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Saturday, August 14, 2021

08-13-2021-2048 - NGC 3372

The Carina Nebula[7] or Eta Carinae Nebula[8] (catalogued as NGC 3372; also known as the Grand Nebula[citation needed], Great Carina Nebula[9]) is a large, complex area of bright and dark nebulosity in the constellation Carina, and it is located in the Carina–Sagittarius Arm. The nebula is approximately 8,500 light-years (2,600 pc) from Earth.

The nebula has within its boundaries the large Carina OB1 association and several related open clusters, including numerous O-type stars and several Wolf–Rayet stars. Carina OB1 encompasses the star clusters Trumpler 14 and Trumpler 16. Trumpler 14 is one of the youngest known star clusters at half a million years old. Trumpler 16 is the home of WR 25, currently the most luminous star known in our Milky Way galaxy, together with the less luminous but more massive and famous Eta Carinae star system and the O2 supergiant HD 93129A. Trumpler 15, Collinder 228, Collinder 232, NGC 3324, and NGC 3293 are also considered members of the association. NGC 3293 is the oldest and furthest from Trumpler 14, indicating sequential and ongoing star formation.

The nebula is one of the largest diffuse nebulae in our skies. Although it is four times as large as and even brighter than the famous Orion Nebula, the Carina Nebula is much less well known due to its location in the southern sky. It was discovered by Nicolas-Louis de Lacaille in 1752 from the Cape of Good Hope.

https://en.wikipedia.org/wiki/Carina_Nebula 

Emission nebula
Carina Nebula by Harel Boren (151851961, modified).jpg
The Carina Nebula. Eta Carinae and the Keyhole Nebula are just left of center, while NGC 3324 is at upper right. Photo was taken in 2013.

Observation data: J2000.0 epoch
Right ascension10h 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 × 120 arcmins
ConstellationCarina
Physical characteristics
Radius~230[4] ly   (~70 pc)
Notable features
  • Eta Carinae
  • Keyhole Nebula
  • Includes numerous open clusters and dark nebulae
DesignationsNGC 3372,[5] ESO 128-EN013,[1]GC 2197,[1] h 3295,[1] Caldwell 92[6]
See also: Lists of nebulae

Eta Carinae's effects on the nebula can be seen directly. Dark globules 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 of ultraviolet light it put into the nebula.

They are quite rare—only a few dozen in a galaxy as big as ours—and they flirt with disaster near the Eddington limit, i.e., the outward pressure of their radiation is almost strong enough to counteract gravity.

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 possible supernova or hypernova in the near future.

https://en.wikipedia.org/wiki/Carina_Nebula

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The Keyhole Nebula is a dark nebulosity superimposed on the brightest part of the Carina Nebula.

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-oval vacuity" when first describing it,[13] and subsequently referred to it simply as the "oval vacuity".[14] The term lemniscate continued to be used to describe this portion of the nebula[15]

https://en.wikipedia.org/wiki/Carina_Nebula

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Eta Carinae, surrounded by the Homunculus Nebula

The Homunculus Nebula is a small H II region, with gas shocked into ionised and excited states.[10] It also absorbs much of the light from the extremely luminous central stellar system and re-radiates it as infrared (IR). It is the brightest object in the sky at mid-IR wavelengths.[11]:145–169


https://en.wikipedia.org/wiki/Carina_Nebula

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Hubble image of the Defiant Finger. North is down.

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.[25]

https://en.wikipedia.org/wiki/Carina_Nebula

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Hubble image of the open cluster Trumpler 14

 open cluster T 14

https://en.wikipedia.org/wiki/Carina_Nebula

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Mystic Mountain

Mystic Mountain is the term for a dust–gas pillar in the Carina Nebula, a photo of which was taken by Hubble Space Telescope on its 20th anniversary. The area was observed by Hubble's Wide Field Camera 3 on 1–2 February 2010. 

https://en.wikipedia.org/wiki/Carina_Nebula

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HD 93205

The spectrum shows some ionised nitrogen and helium emission lines, indicating some mixing of fusion products to the surface and a strong stellar wind.


https://en.wikipedia.org/wiki/Carina_Nebula

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An H II region or HII region is a region of interstellar atomic hydrogen that is ionized.[1] It is typically a cloud in a molecular cloud of partially ionized gas in which star formation has recently taken place, with a size ranging from one to hundreds of light years, and density from a few to about a million particles per cubic cm. The Orion Nebula, now known to be an H II region, was observed in 1610 by Nicolas-Claude Fabri de Peiresc by telescope, the first such object discovered.

