Instruct: Given a question, retrieve documents that answer the question.
Query: What is a constellation?
Constellation provides to commercial and industrial customers fixed, index, and blended pricing solutions of electric power, including renewable energy. Its wholesale electricity supply business manages the sales, dispatch, and delivery of energy from Exelon's power generation portfolio to utilities, municipal co-ops, and energy retailers nationwide. , Constellation had around 360 megawatts of solar generation assets that is either in operation or under construction across the United States, including Maryland, California, Arizona, New Jersey, and Texas. In 2011, Constellation was contracted to construct and operate what was then the largest rooftop solar array ever constructed for the Toys-R-Us distribution center in Flanders, NJ.
Traditionally, small bodies orbiting the Sun were classified as comets, asteroids, or meteoroids, with anything smaller than one meter across being called a meteoroid. Beech and Steel's 1995 paper proposed a meteoroid definition including size limits. The term "asteroid", from the Greek word for "star-like", never had a formal definition, with the broader term minor planet being preferred by the International Astronomical Union.
The overall structure of the charted regions of the Solar System consists of the Sun, four relatively small inner planets surrounded by a belt of mostly rocky asteroids, and four giant planets surrounded by the Kuiper belt of mostly icy objects. Astronomers sometimes informally divide this structure into separate regions. The inner Solar System includes the four terrestrial planets and the asteroid belt. The outer Solar System is beyond the asteroids, including the four giant planets. Since the discovery of the Kuiper belt, the outermost parts of the Solar System are considered a distinct region consisting of the objects beyond Neptune.
The pattern of the brightest stars resembles that of Ursa Minor, in that the stars form a pattern reminiscent of a bowl with a handle. Lying south-southeast of Acrux in neighbouring Crux is Alpha Muscae. It is the brightest star in the constellation with an apparent magnitude of 2.7. Lying around 310 light-years away, it is a blue-white star of spectral type B2IV-V that is around 4520 times as luminous and 8 times as massive as the Sun. The star is a Beta Cephei variable with about 4.7 times the Sun's diameter, and pulsates every 2.2 hours, varying by 1% in brightness. A nearby star of magnitude 13 may or may not be a companion star. Marking the fly's tail is Gamma Muscae, a blue-white star of spectral type B5V that varies between magnitudes 3.84 and 3.86 over a period of 2.7 days. It is a variable of a different type, classed as a slowly pulsating B star, a type of variable. It is around five times as massive as our Sun.
The expression "asteroid belt" came into use in the very early 1850s, although it is hard to pinpoint who coined the term. The first English use seems to be in the 1850 translation (by E. C. Otté) of Alexander von Humboldt's "Cosmos": "[...] and the regular appearance, about the 13th of November and the 11th of August, of shooting stars, which probably form part of a belt of asteroids intersecting the Earth's orbit and moving with planetary velocity". Another early appearance occurred in Robert James Mann's "A Guide to the Knowledge of the Heavens": "The orbits of the asteroids are placed in a wide belt of space, extending between the extremes of [...]". The American astronomer Benjamin Peirce seems to have adopted that terminology and to have been one of its promoters.
The dwarf planet Ceres is by far the largest asteroid, with a diameter of . The next largest are 4 Vesta and 2 Pallas, both with diameters of just over . Vesta is the only main-belt asteroid that can, on occasion, be visible to the naked eye. On some rare occasions, a near-Earth asteroid may briefly become visible without technical aid; see 99942 Apophis.
Ceres is the largest object in the asteroid belt.
It is sometimes assumed that Ceres has been "re"classified as a dwarf planet, and that it is therefore no longer considered an asteroid. For example, a news update at Space.com spoke of "Pallas, the largest asteroid, and Ceres, the dwarf planet formerly classified as an asteroid", whereas an IAU question-and-answer posting states, "Ceres is (or now we can say it was) the largest asteroid", though it then speaks of "other asteroids" crossing Ceres' path and otherwise implies that Ceres is still considered an asteroid. The Minor Planet Center notes that such bodies may have dual designations. The 2006 IAU decision that classified Ceres as a dwarf planet never addressed whether it is or is not an asteroid. Indeed, the IAU has never defined the word 'asteroid' at all, having preferred the term 'minor planet' until 2006, and preferring the terms 'small Solar System body' and 'dwarf planet' after 2006. Lang (2011) comments "the [IAU has] added a new designation to Ceres, classifying it as a dwarf planet. ... By [its] definition, Eris, Haumea, Makemake and Pluto, as well as the largest asteroid, 1 Ceres, are all dwarf planets", and describes it elsewhere as "the dwarf planet–asteroid 1 Ceres". NASA continues to refer to Ceres as an asteroid, as do various academic textbooks.
