Trapezium Cluster

{{Short description|Open cluster in the Orion Nebula in the constellation Orion}}

{{for|other stars with this Bayer designation|theta Orionis{{!}}θ Orionis}}

{{Infobox open cluster

|image=250px

|caption=Trapezium in optical (left) and infrared light (right) from Hubble. NASA photo

|name=Trapezium

|epoch= J2000

|class=?

|constellation=Orion

|ra={{RA|05|35.4}}

|dec={{DEC|−05|27}}

|dist_ly=1,344±20 ly

|dist_pc= 412 pc

{{cite journal

| last1=Reid | first1=M. J.

| last2=Menten | first2=K. M.

| last3=Zheng | first3=X. W.

| last4=Brunthaler | first4=A.

| last5=Moscadelli | first5=L.

| last6=Xu | first6=Y.

| last7=Zhang | first7=B.

| last8=Sato | first8=M.

| last9=Honma | first9=M.

| last10=Hirota | first10=T.

| last11=Hachisuka | first11=K.

| last12=Choi | first12=Y. K.

| last13=Moellenbrock | first13=G. A.

| last14=Bartkiewicz | first14=A.

| display-authors=1

| date=2009

| title=Trigonometric Parallaxes of Massive Star Forming Regions: VI. Galactic Structure, Fundamental Parameters and Non-Circular Motions

| journal=Astrophysical Journal

| volume=700 | issue=1

| pages=137–148

| arxiv=0902.3913

| doi=10.1088/0004-637X/700/1/137

| bibcode=2009ApJ...700..137R

| s2cid=11347166

}}

|appmag_v=4.0

|size_v=47 (seconds of arc)

|mass_kg=?

|mass_msol=?

|radius_ly=10 ly

|v_hb=?

|age=300,000 years

|notes=

|names=

|}}

File:Galileo Trapezium Notebook.png

The Trapezium or Orion Trapezium Cluster, also known by its Bayer designation of Theta¹ Orionis (θ¹ Orionis), is a tight open cluster of stars in the heart of the Orion Nebula, in the constellation of Orion. It was discovered by Galileo Galilei. On 4 February 1617 he sketched three of the stars (A, C and D), but missed the surrounding nebulosity.Galileo Galilei: Siderius Nuncius, Venice, 1610. English Translation published at Bard College, Hudson, New York, October 9, 2003 English Translation [http://www.bard.edu/admission/forms/pdfs/galileo.pdf] {{Webarchive|url=https://web.archive.org/web/20040706125127/http://www.bard.edu/admission/forms/pdfs/galileo.pdf |date=2004-07-06 }} Original Latin version [http://www.liberliber.it/biblioteca/g/galilei/sidereus_nuncius/html/sidereus.htm]Tom Pope and Jim Mosher: Galilean telescope homepage" March 17, 2006 {{cite web |url=http://www.pacifier.com/~tpope/Trapezium_Page.htm |title=The Trapezium Through the Galilean Telescope|access-date=2008-01-30 |url-status=dead |archive-url=https://web.archive.org/web/20080130003147/http://www.pacifier.com/~tpope/Trapezium_Page.htm |archive-date=2008-01-30 }}, "Some have expressed puzzlement that in his text Galileo does not mention the nebulosity (known in modern nomenclature as M42) enveloping these stars. ... Galileo believed, as he explains in Sidereus Nuncius, that what looks nebulous to the eye is resolved into stars by his telescope; what looks nebulous through his telescope could presumably also be resolved into stars by a still larger and more powerful telescope. Hence, a diffuse glow would be, more than anything, an indication of the limitations of his telescope and not particularly worthy of special note."Tom Pope and Jim Mosher: Page on Galileo's February 4, 1617 notebook drawing of the Trapezium region, May 2, 2006 "Perhaps significantly, Galileo makes no mention of having noticed the now well-known gas cloud, M42, surrounding the Trapezium stars."[http://www.pacifier.com/~tpope/Photo_Drawing_Comparison_Page.htm#TRAPEZIUM] {{webarchive|url=https://web.archive.org/web/20110811115851/http://www.pacifier.com/~tpope/Photo_Drawing_Comparison_Page.htm |date=2011-08-11 }} A fourth component (B) was identified by several observers in 1673, and several more components were discovered later like E, for a total of eight by 1888. Subsequently, several of the stars were determined to be binaries. Telescopes of amateur astronomers from about {{convert|5|in|adj=on}} aperture can resolve six stars under good seeing conditions.{{cite web | title = Trapezium Cluster | date = 15 May 2015 | url = http://www.messier-objects.com/trapezium-cluster/ | access-date = 2018-03-06}}

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 30 solar masses in size. They are within a diameter of 1.5 light-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.

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