A nebula ( Latin for 'cloud, fog'; pl. : nebulae , nebulæ , or nebulas ) is a distinct luminescent part of interstellar medium , which can consist of ionized, neutral, or molecular hydrogen and also cosmic dust . Nebulae are often star-forming regions, such as in the Pillars of Creation in the Eagle Nebula . In these regions, the formations of gas, dust, and other materials "clump" together to form denser regions, which attract further matter and eventually become dense enough to form stars . The remaining material is then thought to form planets and other planetary system objects.
52-741: 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 the large Carina OB1 association and several related open clusters , including numerous O-type stars and several Wolf–Rayet stars . Carina OB1 encompasses
104-412: 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
156-402: A mass of about two to 50 solar masses contained within a region about a light year or so across (about 4.5 × 10 m ). They contain molecular hydrogen (H 2 ), carbon oxides and helium , and around 1% (by mass) silicate dust. Bok globules most commonly result in the formation of double - or multiple-star systems. Bok globules were first observed by astronomer Bart Bok in
208-604: A supernova remnant , a special diffuse nebula . Although much of the optical and X-ray emission from supernova remnants originates from ionized gas, a great amount of the radio emission is a form of non-thermal emission called synchrotron emission . This emission originates from high-velocity electrons oscillating within magnetic fields . Bok globule In astronomy , Bok globules are isolated and relatively small dark nebulae containing dense cosmic dust and gas from which star formation may take place. Bok globules are found within H II regions , and typically have
260-433: A class of emission nebula associated with giant molecular clouds. These form as a molecular cloud collapses under its own weight, producing stars. Massive stars may form in the center, and their ultraviolet radiation ionizes the surrounding gas, making it visible at optical wavelengths . The region of ionized hydrogen surrounding the massive stars is known as an H II region while the shells of neutral hydrogen surrounding
312-445: A few kilograms . Earth's air has a density of approximately 10 molecules per cubic centimeter; by contrast, the densest nebulae can have densities of 10 molecules per cubic centimeter. Many nebulae are visible due to fluorescence caused by embedded hot stars, while others are so diffused that they can be detected only with long exposures and special filters. Some nebulae are variably illuminated by T Tauri variable stars. Originally,
364-779: A relatively recently identified astronomical phenomenon. In contrast to the typical and well known gaseous nebulae within the plane of the Milky Way galaxy , IFNs lie beyond the main body of the galaxy. Most nebulae can be described as diffuse nebulae, which means that they are extended and contain no well-defined boundaries. Diffuse nebulae can be divided into emission nebulae , reflection nebulae and dark nebulae . Visible light nebulae may be divided into emission nebulae, which emit spectral line radiation from excited or ionized gas (mostly ionized hydrogen ); they are often called H II regions , H II referring to ionized hydrogen), and reflection nebulae which are visible primarily due to
416-464: 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
468-453: 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
520-423: 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,
572-492: Is considered to be a relativistic binary, which causes the apses of the orbit to change in a predictable way. As of 1998, there are eight known open clusters in the Carina Nebula: Bright nebulae Most nebulae are of vast size; some are hundreds of light-years in diameter. A nebula that is visible to the human eye from Earth would appear larger, but no brighter, from close by. The Orion Nebula ,
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#1732775580188624-460: 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
676-412: Is expected to spawn a planetary nebula about 12 billion years after its formation. A supernova occurs when a high-mass star reaches the end of its life. When nuclear fusion in the core of the star stops, the star collapses. The gas falling inward either rebounds or gets so strongly heated that it expands outwards from the core, thus causing the star to explode. The expanding shell of gas forms
728-407: 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
780-517: 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
832-704: The Andromeda Galaxy is located. He also cataloged the Omicron Velorum star cluster as a "nebulous star" and other nebulous objects, such as Brocchi's Cluster . The supernovas that created the Crab Nebula , SN 1054 , was observed by Arabic and Chinese astronomers in 1054. In 1610, Nicolas-Claude Fabri de Peiresc discovered the Orion Nebula using a telescope. This nebula was also observed by Johann Baptist Cysat in 1618. However,
