The Carina Nebula or Eta Carinae Nebula (catalogued as NGC 3372; also known as the Great Carina Nebula) is a large, complex area of bright and dark nebulosity in the constellation Carina, located in the Carina–Sagittarius Arm of the Milky Way galaxy. The nebula is approximately from Earth.

Discovery and basic information

Nicolas-Louis de Lacaille discovered the nebula on 25 January 1752. Its dimensions are 120×120 arcminutes centered on the coordinates of right ascension and declination . 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.

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 . 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".

Keyhole Nebula

thumb|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, and subsequently referred to it simply as the "oval vacuity". The term lemniscate continued to be used to describe this portion of the nebula until popular astronomy writer Emma Converse described the shape of the nebula as "resembling a keyhole" in an 1873 Appleton's Journal article. 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").

The diameter of the Keyhole structure is approximately . Its appearance has changed significantly since it was first observed, possibly due to changes in the ionizing radiation from Eta Carinae. The Keyhole does not have its own NGC designation. It is sometimes erroneously called NGC 3324, but that catalogue designation refers to a reflection and emission nebula just northwest of the Carina Nebula (or to its embedded star cluster).

Defiant Finger

thumb|200px|Hubble image of the Defiant Finger. North is down.

A small Bok globule in the Keyhole Nebula (at RA 10h44m30s, Dec −59°40') has been photographed by the Hubble Space Telescope and is nicknamed the "Carina Defiant Finger" due to its shape. 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 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 , 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.

Trumpler 14

thumb|Hubble image of the open cluster Trumpler 14

Trumpler 14 is an open cluster with a diameter of , located within the inner regions of the Carina Nebula, approximately from Earth. It is one of the main clusters of the stellar association, which is the largest association in the Carina Nebula. and the total mass of the cluster is estimated to be .

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. The spectroscopic mass of the primary has been calculated at or .

WR 25

thumb|The brightest star is WR 25

WR 25 is a binary system in the central portion of the Carina Nebula, a member of the 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

HD 93129 is a triple star system of O-class stars in Carina. All three stars of are among the most luminous in the galaxy; consists of two clearly resolved components, and , and itself is made up of two much closer stars.

HD 93129 A has been resolved into two components. The brighter component dominates the spectrum, although the secondary is only 0.9 magnitudes fainter. is an O2 supergiant and Ab is an O3.5 main sequence star. Their separation has decreased from 55 milliarcseconds in 2004 to only 27 mas in 2013, but an accurate orbit is not available.

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 , and is approximately the same brightness as .

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, and is considered to be a member of the same loose open cluster , although it appears closer to the more compact .

HD 93250 is known to be a binary star; however, individual spectra of the two components have never been observed, and they are thought to be very similar. The spectral type of has variously been given as O5, O6/7, O4, and O3. It has sometimes been classified as a main sequence star and sometimes as a giant star.

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 ionized 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 . This is somewhat lower than expected from evolutionary modeling of a star with its observed parameters.

The less massive member is an O8 main sequence star of approximately . It moves in its orbit at a speed of over and is considered to be a relativistic binary, which causes the apses of the orbit to change predictably.

Catalogued open clusters in Carina Nebula

, there are eight known open clusters in the Carina Nebula:

  • 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

thumb|600px|center|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 view.

300px|thumb|A celestial map of the nebula.

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File:The spectacular star-forming Carina Nebula imaged by the VLT Survey Telescope.jpg|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.

File:The Carina Nebula in infrared light.jpg|Carina Nebula in infrared light

File:Nearby Supernova Factory Ramps Up- A star-forming region about 7,500 light years from Earth. (6261054663).jpg|X-rays from stars and diffuse multimillion-Kelvin plasma light up the Carina Nebula in this Chandra X-ray Observatory image

File:ESO - The Carina Nebula (by).jpg|Close-up of the Carina Nebula's central region

File:Carina Nebula around the Wolf–Rayet star WR 22.jpg|Wolf–Rayet star WR 22

File:Hs-2007-16-e-800x800.jpg|Bok globule nicknamed "The Caterpillar"

File:Region R44 in the Carina Nebula.jpg|Region R44 in the Carina Nebula

File:Carina Nebula Jets (NIRCam Narrowband Filters - Annotated) (carinanebula1).jpeg|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.

File:Carina Nebula.jpg|Detail of NGC 3372 taken by the VLT telescope

</gallery>

See also

  • Tarantula Nebula

References

  • Carina Nebula at SEDS.org
  • Carina Nebula at Atlas of the Universe
  • Carina Nebula at Constellation Guide