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Asteroseismology
Asteroseismology or astroseismology is the study of oscillations in stars. Stars have many resonant modes and frequencies, and the path of sound waves passing through a star depends on the speed of sound, which in turn depends on local temperature and chemical composition. Because the resulting oscillation modes are sensitive to different parts of the star, they inform astronomers about the internal structure of the star, which is otherwise not directly possible from overall properties like brightness and surface temperature. Asteroseismology is closely related to helioseismology, the study of stellar pulsation specifically in the Sun. Though both are based on the same underlying physics, more and qualitatively different information is available for the Sun because its surface can be resolved. Theoretical background By linearly perturbing the equations defining the mechanical equilibrium of a star (i.e. mass conservation and hydrostatic equilibrium) and assuming that th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CoRoT
CoRoT (French: ; English: Convection, Rotation and planetary Transits) was a space telescope mission which operated from 2006 to 2013. The mission's two objectives were to search for extrasolar planets with short orbital periods, particularly those of large terrestrial size, and to perform asteroseismology by measuring solar-like oscillations in stars. The mission was led by the French Space Agency (CNES) in conjunction with the European Space Agency (ESA) and other international partners. Among the notable discoveries was CoRoT-7b, discovered in 2009 which became the first exoplanet shown to have a rock or metal-dominated composition. CoRoT was launched at 14:28:00 UTC on 27 December 2006, atop a Soyuz 2.1b rocket, reporting first light on 18 January 2007. Subsequently, the probe started to collect science data on 2 February 2007. CoRoT was the first spacecraft dedicated to the detection of transiting extrasolar planets, opening the way for more advanced probes such as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wide Field Infrared Explorer
Wide-field Infrared Explorer (WIRE, also Explorer 75 and SMEX-5) was a NASA satellite launched on 5 March 1999, on the Pegasus XL launch vehicle into polar orbit between above the surface of Earth. WIRE was intended to be a four-month infrared survey of the entire sky at 21-27 µm and 9-15 µm, specifically focusing on starburst galaxies and luminous protogalaxies. WIRE had problems and was unable to carry out its IR survey, and was deactivated on 30 September 2000, and finally reentered and burned up in 2011. Science The science team was based at the Infrared Processing and Analysis Center (IPAC) in Pasadena, California. Flight operations, integration, and testing were from Goddard Space Flight Center in Maryland. The telescope was built by Space Dynamics Laboratory in Utah. Premature ejection of the spacecraft aperture cover led to depletion of the solid hydrogen shortly after launch, ending the primary science mission. The onboard star tracker remained functiona ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helioseismology
Helioseismology, a term coined by Douglas Gough, is the study of the structure and dynamics of the Sun through its oscillations. These are principally caused by sound waves that are continuously driven and damped by convection near the Sun's surface. It is similar to geoseismology, or asteroseismology (also coined by Gough), which are respectively the studies of the Earth or stars through their oscillations. While the Sun's oscillations were first detected in the early 1960s, it was only in the mid-1970s that it was realized that the oscillations propagated throughout the Sun and could allow scientists to study the Sun's deep interior. The modern field is separated into global helioseismology, which studies the Sun's resonant modes directly, and local helioseismology, which studies the propagation of the component waves near the Sun's surface. Helioseismology has contributed to a number of scientific breakthroughs. The most notable was to show the predicted neutrino flux fro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transiting Exoplanet Survey Satellite
Transiting Exoplanet Survey Satellite (TESS, Explorer 95 or MIDEX-7) 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 18 April 2018, atop a Falcon 9 launch vehicle and was placed into a highly elliptical 13.70-day orbit around the Earth. The first light image from TESS was taken on 7 August 2018, and released publicly on 17 September 2018. Over the course of the two-year primary mission, TESS was expected to ultimately detect about 1,250 transiting exoplanets orbiting the targeted stars, and an additional 13,000 transiting planets orbiting additional stars in the fields that TESS would observe. As of 5 November 2022, TESS had identified 5,969 candidate exoplanets, of which only 268 had been confirmed and 1720 had been dismissed as false positives. After the end of the primary mission around 4 July 2020, data from the prim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microvariability And Oscillations Of STars Telescope
The Microvariability and Oscillations of Stars/Microvariabilité et Oscillations STellaire (MOST), was Canada's first space telescope. Up until nearly 10 years after its launch it was also the smallest space telescope in orbit (for which its creators nicknamed it the "Humble Space Telescope", in reference to one of the largest, the Hubble). MOST was the first spacecraft dedicated to the study of asteroseismology, subsequently followed by the now-completed CoRoT and Kepler missions. It was also the first Canadian science satellite launched since ISIS II, 32 years previously. Description As its name suggests, its primary mission was to monitor variations in star light, which it did by observing a single target for a long period of time (up to 60 days). Typically, larger space telescopes cannot afford to remain focused on a single target for so long due to the demand for their resources. At , wide and tall, and deep, it was the size and weight of a small chest or an extra-large ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kepler (spacecraft)
