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Sagittarius Dwarf Elliptical Galaxy
The Sagittarius Dwarf Spheroidal Galaxy (Sgr dSph), also known as the Sagittarius Dwarf Elliptical Galaxy (Sgr dE or Sag DEG), is an elliptical loop-shaped satellite galaxy of the Milky Way. It contains four globular clusters in its main body, with the brightest of them — NGC 6715 (M54) — known well before the discovery of the galaxy itself in 1994. Sgr dSph is roughly 10,000 light-years in diameter, and is currently about 70,000 light-years from Earth, travelling in a polar orbit (an orbit passing over the Milky Way's galactic poles) at a distance of about 50,000 light-years from the core of the Milky Way (about one third of the distance of the Large Magellanic Cloud). In its looping, spiraling path, it has passed through the plane of the Milky Way several times in the past. In 2018, the Gaia project of the European Space Agency showed that Sgr dSph had caused perturbations in a set of stars near the Milky Way's core, causing unexpected rippling movements of the stars trig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epoch (astronomy)
In astronomy, an epoch or reference epoch is a instant, moment in time used as a reference point for some time-varying astronomical quantity. It is useful for the celestial coordinates or orbital elements of a Astronomical object, celestial body, as they are subject to Perturbation (astronomy), perturbations and vary with time. These time-varying astronomical quantities might include, for example, the mean longitude or mean anomaly of a body, the node of its orbit relative to a reference plane, the direction of the apogee or Perihelion and aphelion, aphelion of its orbit, or the size of the major axis of its orbit. The main use of astronomical quantities specified in this way is to calculate other relevant parameters of motion, in order to predict future positions and velocities. The applied tools of the disciplines of celestial mechanics or its subfield orbital mechanics (for predicting orbital paths and positions for bodies in motion under the gravitational effects of other bodi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scientific American
''Scientific American'', informally abbreviated ''SciAm'' or sometimes ''SA'', is an American popular science magazine. Many scientists, including Albert Einstein and Nikola Tesla, have contributed articles to it, with more than 150 Nobel Prize-winners being featured since its inception. In print since 1845, it is the oldest continuously published magazine in the United States. ''Scientific American'' is owned by Springer Nature, which is a subsidiary of Holtzbrinck Publishing Group. History ''Scientific American'' was founded by inventor and publisher Rufus Porter (painter), Rufus Porter in 1845 as a four-page weekly newspaper. The first issue of the large-format New York City newspaper was released on August 28, 1845. Throughout its early years, much emphasis was placed on reports of what was going on at the United States Patent and Trademark Office, U.S. Patent Office. It also reported on a broad range of inventions including perpetual motion machines, an 1860 devi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Messier 54
Messier 54 (also known as M54 or NGC 6715) is a globular cluster in the constellation Sagittarius. It was discovered by Charles Messier in 1778 and then included in his catalog of objects that could be mistaken for comets. It is easily found in the sky, being close to the star ζ Sagittarii. It is, however, not resolvable into individual stars even with larger amateur telescopes. In July 2009, a team of astronomers reported that they had found evidence of an intermediate-mass black hole in the core of M54. Distance Previously thought to belong to the Milky Way at a distance from Earth of about 50,000 light-years, it was discovered in 1994 that M54 most likely belongs to the Sagittarius Dwarf Elliptical Galaxy (SagDEG), making it the first globular cluster formerly thought to be part of our galaxy reassigned to extragalactic status, even if not recognized as such for more than two centuries. As it is located in SagDEG's center, some authors think it actually may be its core ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2MASS
The Two Micron All-Sky Survey, or 2MASS, was an astronomical survey of the whole sky in infrared light. It took place between 1997 and 2001, in two different locations: at the U.S. Fred Lawrence Whipple Observatory on Mount Hopkins, Arizona, and at the Cerro Tololo Inter-American Observatory in Chile, each using a 1.3-meter telescope for the Northern and Southern Hemisphere, respectively. It was conducted in the short-wavelength infrared at three distinct frequency bands ( J, H, and K) near 2 micrometres, from which the photometric survey with its HgCdTe detectors derives its name. 2MASS produced an astronomical catalog with over 300 million observed objects, including minor planets of the Solar System, brown dwarfs, low-mass stars, nebulae, star clusters and galaxies. In addition, 1 million objects were cataloged in the ''2MASS Extended Source Catalog'' (''2MASX''). The cataloged objects are designated with a "2MASS" and "2MASX"-prefix respectively. Catalog The fina ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of Massachusetts Amherst
The University of Massachusetts Amherst (UMass Amherst) is a public land-grant research university in Amherst, Massachusetts, United States. It is the flagship campus of the University of Massachusetts system and was founded in 1863 as the Massachusetts Agricultural College. It is also a member of the Five College Consortium, along with four other colleges in the Pioneer Valley. UMass Amherst has the largest undergraduate population in Massachusetts with roughly 24,000 enrolled undergraduates. The university offers academic degrees in 109 undergraduate, 77 master's, and 48 doctoral programs in nine schools and colleges. It is classified among "R1: Doctoral Universities – Very high research activity". According to the National Science Foundation, the university spent $211 million on research and development in 2018. The university's 21 varsity athletic teams compete in NCAA Division I and are collectively known as the Minutemen and Minutewomen. The university is a memb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of Virginia