They may be of any shape, because the distribution of the stars and gas inside them is irregular.  The short-lived blue stars created in these regions emit copious amounts of ultraviolet light that ionize the surrounding gas. H II regions—sometimes several hundred light-years across—are often associated with giant molecular clouds. They often appear clumpy and filamentary, sometimes showing intricate shapes such as the Horsehead Nebula. H II regions may give birth to thousands of stars over a period of several million years. In the end, supernova explosions and strong stellar winds from the most massive stars in the resulting star cluster will disperse the gases of the H II region, leaving behind a cluster of stars which have formed, such as the Pleiades.

H II regions can be observed at considerable distances in the universe, and the study of extragalactic H II regions is important in determining the distance and chemical composition of galaxies. Spiral and irregulargalaxies contain many H II regions, while elliptical galaxies are almost devoid of them. In spiral galaxies, including our Milky Way, H II regions are concentrated in the spiral arms, while in irregular galaxies they are distributed chaotically. Some galaxies contain huge H II regions, which may contain tens of thousands of stars. Examples include the 30 Doradus region in the Large Magellanic Cloud and NGC 604 in the Triangulum Galaxy.

The term H II is pronounced "H two" by astronomers. "H" is the chemical symbol for hydrogen, and "II" is the Roman numeral for 2. It is customary in astronomy to use the Roman numeral I for neutral atoms, II for singly-ionised—H II is H+ in other sciences—III for doubly-ionised, e.g. O III is O++, etc.[3] H II, or H+, consists of free protons. An H I region is neutral atomic hydrogen, and a molecular cloud is molecular hydrogen, H2. In spoken discussion with non-astronomers there is sometimes confusion between the identical spoken forms of "H II" and "H2".

 Over a period of several million years, a cluster of stars will form in an H II region, before radiation pressure from the hot young stars causes the nebula to disperse.[13] The Pleiades are an example of a cluster which has 'boiled away' the H II region from which it was formed. Only a trace of reflection nebulosity remains.

https://en.wikipedia.org/wiki/H_II_region


The Eddington luminosity, also referred to as the Eddington limit, is the maximum luminosity a body (such as a star) can achieve when there is balance between the force of radiation acting outward and the gravitational force acting inward. The state of balance is called hydrostatic equilibrium. When a star exceeds the Eddington luminosity, it will initiate a very intense radiation-driven stellar wind from its outer layers. Since most massive stars have luminosities far below the Eddington luminosity, their winds are mostly driven by the less intense line absorption.[1] The Eddington limit is invoked to explain the observed luminosity of accreting black holes such as quasars.

Originally, Sir Arthur Eddington took only the electron scattering into account when calculating this limit, something that now is called the classical Eddington limit. Nowadays, the modified Eddington limit also counts on other radiation processes such as bound-free and free-free radiation (see Bremsstrahlung) interaction.

The limit is obtained by setting the outward radiation pressure equal to the inward gravitational force. Both forces decrease by inverse square laws, so once equality is reached, the hydrodynamic flow is the same throughout the star.

From Euler's equation in hydrostatic equilibrium, the mean acceleration is zero, 

where  is the velocity,  is the pressure,  is the density, and  is the gravitational potential. If the pressure is dominated by radiation pressure associated with a radiation flux , 

Here  is the opacity of the stellar material which is defined as the fraction of radiation energy flux absorbed by the medium per unit density and unit length. For ionized hydrogen , where  is the Thomson scattering cross-section for the electron and  is the mass of a proton. Note that  is defined as the energy flux over a surface, which can be expressed with the momentum flux using  for radiation. Therefore, the rate of momentum transfer from the radiation to the gaseous medium per unit density is , which explains the right hand side of the above equation.

The luminosity of a source bounded by a surface  may be expressed with these relations as

Now assuming that the opacity is a constant, it can be brought outside of the integral. Using Gauss's theorem and Poisson's equation gives 

where  is the mass of the central object. This is called the Eddington Luminosity.[2] For pure ionized hydrogen

where ☉ is the mass of the Sun and ☉ is the luminosity of the Sun.

