| Trapezium | |
|---|---|
 | |
| Observation data (J2000epoch) | |
| Right ascension | 05h 35.4m |
| Declination | −05° 27′ |
| Distance | 1,344±20ly (412pc[1]) |
| Apparent magnitude (V) | 4.0 |
| Apparent dimensions (V) | 47 (seconds of arc) |
| Physical characteristics | |
| Mass | ? M☉ |
| Radius | 10ly |
| Estimated age | 300,000 years |
| Associations | |
| Constellation | Orion |
| See also:Open cluster,List of open clusters | |
TheTrapezium orOrion Trapezium Cluster, also known by itsBayer designation ofTheta1 Orionis (θ1 Orionis), is a tightopen cluster ofstars in the heart of theOrion Nebula, in theconstellation ofOrion. It was discovered byGalileo Galilei. On 4 February 1617 he sketched three of the stars (A,C andD), but missed the surrounding nebulosity.[2][3][4] A fourth component (B) was identified by several observers in 1673, and several more components were discovered later likeE, for a total of eight by 1888. Subsequently, several of the stars were determined to be binaries. Telescopes of amateur astronomers from about 5-inch (130 mm)aperture can resolve six stars under goodseeing conditions.[5]
The Trapezium is a relatively young cluster that has formed directly out of the parent nebula. The five brightest stars are on the order of 15 to 30solar masses in size. They are within a diameter of 1.5light-years of each other and are responsible for much of the illumination of the surrounding nebula. The Trapezium may be a sub-component of the larger Orion Nebula Cluster, a grouping of about 2,000 stars within a diameter of 20 light-years.
The Trapezium is most readily identifiable by theasterism of four relatively bright stars for which it is named. The four are often identified as A, B, C and D in order of increasingright ascension. The brightest of the four stars is C, orTheta1 Orionis C, with anapparent magnitude of 5.13. Both A and B have been identified aseclipsing binaries.
Infrared images of the Trapezium are better able to penetrate the surrounding clouds of dust, and have located many more stellar components. About half the stars within the cluster exhibit circumstellar disks that are dwindling, a likely precursor to planetary formation. In addition,brown dwarfs and low-massrunaway stars have been identified.
A 2012 paper suggests anintermediate-mass black hole with a mass more than 100 times that of theSun may be present within the Trapezium, something that could explain the largevelocity dispersion of the stars of the cluster.[6]
![One of the components of the cluster (Theta1 Orionis F, lower left) is a double star.[7]](/mt/?noimg=&dark=on&url=http%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aGRAVITY_discovers_new_double_star_in_Orion_Trapezium_Cluster.jpg)
| Star | Stellar components |
|---|---|
| A | A1, A2, A3 |
| B | B1, B2, B3, B4, B5 |
| C | C1, C2 |
| D | / |
| E | E1, E2 |
| F | F1, F2 |
| G | / |
| H | / |
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Authority control databases: National |
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