heavier elements hails from stellar nucleosynthesis, where the majority of elements heavier than hydrogen and helium in the Universe (''metals'', hereafter) are formed in the cores of stars as they evolve. Over time, stellar winds and supernovae deposit the metals into the surrounding environment, enriching the interstellar medium and provid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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