A small Solar System body (SSSB) is an object in the Solar System that is neither a planet, a dwarf planet, nor a natural satellite. The term was first defined in 2006 by the International Astronomical Union (IAU) as follows: "All other objects, except satellites, orbiting the Sun shall be referred to collectively as 'Small Solar System Bodies' ".
This encompasses all comets and all minor planets other than those that are dwarf planets. Thus SSSBs are: the comets; the classical asteroids, with the exception of the dwarf planet Ceres; the trojans; and the centaurs and trans-Neptunian objects, with the exception of the dwarf planets Pluto, Haumea, Makemake, and Eris and others that may turn out to be dwarf planets.
Although their location in the asteroid belt excludes them from planet status, the three largest objects, Ceres, Vesta, and Pallas, are intact protoplanets that share many characteristics common to planets, and are atypical compared to the majority of "potato"-shaped asteroids. The fourth largest asteroid, Hygiea, has an undifferentiated interior, like the majority of asteroids. Between them, the four largest asteroids constitute half the mass of the asteroid belt.
A conurbation is a region comprising a number of cities, large towns, and other urban areas that, through population growth and physical expansion, have merged to form one continuous urban or industrially developed area. In most cases, a conurbation is a polycentric urbanised area, in which transportation has developed to link areas to create a single urban labour market or travel to work area.
In astronomy, the velocity dispersion ("σ") is the statistical dispersion of velocities about the mean velocity for a group of objects, such as an open cluster, globular cluster, galaxy, galaxy cluster, or supercluster. By measuring the radial velocities of its members, the velocity dispersion of a cluster can be estimated and used to derive the cluster's mass from the virial theorem. Radial velocity is found by measuring the Doppler width of spectral lines of a collection of objects. The more radial velocities one measures, the more accurately one knows their dispersion. A central velocity dispersion refers to the σ of the interior regions of an extended object, such as a galaxy or cluster.
Zeta Muscae, Latinized from ζ Muscae, is a star in the constellation Musca. Its apparent magnitude is 5.74. Located around 326 light-years distant, it is an orange giant of spectral type K0III, a star that has used up its core hydrogen and is cooling and expanding. The star is radiating 64 times the Sun's luminosity.
Vega, also designated α Lyrae (Latinised to Alpha Lyrae, abbreviated Alpha Lyr or α Lyr), is the brightest star in the constellation of Lyra, the fifth-brightest star in the night sky, and the second-brightest star in the northern celestial hemisphere, after Arcturus. It is relatively close at only 25 light-years from the Sun, and, together with Arcturus and Sirius, one of the most luminous stars in the Sun's neighborhood.
Red dwarf stars are the smallest, coolest, and most common type of star. Estimates of their abundance range from 70% of stars in spiral galaxies to more than 90% of all stars in elliptical galaxies, an often quoted median figure being 73% of the stars in the Milky Way (known since the 1990s from radio telescopic observation to be a barred spiral). Red dwarfs are either late K or M spectral type. Given their low energy output, red dwarfs are never visible by the unaided eye from Earth; neither the closest red dwarf to the Sun when viewed individually, Proxima Centauri (which is also the closest star to the Sun), nor the closest solitary red dwarf, Barnard's star, is anywhere near visual magnitude.
Some scientists argue that the concept of a circumstellar habitable zone is actually limited to stars in certain types of systems or of certain spectral types. Binary systems, for example, have circumstellar habitable zones that differ from those of single-star planetary systems, in addition to the orbital stability concerns inherent with a three-body configuration. If the Solar System were such a binary system, the outer limits of the resulting circumstellar habitable zone could extend as far as 2.4 AU.
Halley's Comet, named after English astronomer Edmund Halley who first demonstrated its periodicity, returns to the vicinity of the Sun and Earth approximately every 76 years. Since comets are believed to be the most primordial objects in the solar system, their study is of great importance to planetary science. At the time of the 1986 return (technically, "apparition") of the comet, astronomical telescopes and related instrumentation were vastly more sensitive than for any previous apparition. Consequently, the International Halley Watch (IHW) was organized to stimulate, standardize, collect, and archive observations of the comet.
