127-596: The Calán/Tololo Supernova Survey was a supernova survey that ran from 1989 to 1995 at the University of Chile and the Cerro Tololo Inter-American Observatory to measure a Hubble diagram out to redshifts of 0.1. It was founded by Mario Hamuy , José Maza Sancho , Mark M. Phillips , and Nicholas B. Suntzeff in 1989 out of discussions at the UC Santa Cruz meeting on supernovae on how to improve
254-485: A conjunction of Jupiter and Mars in 1106 or 1107 as evidence. The Persian astronomer Nasir al-Din al-Tusi (1201–1274) in his Tadhkira wrote: "The Milky Way, i.e. the Galaxy, is made up of a very large number of small, tightly clustered stars, which, on account of their concentration and smallness, seem to be cloudy patches. Because of this, it was likened to milk in color." Ibn Qayyim al-Jawziyya (1292–1350) proposed that
381-452: A neutron star or black hole , or is completely destroyed to form a diffuse nebula . The peak optical luminosity of a supernova can be comparable to that of an entire galaxy before fading over several weeks or months. The last supernova directly observed in the Milky Way was Kepler's Supernova in 1604, appearing not long after Tycho's Supernova in 1572, both of which were visible to
508-654: A radius of about 39.5 kpc (130,000 ly), over twice as much as was determined in earlier studies, suggesting that about 90% of the mass of the galaxy is dark matter . In September 2023, astronomers reported that the virial mass of the Milky Way Galaxy is only 2.06 10 solar masses , only a 10th of the mass of previous studies. The mass was determined from data of the Gaia spacecraft . The Milky Way contains between 100 and 400 billion stars and at least that many planets. An exact figure would depend on counting
635-603: A 2016 study. Such Earth-sized planets may be more numerous than gas giants, though harder to detect at great distances given their small size. Besides exoplanets, " exocomets ", comets beyond the Solar System, have also been detected and may be common in the Milky Way. More recently, in November 2020, over 300 million habitable exoplanets are estimated to exist in the Milky Way Galaxy. When compared to other more distant galaxies in
762-518: A dim un-resolved "milky" glowing band arching across the night sky. The term is a translation of the Classical Latin via lactea , in turn derived from the Hellenistic Greek γαλαξίας , short for γαλαξίας κύκλος ( galaxías kýklos ), meaning "milky circle". The Ancient Greek γαλαξίας ( galaxias ) – from root γαλακτ -, γάλα ("milk") + -ίας (forming adjectives) – is also
889-456: A great deal of detail at +6.1. This makes the Milky Way difficult to see from brightly lit urban or suburban areas, but very prominent when viewed from rural areas when the Moon is below the horizon. Maps of artificial night sky brightness show that more than one-third of Earth's population cannot see the Milky Way from their homes due to light pollution. As viewed from Earth, the visible region of
1016-412: A journal article came the following year in a publication by Knut Lundmark , who may have coined it independently. Compared to a star's entire history, the visual appearance of a supernova is very brief, sometimes spanning several months, so that the chances of observing one with the naked eye are roughly once in a lifetime. Only a tiny fraction of the 100 billion stars in a typical galaxy have
1143-466: A measurement of the radial velocity of halo stars found that the mass enclosed within 80 kilo parsecs is 7 × 10 M ☉ . In a 2014 study, the mass of the entire Milky Way is estimated to be 8.5 × 10 M ☉ , but this is only half the mass of the Andromeda Galaxy. A recent 2019 mass estimate for the Milky Way is 1.29 × 10 M ☉ . Much of the mass of
1270-453: A non-rotating star), it would no longer be able to support the bulk of its mass through electron degeneracy pressure and would begin to collapse. However, the current view is that this limit is not normally attained; increasing temperature and density inside the core ignite carbon fusion as the star approaches the limit (to within about 1%) before collapse is initiated. In contrast, for a core primarily composed of oxygen, neon and magnesium,
1397-557: A one or two-letter designation. The first 26 supernovae of the year are designated with a capital letter from A to Z . Next, pairs of lower-case letters are used: aa , ab , and so on. Hence, for example, SN 2003C designates the third supernova reported in the year 2003. The last supernova of 2005, SN 2005nc, was the 367th (14 × 26 + 3 = 367). Since 2000, professional and amateur astronomers have been finding several hundred supernovae each year (572 in 2007, 261 in 2008, 390 in 2009; 231 in 2013). Historical supernovae are known simply by
