Visible at latitudes between +30° and −90°. Best visible at 21:00 (9 p.m.) during the month ofMarch.
Vela is aconstellation in the southern sky, which contains theVela Supercluster. Its name isLatin for thesails of a ship, and it was originally part of a larger constellation, the shipArgo Navis, which was later divided into three parts, the others beingCarina andPuppis. With an apparent magnitude of 1.8, its brightest star is the hot blue multiple starGamma Velorum, one component of which is the closest and brightestWolf-Rayet star in the sky.Delta andKappa Velorum, together withEpsilon andIota Carinae, form theasterism known as theFalse Cross. 1.95-magnitude Delta is actually a triple or quintuple star system.
Argo Navis was one of the 48 classical constellations listed by the 2nd-century astronomerPtolemy, and represented the shipArgo, used byJason and theArgonauts on their quest for theGolden Fleece inGreek mythology. German cartographerJohann Bayer depicted the constellation on hisUranometria of 1603, and gave the starsBayer designations from Alpha to Omega. However, his chart was inaccurate as the constellation was not fully visible from the Northern Hemisphere.[1]
Argo was more accurately charted and subdivided in 1752 by the French astronomerNicolas Louis de Lacaille, forming Carina (thekeel), Vela (the sails), and Puppis (thepoop deck). Despite the division, Lacaille kept Argo'sBayer designations. Therefore, Carina has the Alpha, Beta and Epsilon originally assigned to Argo Navis, while Vela's brightest stars are Gamma and Delta, Puppis has Zeta as its brightest star, and so on.[1]
The constellation of Vela, the sails, as it can be seen by the naked eye
Vela is bordered byAntlia andPyxis to the north, Puppis to the northwest, Carina to the south and southwest, andCentaurus to the east. Covering 500 square degrees, it ranks 32nd of the 88modern constellations in size. The three-letter abbreviation for the constellation, as adopted by theInternational Astronomical Union in 1922, is "Vel".[2]
The official constellation boundaries, as set byEugène Delporte in 1930, are defined by a polygon of 14 segments. In theequatorial coordinate system, theright ascension coordinates of these borders lie between08h 13.3m and11h 05.5m, while thedeclination coordinates are between −37.16° and −57.17°.[3]
The brightest star in the constellation, Gamma Velorum, is a complex multiple star system. The brighter component, known as Gamma2 Velorum, shines as a blue-white star of apparent magnitude 1.83.[4] It is a spectroscopic binary made up of two very hot blue stars orbiting each other every 78.5 days and separated by somewhere between 0.8 and 1.6 Astronomical Units (AU). The brighter component is a hot blue main-sequence star of spectral type O7.5 and is around 280,000 times as luminous, is around 30 times as massive and is 17 times the diameter of the Sun with a surface temperature of 35,000 K. The second component is an extremely rare example of hot star known as aWolf–Rayet star, and is the closest and brightest example in the sky. It has a surface temperature of 57,000 and is around 170,000 times as luminous as the Sun, though it radiates most of its energy in the ultraviolet spectrum.[5] Gamma1 is a blue-white star of spectral type B2III and apparent magnitude 4.3.[6] The two pairs are separated by 41 arcseconds, easily separable in binoculars.[6] Parallax measurements give a distance of 1,116 light-years,[7] meaning that they are at least 12,000 AU apart. Further afield are 7.3-magnitude Gamma Velorum C and 9.4-magnitude Gamma Velorum D, lying 62 and 93 arcseconds south-southeast from Gamma2. These stars are the most prominent members ofVela OB2, an extendedassociation of young stars.[6]
The next brightest star isDelta Velorum or Alsephina,[9] also a multiple star system and one of the brightest eclipsing binaries in the sky. Together withKappa Velorum or Markeb,[9]Iota Carinae or Aspidiske[9] andEpsilon Carinae or Avior,[9] it forms the diamond-shapedasterism known as theFalse Cross—so called because it is sometimes mistaken for theSouthern Cross, causing errors inastronavigation.[10] Appearing as a white star of magnitude 1.95,[11] Delta is actually a triple or possibly quintuple star system located around 80 light-years from theSolar System. Delta A has a magnitude of 1.99 and is aneclipsing binary composed of two A-type white stars (Delta Aa and Ab) which orbit each other every 45.2 days and lie 0.5 AU from each other, with a resulting drop in magnitude of 0.4 when the dimmer one passes.in front of the brighter. Delta B is a 5.1 magnitude yellow G-class star of similar dimensions to the Sun which ranges between 26 and 72 AU away from the brighter pair, taking 142 years to complete a revolution. Further out still, at a distance of 1700 AU, are two red dwarfs of magnitudes 11 and 13. If they are part of the multiple system, they take 28000 years to complete an orbit.[12] Also called Markeb, Kappa appears as a blue-white star of spectral type B2IV-V and magnitude 2.47 but is in fact a spectroscopic binary.[13] The two orbit around each other with a period of 116.65 days,[14] but the size, mass and nature of the companion are as yet unclear.[15]
The orange-huedLambda Velorum, or Suhail,[9] is the third-brightest star in the constellation. A supergiant of spectral type K4Ib-II, it varies between magnitudes 2.14 and 2.3,[16] and lies 545 light-years distant.[17] It has around 11,000 times the luminosity, 9 to 12 times the mass and 207 times the diameter of the Sun.[18]
AH Velorum is a Cepheid variable located less than a degree to the northeast of Gamma.[19] A yellow-white supergiant of spectral type F7Ib-II, it pulsates between magnitudes 5.5 and 5.89 over 4.2 days.[20] Also lying close to Gamma,[21]V Velorum is a Cepheid of spectral type F6-F9II ranging from magnitude 7.2 to 7.9 over 4.4 days.[22]AI Velorum is located 2.8 degrees north-northeast of Gamma,[19] a Delta Scuti variable of spectral type A2p-F2pIV/V that ranges between magnitudes 6.15 and 6.76 in around 2.7 hours.[23]
V390 Velorum is an aged star that has been found to be surrounded by a dusty disk. AnRV Tauri variable, it has a spectral type of F3e and ranges between magnitudes 9.01 and 9.27 over nearly 95 days.[24]
Omicron Velorum is a blue-white subgiant of spectral type B3III-IV located around 495 light-years from the Solar System. A slowly pulsating B star, it ranges between magnitudes 3.57 and 3.63 over 2.8 days.[25] It is the brightest star in, and gives its name to, the Omicron Velorum Cluster, also known asIC 2391, anopen cluster located around 500 light-years away.