The Kepler space telescope is a disused space telescope launched by NASA in 2009 to discover Earth-sized planets orbiting other stars. Named after astronomer Johannes Kepler, the spacecraft was launched into an Earth-trailing heliocentric orbit. The principal investigator was William J. Borucki. After nine and a half years of operation, the telescope's reaction control system fuel was depleted, and NASA announced its retirement on October 30, 2018. Designed to survey a portion of Earth's region of the Milky Way to discover Earth-size exoplanets in or near habitable zones and estimate how many of the billions of stars in the Milky Way have such planets, Kepler's sole scientific instrument is a photometer that continually monitored the brightness of approximately 150,000 main sequence stars in a fixed field of view. These data were transmitted to Earth, then analyzed to detect periodic dimming caused by exoplanets that cross in front of their host star. Only planets whose ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brunt–Väisälä Frequency
In atmospheric dynamics, oceanography, asteroseismology and geophysics, the Brunt–Väisälä frequency, or buoyancy frequency, is a measure of the stability of a fluid to vertical displacements such as those caused by convection. More precisely it is the frequency at which a vertically displaced parcel will oscillate within a statically stable environment. It is named after David Brunt and Vilho Väisälä. It can be used as a measure of atmospheric stratification. Derivation for a general fluid Consider a parcel of water or gas that has density \rho_0. This parcel is in an environment of other water or gas particles where the density of the environment is a function of height: \rho = \rho (z). If the parcel is displaced by a small vertical increment z', ''and it maintains its original density, so that its volume does not change,'' it will be subject to an extra gravitational force against its surroundings of: :\rho_0 \frac = - g \left rho (z)-\rho (z+z')\right/math> where g i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Color Index
In astronomy, the color index is a simple numerical expression that determines the color of an object, which in the case of a star gives its temperature. The lower the color index, the more blue (or hotter) the object is. Conversely, the larger the color index, the more red (or cooler) the object is. This is a consequence of the logarithmic magnitude scale, in which brighter objects have smaller (more negative) magnitudes than dimmer ones. For comparison, the whitish Sun has a B−V index of , whereas the bluish Rigel has a B−V of −0.03 (its B magnitude is 0.09 and its V magnitude is 0.12, B−V = −0.03). Traditionally, the color index uses Vega as a zero point. To measure the index, one observes the magnitude of an object successively through two different filters, such as U and B, or B and V, where U is sensitive to ultraviolet rays, B is sensitive to blue light, and V is sensitive to visible (green-yellow) light (see also: UBV system). The set of passbands or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frequency Separation
Frequency separation within astrophysics, is a term used in both Helioseismology and Asteroseismology Asteroseismology or astroseismology is the study of oscillations in stars. Stars have many resonant modes and frequencies, and the path of sound waves passing through a star depends on the speed of sound, which in turn depends on local temperature .... It refers to the spacing in frequency between adjacent modes of oscillation, having the same angular degree (l) but different radial order (n). For a Sun-like star, the frequency can be further described using the 'large frequency spacing' between modes of different radial order (136 μHz in the Sun), and the 'small frequency spacing' between modes of even and odd angular degree within the same radial order (9.0 μHz in the Sun). The period corresponding to the large frequency spacing can be shown to be approximately the same as the time required for a sound wave to travel to the centre of the Sun and return, confirming the global ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PLATO (spacecraft)
PLAnetary Transits and Oscillations of stars (PLATO) is a space telescope under development by the European Space Agency for launch in 2026. The mission goals are to search for planetary transits across up to one million stars, and to discover and characterize rocky extrasolar planets around yellow dwarf stars (like the Sun), subgiant stars, and red dwarf stars. The emphasis of the mission is on Earth-like planets in the habitable zone around Sun-like stars where water can exist in a liquid state. It is the third medium-class mission in ESA's Cosmic Vision programme and is named after the influential Greek philosopher Plato. A secondary objective of the mission is to study stellar oscillations or seismic activity in stars to measure stellar masses and evolution and enable the precise characterization of the planet host star, including its age. History PLATO was first proposed in 2007 to the European Space Agency (ESA) by a team of scientists in response to the call for ESA's ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BRITE
BRITE-Constellation is an ongoing space mission carrying out two-band photometry in wide fields with a constellation of six (presently, three operational) BRIght Target Explorer (BRITE) nanosatellites. The mission was built by a consortium of three countries, Canada, Austria, and Poland, each operating two BRITE satellites. The six satellites were launched into low-Earth orbits between February 2013 and August 2014. Each satellite is a cube-shaped spacecraft with sides of hosting an optical telescope of aperture feeding an uncooled CCD with a field of view of approximately 20° × 24°. The satellites were intended for photometry of the brightest stars in single passband located in the blue (three satellites) or red (the other three satellites) part of the optical range. Early history The idea of using microsatellite for scientific observations, especially for photometry of bright stars, was born during discussions on possible designs for Canada's first scientific satellite. Dis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
