Alpha Centauri - Wikipedia, the free encyclopedia. Alpha Centauri. Proxima is at the slightly smaller distance of 1. Sun, making it the closest star to the Sun, even though it is not visible to the naked eye. The separation of Proxima from Alpha Centauri AB is about 0. AU). Proxima b, an Earth- sizedexoplanet in the habitable zone of Proxima Centauri, has been detected. The next- brightest star in the night sky is Arcturus. Alpha Centauri is a multiple- star system, with its two main stars being Alpha Centauri A (. As viewed from Earth, it is located at an angular separation of 2. Proxima Centauri would appear to the naked eye as a separate star from . Alpha Centauri AB and Proxima Centauri form a visualdouble star. Direct evidence that Proxima Centauri has an elliptical orbit typical of binary stars has yet to be found. Some older references use the confusing and now discontinued designation of A. Because the distance between the Sun and Alpha Centauri AB does not differ significantly from either star, gravitationally this binary system is considered as if it were one object. It is a solar- like main- sequence star with a similar yellowish colour. From the determined mutual orbital parameters, Alpha Centauri A is about 1. Read the latest local news, from Kansas City and the KC area, and around the country and world by The Kansas City Star and KansasCity.com.Sun, with a radius about 2. The projected rotational velocity( v. When considered among the individual brightest stars in the sky (excluding the Sun), Alpha Centauri A is the fourth brightest at an apparent visual magnitude of +0.
MegaPath is a leading cloud communications and connectivity company delivering business phone and internet, unified communications, secure networks, and hosted IT. Arcturus at an apparent visual magnitude of . It is a main- sequence star of spectral type K1 V, making it more an orange colour than the primary star. The projected rotational velocity ( v. The light curve of B varies on a short time scale and there has been at least one observed flare. Proxima usually appears as a deep- red star of an apparent visual magnitude of 1. Listed as V6. 45 Cen in the General Catalogue of Variable Stars (G. C. V. S.) Version 4. UV Ceti- type flare star can unexpectedly brighten rapidly by as much as 0. The first of these is that bright Star in the sterne of Argo which they call Canobus. The second is in the end of Eridanus. The finding was made incidentally while observing a passing comet from his station in Puducherry. Alpha Centauri was only the second binary star system to be discovered, preceded only by Alpha Crucis. The parallax of Alpha Centauri was subsequently determined by Henderson from many exacting positional observations of the AB system between April 1. May 1. 83. 3. He withheld his results, however, because he suspected they were too large to be true, but eventually published them in 1. Friedrich Wilhelm Bessel released his own accurately determined parallax for 6. Cygni in 1. 83. 8. Pourbaix (2. 00. 2), have regularly refined the precision of any new published orbital elements. Innes discovered Proxima Centauri in 1. This showed the large proper motion and parallax of the star was similar in both size and direction to those of Alpha Centauri AB, suggesting immediately it was part of the system and slightly closer to Earth than Alpha Centauri AB. Lying 4. 2. 4 light- years away, Proxima Centauri is the nearest star to the Sun. All current derived distances for the three stars are from the parallaxes obtained from the Hipparcos star catalogue (HIP). The A component is held stationary and the relative orbital motion of the B component is shown. The apparent orbit (thin ellipse) is the shape of the orbit as seen by an observer on Earth. The true orbit is the shape of the orbit viewed perpendicular to the plane of the orbital motion. According to the radial velocity vs. The orbit is divided here into 8. With the orbital period of 7. Alpha Centauri A and B have absolute magnitudes of +4. Stellar evolution theory implies both stars are slightly older than the Sun at 5 to 6 billion years, as derived by both mass and their spectral characteristics. Observed stellar positions in 2. PA of 2. 45. 7. Furthest orbital separation at apastron last occurred in May 1. The apparent distance between the two stars is rapidly decreasing, at least until 2. Proxima is likely gravitationally bound to Alpha Centauri AB, orbiting it with a period between 1. Grey dot is projection of Proxima Centauri, located at the same distance as Alpha Centauri AB. Proxima is a red dwarf of spectral class M6 Ve with an absolute magnitude of +1. Sun's luminosity. By mass, Proxima is calculated as 0. Over the centuries, this causes the apparent stellar positions to slowly change. Such motions define the high- proper- motion stars. Most assumed that all stars were immortal and permanently fixed on the celestial sphere, as stated in the works of the philosopher Aristotle. Using the Hipparcos Star Catalogue (HIP) data, the mean individual proper motions are . These motions are about one- fifth and twice, respectively, the diameter of the full Moon. By about 2. 