Seven star systems have been found to haveplanets.HD 75289 is a Sun-like star of spectral type G0V with ahot Jupiter planetary companion that takes only about 3.51 days to revolve at anorbital distance of 0.0482AU.WASP-19 is a star of apparent magnitude 12.3 located 815 light-years away, which has a hot Jupiter-like planet that orbits every 0.7 days.HD 73526 is a Sun-like star of spectral type G6V that has two planets around double the mass of Jupiter each with orbits of 187 and 377 days, respectively.
HD 85390 is an orange dwarf of spectral type K1.5V lying around 111 light-years distant with a planet 42 times as massive as Earth orbiting every 788 days.
HD 93385 is a Sun-like star of spectral type G2/G3V located around 138 light-years away that is orbited by two super-Earths with periods of 13 and 46 days and masses 8.3 and 10.1 times that of Earth, respectively.
The discovery of a binarybrown dwarf system namedLuhman 16 only 6.6 light-years away, the third-closest system to the Solar System, was announced on 11 March 2013.
Of thedeep-sky objects of interest in Vela is aplanetary nebula known asNGC 3132, nicknamed the 'Eight-Burst Nebula' or 'Southern Ring Nebula' (see accompanying photo). It lies on the border of the constellation with Antlia.[19]NGC 2899 is an unusual red-hued example. This constellation has 32 more planetary nebulae.
TheGum Nebula is a faintemission nebula, believed to be the remains of a million-year-old supernova. Within it lies the smaller and youngerVela Supernova Remnant. This is thenebula of asupernova explosion that is believed to have been visible from Earth around 10,000 years ago. The remnant contains theVela Pulsar, the firstpulsar to be identified optically. Nearby isNGC 2736, also known as the Pencil Nebula.
HH-47 is aHerbig-Haro Object, a young star around 1,400light-years from the Sun that is ejecting material at tremendous speed (up to a million kilometres per hour) into its surrounds. This material glows as it hits surrounding gas.[26]
NGC 2670 is anopen cluster located in Vela. It has an overall magnitude of 7.8 and is 3,200 light-years from Earth. The stars of NGC 2670, a Trumpler class II 2 p and Shapley class-d cluster, are in a conformation suggesting a bow and arrow. Its class indicates that it is a poor, loose cluster, though detached from the star field. It is somewhat concentrated at its center, and its less than 50 stars range moderately in brightness.[27]
Located 2 degrees south of Gamma Velorum,NGC 2547 is an open cluster containing around 50 stars of magnitudes 7 to 15.[19]
NGC 3201 is aglobular cluster discovered byJames Dunlop on May 28, 1826. Its stellar population is inhomogeneous, varying with distance from the core. Theeffective temperature of the stars shows an increase with greater distance, with the redder and cooler stars tending to be located closer to the core. As of 2010, is one of only two clusters (includingMessier 4) that shows a definite inhomogeneous population.[28]
RCW 36 is a star-forming region in Vela, and one of the nearest sites of massive star formation. This star-forming region has given rise to a cluster of several hundred young stars that power an HII region.[29] The star-forming region lies in Clump 6 in theVela Molecular Ridge Cloud C.[30]
^abWagman, Morton (2003).Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others. Blacksburg,VA: The McDonald & Woodward Publishing Company. pp. 83,315–19.ISBN978-0-939923-78-6.
^Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system".CDS/ADC Collection of Electronic Catalogues.2237: 0.Bibcode:2002yCat.2237....0D.
^Kaler, Jim."Suhail".Stars. University of Illinois. Retrieved10 October 2013.
^abcdMotz, Lloyd; Nathanson, Carol (1991).The Constellations: An Enthusiast's Guide to the Night Sky. London, United Kingdom: Aurum Press. pp. 381–83.ISBN978-1-85410-088-7.
^"AH Velorum".International Variable Star Index. American Association of Variable Star Observers. 4 January 2010. Retrieved11 October 2013.
