|
Whole Earth Telescope
The Whole Earth Telescope is an international network of astronomers that collaborate to study variable stars. The distribution of the observatories in longitude allow the selected targets to be continuously monitored despite the rotation of the Earth. History This concept was devised by American astronomer R. Edward Nather and Don E. Winget of the University of Texas at Austin. The consortium consists of individual astronomers interested in collaborating to study targets designated by a principal investigator. Where colleagues are not available, astronomers are dispatched to sites that allow telescope time to visitors. Initial funding for WET came from a grant by the US National Science Foundation, which lasted through 1998. For each site, an observing run begins when the sky is dark, and continues until stopped by weather or dawn. A photometer is used to observe the target object, a nearby comparison star, and the background sky. The data is then sent to the control center. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Don Winget
Don E. Winget is an American astronomer and astrophysicist who studies white dwarf stars. He is the Harlan J. Smith Centennial Professor in Astronomy and a university distinguished teaching professor at the University of Texas at Austin. Research Much of Winget's research concerns the study of white dwarf stars. Winget's doctoral research at the University of Rochester predicted the existence of DBV stars, a certain class of pulsating white dwarf. After becoming a faculty member at the University of Texas, he and his colleagues discovered GD 358, a star of this class, fulfilling the prediction of his dissertation and marking the first time in which a class of variable stars was predicted to exist before any instances of it were observed. With Ed Nather, his colleague at University of Texas, Winget introduced the technique for studying the seismology and the inner structure of white dwarfs called "Whole Earth Telescope". The technique involves coordinating a network of small ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Ultraviolet Explorer
International Ultraviolet Explorer (IUE or Explorer 57, formerly SAS-D), was the first space observatory primarily designed to take ultraviolet (UV) electromagnetic spectrum. The satellite was a collaborative project between NASA, the United Kingdom's Science and Engineering Research Council (SERC, formerly UKSRC) and the European Space Agency (ESA), formerly European Space Research Organisation (ESRO). The mission was first proposed in early 1964, by a group of scientists in the United Kingdom, and was launched on 26 January 1978 aboard a NASA Thor-Delta 2914 launch vehicle. The mission lifetime was initially set for 3 years, but in the end it lasted 18 years, with the satellite being shut down in 1996. The switch-off occurred for financial reasons, while the telescope was still functioning at near original efficiency. It was the first space observatory to be operated in real time by astronomers who visited the groundstations in the United States and Europe. Astronomers made ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of Delaware
The University of Delaware (colloquially UD or Delaware) is a public land-grant research university located in Newark, Delaware. UD is the largest university in Delaware. It offers three associate's programs, 148 bachelor's programs, 121 master's programs (with 13 joint degrees), and 55 doctoral programs across its eight colleges. The main campus is in Newark, with satellite campuses in Dover, Wilmington, Lewes, and Georgetown. It is considered a large institution with approximately 18,200 undergraduate and 4,200 graduate students. It is a privately governed university which receives public funding for being a land-grant, sea-grant, and space-grant state-supported research institution. UDel is ranked among the top 150 universities in the U.S. UD is classified among "R1: Doctoral Universities – Very high research activity". According to the National Science Foundation, UD spent $186 million on research and development in 2018, ranking it 119th in the nation. It is rec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iowa State University
Iowa State University of Science and Technology (Iowa State University, Iowa State, or ISU) is a public land-grant research university in Ames, Iowa. Founded in 1858 as the Iowa Agricultural College and Model Farm, Iowa State became one of the nation's first designated land-grant institution when the Iowa Legislature accepted the provisions of the 1862 Morrill Act on September 11, 1862, making Iowa the first state in the nation to do so. On July 4, 1959, the college was officially renamed Iowa State University of Science and Technology. Iowa State is classified among "R1: Doctoral Universities – Very high research activity". The university is home to the Ames Laboratory, one of ten national U.S. Department of Energy Office of Science research laboratories, the Biorenewables Research Laboratory, the Plant Sciences Institute, and various other research institutes. Iowa State is the second-largest university in the State of Iowa by undergraduate enrollment. The university's ac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mount Cuba Astronomical Observatory
Mount Cuba Astronomical Observatory is an astronomical observatory is located at 1610 Hillside Mill Road, Greenville, Delaware, United States. This observatory is home to a 0.6-meter telescope used by the Delaware Astronomical Society, the University of Delaware, and the Whole Earth Telescope. Associated with the Observatory is the Mt. Cuba Astronomy Group (MCAG). The MCAG is composed of interested amateurs and engages in astronomy education and public outreach. Meetings are held the second Tuesday of each month at the Mt. Cuba Astronomical Observatory. A Sunquest sundial, designed and machined by Richard L. Schmoyer, is on the Mount Cuba Observatory grounds near the parking lot. This mean time sundial automatically corrects for the equation of time through the use of an analemma-inspired gnomon. See also *Mt. Cuba Center *List of astronomical observatories *Whole Earth Telescope The Whole Earth Telescope is an international network of astronomers that collaborate to st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cataclysmic Variables