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#17328697150151524-410: A range in mass, as large as 4.5 × 10 M ☉ and as small as 8 × 10 M ☉ . By comparison, the total mass of all the stars in the Milky Way is estimated to be between 4.6 × 10 M ☉ and 6.43 × 10 M ☉ . In addition to the stars, there is also interstellar gas, comprising 90% hydrogen and 10% helium by mass, with two thirds of
1651-675: A rare type of very fast supernova with unusually strong calcium lines in their spectra. Models suggest they occur when material is accreted from a helium -rich companion rather than a hydrogen -rich star. Because of helium lines in their spectra, they can resemble type Ib supernovae, but are thought to have very different progenitors. The supernovae of type II can also be sub-divided based on their spectra. While most type II supernovae show very broad emission lines which indicate expansion velocities of many thousands of kilometres per second , some, such as SN 2005gl , have relatively narrow features in their spectra. These are called type IIn, where
1778-703: A stellar companion to raise its core temperature enough to ignite carbon fusion , at which point it undergoes runaway nuclear fusion, completely disrupting it. There are three avenues by which this detonation is theorised to happen: stable accretion of material from a companion, the collision of two white dwarfs, or accretion that causes ignition in a shell that then ignites the core. The dominant mechanism by which type Ia supernovae are produced remains unclear. Despite this uncertainty in how type Ia supernovae are produced, type Ia supernovae have very uniform properties and are useful standard candles over intergalactic distances. Some calibrations are required to compensate for
1905-470: A supernova's spectrum contains lines of hydrogen (known as the Balmer series in the visual portion of the spectrum) it is classified Type II ; otherwise it is Type I . In each of these two types there are subdivisions according to the presence of lines from other elements or the shape of the light curve (a graph of the supernova's apparent magnitude as a function of time). Type I supernovae are subdivided on
2032-415: A treatise in 1755, Immanuel Kant , drawing on earlier work by Thomas Wright , speculated (correctly) that the Milky Way might be a rotating body of a huge number of stars, held together by gravitational forces akin to the Solar System but on much larger scales. The resulting disk of stars would be seen as a band on the sky from our perspective inside the disk. Wright and Kant also conjectured that some of
2159-449: Is a dimensionless measure of the spectrum's frequency shift. High redshift searches for supernovae usually involve the observation of supernova light curves. These are useful for standard or calibrated candles to generate Hubble diagrams and make cosmological predictions. Supernova spectroscopy, used to study the physics and environments of supernovae, is more practical at low than at high redshift. Low redshift observations also anchor
2286-428: Is a disk of gas and dust called the interstellar medium . This disk has at least a comparable extent in radius to the stars, whereas the thickness of the gas layer ranges from hundreds of light-years for the colder gas to thousands of light-years for warmer gas. The disk of stars in the Milky Way does not have a sharp edge beyond which there are no stars. Rather, the concentration of stars decreases with distance from
2413-405: Is a ring-like filament of stars called Triangulum–Andromeda Ring (TriAnd Ring) rippling above and below the relatively flat galactic plane , which alongside Monoceros Ring were both suggested to be primarily the result of disk oscillations and wrapping around the Milky Way, at a diameter of at least 50 kpc (160,000 ly), which may be part of the Milky Way's outer disk itself, hence making
2540-584: Is an intense radio source known as Sagittarius A* , a supermassive black hole of 4.100 (± 0.034) million solar masses . The oldest stars in the Milky Way are nearly as old as the Universe itself and thus probably formed shortly after the Dark Ages of the Big Bang . Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610. Until the early 1920s, most astronomers thought that
2667-537: Is approximately 890 billion to 1.54 trillion times the mass of the Sun in total (8.9 × 10 to 1.54 × 10 solar masses), although stars and planets make up only a small part of this. Estimates of the mass of the Milky Way vary, depending upon the method and data used. The low end of the estimate range is 5.8 × 10 solar masses ( M ☉ ), somewhat less than that of the Andromeda Galaxy . Measurements using
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#17328697150152794-449: Is called the Zone of Avoidance . The Milky Way has a relatively low surface brightness . Its visibility can be greatly reduced by background light, such as light pollution or moonlight. The sky needs to be darker than about 20.2 magnitude per square arcsecond in order for the Milky Way to be visible. It should be visible if the limiting magnitude is approximately +5.1 or better and shows
