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Galactic Plane
The galactic plane is the plane (geometry), plane on which the majority of a disk-shaped galaxy's mass lies. The directions perpendicular to the galactic plane point to the galactic poles. In actual usage, the terms ''galactic plane'' and ''galactic poles'' usually refer specifically to the plane and poles of the Milky Way, in which Planet Earth is located. Some irregular galaxy, galaxies are irregular and do not have any well-defined disk. Even in the case of a barred spiral galaxy like the Milky Way, defining the galactic plane is slightly imprecise and arbitrary since the stars are not perfectly coplanar. In 1959, the International Astronomical Union, IAU defined the position of the Milky Way's north galactic pole as exactly right ascension, RA = , declination, Dec = in the then-used B1950 epoch (astronomy), epoch; in the currently-used J2000 epoch, after precession is taken into account, its position is RA , Dec . This position is in Coma Berenices, near the bright star Arctu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Precession
Precession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In other words, if the axis of rotation of a body is itself rotating about a second axis, that body is said to be precessing about the second axis. A motion in which the second Euler angle changes is called '' nutation''. In physics, there are two types of precession: torque-free and torque-induced. In astronomy, ''precession'' refers to any of several slow changes in an astronomical body's rotational or orbital parameters. An important example is the steady change in the orientation of the axis of rotation of the Earth, known as the precession of the equinoxes. Torque-free or torque neglected Torque-free precession implies that no external moment (torque) is applied to the body. In torque-free precession, the angular momentum is a constant, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Zone Of Avoidance
The Zone of Avoidance (ZOA, ZoA), or Zone of Galactic Obscuration (ZGO), is the area of the sky that is obscured by the Milky Way. The Zone of Avoidance was originally called the Zone of Few Nebulae in an 1878 paper by English astronomer Richard Proctor that referred to the distribution of "nebulae" in John Herschel's '' General Catalogue of Nebulae''.Kraan-Korteweg & Lahav. 2000, p. 2 Background When viewing space from Earth, the attenuation, interstellar dust and stars in the plane of the Milky Way (the galactic plane) obstruct the view of around 20% of the extragalactic sky at visible wavelengths. As a result, optical galaxy catalogues are usually incomplete close to the galactic plane. Modern developments Many projects have attempted to bridge the gap in knowledge caused by the Zone of Avoidance. The dust and gas in the Milky Way cause extinction at optical wavelengths, and foreground stars can be confused with background galaxies. However, the effect of extinction drops a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
LHS 1815b
LHS 1815 b (also known as TOI-704 b) is a thick disk exoplanet discovered in 2020 by TESS. The planet is located outside the galactic plane. Characteristics LHS 1815 b is a terrestrial planet (super-Earth) with a mass of 0.0132 and a radius of 0.09707 , discovered by TESS Tess or TESS may refer to: Film and theatre * Tess (1979 film), ''Tess'' (1979 film), a 1979 film adaptation of ''Tess of the d'Urbervilles'' * Tess (2016 film), ''Tess'' (2016 film), a South African production Music * Tess (band), a Spanish pop ... in 2020. It is the first known example of a "thick-disk planet" located within the galactic thick disk, a structure much higher than the positions of other planetary systems discovered by TESS." Orbit The orbital period is 3.81433 days and the semimajor axis is 0.0404 au. Other designations LHS 1815 b is also known as TOI-704 b and TIC 260004324 b. References Exoplanets discovered in 2020 Pictor Exoplanets discovered by TESS {{exoplanet-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
NGC 891
NGC 891 (also known as Caldwell 23, the Silver Sliver Galaxy, and the Outer Limits Galaxy) is an edge-on unbarred spiral galaxy about 30 million light-years away in the constellation Andromeda. It was discovered by William Herschel on October 6, 1784. The galaxy is a member of the NGC 1023 group of galaxies in the Local Supercluster. It has an H II nucleus. The object is visible in small to moderate size telescopes as a faint elongated smear of light with a dust lane visible in larger apertures. In 1999, the Hubble Space Telescope imaged NGC 891 in infrared. In 2005, due to its attractiveness and scientific interest, NGC 891 was selected to be the first light image of the Large Binocular Telescope. In 2012, it was again used as a first light image of the Lowell Discovery Telescope with the Large Monolithic Imager. Supernova SN 1986J was discovered on August 21, 1986 at apparent magnitude 14. Properties NGC 891 looks as the Milky Way would look like when viewed edge-on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Spiral Galaxy
Spiral galaxies form a galaxy morphological classification, class of galaxy originally described by Edwin Hubble in his 1936 work ''The Realm of the Nebulae''Alt URL pp. 124–151) and, as such, form part of the Hubble sequence. Most spiral galaxies consist of a flat, rotating Disc (galaxy), disk containing stars, Interstellar medium, gas and dust, and a central concentration of stars known as the Bulge (astronomy), bulge. These are often surrounded by a much fainter Galactic halo, halo of stars, many of which reside in globular clusters. Spiral galaxies are named by their spiral structures that extend from the center into the galactic disc. The spiral arms are sites of ongoing star formation and are brighter than the surrounding disc because of the young, hot OB stars that inhabit them. Roughly two-thirds of all spirals are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