9,7. 00 AD, in the present- day constellation of Hydra, Alpha Centauri will be 1. Even during the time of this nearest approach, however, the apparent magnitude of Alpha Centauri will still not surpass that of Sirius, which will brighten incrementally over the next 6. Earth for the next 2. Here this once bright yellow star will fall below naked- eye visibility somewhere in the faint present day southern constellation of Telescopium. This unusual location results from the fact that Alpha Centauri's orbit around the galactic centre is highly tilted with respect to the plane of the Milky Way. Beta Centauri is in reality far more distant than Alpha Centauri. Planets. From these readings, the radial velocity of the parent star relative to the Earth is varying with an amplitude of about 2 metres (6. This planet would most likely orbit Alpha Centauri B with an orbital period of 2. The median average of the likely orbits is 1. Its orbit would likely have an eccentricity of 0. If confirmed, this planet would be called Alpha Centauri Bc. Like the probably spurious Alpha Centauri Bb, it would be far too close to Alpha Centauri B to harbour life. Such planets could orbit Alpha Centauri A or Alpha Centauri B individually, or be on large orbits around the binary Alpha Centauri AB. Because both the principal stars are fairly similar to the Sun (for example, in age and metallicity), astronomers have been especially interested in making detailed searches for planets in the Alpha Centauri system. Several established planet- hunting teams have used various radial velocity or star transit methods in their searches around these two bright stars. Certain special assumptions, such as considering that Alpha Centauri A and B may have initially formed with a wider separation and later moved closer to each other (as might be possible if they formed in a dense star cluster) would permit an accretion- friendly environment farther from the star. In addition, the lack of any brown dwarfs or gas giants in close orbits around A or B make the likelihood of terrestrial planets greater than otherwise. Here, the comets provided the inner planets with their own source of water and various other ices. Such icy bodies probably also reside in Oort clouds of other planetary systems, when they are influenced gravitationally by either the gas giants or disruptions by passing nearby stars many of these icy bodies then travel starwards. For the slightly less luminous and cooler Alpha Centauri B, the habitable zone would lie closer at about 0. AU (1. 00 million km), approximately the distance that Venus is from the Sun. Detecting planets as small as three Earth- masses or smaller within two astronomical units of a . The Sun would be a yellow star of an apparent visual magnitude of +0. Cassiopeia, at the antipodal point of Alpha Centauri's current right ascension and declination, at 0. This place is close to the 3. Because of the placement of the Sun, an interstellar or alien observer would find the \/\/ of Cassiopeia had become a /\/\/ shape. Sirius lies less than a degree from Betelgeuse in the otherwise unmodified Orion and is with . Procyon is also displaced into the middle of Gemini, outshining Pollux, whereas both Vega and Altair are shifted northwestward relative to Deneb (which barely moves, due to its great distance), giving the Summer Triangle a more equilateral appearance. View from Proxima b. Depending on the binary's orbital position, the bright stars would appear noticeably divisible to the naked eye, or occasionally, but briefly, as a single unresolved star. Based on the calculated absolute magnitudes, the visual apparent magnitudes of Alpha Centauri A and B would be . Near apoapse, the disc would shrink to 6. A, 4. 3 arc seconds for B, being too small to resolve by naked eye. In any case, the dazzling surface brightness could make the discs harder to resolve than a similarly sized less bright object. For example, some theoretical planet orbiting about 1. AU from Alpha Centauri A (so that the star appears roughly as bright as the Sun viewed from the Earth) would see Alpha Centauri B orbit the entire sky once roughly every one year and three months (or 1. Added to this would be the changing apparent position of Alpha Centauri B during its long eighty- year elliptical orbit with respect to Alpha Centauri A (The average speed, at 4,5 degrees per Earth year, is comparable in speed to Uranus here. With the eccentricity of the orbit, the maximum speed near periapse, about 1. Earth year, is faster than Saturn, but slower than Jupiter. The minimum speed near apoapse, about 1,8 degrees per Earth year, is slower than Neptune.). Depending on its and planet. These visual apparent magnitudes are much dimmer than the apparent magnitude of the Sun as viewed from the Earth (. The difference of 5. Alpha Centauri B would appear, on a linear scale, 2. Alpha Centauri A (or the Sun viewed from the Earth), but also 1. Moon as seen from the Earth (. Thus Alpha Centauri A would appear between 8. Sun but some 5. 80 to 6. Moon. During such planet's orbital period of 0. Solar System's planets.
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