In astronomy, cataclysmic variable stars (CVs) are stars which irregularly increase in brightness by a large factor, then drop back down to a quiescent state. They were initially called novae (), since ones with an outburst brightness visible to the naked eye and an invisible quiescent brightness appeared as new stars in the sky. Cataclysmic variable stars are binary stars that consist of two components; a white dwarf primary, and a mass transferring secondary. The stars are so close to each other that the gravity of the white dwarf distorts the secondary, and the white dwarf accretes matter from the companion. The tightest currently observed orbit in a hydrogen-rich system is 51 minutes in ZTF J1813+4251. Therefore, the secondary is often referred to as the ''donor star''. The infalling matter, which is usually rich in hydrogen, forms in most cases an accretion disk around the white dwarf. Strong UV and X-ray emission is often seen from the accretion disc, powered by the lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rapidly Oscillating Ap Star
Rapidly oscillating Ap stars (roAp stars) are a subtype of the Ap star class that exhibit short-timescale rapid photometric or radial velocity variations. The known periods range between 5 and 23 minutes. They lie in the δ Scuti instability strip on the main sequence. Discovery The first roAp star to be discovered was HD 101065 ( Przybylski's Star). The oscillations were discovered by Donald Kurtz using the telescope at the South African Astronomical Observatory, who saw 10–20-millimagnitude variations in the light curve of the star with a period of 12.15 minutes. Classification The roAp stars are sometimes referred to as rapidly oscillating α2 Canum Venaticorum variables. Both the roAp stars and some α2 CVn variables lie on the δ Scuti instability strip and are magnetic chemically peculiar stars, but the roAp stars have very short periods less than an hour. Oscillations The roAp stars oscillate in high-overtone, low-degree, non-radial pressure modes. The usual model t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Delta Scuti Variable
A Delta Scuti variable (sometimes termed dwarf cepheid when the V-band amplitude is larger than 0.3 mag.) is a subclass of young pulsating star. These variables as well as classical cepheids are important standard candles and have been used to establish the distance to the Large Magellanic Cloud, globular clusters, open clusters, and the Galactic Center. The variables follow a period-luminosity relation in certain passbands like other standard candles such as Cepheids. SX Phoenicis variables are generally considered to be a subclass of Delta Scuti variables that contain old stars, and can be found in globular clusters. SX Phe variables also follow a period-luminosity relation. One last sub-class are the pre-main sequence (PMS) Delta Scuti variables. The OGLE and MACHO surveys have detected nearly 3000 Delta Scuti variables in the Large Magellanic Cloud. Typical brightness fluctuations are from 0.003 to 0.9 magnitudes in V over a period of a few hours, although the amplitude ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astroseismology
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 the pe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PG 1159-035
PG 1159-035 is the prototypical PG 1159 star after which the class of PG 1159 stars was named. It was discovered in the Palomar-Green survey of ultraviolet-excess stellar objects and, like the other PG 1159 stars, is in transition between being the central star of a planetary nebula and being a white dwarf. The luminosity of PG 1159-035 was observed to vary in 1979, and it was given the variable star designation ''GW Vir'' in 1985. Variable PG 1159 stars may be called ''GW Vir'' stars, or the class may be split into ''DOV'' and ''PNNV'' stars. The variability of PG 1139-035, like that of other GW Vir stars, arises from non-radial gravity wave pulsations within itself. Its light curve has been observed intensively by the Whole Earth Telescope over a 264-hour period in March 1989, and over 100 of its vibrational modes have been found in the resulting vibrational spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a spe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frequency
Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is equal to one event per second. The period is the interval of time between events, so the period is the reciprocal of the frequency. For example, if a heart beats at a frequency of 120 times a minute (2 hertz), the period, —the interval at which the beats repeat—is half a second (60 seconds divided by 120 beats). Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals (sound), radio waves, and light. Definitions and units For cyclical phenomena such as oscillations, waves, or for examples of simple harmonic motion, the term ''frequency'' is defined as the number of cycles or vibrations per unit of time. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pulsating White Dwarf
A pulsating white dwarf is a white dwarf star whose luminosity varies due to non-radial gravity wave pulsations within itself. Known types of pulsating white dwarfs include DAV, or ZZ Ceti, stars, with hydrogen-dominated atmospheres and the spectral type DA; DBV, or V777 Her, stars, with helium-dominated atmospheres and the spectral type DB; and GW Vir stars, with atmospheres dominated by helium, carbon, and oxygen, and the spectral type PG 1159. (Some authors also include non-PG 1159 stars in the class of GW Vir stars.) GW Vir stars may be subdivided into DOV and PNNV stars; they are not, strictly speaking, white dwarfs but ''pre-white dwarfs'' which have not yet reached the white dwarf region on the Hertzsprung-Russell diagram. A subtype of DQV stars, with carbon-dominated atmospheres, has also been proposed, and in May 2012, the first extremely low mass variable (ELMV) white dwarf was reported. These variables all exhibit small (1%–30%) variations in light output, arisi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