884-548: The Cape of Good Hope , most of which were previously unknown. Charles Messier then compiled a catalog of 103 "nebulae" (now called Messier objects , which included what are now known to be galaxies) by 1781; his interest was detecting comets , and these were objects that might be mistaken for them. The number of nebulae was then greatly increased by the efforts of William Herschel and his sister, Caroline Herschel . Their Catalogue of One Thousand New Nebulae and Clusters of Stars
936-560: 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 the Cosmic Cliffs. Nicolas-Louis de Lacaille discovered the nebula on 25 January 1752. Its dimensions are 120×120 arcminutes centered on
988-553: The Great Debate , it became clear that many "nebulae" were in fact galaxies far from the Milky Way . Slipher and Edwin Hubble continued to collect the spectra from many different nebulae, finding 29 that showed emission spectra and 33 that had the continuous spectra of star light. In 1922, Hubble announced that nearly all nebulae are associated with stars and that their illumination comes from star light. He also discovered that
1040-514: 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 the mass of the Sun , and its luminosity is about four million times that of the Sun. This object
1092-533: 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 the Eta Carinae star system. Trumpler 15 , Collinder 228 , Collinder 232 , NGC 3324 , and NGC 3293 are also considered members of
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#17327755801881144-548: The ultraviolet radiation it emits can ionize the surrounding nebula that it has thrown off. The Sun will produce a planetary nebula and its core will remain behind in the form of a white dwarf . Objects named nebulae belong to four major groups. Before their nature was understood, galaxies ("spiral nebulae") and star clusters too distant to be resolved as stars were also classified as nebulae, but no longer are. Not all cloud-like structures are nebulae; Herbig–Haro objects are an example. Integrated flux nebulae are
1196-868: The 1940s. In an article published in 1947, he and Edith F. Reilly hypothesized that these clouds were "similar to insect's cocoons " that were undergoing gravitational collapse to form new stars, from which stars and star clusters were born. This hypothesis was difficult to verify due to the observational difficulties of establishing what was happening inside a dense dark cloud that obscured all visible light emitted from within it. An analysis of near- infrared observations published in 1990 confirmed that stars were being born inside Bok globules. Further observations have revealed that some Bok globules contain embedded warm sources, some contain Herbig–Haro objects , and some show outflows of molecular gas . Millimeter-wave emission line studies have provided evidence for
1248-536: 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
1300-550: 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
1352-555: The H II region are known as photodissociation region . Examples of star-forming regions are the Orion Nebula , the Rosette Nebula and the Omega Nebula . Feedback from star-formation, in the form of supernova explosions of massive stars, stellar winds or ultraviolet radiation from massive stars, or outflows from low-mass stars may disrupt the cloud, destroying the nebula after several million years. Other nebulae form as
1404-599: 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,
1456-422: 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
1508-456: The brightest nebula in the sky and occupying an area twice the angular diameter of the full Moon , can be viewed with the naked eye but was missed by early astronomers. Although denser than the space surrounding them, most nebulae are far less dense than any vacuum created on Earth (10 to 10 molecules per cubic centimeter) – a nebular cloud the size of the Earth would have a total mass of only
1560-471: The different types of nebulae. Some nebulae form from gas that is already in the interstellar medium while others are produced by stars. Examples of the former case are giant molecular clouds , the coldest, densest phase of interstellar gas, which can form by the cooling and condensation of more diffuse gas. Examples of the latter case are planetary nebulae formed from material shed by a star in late stages of its stellar evolution . Star-forming regions are
1612-405: The emission spectrum nebulae are nearly always associated with stars having spectral classifications of B or hotter (including all O-type main sequence stars ), while nebulae with continuous spectra appear with cooler stars. Both Hubble and Henry Norris Russell concluded that the nebulae surrounding the hotter stars are transformed in some manner. There are a variety of formation mechanisms for
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1664-510: The expelled gases, producing emission nebulae with spectra similar to those of emission nebulae found in star formation regions. They are H II regions , because mostly hydrogen is ionized, but planetary are denser and more compact than nebulae found in star formation regions. Planetary nebulae were given their name by the first astronomical observers who were initially unable to distinguish them from planets, and who tended to confuse them with planets, which were of more interest to them. The Sun
