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Scorpius–Centaurus Association
The Scorpius–Centaurus association (sometimes called Sco–Cen or Sco OB2) is the nearest OB association to the Sun. This stellar association is composed of three subgroups (Upper Scorpius, Upper Centaurus–Lupus, and Lower Centaurus–Crux) and its distance is about 130 parsecs or 420 light-years. Using improved Hipparcos data, Rizzuto and colleagues analysed nearby stars more closely, bringing the number of known members to 436. They doubt the need to add a subclassification because they found a more continuous spread of stars. The Sco–Cen subgroups range in age from 11 million years (Upper Scorpius) to roughly 15 million years (Upper Centaurus–Lupus and Lower Centaurus–Crux). Many of the bright stars in the constellations Scorpius, Lupus, Centaurus, and Crux are members of the Sco–Cen association, including Antares (the most massive member of Upper Scorpius), and most of the stars in the Southern Cross. Hundreds of stars have been identified as members of Sco-Cen, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Brown Dwarfs
Brown dwarfs (also called failed stars) are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen ( 1H) into helium in their cores, unlike a main-sequence star. Instead, they have a mass between the most massive gas giant planets and the least massive stars, approximately 13 to 80 times that of Jupiter (). However, they can fuse deuterium ( 2H), and the most massive ones (> ) can fuse lithium ( 7Li). Astronomers classify self-luminous objects by spectral class, a distinction intimately tied to the surface temperature, and brown dwarfs occupy types M, L, T, and Y. As brown dwarfs do not undergo stable hydrogen fusion, they cool down over time, progressively passing through later spectral types as they age. Despite their name, to the naked eye, brown dwarfs would appear in different colors depending on their temperature. The warmest ones are possibly orange or red, while cooler brown dwarfs would likely appear magenta or black to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arcseconds
A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The nautical mile (nmi) was originally defined as the arc length of a minute of latitude on a spherical Earth, so the actual Earth circumference is very near . A minute of arc is of a radian. A second of arc, arcsecond (arcsec), or arc second, denoted by the symbol , is of an arcminute, of a degree, of a turn, and (about ) of a radian. These units originated in Babylonian astronomy as sexagesimal subdivisions of the degree; they are used in fields that involve very small angles, such as astronomy, optometry, ophthalmology, optics, navigation, land surveying, and marksmanship. To express even smaller angles, standard SI prefixes can be employed; the milliarcsecond (mas) and microarcsecond (μas), for instance, are commonly used in astron ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proper Motions
Proper motion is the astrometric measure of the observed changes in the apparent places of stars or other celestial objects in the sky, as seen from the center of mass of the Solar System, compared to the abstract background of the more distant stars. The components for proper motion in the equatorial coordinate system (of a given epoch, often J2000.0) are given in the direction of right ascension (''μ''α) and of declination (''μ''δ). Their combined value is computed as the ''total proper motion'' (''μ''). It has dimensions of angle per time, typically arcseconds per year or milliarcseconds per year. Knowledge of the proper motion, distance, and radial velocity allows calculations of an object's motion from our star system's frame of reference and its motion from the galactic frame of reference – that is motion in respect to the Sun, and by coordinate transformation, that in respect to the Milky Way. Introduction Over the course of centuries, stars appear to ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IC 2602
IC 2602 (also known as the Southern Pleiades, Theta Carinae Cluster, or Caldwell 102) is an open cluster in the constellation Carina (constellation), Carina. Discovered by Abbe Lacaille in 1751 from South Africa, the cluster is easily visible to the Naked eye, unaided eye, and is one of the nearest star clusters, centred about 149 parsecs (486 Light-year, light-years) away from Earth. Description IC 2602 has a total apparent magnitude of 1.9, and contains about 75 stars. It is the third-brightest open cluster in the sky, following the Hyades (star cluster), Hyades and the Pleiades. Its apparent diameter is about 50 arcminutes. IC 2602 is likely about the same age as the open cluster IC 2391,, which has a lithium depletion boundary age of 50 million years old, though the age estimated from its Hertzsprung-Russell diagram is about 13.7 million years. IC 2602 is thought to form part of the Lower Scorpius–Centaurus association. Components Θ Carinae, Theta Carinae is the brightes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beta Pictoris Moving Group
The Beta Pictoris Moving Group is a young moving group of stars located relatively near Earth. A moving group, in astronomy, is a group of stars that share a common motion through space as well as a common origin. This moving group is named for Beta Pictoris. The Beta Pictoris Moving Group is an important object for astronomical study as it is the closest youthful group of stars to the Earth. The star Beta Pictoris is known to have a large disk of gas and dust, possibly a protoplanetary disk. There is also evidence of a young gas giant planet around the star. A free-floating planet has also been found in the moving group, PSO J318.5-22. The age and distance of the group makes it a candidate for directly imaging extrasolar planets. Constituents The Beta Pictoris Moving Group consists of 17 stellar systems, comprising a total of 28 individual component stars, including identified brown dwarfs. The core of the group is located some 115 light-years from Earth, and has an average ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TW Hydrae Association