2921-522: Is celestial. This idea would be influential later in the Muslim world . The Persian astronomer Al-Biruni (973–1048) proposed that the Milky Way is "a collection of countless fragments of the nature of nebulous stars". The Andalusian astronomer Avempace ( d 1138) proposed that the Milky Way was made up of many stars but appeared to be a continuous image in the Earth's atmosphere, citing his observation of
3048-485: Is debated and several alternative explanations, such as tidal disruption of a star by a black hole, have been suggested. SN 2013fs was recorded three hours after the supernova event on 6 October 2013, by the Intermediate Palomar Transient Factory . This is among the earliest supernovae caught after detonation, and it is the earliest for which spectra have been obtained, beginning six hours after
3175-529: Is estimated to contain 100–400 billion stars and at least that number of planets . The Solar System is located at a radius of about 27,000 light-years (8.3 kpc) from the Galactic Center , on the inner edge of the Orion Arm , one of the spiral-shaped concentrations of gas and dust. The stars in the innermost 10,000 light-years form a bulge and one or more bars that radiate from the bulge. The Galactic Center
3302-451: Is generated, with matter reaching velocities on the order of 5,000–20,000 km/s , or roughly 3% of the speed of light. There is also a significant increase in luminosity, reaching an absolute magnitude of −19.3 (or 5 billion times brighter than the Sun), with little variation. The model for the formation of this category of supernova is a close binary star system. The larger of the two stars
3429-472: Is inclined by about 60° to the ecliptic (the plane of Earth's orbit ). Relative to the celestial equator , it passes as far north as the constellation of Cassiopeia and as far south as the constellation of Crux , indicating the high inclination of Earth's equatorial plane and the plane of the ecliptic, relative to the galactic plane. The north galactic pole is situated at right ascension 12 49 , declination +27.4° ( B1950 ) near β Comae Berenices , and
3556-542: Is much variation in this type of event, and, in many cases, there may be no supernova at all, in which case they will have a less luminous light curve than the more normal SN type Ia. Abnormally bright type Ia supernovae occur when the white dwarf already has a mass higher than the Chandrasekhar limit, possibly enhanced further by asymmetry, but the ejected material will have less than normal kinetic energy. This super-Chandrasekhar-mass scenario can occur, for example, when
3683-579: Is required. It is therefore important to discover them well before they reach their maximum. Amateur astronomers , who greatly outnumber professional astronomers, have played an important role in finding supernovae, typically by looking at some of the closer galaxies through an optical telescope and comparing them to earlier photographs. Toward the end of the 20th century, astronomers increasingly turned to computer-controlled telescopes and CCDs for hunting supernovae. While such systems are popular with amateurs, there are also professional installations such as
3810-434: Is significantly smaller than the Andromeda Galaxy's isophotal diameter, and slightly below the mean isophotal sizes of the galaxies being at 28.3 kpc (92,000 ly). The paper concludes that the Milky Way and Andromeda Galaxy were not overly large spiral galaxies, nor were among the largest known (if the former not being the largest) as previously widely believed, but rather average ordinary spiral galaxies. To compare
3937-637: Is the Large Sagittarius Star Cloud , a portion of the central bulge of the galaxy. Dark regions within the band, such as the Great Rift and the Coalsack , are areas where interstellar dust blocks light from distant stars. Peoples of the southern hemisphere, including the Inca and Australian aborigines , identified these regions as dark cloud constellations . The area of sky that the Milky Way obscures
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4064-414: Is the first to evolve off the main sequence , and it expands to form a red giant . The two stars now share a common envelope, causing their mutual orbit to shrink. The giant star then sheds most of its envelope, losing mass until it can no longer continue nuclear fusion . At this point, it becomes a white dwarf star, composed primarily of carbon and oxygen. Eventually, the secondary star also evolves off
4191-405: Is the traditional Welsh name for the constellation Cassiopeia . At least three of Dôn's children also have astronomical associations: Caer Gwydion ("The fortress of Gwydion ") is the traditional Welsh name for the Milky Way, and Caer Arianrhod ("The Fortress of Arianrhod ") being the constellation of Corona Borealis . In Western culture, the name "Milky Way" is derived from its appearance as