The University of Virginia (UVA) is a Public university#United States, public research university in Charlottesville, Virginia, United States. It was founded in 1819 by Thomas Jefferson and contains his The Lawn, Academical Village, a World Heritage Site, UNESCO World Heritage Site. The original governing Board of Visitors included three List of presidents of the United States, U.S. presidents: Jefferson, James Madison, and James Monroe, the latter as sitting president of the United States at the time of its foundation. As its first two Rector (academia)#United States, rectors, Presidents Jefferson and Madison played key roles in the university's foundation, with Jefferson designing both the #1800s, original courses of study and the university's #Academical Village, architecture. Located within its 1,135-acre central campus, the university is composed of eight undergraduate and three professional schools: the University of Virginia School of Law, School of Law, the University ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Astrophysics
Astrophysics is a science that employs the methods and principles of physics and chemistry in the study of astronomical objects and phenomena. As one of the founders of the discipline, James Keeler, said, astrophysics "seeks to ascertain the nature of the heavenly bodies, rather than their positions or motions in space—''what'' they are, rather than ''where'' they are", which is studied in celestial mechanics. Among the subjects studied are the Sun ( solar physics), other stars, galaxies, extrasolar planets, the interstellar medium, and the cosmic microwave background. Emissions from these objects are examined across all parts of the electromagnetic spectrum, and the properties examined include luminosity, density, temperature, and chemical composition. Because astrophysics is a very broad subject, ''astrophysicists'' apply concepts and methods from many disciplines of physics, including classical mechanics, electromagnetism, statistical mechanics, thermodynamics, quantum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Publications Of The Astronomical Society Of The Pacific
''Publications of the Astronomical Society of the Pacific'' (often abbreviated as ''PASP'' in references and literature) is a monthly peer-reviewed scientific journal managed by the Astronomical Society of the Pacific. It publishes research and review papers, instrumentation papers and dissertation summaries in the fields of astronomy and astrophysics. Between 1999 and 2016 it was published by the University of Chicago Press and since 2016, it has been published by IOP Publishing. The current editor-in-chief is Jeff Mangum of the National Radio Astronomy Observatory. ''PASP'' has been published monthly since 1899, and along with ''The Astrophysical Journal'', ''The Astronomical Journal'', ''Astronomy and Astrophysics'', and the ''Monthly Notices of the Royal Astronomical Society'', is one of the primary journals for the publication of astronomical research. See also * ''List of astronomy journals'' References Astronomy journals IOP Publishing academic journals Publications ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neutral Hydrogen
The hydrogen line, 21 centimeter line, or H I line is a spectral line that is created by a change in the energy state of solitary, electrically neutral hydrogen atoms. It is produced by a spin-flip transition, which means the direction of the electron's spin is reversed relative to the spin of the proton. This is a quantum state change between the two hyperfine levels of the hydrogen 1 s ground state. The electromagnetic radiation producing this line has a frequency of (1.42 GHz), which is equivalent to a wavelength of in a vacuum. According to the Planck–Einstein relation , the photon emitted by this transition has an energy of []. The constant of proportionality, , is known as the Planck constant. The hydrogen line frequency lies in the L band, which is located in the lower end of the microwave region of the electromagnetic spectrum. It is frequently observed in radio astronomy because those radio waves can penetrate the large clouds of interstellar cosm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Population II
In 1944, Walter Baade categorized groups of stars within the Milky Way into stellar populations. In the abstract of the article by Baade, he recognizes that Jan Oort originally conceived this type of classification in 1926. Baade observed that bluer stars were strongly associated with the spiral arms, and yellow stars dominated near the central galactic bulge and within globular star clusters. Two main divisions were deemed ''populationI'' and ''populationII stars'', with another newer, hypothetical division called ''populationIII'' added in 1978. Among the population types, significant differences were found with their individual observed stellar spectra. These were later shown to be very important and were possibly related to star formation, observed kinematics, stellar age, and even galaxy evolution in both spiral and elliptical galaxies. These three simple population classes usefully divided stars by their chemical composition, or '' metallicity''. In astrophysics n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Galactic Center
The Galactic Center is the barycenter of the Milky Way and a corresponding point on the rotational axis of the galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a compact Astronomical radio source, radio source which is almost exactly at the galactic rotational center. The Galactic Center is approximately away from Earth in the direction of the constellations Sagittarius (constellation), Sagittarius, Ophiuchus, and Scorpius, where the Milky Way appears brightest, visually close to the Butterfly Cluster (M6) or the star Shaula, south to the Pipe Nebula. There are around 10 million stars within one parsec of the Galactic Center, dominated by red giants, with a significant population of massive supergiants and Wolf–Rayet stars from star formation in the region around 1 million years ago. The core stars are a small part within the much wider central region, called ''galactic bulge''. Discovery Be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Canis Major Dwarf Galaxy
The Canis Major Overdensity (''CMa Overdensity'') or Canis Major Dwarf Galaxy (''CMa Dwarf'') is a disputed dwarf irregular galaxy in the Local Group, located in the same part of the sky as the constellation Canis Major. The supposed small galaxy contains a relatively high percentage of red giants and is thought to contain an estimated one billion stars in all. At the time of its announcement, the Canis Major Dwarf Galaxy was classified as an irregular galaxy and was thought to be the closest neighboring galaxy to the Earth's location in the Milky Way, located about away from the Solar System and from the Galactic Center. It has a roughly elliptical shape and is thought to contain as many stars as the Sagittarius Dwarf Elliptical Galaxy, the previous contender for closest galaxy to Earth, though later studies disputed this conclusion. Discovery The existence of a strong elliptical-shaped stellar overdensity was reported in November 2003 by an international team of French, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