The maximum luminosity of a source in hydrostatic equilibrium is the Eddington luminosity. If the luminosity exceeds the Eddington limit, then the radiation pressure drives an outflow.

The mass of the proton appears because, in the typical environment for the outer layers of a star, the radiation pressure acts on electrons, which are driven away from the center. Because protons are negligibly pressured by the analog of Thomson scattering, due to their larger mass, the result is to create a slight charge separation and therefore a radially directed electric field, acting to lift the positive charges, which are typically free protons under the conditions in stellar atmospheres. When the outward electric field is sufficient to levitate the protons against gravity, both electrons and protons are expelled together.

Different limits for different materials[edit]

The derivation above for the outward light pressure assumes a hydrogen plasma. In other circumstances the pressure balance can be different from what it is for hydrogen.

In an evolved star with a pure helium atmosphere, the electric field would have to lift a helium nucleus (an alpha particle), with nearly 4 times the mass of a proton, while the radiation pressure would act on 2 free electrons. Thus twice the usual Eddington luminosity would be needed to drive off an atmosphere of pure helium.

At very high temperatures, as in the environment of a black hole or neutron star, high energy photon interactions with nuclei or even with other photons, can create an electron-positron plasma. In that situation the combined mass of the positive-negative charge carrier pair is approximately 918 times smaller (the proton to electron mass ratio), while the radiation pressure on the positrons doubles the effective upward force per unit mass, so the limiting luminosity needed is reduced by a factor of ≈918×2.

The exact value of the Eddington luminosity depends on the chemical composition of the gas layer and the spectral energy distribution of the emission. A gas with cosmological abundances of hydrogen and helium is much more transparent than gas with solar abundance ratios. Atomic line transitions can greatly increase the effects of radiation pressure, and line driven winds exist in some bright stars (e.g., Wolf-Rayet and O stars).

Super-Eddington luminosities[edit]

The role of the Eddington limit in today's research lies in explaining the very high mass loss rates seen in for example the series of outbursts of η Carinae in 1840–1860.[3] The regular, line driven stellar winds can only stand for a mass loss rate of around 10−4–10−3 solar masses per year, whereas mass loss rates of up to 0.5 solar masses per year are needed to understand the η Carinae outbursts. This can be done with the help of the super-Eddington broad spectrum radiation driven winds.

Gamma-ray bursts, novae and supernovae are examples of systems exceeding their Eddington luminosity by a large factor for very short times, resulting in short and highly intensive mass loss rates. Some X-ray binaries and active galaxies are able to maintain luminosities close to the Eddington limit for very long times. For accretion-powered sources such as accreting neutron stars or cataclysmic variables (accreting white dwarfs), the limit may act to reduce or cut off the accretion flow, imposing an Eddington limit on accretion corresponding to that on luminosity. Super-Eddington accretion onto stellar-mass black holes is one possible model for ultraluminous X-ray sources (ULXs).

For accreting black holes, not all the energy released by accretion has to appear as outgoing luminosity, since energy can be lost through the event horizon, down the hole. Such sources effectively may not conserve energy. Then the accretion efficiency, or the fraction of energy actually radiated of that theoretically available from the gravitational energy release of accreting material, enters in an essential way.

Other factors[edit]

The Eddington limit is not a strict limit on the luminosity of a stellar object. The limit does not consider several potentially important factors, and super-Eddington objects have been observed that do not seem to have the predicted high mass-loss rate. Other factors that might affect the maximum luminosity of a star include:

  • Porosity. A problem with steady winds driven by broad-spectrum radiation is that both the radiative flux and gravitational acceleration scale with r −2. The ratio between these factors is constant, and in a super-Eddington star, the whole envelope would become gravitationally unbound at the same time. This is not observed. A possible solution is introducing an atmospheric porosity, where we imagine the stellar atmosphere to consist of denser regions surrounded by lower density gas regions. This would reduce the coupling between radiation and matter, and the full force of the radiation field would only be seen in the more homogeneous outer, lower density layers of the atmosphere.
  • Turbulence. A possible destabilizing factor might be the turbulent pressure arising when energy in the convection zones builds up a field of supersonic turbulence. The importance of turbulence is being debated, however.[4]
  • Photon bubbles. Another factor that might explain some stable super-Eddington objects is the photon bubble effect. Photon bubbles would develop spontaneously in radiation-dominated atmospheres when the radiation pressure exceeds the gas pressure. We can imagine a region in the stellar atmosphere with a density lower than the surroundings, but with a higher radiation pressure. Such a region would rise through the atmosphere, with radiation diffusing in from the sides, leading to an even higher radiation pressure. This effect could transport radiation more efficiently than a homogeneous atmosphere, increasing the allowed total radiation rate. In accretion discs, luminosities may be as high as 10–100 times the Eddington limit without experiencing instabilities.[5]