4318-486: Is visible as a hazy band of white light, some 30° wide, arching the night sky . Although all the individual naked-eye stars in the entire sky are part of the Milky Way Galaxy, the term "Milky Way" is limited to this band of light. The light originates from the accumulation of unresolved stars and other material located in the direction of the galactic plane . Brighter regions around the band appear as soft visual patches known as star clouds . The most conspicuous of these
4445-461: The Andromeda Galaxy . A second supernova, SN 1895B , was discovered in NGC 5253 a decade later. Early work on what was originally believed to be simply a new category of novae was performed during the 1920s. These were variously called "upper-class Novae", "Hauptnovae", or "giant novae". The name "supernovae" is thought to have been coined by Walter Baade and Zwicky in lectures at Caltech in 1931. It
4572-508: The Chandrasekhar limit ; electron capture ; pair-instability ; or photodisintegration . The table below lists the known reasons for core collapse in massive stars, the types of stars in which they occur, their associated supernova type, and the remnant produced. The metallicity is the proportion of elements other than hydrogen or helium, as compared to the Sun. The initial mass is the mass of
4699-555: The Eta Carinae Great Outburst was noted. Supernovae in M101 (1909) and M83 (1923 and 1957) were also suggested as possible type IV or type V supernovae. These types would now all be treated as peculiar type II supernovae (IIpec), of which many more examples have been discovered, although it is still debated whether SN 1961V was a true supernova following an LBV outburst or an impostor. Supernova type codes, as summarised in
4826-590: The Hubble diagram using Type Ia supernovae . It was also motivated by the suggestion of Allan Sandage to restart a supernova survey after the Sandage and Tammann survey failed due to poor quality photographic plates in 1986. The Survey built on the original supernova survey of Maza done at the f/3 Maksutov Camera at the Cerro Roble Observatory of the University of Chile between 1979 and 1984. The Survey used
4953-593: The Katzman Automatic Imaging Telescope . The Supernova Early Warning System (SNEWS) project uses a network of neutrino detectors to give early warning of a supernova in the Milky Way galaxy. Neutrinos are subatomic particles that are produced in great quantities by a supernova, and they are not significantly absorbed by the interstellar gas and dust of the galactic disk. Supernova searches fall into two classes: those focused on relatively nearby events and those looking farther away. Because of
5080-516: The Large Magellanic Cloud , a satellite galaxy of the Milky Way. Theoretical studies indicate that most supernovae are triggered by one of two basic mechanisms: the sudden re-ignition of nuclear fusion in a white dwarf , or the sudden gravitational collapse of a massive star's core . Supernovae can expel several solar masses of material at speeds up to several percent of the speed of light . This drives an expanding shock wave into
5207-673: The Phillips relationship , as well as providing data for a Hubble diagram of Type II supernovae using the Expanding Photosphere method. In 1994, the Calán/Tololo team formed a parallel project, the High-Z Supernova Search Team , organized by Nicholas Suntzeff and Brian Schmidt , which later discovered the accelerated expansion of the universe in 1998. The calibration of Type Ia supernovae as standard candles led to
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5334-489: The Very Long Baseline Array in 2009 found velocities as large as 254 km/s (570,000 mph) for stars at the outer edge of the Milky Way. Because the orbital velocity depends on the total mass inside the orbital radius, this suggests that the Milky Way is more massive, roughly equaling the mass of Andromeda Galaxy at 7 × 10 M ☉ within 160,000 ly (49 kpc) of its center. In 2010,
5461-413: The expansion of the universe , the distance to a remote object with a known emission spectrum can be estimated by measuring its Doppler shift (or redshift ); on average, more-distant objects recede with greater velocity than those nearby, and so have a higher redshift. Thus the search is split between high redshift and low redshift, with the boundary falling around a redshift range of z=0.1–0.3, where z
5588-476: The light-gathering power of this new telescope, he was able to produce astronomical photographs that resolved the outer parts of some spiral nebulae as collections of individual stars. He was also able to identify some Cepheid variables that he could use as a benchmark to estimate the distance to the nebulae. He found that the Andromeda Nebula is 275,000 parsecs from the Sun, far too distant to be part of