1716-480: The explosion lies in the center of the Crab Nebula and its core is now a neutron star . Still other nebulae form as planetary nebulae . This is the final stage of a low-mass star's life, like Earth's Sun. Stars with a mass up to 8–10 solar masses evolve into red giants and slowly lose their outer layers during pulsations in their atmospheres. When a star has lost enough material, its temperature increases and
1768-522: The first detailed study of the Orion Nebula was not performed until 1659 by Christiaan Huygens , who also believed he was the first person to discover this nebulosity. In 1715, Edmond Halley published a list of six nebulae. This number steadily increased during the century, with Jean-Philippe de Cheseaux compiling a list of 20 (including eight not previously known) in 1746. From 1751 to 1753, Nicolas-Louis de Lacaille cataloged 42 nebulae from
1820-520: 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
1872-455: The infall of material onto an accreting protostar . It is now thought that a typical Bok globule contains about 10 solar masses of material in a region about a light-year or so across, and that Bok globules most commonly result in the formation of double- or multiple-star systems. Bok globules are still a subject of intense research. Known to be some of the coldest objects in the natural universe, their structure and density remains somewhat
1924-503: The light they reflect. Reflection nebulae themselves do not emit significant amounts of visible light, but are near stars and reflect light from them. Similar nebulae not illuminated by stars do not exhibit visible radiation, but may be detected as opaque clouds blocking light from luminous objects behind them; they are called dark nebulae . Although these nebulae have different visibility at optical wavelengths, they are all bright sources of infrared emission, chiefly from dust within
1976-544: 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
2028-401: The nebulae. Planetary nebulae are the remnants of the final stages of stellar evolution for mid-mass stars (varying in size between 0.5-~8 solar masses). Evolved asymptotic giant branch stars expel their outer layers outwards due to strong stellar winds, thus forming gaseous shells while leaving behind the star's core in the form of a white dwarf . Radiation from the hot white dwarf excites
2080-488: 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
2132-456: The result of supernova explosions; the death throes of massive, short-lived stars. The materials thrown off from the supernova explosion are then ionized by the energy and the compact object that its core produces. One of the best examples of this is the Crab Nebula , in Taurus . The supernova event was recorded in the year 1054 and is labeled SN 1054 . The compact object that was created after
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2184-590: 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
2236-506: 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
2288-408: 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
2340-514: The spectra of about 70 nebulae. He found that roughly a third of them had the emission spectrum of a gas . The rest showed a continuous spectrum and were thus thought to consist of a mass of stars. A third category was added in 1912 when Vesto Slipher showed that the spectrum of the nebula that surrounded the star Merope matched the spectra of the Pleiades open cluster . Thus, the nebula radiates by reflected star light. In 1923, following
2392-408: 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
2444-589: The term "nebula" was used to describe any diffused astronomical object , including galaxies beyond the Milky Way . The Andromeda Galaxy , for instance, was once referred to as the Andromeda Nebula (and spiral galaxies in general as "spiral nebulae") before the true nature of galaxies was confirmed in the early 20th century by Vesto Slipher , Edwin Hubble , and others. Edwin Hubble discovered that most nebulae are associated with stars and illuminated by starlight. He also helped categorize nebulae based on
2496-406: 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
2548-548: The type of light spectra they produced. Around 150 AD, Ptolemy recorded, in books VII–VIII of his Almagest , five stars that appeared nebulous. He also noted a region of nebulosity between the constellations Ursa Major and Leo that was not associated with any star . The first true nebula, as distinct from a star cluster , was mentioned by the Muslim Persian astronomer Abd al-Rahman al-Sufi in his Book of Fixed Stars (964). He noted "a little cloud" where
2600-526: 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
2652-441: 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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#17327755801882704-442: Was published in 1786. A second catalog of a thousand was published in 1789, and the third and final catalog of 510 appeared in 1802. During much of their work, William Herschel believed that these nebulae were merely unresolved clusters of stars. In 1790, however, he discovered a star surrounded by nebulosity and concluded that this was a true nebulosity rather than a more distant cluster. Beginning in 1864, William Huggins examined
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