Humphreys–Davidson limit[edit]

The upper H–R diagram with the empirical Humphreys-Davidson limit marked (green line). Stars are observed above the limit only during brief outbursts.

Observations of massive stars show a clear upper limit to their luminosity, termed the Humphreys–Davidson limit after the researchers who first wrote about it.[6] Only highly unstable objects are found, temporarily, at higher luminosities. Efforts to reconcile this with the theoretical Eddington limit have been largely unsuccessful.[7]

See also[edit]

References[edit]

  1. ^ A. J. van Marle; S. P. Owocki; N. J. Shaviv (2008). "Continuum driven winds from super-Eddington stars. A tale of two limits". AIP Conference Proceedings. 990: 250–253. arXiv:0708.4207. Bibcode:2008AIPC..990..250V. doi:10.1063/1.2905555.
  2. ^ Rybicki, G.B., Lightman, A.P.: Radiative Processes in Astrophysics, New York: J. Wiley & Sons 1979.
  3. ^ N. Smith; S. P. Owocki (2006). "On the role of continuum driven eruptions in the evolution of very massive stars and population III stars". Astrophysical Journal. 645 (1): L45–L48. arXiv:astro-ph/0606174. Bibcode:2006ApJ...645L..45S. doi:10.1086/506523.
  4. ^ R. B. Stothers (2003). "Turbulent pressure in the envelopes of yellow hypergiants and luminous blue variables". Astrophysical Journal. 589 (2): 960–967. Bibcode:2003ApJ...589..960S. doi:10.1086/374713.
  5. ^ J. Arons (1992). "Photon bubbles: Overstability in a magnetized atmosphere". Astrophysical Journal. 388: 561–578. Bibcode:1992ApJ...388..561A. doi:10.1086/171174.
  6. ^ Humphreys, R. M.; Davidson, K. (1979). "Studies of luminous stars in nearby galaxies. III - Comments on the evolution of the most massive stars in the Milky Way and the Large Magellanic Cloud". The Astrophysical Journal. 232: 409. Bibcode:1979ApJ...232..409H. doi:10.1086/157301. ISSN 0004-637X.
  7. ^ Glatzel, W.; Kiriakidis, M. (15 July 1993). "Stability of massive stars and the Humphreys–Davidson limit" (PDF). Monthly Notices of the Royal Astronomical Society. 263 (2): 375–384. Bibcode:1993MNRAS.263..375G. doi:10.1093/mnras/263.2.375.

External links[edit]

  • Juhan Frank; Andrew King; Derek Raine (2002). Accretion Power in Astrophysics (Third ed.). Cambridge University Press. ISBN 0-521-62957-8.
  • John A Regan; Turlough P Downes; Marta Volonteri; Ricarda Beckmann; Alessandro Lupi; Maxime Trebitsch; Yohan Dubois (2019). "Super-Eddington accretion and feedback from the first massive seed black holes". 486 (3). Monthly Notices of the Royal Astronomical Society. arXiv:1811.04953. doi:10.1093/mnras/stz1045.

External links[edit]

https://en.wikipedia.org/wiki/Eddington_luminosity

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Carina Nebula

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Carina Nebula
Emission nebula
Carina Nebula by Harel Boren (151851961, modified).jpg
The Carina Nebula. Eta Carinae and the Keyhole Nebula are just left of center, while NGC 3324 is at upper right. Photo was taken in 2013.
Observation data: J2000.0 epoch
Right ascension10h 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 × 120 arcmins
ConstellationCarina
Physical characteristics
Radius~230[4] ly   (~70 pc)
Notable features
  • Eta Carinae
  • Keyhole Nebula
  • Includes numerous open clusters and dark nebulae
DesignationsNGC 3372,[5] ESO 128-EN013,[1]GC 2197,[1] h 3295,[1] Caldwell 92[6]
See also: Lists of nebulae

Coordinates: Sky map 10h 45m 08.5s, −59° 52′ 04″

The Carina Nebula[7] or Eta Carinae Nebula[8] (catalogued as NGC 3372; also known as the Grand Nebula[citation needed], Great Carina Nebula[9]) is a large, complex area of bright and dark nebulosity in the constellation Carina, and it is located in the Carina–Sagittarius Arm. The nebula is approximately 8,500 light-years (2,600 pc) from Earth.