5715-597: The magnetic fields of the Milky Way were reported. The Sun is near the inner rim of the Orion Arm , within the Local Fluff of the Local Bubble , between the Radcliffe wave and Split linear structures (formerly Gould Belt ). Based upon studies of stellar orbits around Sgr A* by Gillessen et al. (2016), the Sun lies at an estimated distance of 27.14 ± 0.46 kly (8.32 ± 0.14 kpc) from
5842-416: The naked eye . The remnants of more recent supernovae have been found, and observations of supernovae in other galaxies suggest they occur in the Milky Way on average about three times every century. A supernova in the Milky Way would almost certainly be observable through modern astronomical telescopes. The most recent naked-eye supernova was SN 1987A , which was the explosion of a blue supergiant star in
5969-440: The nebulae visible in the night sky might be separate "galaxies" themselves, similar to our own. Kant referred to both the Milky Way and the "extragalactic nebulae" as "island universes", a term still current up to the 1930s. The first attempt to describe the shape of the Milky Way and the position of the Sun within it was carried out by William Herschel in 1785 by carefully counting the number of stars in different regions of
6096-529: The plural form supernovae ( /- v iː / ) or supernovas and is often abbreviated as SN or SNe. It is derived from the Latin word nova , meaning ' new ' , which refers to what appears to be a temporary new bright star. Adding the prefix "super-" distinguishes supernovae from ordinary novae, which are far less luminous. The word supernova was coined by Walter Baade and Fritz Zwicky , who began using it in astrophysics lectures in 1931. Its first use in
6223-460: The solar apex , is the direction that the Sun travels through space in the Milky Way. The general direction of the Sun's Galactic motion is towards the star Vega near the constellation of Hercules , at an angle of roughly 60 sky degrees to the direction of the Galactic Center. The Sun's orbit about the Milky Way is expected to be roughly elliptical with the addition of perturbations due to
6350-431: The "n" stands for "narrow". A few supernovae, such as SN 1987K and SN 1993J , appear to change types: they show lines of hydrogen at early times, but, over a period of weeks to months, become dominated by lines of helium. The term "type IIb" is used to describe the combination of features normally associated with types II and Ib. Type II supernovae with normal spectra dominated by broad hydrogen lines that remain for
6477-507: The Babylonian national god , after slaying her. This story was once thought to have been based on an older Sumerian version in which Tiamat is instead slain by Enlil of Nippur , but is now thought to be purely an invention of Babylonian propagandists with the intention to show Marduk as superior to the Sumerian deities. In Greek mythology , Zeus places his son born by a mortal woman,
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#17328697150156604-524: The CTIO Curtis Schmidt telescope with IIa-O photographic plates, each plate covering a field of 25 sq-deg on the sky. The plates were developed and sent to Santiago Chile the next morning and searched for supernovae at the Department of Astronomy at the University of Chile . Any supernova candidates were then observed the next night using the 0.9m telescope at CTIO with a CCD camera. This was one of
6731-563: The Galactic Center is about 180,000 ly (55 kpc). At this distance or beyond, the orbits of most halo objects would be disrupted by the Magellanic Clouds. Hence, such objects would probably be ejected from the vicinity of the Milky Way. The integrated absolute visual magnitude of the Milky Way is estimated to be around −20.9. Both gravitational microlensing and planetary transit observations indicate that there may be at least as many planets bound to stars as there are stars in
6858-519: The Galactic Center. Boehle et al. (2016) found a smaller value of 25.64 ± 0.46 kly (7.86 ± 0.14 kpc), also using a star orbit analysis. The Sun is currently 5–30 parsecs (16–98 ly) above, or north of, the central plane of the Galactic disk. The distance between the local arm and the next arm out, the Perseus Arm , is about 2,000 parsecs (6,500 ly). The Sun, and thus
6985-399: The Galactic spiral arms and non-uniform mass distributions. In addition, the Sun passes through the Galactic plane approximately 2.7 times per orbit. This is very similar to how a simple harmonic oscillator works with no drag force (damping) term. These oscillations were until recently thought to coincide with mass lifeform extinction periods on Earth. A reanalysis of the effects of
7112-569: The Milky Way contained all the stars in the Universe . Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Doust Curtis , observations by Edwin Hubble showed that the Milky Way is just one of many galaxies. In the Babylonian epic poem Enūma Eliš , the Milky Way is created from the severed tail of the primeval salt water dragoness Tiamat , set in the sky by Marduk ,
