An emission nebula is a nebula formed of ionized gases that emit light of various wavelengths. The most common source of ionization is high-energy ultraviolet photons emitted from a nearby hot star . Among the several different types of emission nebulae are H II regions , in which star formation is taking place and young, massive stars are the source of the ionizing photons; and planetary nebulae , in which a dying star has thrown off its outer layers, with the exposed hot core then ionizing them.
34-562: The Flame Nebula , designated as NGC 2024 and Sh2-277 , is an emission nebula in the constellation Orion . It is about 1350 light-years away. At that distance, the Flame Nebula lies within the Orion B cloud of the larger Orion Molecular Cloud Complex . The bright star Alnitak (ζ Ori) , the easternmost star in the Belt of Orion , appears very close to the Flame Nebula in the sky. But
68-415: A main sequence star and sometimes as a giant star . The Galactic O-Star Spectroscopic Survey has used it as the standard star for the newly created O4 subgiant spectral type. 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
102-408: A young star will ionize part of the same cloud from which it was born, although only massive, hot stars can release sufficient energy to ionize a significant part of a cloud. In many emission nebulae, an entire cluster of young stars is contributing energy. Stars that are hotter than 25,000 K generally emit enough ionizing ultraviolet radiation (wavelength shorter than 91.2 nm) to cause
136-466: 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
170-454: 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; 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
204-424: 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". The Keyhole, or Keyhole Nebula,
238-409: Is only 0.9 magnitudes fainter. HD 93129 Aa 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 HD 93129 A , and is approximately
272-520: Is the largest association in the Carina Nebula. About 2,000 stars have been identified in Trumpler 14 . and the total mass of the cluster is estimated to be 4,300 M ☉ . 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
306-474: The Balmer series . If more energy is available, other elements will be ionized, and green and blue nebulae become possible. By examining the spectra of nebulae, astronomers infer their chemical content. Most emission nebulae are about 90% hydrogen, with the remaining helium , oxygen , nitrogen , and other elements. Some of the most prominent emission nebulae visible from the northern celestial hemisphere are
340-480: The Eta Carinae star system. 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 ,
374-779: The North America Nebula (NGC 7000) and Veil Nebula NGC 6960/6992 in Cygnus , while in the south celestial hemisphere, the Lagoon Nebula M8 / NGC 6523 in Sagittarius and the Orion Nebula M42. Further in the southern hemisphere is the bright Carina Nebula NGC 3372. Emission nebulae often have dark areas in them which result from clouds of dust which block the light. Many nebulae are made up of both reflection and emission components such as
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#1732772379082408-691: The Trifid Nebula . Carina Nebula 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 8,500 light-years (2,600 pc ) from Earth . The nebula has within its boundaries
442-549: 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 . The Carina Nebula was selected as one of five cosmic objects observed by the James Webb Space Telescope , as part of the release of its first official science images . A detailed image was made of an early star-forming region of NGC 3324 known as
476-530: The Cosmic Cliffs. Nicolas-Louis de Lacaille discovered the nebula on 25 January 1752. Its dimensions are 120×120 arcminutes centered on the coordinates of right ascension 10 45 08.5 and declination −59° 52′ 04″. In modern times it is calculated to be around 8,500 light-years (2,600 pc ) from Earth. Eta Carinae is a highly luminous hypergiant star . Estimates of its mass range from 100 to 150 times
510-538: 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 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. It is one of the main clusters of the Carina OB1 stellar association, which
544-526: The Flame Nebula causes the gas to be excited and heated. The glow of the nebula results from the energy input from this central star. Within the nebula and surrounding the central hot star is a cluster of young, lower-mass stars, 86% of which have circumstellar disks . X-ray observations by the Chandra X-ray Observatory show several hundred young stars, out of an estimated population of 800 stars. X-ray and infrared images indicate that
578-550: The Great Eruption in the 1840s surrounded Eta Carinae with dust, drastically reducing the amount of ultraviolet light it put into the 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
612-600: 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 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,
646-525: The emission nebulae around them to be brighter than the reflection nebulae. The radiation emitted by cooler stars is generally not energetic enough to ionize hydrogen, which results in the reflection nebulae around these stars giving off less light than the emission nebulae. The nebula's color depends on its chemical composition and degree of ionization. Due to the prevalence of hydrogen in interstellar gas, and its relatively low energy of ionization, many emission nebulae appear red due to strong emissions of
680-569: 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
714-495: 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 and contains stars like the O2 supergiant HD 93129A . Trumpler 16 is the home of many extremely luminous stars , such as WR 25 and
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#1732772379082748-609: 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
782-615: The mid-infrared, but the ALMA survey also observed a smaller region. The eastern part contains the O8 star IRS 2b and the western part contains the B0.5V star IRS 1. Hubble observations have shown that the Flame Nebula contains 4 clear proplyds and 4 candidate proplyds. Three of these are in the older western region and are pointing towards IRS 1. The other 5 are in the younger eastern region and are pointing towards IRS 2b. Emission nebula Usually,
816-548: 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 seven light-years (2.1 pc). Its appearance has changed significantly since it
850-490: The rest of Carina OB1 . 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 . The star Eta 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 by Hubble Space Telescope on its 20th anniversary . The area
884-598: The same brightness as HD 93129 Ab . 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 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 . 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, O6/7, O4, and O3. It has sometimes been classified as
918-509: The second-brightest star in the sky. The Homunculus Nebula is a small H II region , with gas shocked into ionized and excited states. 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
952-411: The secondary. The spectroscopic mass of the primary has been calculated at 74 M ☉ or 78.1 M ☉ . 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
986-431: The star and nebula are not physically associated with one another. The Flame Nebula contains a young cluster of stars which includes at least one hot, luminous O-type star labeled IRS 2b. The dense gas and dust in the foreground of the nebula heavily obscures the star cluster inside the nebula, making studies at infrared wavelengths most useful. The energetic ultraviolet light emitted by the central O-type star IRS 2b into
1020-410: 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. The less massive member is an O8 main sequence star of approximately 20 M ☉ . It moves in its orbit at a speed of over 300 km/s (190 mi/s) and
1054-406: 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
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1088-407: The young stars are concentrated near the center of the cluster. The Flame Nebula was observed with ALMA and this study found two populations, which are separated by a molecular cloud. The eastern population is 0.2-0.5 Myr old and has a disk fraction of 45±7%. The western population is slightly older at 1 Myr and has a lower disk fraction of 15±4%. This disk fraction is lower than the one observed in
1122-531: 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). A small Bok globule in the Keyhole Nebula (at RA 10h 44m 30s, Dec −59° 40') has been photographed by
1156-441: 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 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
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