The nebula has within its boundaries the large Carina OB1 association and several related open clusters, including numerous O-type stars and several Wolf–Rayet stars. Carina OB1 encompasses the star clusters Trumpler 14 and Trumpler 16. Trumpler 14 is one of the youngest known star clusters at half a million years old. Trumpler 16 is the home of WR 25, currently the most luminous star known in our Milky Way galaxy, together with the less luminous but more massive and famous Eta Carinae star system and the O2 supergiant HD 93129A. Trumpler 15, Collinder 228, Collinder 232, NGC 3324, and NGC 3293 are also considered members of the association. NGC 3293 is the oldest and furthest from Trumpler 14, indicating sequential and ongoing star formation.

The nebula is one of the largest diffuse nebulae in our skies. Although it is four times as large as and even brighter than the famous Orion Nebula, the Carina Nebula is much less well known due to its location in the southern sky. It was discovered by Nicolas-Louis de Lacaille in 1752 from the Cape of Good Hope.

Discovery and basic information[edit]

Nicolas-Louis de Lacaille discovered the nebula on 25 January 1752.[3] Its dimensions are 120×120 arcminutes centered on the coordinates of right ascension 10h 45m 08.5s and declination −59° 52′ 04″.[1] In modern times it is calculated to be around 8,500 light-years (2,600 pc) from Earth.[2]

Objects within the Carina Nebula[edit]

Eta Carinae[edit]

Main article: Eta Carinae
Eta Carinae observed in different wavelengths

Eta Carinae is a highly luminous hypergiant star. Estimates of its mass range from 100 to 150 times the mass of the Sun, 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 be more luminous and more massive, but data on them is far less robust. (Caveat: Since examples such as the Pistol 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 highest confirmed 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 the Eddington limit, i.e., the outward pressure of their radiation is almost strong enough to counteract gravity. 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 possible supernova or hypernova in the near future.

Eta Carinae's effects on the nebula can be seen directly. Dark globules 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 of ultraviolet light it put into the nebula.

Homunculus Nebula[edit]

Main article: Homunculus Nebula
Eta Carinae, surrounded by the Homunculus Nebula

Within the large bright nebula is a much smaller feature, immediately surrounding Eta Carinae itself, known as the Homunculus Nebula (from Latin meaning Little 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 small H II region, with gas shocked into ionised and excited states.[10] It also absorbs much of the light from the extremely luminous central stellar system and re-radiates it as infrared (IR). It is the brightest object in the sky at mid-IR wavelengths.[11]: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 ± 160 light-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".[12]

Keyhole Nebula[edit]

The Keyhole Nebula is a dark nebulosity superimposed on the brightest part of the Carina Nebula.

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-oval vacuity" when first describing it,[13] and subsequently referred to it simply as the "oval vacuity".[14] The term lemniscate continued to be used to describe this portion of the nebula[15] until popular astronomy writer Emma Converse described the shape of the nebula as "resembling a keyhole" in an 1873 Appleton's Journal article.[16] 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").[17][18]

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 the ionising radiation from Eta Carinae.[19]The Keyhole does not have its own NGC designation. It is sometimes erroneously called NGC 3324,[20] but that catalogue designation refers to a reflection and emission nebula just northwest of the Carina Nebula (or to its embedded star cluster).[21][22][23]

Defiant Finger[edit]

Hubble image of the Defiant Finger. North is down.

