| Emission nebula | |
|---|---|
.jpg) The Carina Nebula.Eta Carinae and the Keyhole Nebula are left of center,NGC 3324 is at upper right. | |
| Observation data: J2000.0epoch | |
| Right ascension | 10h 45m 08.5s[1] |
| Declination | −59° 52′ 04″[1] |
| Distance | ~8,500 ly (~2,600[2] pc) |
| Apparent magnitude (V) | +1.0[3] |
| Apparent dimensions (V) | 120 × 120arcmins |
| Constellation | Carina |
| Physical characteristics | |
| Radius | ~230[4] ly (~70 pc) |
| Notable features |
|
| Designations | NGC 3372,[5]ESO 128-EN013,[1]GC 2197,[1] h 3295,[1]Caldwell 92[6] |
| See also:Lists of nebulae | |
TheCarina Nebula[7] orEta Carinae Nebula[8] (catalogued asNGC 3372; also known as theGreat Carina Nebula[9]) is a large, complex area ofbright anddark nebulosity in the constellationCarina, located in theCarina–Sagittarius Arm of the Milky Way galaxy. The nebula is approximately 8,500light-years (2,600 pc) fromEarth.[2]
The nebula has within its boundaries the largeCarina OB1association and several relatedopen clusters, including numerousO-type stars and severalWolf–Rayet stars.Carina OB1 encompasses thestar clustersTrumpler 14 andTrumpler 16.Trumpler 14 is one of the youngest known star clusters at half a million years old and contains stars like the O2 supergiantHD 93129A.Trumpler 16 is the home of manyextremely luminous stars, such asWR 25 and theEta Carinae star system.Trumpler 15,Collinder 228,Collinder 232,NGC 3324, andNGC 3293 are also considered members of the association.NGC 3293 is the oldest and furthest fromTrumpler 14, indicating sequential and ongoing star formation.
The nebula is one of the largest diffuse nebulae in Earth's sky. Although it is four times as large as and even brighter than the famousOrion Nebula, the Carina Nebula is much less well known due to its location in the southern sky. It was discovered byNicolas-Louis de Lacaille in 1752 from theCape of Good Hope.
The Carina Nebula was selected as one of five cosmic objects observed by theJames Webb Space Telescope, as part of the release ofits first official science images. A detailed image was made of an early star-forming region of NGC 3324 known as the Cosmic Cliffs.[10]
Nicolas-Louis de Lacaille discovered the nebula on 25 January 1752.[3][11] Its dimensions are 120×120arcminutes centered on thecoordinates ofright ascension10h 45m 08.5s anddeclination −59° 52′ 04″.[1] In modern times it is calculated to be around 8,500light-years (2,600 pc) from Earth.[2]
Eta Carinae is a highlyluminoushypergiantstar. Estimates of itsmass range from 100 to 150 times the mass of theSun, and its luminosity is about four million times that of the Sun.
This object is currently the most massive star that can be studied in great detail, because of its location and size. Several other known stars may bemore luminous andmore massive, but data on them is far less robust. (Caveat: Since examples such as thePistol Star have been demoted by improved data, one should be skeptical of most available lists of "most massive stars". In 2006, Eta Carinae still had the highestconfirmed luminosity, based on data across a broad range of wavelengths.) Stars with more than 80 times the mass of the Sun produce more than a million times as much light as the Sun. They are quite rare—only a few dozen in a galaxy as big as ours—and they flirt with disaster near theEddington limit, i.e., the outward pressure of theirradiation is almost strong enough to counteractgravity. Stars that are more than 120 solar masses exceed the theoretical Eddington limit, and their gravity is barely strong enough to hold in its radiation and gas, resulting in a possiblesupernova orhypernova in the near future.
Eta Carinae's effects on the nebula can be seen directly. Darkglobules and some other less visible objects have tails pointing directly away from the massive star. The entire nebula would have looked very different before the Great Eruption in the 1840s surrounded Eta Carinae with dust, drastically reducing the amount ofultraviolet light it put into the nebula.
Within the large bright nebula is a much smaller feature, immediately surrounding Eta Carinae itself, known as theHomunculus Nebula (fromLatin meaningLittle Man). It is believed to have been ejected in an enormous outburst in 1841 which briefly made Eta Carinae the second-brightest star in the sky.