7239-405: The Milky Way is "a myriad of tiny stars packed together in the sphere of the fixed stars". Proof of the Milky Way consisting of many stars came in 1610 when Galileo Galilei used a telescope to study the Milky Way and discovered that it is composed of a huge number of faint stars. Galileo also concluded that the appearance of the Milky Way was due to refraction of the Earth's atmosphere. In
7366-446: The Milky Way is approximately 220 km/s (490,000 mph) or 0.073% of the speed of light . The Sun moves through the heliosphere at 84,000 km/h (52,000 mph). At this speed, it takes around 1,400 years for the Solar System to travel a distance of 1 light-year, or 8 days to travel 1 AU ( astronomical unit ). The Solar System is headed in the direction of the zodiacal constellation Scorpius , which follows
7493-449: The Milky Way is the glow of stars not directly visible due to Earth's shadow, while other stars receive their light from the Sun, but have their glow obscured by solar rays. Aristotle himself believed that the Milky Way was part of the Earth's upper atmosphere, along with the stars, and that it was a byproduct of stars burning that did not dissipate because of its outermost location in the atmosphere, composing its great circle . He said that
7620-428: The Milky Way seems to be dark matter , an unknown and invisible form of matter that interacts gravitationally with ordinary matter. A dark matter halo is conjectured to spread out relatively uniformly to a distance beyond one hundred kiloparsecs (kpc) from the Galactic Center. Mathematical models of the Milky Way suggest that the mass of dark matter is 1–1.5 × 10 M ☉ . 2013 and 2014 studies indicate
7747-404: The Milky Way". Viewing from the north galactic pole with 0° (zero degrees) as the ray that runs starting from the Sun and through the Galactic Center, the quadrants are: with the galactic longitude (ℓ) increasing in the counter-clockwise direction ( positive rotation ) as viewed from north of the Galactic Center (a view-point several hundred thousand light-years distant from Earth in
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#17328697150157874-510: The Milky Way's galactic plane occupies an area of the sky that includes 30 constellations . The Galactic Center lies in the direction of Sagittarius , where the Milky Way is brightest. From Sagittarius, the hazy band of white light appears to pass around to the galactic anticenter in Auriga . The band then continues the rest of the way around the sky, back to Sagittarius, dividing the sky into two roughly equal hemispheres . The galactic plane
8001-526: The Milky Way, and microlensing measurements indicate that there are more rogue planets not bound to host stars than there are stars. The Milky Way contains an average of at least one planet per star, resulting in 100–400 billion planets, according to a January 2013 study of the five-planet star system Kepler-32 by the Kepler space observatory. A different January 2013 analysis of Kepler data estimated that at least 17 billion Earth-sized exoplanets reside in
8128-438: The Milky Way. The ESA spacecraft Gaia provides distance estimates by determining the parallax of a billion stars and is mapping the Milky Way with four planned releases of maps in 2016, 2018, 2021 and 2024. Data from Gaia has been described as "transformational". It has been estimated that Gaia has expanded the number of observations of stars from about 2 million stars as of the 1990s to 2 billion. It has expanded
8255-437: The Milky Way. In November 2013, astronomers reported, based on Kepler space mission data, that there could be as many as 40 billion Earth-sized planets orbiting in the habitable zones of Sun-like stars and red dwarfs within the Milky Way. 11 billion of these estimated planets may be orbiting Sun-like stars. The nearest exoplanet may be 4.2 light-years away, orbiting the red dwarf Proxima Centauri , according to
8382-501: The Solar System, is located in the Milky Way's galactic habitable zone . There are about 208 stars brighter than absolute magnitude 8.5 within a sphere with a radius of 15 parsecs (49 ly) from the Sun, giving a density of one star per 69 cubic parsecs, or one star per 2,360 cubic light-years (from List of nearest bright stars ). On the other hand, there are 64 known stars (of any magnitude, not counting 4 brown dwarfs ) within 5 parsecs (16 ly) of
8509-411: The Sun's transit through the spiral structure based on CO data has failed to find a correlation. It takes the Solar System about 240 million years to complete one orbit of the Milky Way (a galactic year ), so the Sun is thought to have completed 18–20 orbits during its lifetime and 1/1250 of a revolution since the origin of humans . The orbital speed of the Solar System about the center of