The TW Hydrae association is a group of very young low-mass stars and substellar objects located approximately 25–75 parsecs (80–240 light years) from Earth. They share a common motion and appear to all be roughly the same age, 10±3 million years old. It is the youngest such association within 100 pc from Earth. As of 2017, 42 objects (in 23 systemsSingular objects are also regarded as "systems" here.) are assigned to the association confidently, and several dozens — uncertainly. Masses of its known members vary from 5 Jupiter masses to 2 solar masses, and their spectral types vary from A0 to L7. Some of the best studied members of this stellar association are TW Hydrae (nearest known accreting T Tauri star to the Earth), HR 4796 (an A-type star with resolved dusty debris disk; the most massive known group member), HD 98800 (a quadruple star system with debris disk), and 2M1207 (accreting brown dwarf with remarkable planetary-mass companion 2M1207b). Included in the associa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eta Chamaeleontis Cluster
Eta (uppercase , lowercase ; grc, ἦτα ''ē̂ta'' or ell, ήτα ''ita'' ) is the seventh letter of the Greek alphabet, representing the close front unrounded vowel . Originally denoting the voiceless glottal fricative in most dialects, its sound value in the classical Attic dialect of Ancient Greek was a long open-mid front unrounded vowel , raised to in hellenistic Greek, a process known as iotacism or itacism. In the ancient Attic number system (Herodianic or acrophonic numbers), the number 100 was represented by "", because it was the initial of , the ancient spelling of = "one hundred". In the later system of (Classical) Greek numerals eta represents 8. Eta was derived from the Phoenician letter heth . Letters that arose from eta include the Latin H and the Cyrillic letter И and Й. History Consonant h The letter shape 'H' was originally used in most Greek dialects to represent the voiceless glottal fricative . In this function, it was borrowed in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epsilon Cha Group
Epsilon (, ; uppercase , lowercase or lunate ; el, έψιλον) is the fifth letter of the Greek alphabet, corresponding phonetically to a mid front unrounded vowel or . In the system of Greek numerals it also has the value five. It was derived from the Phoenician letter He . Letters that arose from epsilon include the Roman E, Ë and Ɛ, and Cyrillic Е, È, Ё, Є and Э. The name of the letter was originally (), but it was later changed to ( 'simple e') in the Middle Ages to distinguish the letter from the digraph , a former diphthong that had come to be pronounced the same as epsilon. The uppercase form of epsilon is identical to Latin E but has its own code point in Unicode: . The lowercase version has two typographical variants, both inherited from medieval Greek handwriting. One, the most common in modern typography and inherited from medieval minuscule, looks like a reversed number "3" and is encoded . The other, also known as lunate or uncial epsilon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coalsack
The Coalsack Nebula (Southern Coalsack, or simply the Coalsack) is a prominent dark nebula in the skies, being easily visible to the naked eye as a dark patch obscuring a brief section of Milky Way stars as they cross their southernmost region of the sky, east of Acrux (Alpha Crucis) which is the bright, southern pointer star of the southern cross. It dominates and overspills the southeast corner of what is considered the extent of the constellation Crux at a little less than twice the distance of Acrux, away from Earth. General information The Coalsack Nebula covers nearly 7degree (angle), ° by 5° and overlaps somewhat with the neighbor constellations Centaurus and Musca. The first observation was reported by Vicente Yáñez Pinzón in 1499. It was named "''il Canopo fosco''" (the dark Canopus) by Amerigo Vespucci and was also called "''Macula Magellani''" (Magellan's Spot) or "''Black Magellanic Cloud''" in opposition to the Magellanic Clouds. The Coalsack is omitted in most ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corona Australis
Corona Australis is a constellation in the Southern Celestial Hemisphere. Its Latin name means "southern crown", and it is the southern counterpart of Corona Borealis, the northern crown. It is one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. The Ancient Greeks saw Corona Australis as a wreath rather than a crown and associated it with Sagittarius (constellation), Sagittarius or Centaurus. Other cultures have likened the pattern to a turtle, ostrich nest, a tent, or even a hut belonging to a rock hyrax. Although fainter than its northern counterpart, the oval- or horseshoe-shaped pattern of its brighter stars renders it distinctive. Alpha Coronae Australis, Alpha and Beta Coronae Australis are the two brightest stars with an apparent magnitude of around 4.1. Epsilon Coronae Australis is the brightest example of a W Ursae Majoris variable in the southern sky. Lying alongside the Milky Way, Corona Australi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chamaeleon
Chamaeleon () is a small constellation in the deep southern sky. It is named after the chameleon, a kind of lizard. It was first defined in the 16th century. History Chamaeleon was one of twelve constellations created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman. It first appeared on a 35-cm diameter celestial globe published in 1597 (or 1598) in Amsterdam by Plancius and Jodocus Hondius. Johann Bayer was the first uranographer to put Chamaeleon in a celestial atlas. It was one of many constellations created by European explorers in the 15th and 16th centuries out of unfamiliar Southern Hemisphere stars. Features Stars There are four bright stars in Chamaeleon that form a compact diamond-shape approximately 10 degrees from the south celestial pole and about 15 degrees south of Acrux, along the axis formed by Acrux and Gamma Crucis. Alpha Chamaeleontis is a white-hued star of magnitude 4.1, 63 light-years from Earth. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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