The Homunculus Nebula is a smallH II region, with gas shocked into ionized and excited states.[12] It also absorbs much of the light from the extremely luminous central stellar system and re-radiates it asinfrared (IR). It is the brightest object in the sky at mid-IR wavelengths.[13]: 145–169
The distance to the Homunculus can be derived from its observed angular dimensions and calculated linear size, assuming it is axially symmetric. The most accurate distance obtained using this method is 7,660 ± 160light-years (2,350 ± 50 pc). The largest radius of the bipolar lobes in this model is about 22,000 AU, and the axis is oriented 41° from the line of sight, or 49° relative to the plane of the sky, which means it is seen from Earth slightly more "end on" than "side on".[14]
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The Keyhole, or Keyhole Nebula, is a small dark cloud of cold molecules and dust within the Carina Nebula, containing bright filaments of hot, fluorescing gas, silhouetted against the much brighter background nebula.John Herschel used the term "lemniscate-ovalvacuity" when first describing it,[15] and subsequently referred to it simply as the "oval vacuity".[16] The term lemniscate continued to be used to describe this portion of the nebula[17] until popular astronomy writer Emma Converse described the shape of the nebula as "resembling a keyhole" in an 1873Appleton's Journal article.[18] The name Keyhole Nebula then came into common use, sometimes for the Keyhole itself, sometimes to describe the whole of the Carina Nebula (signifying "the nebula that contains the Keyhole").[19][20]
The diameter of the Keyhole structure is approximately seven light-years (2.1 pc). Its appearance has changed significantly since it was first observed, possibly due to changes in theionizing radiation from Eta Carinae.[21] The Keyhole does not have its own NGC designation. It is sometimes erroneously calledNGC 3324,[22] but that catalogue designation refers to a reflection and emission nebula just northwest of the Carina Nebula (or to its embedded star cluster).[23][24][25]
A smallBok globule in the Keyhole Nebula (atRA 10h 44m 30s,Dec −59° 40') has been photographed by the Hubble Space Telescope and is nicknamed the "Carina Defiant Finger" due to its shape.[26] In Hubble images, light can be seen radiating off the edges of the globule; this is especially visible in the southern tip, where the "finger" is. It is thought that the Defiant Finger is being ionized by the bright Wolf–Rayet star WR 25, and/or Trumpler 16-244, a brightblue supergiant. It has a mass of at least 6 M☉, and stars may be forming within it. Like other interstellar clouds under intense radiation, the Defiant Finger will eventually be completely evaporated; for this cloud the time frame is predicted to be 200,000 to 1,000,000 years.[27]
Trumpler 14 is an open cluster with a diameter of six light-years (1.8 pc), located within the inner regions of the Carina Nebula, approximately 8,000 light-years (2,500 pc) from Earth.[28] It is one of the main clusters of theCarina OB1 stellar association, which is the largest association in the Carina Nebula.[13] About 2,000 stars have been identified inTrumpler 14.[29] and the total mass of the cluster is estimated to be 4,300 M☉.[30]
Trumpler 15 is a star cluster on the north-east edge of the Carina Nebula. Early studies disagreed about the distance, butastrometric measurements by theGaia mission have confirmed that it is the same distance as the rest ofCarina OB1.[2]
Trumpler 16 is one of the main clusters of theCarina OB1 stellar association, which is the largest association in the Carina Nebula, and it is bigger and more massive thanTrumpler 14.[13] The starEta Carinae is part of this cluster.
Mystic Mountain is the term for a dust–gas pillar in the Carina Nebula, a photo of which was taken byHubble Space Telescope onits 20th anniversary. The area was observed by Hubble'sWide Field Camera 3 on 1–2 February 2010. The pillar measures three light-years (0.92 pc) in height; nascent stars inside the pillar fire off gas jets that stream from towering “peaks”.
WR 22 is an eclipsing binary. The dynamical masses derived from orbital fitting vary from over 70 M☉ to less than 60 M☉ for the primary and about 21 to 27 M☉ for the secondary.[31] The spectroscopic mass of the primary has been calculated at 74 M☉[32] or 78.1 M☉.[33]
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WR 25 is a binary system in the central portion of the Carina Nebula, a member of theTrumpler 16 cluster. The primary is a Wolf–Rayet star, possibly the most luminous star in the galaxy. The secondary is hard to detect but thought to be a luminousOB star.
HD 93129 is a triple star system of O-class stars in Carina. All three stars ofHD 93129 are among the most luminous in the galaxy;[34]HD 93129 consists of two clearly resolved components,HD 93129 A andHD 93129 B, andHD 93129 A itself is made up of two much closer stars.
HD 93129 A has been resolved into two components. The spectrum is dominated by the brighter component, although the secondary is only 0.9 magnitudes fainter.HD 93129 Aa is an O2 supergiant and Ab is an O3.5 main sequence star.[35] Their separation has decreased from 55milliarcseconds in 2004 to only 27 mas in 2013, but an accurate orbit is not available.[36]
HD 93129 B is anO3.5 main-sequence star 3arcseconds away from the closer pair. It is about 1.5 magnitudes fainter than the combinedHD 93129 A, and is approximately the same brightness asHD 93129 Ab.[37][38]
HD 93250 is one of the brightest stars in the region of the Carina Nebula. It is only 7.5arcminutes fromEta Carinae,[39] andHD 93250 is considered to be a member of the same looseopen clusterTrumpler 16, although it appears closer to the more compactTrumpler 14.[40]
HD 93250 is known to be a binary star, however, individual spectra of the two components have never been observed but are thought to be very similar. The spectral type ofHD 93250 has variously been given as O5,[41] O6/7,[42] O4,[43] and O3.[44] It has sometimes been classified as amain sequence star and sometimes as agiant star.[43][44] The Galactic O-Star Spectroscopic Survey has used it as the standard star for the newly created O4subgiant spectral type.[45]
HD 93205 is a binary system of two large stars.
The more massive member of the pair is an O3.5 main sequence star. The spectrum shows some ionized nitrogen and helium emission lines, indicating some mixing of fusion products to the surface and a strongstellar wind. The mass calculated from apsidal motion of the orbits is 40 to 60 M☉. This is somewhat lower than expected from evolutionary modelling of a star with its observed parameters.[46]
The less massive member is an O8 main sequence star of approximately 20 M☉.[47] It moves in its orbit at a speed of over 300 km/s (190 mi/s) and is considered to be a relativistic binary, which causes the apses of the orbit to change in a predictable way.[48]
As of 1998[update], there are eight known open clusters in the Carina Nebula:[3]
![Carina Nebula in infrared light[51]](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aThe_Carina_Nebula_in_infrared_light.jpg)
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![Bok globule nicknamed "The Caterpillar"[52]](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aHs-2007-16-e-800x800.jpg)
![Region R44 in the Carina Nebula[53]](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aRegion_R44_in_the_Carina_Nebula.jpg)
![Scientists taking a “deep dive” into one of the iconic first images from the James Webb Space Telescope have discovered dozens of energetic jets and outflows from young stars previously hidden by dust clouds. [54]](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aCarina_Nebula_Jets_(NIRCam_Narrowband_Filters_-_Annotated)_(carinanebula1).jpeg)
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