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HD 219134 H
HD 219134 h, also known as HR 8832 h, is an exoplanet orbiting around the K-type star HD 219134 in the constellation of Cassiopeia. It has a minimum mass of 108 Earth masses, which indicates that the planet is likely a 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" .... Unlike HD 219134 b and c it is not observed to transit and thus its radius and density are unknown. This planet was initially reported in two 2015 papers; one referred to it as HD 219134 e, while the other found different, and more accurate, parameters for it and so treated it as a different planet, designated HD 219134 h. It is now generally referred to by the HD 219134 h designation. References {{Extrasolar-planet-stub Cassiopeia (constellation) Exoplanets discovered in 2015 Exoplanets detected ... [...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] |
HD 219134
HD 219134 (also known as Gliese 892 or HR 8832) is a main-sequence star in the constellation of Cassiopeia. It is smaller and less luminous than the Sun, with a spectral class of K3V, which makes it an orange-hued star. HD 219134 is relatively close to our system, with an estimated distance of 21.34 light years. This star is close to the limit of apparent magnitude that can still be seen by the unaided eye. The limit is considered to be magnitude 6 for most observers. This star has a magnitude 9.4 optical companion at an angular separation of 106.6 arcseconds. Planetary system HD 219134 has a system of six known exoplanets. The innermost planet, HD 219134 b, is a rocky super-Earth based on size (1.6 times the size of Earth), and density (6.4 grams per cubic cm). This and three additional exoplanets; one super-Earth (designated ''c'' and later found to be rocky as well), one Neptunian world (''d''), and one Jovian world (''e''); were deduced using HARPS-N radial ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
K-type Main Sequence Star
A K-type main-sequence star, also referred to as a K-type dwarf or an orange dwarf, is a main-sequence (hydrogen-burning) star of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence stars ("red dwarfs") and yellow/white G-type main-sequence stars. They have masses between 0.6 and 0.9 times the mass of the Sun and surface temperatures between 3,900 and 5,300 K. These stars are of particular interest in the search for extraterrestrial life due to their stability and long lifespan. Well-known examples include Alpha Centauri B (K1 V) and Epsilon Indi (K5 V). Spectral standard stars The revised Yerkes Atlas system (Johnson & Morgan 1953) listed 12 K-type dwarf spectral standard stars, however not all of these have survived to this day as standards. The "anchor points" of the MK classification system among the K-type main-sequence dwarf stars, i.e. those standard stars that have remain unchanged over the years, are: * Sigm ... [...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] |
Minimum Mass
In astronomy, minimum mass is the lower-bound calculated mass of observed objects such as planets, stars and binary systems, nebulae, and black holes. Minimum mass is a widely cited statistic for extrasolar planets detected by the radial velocity method or Doppler spectroscopy, and is determined using the binary mass function. This method reveals planets by measuring changes in the movement of stars in the line-of-sight, so the real orbital inclinations and true masses of the planets are generally unknown. This is a result of sin ''i'' degeneracy. If inclination ''i'' can be determined, the true mass can be obtained from the calculated minimum mass using the following relationship: M_\text = \frac Exoplanets Orientation of the transit to Earth Most stars will not have their planets lined up and orientated so that they eclipse over the center of the star and give the viewer on earth a perfect transit. It is for this reason that when we often are only able to extrapolat ... [...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 metalli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HD 219134 B
HD 219134 b (or HR 8832 b) is one of at least five exoplanets orbiting HD 219134, a main-sequence star in the constellation of Cassiopeia. HD 219134 b has a size of about 1.6 , and a density of 6.4 g/cm3 and orbits at 21.25 light-years away. The exoplanet was initially detected by the instrument HARPS-N of the Italian Telescopio Nazionale Galileo via the radial velocity method and subsequently observed by the Spitzer telescope as transiting in front of its star. The exoplanet has a mass of about 4.5 times that of Earth and orbits its host star every three days. In 2017, it was found that the planet likely hosts an atmosphere. Characteristics Mass, radius and temperature HD 219134 b is a super-Earth, an exoplanet with a radius and mass bigger than Earth, but smaller than that of the ice giants Neptune and Uranus. Using both the radial velocity and transit method, both its mass and radius have been well determined, allowing for accurate modelling of the planet's composition. HD ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HD 219134 C
HD 219134 c, also known as HR 8832 c, is a hot, dense, rocky exoplanet orbiting around the K-type star HD 219134 in the constellation of Cassiopeia. Originally thought to be a little less than three times the mass of Earth, it is now known to be over 4 times the mass and 51% larger in radius, suggesting a rocky composition with a higher quantity of iron than Earth. The exoplanet was initially detected by the instrument HARPS-N of the Italian Telescopio Nazionale Galileo via the radial velocity method. Transits of the planet were observed by the Spitzer Space Telescope in 2017. Later that year, it was predicted that HD 219134 c has an atmosphere. Characteristics Mass, radius, and temperature HD 219134 c is confirmed to be a rocky super-Earth, meaning that it has a solid surface but is significantly larger than Earth. The mass of the planet has been determined to be around 4.36 with very low uncertainty. Its radius was found to be 1.511 (9,627 km), once again with a small e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astronomy & Astrophysics
''Astronomy & Astrophysics'' is a monthly peer-reviewed scientific journal covering theoretical, observational, and instrumental astronomy and astrophysics. The journal is run by a Board of Directors representing 27 sponsoring countries plus a representative of the European Southern Observatory. The journal is published by EDP Sciences and the editor-in-chief is . History Origins ''Astronomy and Astrophysics'' (A&A) was created as an answer to the publishing scenario found in Europe in the 1960s. At that time, multiple journals were being published in several countries around the continent. These journals usually had a limited number of subscribers, and published articles in languages other than English, resulting in a small number of citations compared to American and British journals. Starting in 1963, conversations between astronomers from European countries assessed the need for a common astronomical journal. On 8 April 1968, leading astronomers from Belgium, Denmark, Fran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The Astrophysical Journal
''The Astrophysical Journal'', often abbreviated ''ApJ'' (pronounced "ap jay") in references and speech, is a peer-reviewed scientific journal of astrophysics and astronomy, established in 1895 by American astronomers George Ellery Hale and James Edward Keeler. The journal discontinued its print edition and became an electronic-only journal in 2015. Since 1953 ''The Astrophysical Journal Supplement Series'' (''ApJS'') has been published in conjunction with ''The Astrophysical Journal'', with generally longer articles to supplement the material in the journal. It publishes six volumes per year, with two 280-page issues per volume. ''The Astrophysical Journal Letters'' (''ApJL''), established in 1967 by Subrahmanyan Chandrasekhar as Part 2 of ''The Astrophysical Journal'', is now a separate journal focusing on the rapid publication of high-impact astronomical research. The three journals were published by the University of Chicago Press for the American Astronomical Society u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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