NGC 4452
NGC 4452 is an edge-on lenticular galaxy that is part of the Virgo Cluster. NGC 4452 is about away from Earth and in diameter. This galaxy was first seen by William Herschel in 1784 with his telescope. NGC 4452 is so thin that it is actually difficult to determine what type of disk galaxy it is. Its lack of a visible dust lane indicates that it is a low-dust lenticular galaxy, although it is still possible that a view from on top would reveal spiral structure. The unusual stellar line segment spans about 35,000 light-years from end to end. Near NGC 4452's center is a slight bulge of stars, while hundreds of background galaxies are visible far in the distance. Galaxies that appear this thin are rare mostly because Earth must reside (nearly) in the extrapolated planes of their thin galactic disks. Galaxies that actually are this thin are relatively common; for example, the Milky Way Galaxy is thought to be about this thin. NGC 4452 appears to be very similar to galaxy IC 335 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
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] [Amazon] |
Celestial Pole
The north and south celestial poles are the two points in the sky where Earth's axis of rotation, indefinitely extended, intersects the celestial sphere. The north and south celestial poles appear permanently directly overhead to observers at Earth's North Pole and South Pole, respectively. As Earth spins on its axis, the two celestial poles remain fixed in the sky, and all other celestial points appear to rotate around them, completing one circuit per day (strictly, per sidereal day). The celestial poles are also the poles of the celestial equatorial coordinate system, meaning they have declinations of +90 degrees and −90 degrees (for the north and south celestial poles, respectively). Despite their apparently fixed positions, the celestial poles in the long term do not actually remain permanently fixed against the background of the stars. Because of a phenomenon known as the precession of the equinoxes, the poles trace out circles on the celestial sphere, with a period ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Galactic Coordinate System
The galactic coordinate system is a celestial coordinate system in spherical coordinates, with the Sun as its center, the primary direction aligned with the approximate center of the Milky Way Galaxy, and the fundamental plane (spherical coordinates), fundamental plane parallel to an approximation of the galactic plane but offset to its north. It uses the Right-hand rule, right-handed convention, meaning that coordinates are positive toward the north and toward the east in the fundamental plane (spherical coordinates), fundamental plane. Spherical coordinates Galactic longitude Longitude (symbol ) measures the angle, angular distance of an object eastward along the galactic equator from the Galactic Center. Analogous to terrestrial longitude, galactic longitude is usually measured in degrees (°). Galactic latitude Latitude (symbol ) measures the angle of an object northward of the galactic equator (or midplane) as viewed from Earth. Analogous to terrestrial latitude, gala ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Sculptor (constellation)
Sculptor is a faint constellation in the southern sky. It represents a sculpture, sculptor. It was introduced by Nicolas Louis de Lacaille in the 18th century. He originally named it Apparatus Sculptoris (the sculptor's studio), but the name was later shortened. History The region to the south of Cetus and Aquarius had been named by Aratus in 270 BC as ''The Waters'' – an area of scattered faint stars with two brighter stars standing out. Professor of astronomy Bradley Schaefer has proposed that these stars were most likely Alpha and Delta Sculptoris. The French astronomer Nicolas-Louis de Lacaille first described the constellation in French as ''l'Atelier du Sculpteur'' (the sculptor's studio) in 1751–52, depicting a three-legged table with a carved head on it, and an artist's mallet and two chisels on a block of marble alongside it. Lacaille had observed and catalogued almost 10,000 southern stars during a two-year stay at the Cape of Good Hope, devising fourteen new const ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Constellation
A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellations were likely defined in prehistory. People used them to relate stories of their beliefs, experiences, creation myth, creation, and mythology. Different cultures and countries invented their own constellations, some of which lasted into the early 20th century before today's constellations were internationally recognized. The recognition of constellations has changed significantly over time. Many changed in size or shape. Some became popular, only to drop into obscurity. Some were limited to a single culture or nation. Naming constellations also helped astronomers and navigators identify stars more easily. Twelve (or thirteen) ancient constellations belong to the zodiac (straddling the ecliptic, which the Sun, Moon, and planets all traver ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