Asteroid 2 Pallas is the third-largest belt asteroid.Asteroid 4 Vesta is the second largest of the asteroids.A common depiction of asteroids (and less often, of comets) in fiction is as a threat, whose impact on Earth could result with incalculable damage and loss of life. This scenario is based on such past events as the impact event responsible for the extinction of the dinosaurs. Such events are, however, sufficiently rare that there is no special reason to expect such an impact in the near future.When the theme of interplanetary colonization first entered SF, the Asteroid Belt was quite low on the list of desirable real estate, far behind such planets as Mars and Venus (often conceived as a kind of paradise planet, until probes in the 1960s revealed uninhabitable temperatures with a deadly carbon dioxide and sulfur atmosphere under its clouds). Thus, in many stories and books the Asteroid Belt, if not a positive hazard, is still a rarely visited backwater in a colonized Solar System.Before colonization of the asteroids became an attractive possibility, a main interest in them was theories as to their origin – specifically, the theory that the asteroids are remnants of an exploded planet. This naturally leads to SF plot lines dealing with the possibility that the planet had been inhabited, and if so – that the inhabitants caused its destruction themselves, by war or gross environmental mismanagement. A further extension is from the past of the existing asteroids to the possible future destruction of Earth or other planets and their rendering into new asteroids.
"For a partial list of members of the National Constituent Assembly, see Alphabetical list of members of the National Constituent Assembly of 1789."
Eta Muscae (η Mus) is a star in the constellation Musca. A multiple star system, the two main components form an eclipsing binary that has a spectral type of B8V and an apparent magnitude of 4.77 that dips by 0.05 magnitude every 2.39 days. Further away are stars of magnitude 7.3 and 10—termed Eta Muscae B and C. It is unclear if these stars are gravitationally bound to the main pair.
The Assembly renamed itself the "National Constituent Assembly" on 9 July and began to function as a governing body and a constitution-drafter. However, it is common to refer to the body even after then as the "National Assembly" or the "Constituent Assembly".
Water has been detected in interstellar clouds within our galaxy, the Milky Way. Water probably exists in abundance in other galaxies, too, because its components, hydrogen and oxygen, are among the most abundant elements in the universe. Based on models of the formation and evolution of the Solar System and that of other star systems, most other planetary systems are likely to have similar ingredients.
Cancer is a medium-sized constellation that is bordered by Gemini to the west, Lynx to the north, Leo Minor to the northeast, Leo to the east, Hydra to the south, and Canis Minor to the southwest. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is 'Cnc'. The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of 10 sides ("illustrated in infobox"). In the equatorial coordinate system, the right ascension coordinates of these borders lie between and , while the declination coordinates are between and . Covering 506 square degrees or 0.921% of the sky, it ranks 31st of the 88 constellations in size. It can be seen at latitudes between +90° and -60° and is best visible at 9 p.m. during the month of March. Cancer Borders the bright constellations of Leo and Gemini and Canis Minor, Under city skies, Cancer is invisible to the naked eye.
Cygnus is a northern constellation lying on the plane of the Milky Way, deriving its name from the Latinized Greek word for swan. The swan is one of the most recognizable constellations of the northern summer and autumn, and it features a prominent asterism known as the Northern Cross (in contrast to the Southern Cross). Cygnus was among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations.
The word "constellation" comes from the Late Latin term , which can be translated as "set of stars"; it came into use in English during the 14th century. The Ancient Greek word for constellation is ἄστρον. A more modern astronomical sense of the term "constellation" is simply as a recognisable pattern of stars whose appearance is associated with mythological characters or creatures, or earthbound animals, or objects. It can also specifically denote the officially recognized 88 named constellations used today.
Colloquial usage does not draw a sharp distinction between "constellations" and smaller "asterisms" (pattern of stars), yet the modern accepted astronomical constellations employ such a distinction. E.g., the Pleiades and the Hyades are both asterisms, and each lies within the boundaries of the constellation of Taurus. Another example is the popular northern asterism known as the Big Dipper (US) or the Plough (UK), composed of the seven brightest stars within the area of the IAU-defined constellation of Ursa Major. The southern False Cross asterism includes portions of the constellations Carina and Vela.
Covering 282.4 square degrees and hence 0.685% of the sky, Crater ranks 53rd of the 88 constellations in area. It is bordered by Leo and Virgo to the north, Corvus to the east, Hydra to the south and west, and Sextans to the northwest. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is 'Crt'. The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of six segments ("illustrated in infobox"). In the equatorial coordinate system, the right ascension coordinates of these borders lie between and , while the declination coordinates are between −6.66° and −25.20°. Its position in the Southern Celestial Hemisphere means that the whole constellation is visible to observers south of 65°N.