A small Bok globule in the Keyhole Nebula has been photographed by the Hubble Space Telescope and is nicknamed the "Carina Defiant Finger" due to its shape.[24] 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 bright blue 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.[25]

Trumpler 14[edit]

Main article: Trumpler 14
Hubble image of the open cluster Trumpler 14

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.[26] It is one of the main clusters of the Carina OB1 stellar association, which is the largest association in the Carina Nebula.[11] About 2,000 stars have been identified in Trumpler 14.[27] and the total mass of the cluster is estimated to be 4,300 M☉.[28]

Trumpler 15[edit]

Main article: Trumpler 15

Trumpler 15 is a star cluster on the north-east edge of the Carina Nebula. Early studies disagreed about the distance, but astrometric measurements by the Gaia mission have confirmed that it is the same distance as the rest of Carina OB1.[2]

Trumpler 16[edit]

Main article: Trumpler 16

Trumpler 16 is one of the main clusters of the Carina OB1 stellar association, which is the largest association in the Carina Nebula, and it is bigger and more massive than Trumpler 14.[11] The star Eta Carinae is part of this cluster.

Mystic Mountain[edit]

Main article: Mystic Mountain
Mystic Mountain

Mystic Mountain is the term for a dust–gas pillar in the Carina Nebula, a photo of which was taken by Hubble Space Telescope on its 20th anniversary. The area was observed by Hubble's Wide 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[edit]

Main article: WR 22

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.[29] The spectroscopic mass of the primary has been calculated at 74 M☉[30] or 78.1 M☉.[31]

WR 25[edit]

Main article: WR 25
The brightest star is WR 25

WR 25 is a binary system in the central portion of the Carina Nebula, a member of the Trumpler 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 luminous OB star.

HD 93129[edit]

Main article: HD 93129

HD 93129 is a triple star system of O-class stars in Carina. All three stars of HD 93129 are among the most luminous in the galaxy;[32] HD 93129 consists of two clearly resolved components, HD 93129 A and HD 93129 B, and HD 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.[33] Their separation has decreased from 55 milliarcseconds in 2004 to only 27 mas in 2013, but an accurate orbit is not available.[34]

HD 93129 B is an O3.5 main-sequence star 3 arcseconds away from the closer pair. It is about 1.5 magnitudes fainter than the combined HD 93129 A, and is approximately the same brightness as HD 93129 Ab.[35][36]

HD 93250[edit]

Main article: HD 93250

HD 93250 is one of the brightest stars in the region of the Carina Nebula. It is only 7.5 arcminutes from Eta Carinae,[37] and HD 93250 is considered to be a member of the same loose open cluster Trumpler 16, although it appears closer to the more compact Trumpler 14.[38]

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 of HD 93250 has variously been given as O5,[39] O6/7,[40] O4,[41] and O3.[42] It has sometimes been classified as a main sequencestar and sometimes as a giant star.[41][42] The Galactic O-Star Spectroscopic Survey has used it as the standard star for the newly created O4 subgiantspectral type.[43]

HD 93205[edit]

Main article: HD 93205

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 ionised nitrogen and helium emission lines, indicating some mixing of fusion products to the surface and a strong stellar 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.[44]

The less massive member is an O8 main sequence star of approximately 20 M☉.[45] 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.[46]

Catalogued open clusters in Carina Nebula[edit]

As of 1998, there are eight known open clusters in the Carina Nebula:[3]

  • Bochum 10 (Bo 10)
  • Bochum 11 (Bo 11)
  • Collinder 228 (Cr 228)[47]
  • Collinder 232 (Cr 232)
  • Collinder 234 (Cr 234)
  • Trumpler 14 (Tr 14, Cr 230)
  • Trumpler 15 (Tr 15, Cr 231)
  • Trumpler 16 (Tr 16, Cr 233)

Annotated map[edit]

Annotated map of part of the Carina Nebula showing the location of various objects in the nebula. This view combines multiple ground and Hubble observatory images in a 50-light-year wide (15 pc) view.[48]
A celestial map of the nebula.

Gallery[edit]

  • Overview of the Carina Nebula. The Keyhole is superimposed on the bright area above center, and Eta Carinae is the bright star just to its left.

    •  

  • Carina Nebula in infrared light[49]

    •  

  • Close-up of the Carina Nebula's central region

  • Wolf–Rayet star WR 22

    •  

  • The turbulent neighborhood around Eta Carinae, shaped by strong stellar winds

    •  

  • A Bok globule within the Carina Nebula, nicknamed the "Finger of God" or "God's birdie" due to its appearance; see pareidolia

    •  

  • Bok globule nicknamed "The Caterpillar"[50]

    •  

  • Region R44 in the Carina Nebula[51]

See also[edit]

References[edit]

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