8636-412: The Sun, giving a density of about one star per 8.2 cubic parsecs, or one per 284 cubic light-years (from List of nearest stars ). This illustrates the fact that there are far more faint stars than bright stars: in the entire sky, there are about 500 stars brighter than apparent magnitude 4 but 15.5 million stars brighter than apparent magnitude 14. The apex of the Sun's way, or
8763-605: The actual explosion. The star is located in a spiral galaxy named NGC 7610 , 160 million light-years away in the constellation of Pegasus. The supernova SN 2016gkg was detected by amateur astronomer Victor Buso from Rosario , Argentina, on 20 September 2016. It was the first time that the initial "shock breakout" from an optical supernova had been observed. The progenitor star has been identified in Hubble Space Telescope images from before its collapse. Astronomer Alex Filippenko noted: "Observations of stars in
8890-688: The basis of their spectra, with type Ia showing a strong ionised silicon absorption line. Type I supernovae without this strong line are classified as type Ib and Ic, with type Ib showing strong neutral helium lines and type Ic lacking them. Historically, the light curves of type I supernovae were seen as all broadly similar, too much so to make useful distinctions. While variations in light curves have been studied, classification continues to be made on spectral grounds rather than light-curve shape. A small number of type Ia supernovae exhibit unusual features, such as non-standard luminosity or broadened light curves, and these are typically categorised by referring to
9017-534: The capacity to become a supernova, the ability being restricted to those having high mass and those in rare kinds of binary star systems with at least one white dwarf . The earliest record of a possible supernova, known as HB9, was likely viewed by an unknown prehistoric people of the Indian subcontinent and recorded on a rock carving in the Burzahama region of Kashmir , dated to 4500 ± 1000 BC . Later, SN 185
9144-478: The center of the Milky Way. Beyond a radius of roughly 40,000 light years (13 kpc) from the center, the number of stars per cubic parsec drops much faster with radius. Surrounding the galactic disk is a spherical galactic halo of stars and globular clusters that extends farther outward, but is limited in size by the orbits of two Milky Way satellites, the Large and Small Magellanic Clouds , whose closest approach to
9271-402: The collapsing white dwarf will typically form a neutron star . In this case, only a fraction of the star's mass will be ejected during the collapse. Within a few seconds of the collapse process, a substantial fraction of the matter in the white dwarf undergoes nuclear fusion, releasing enough energy (1– 2 × 10 J ) to unbind the star in a supernova. An outwardly expanding shock wave
9398-454: The core against its own gravity; passing this threshold is the cause of all types of supernova except type Ia. The collapse may cause violent expulsion of the outer layers of the star resulting in a supernova. However, if the release of gravitational potential energy is insufficient, the star may instead collapse into a black hole or neutron star with little radiated energy. Core collapse can be caused by several different mechanisms: exceeding
9525-465: The direction of the constellation Coma Berenices ); if viewed from south of the Galactic Center (a view-point similarly distant in the constellation Sculptor ), ℓ would increase in the clockwise direction ( negative rotation ). The Milky Way is one of the two largest galaxies in the Local Group (the other being the Andromeda Galaxy ), although the size for its galactic disc and how much it defines
9652-400: The distance to their host galaxies. A second model for the formation of type Ia supernovae involves the merger of two white dwarf stars, with the combined mass momentarily exceeding the Chandrasekhar limit. This is sometimes referred to as the double-degenerate model, as both stars are degenerate white dwarfs. Due to the possible combinations of mass and chemical composition of the pair there
9779-401: The earliest example showing similar features. For example, the sub-luminous SN 2008ha is often referred to as SN 2002cx -like or class Ia-2002cx. A small proportion of type Ic supernovae show highly broadened and blended emission lines which are taken to indicate very high expansion velocities for the ejecta. These have been classified as type Ic-BL or Ic-bl. Calcium-rich supernovae are
9906-469: The ecliptic. A galactic quadrant, or quadrant of the Milky Way, refers to one of four circular sectors in the division of the Milky Way. In astronomical practice, the delineation of the galactic quadrants is based upon the galactic coordinate system , which places the Sun as the origin of the mapping system . Quadrants are described using ordinals – for example, "1st galactic quadrant", "second galactic quadrant", or "third quadrant of
10033-411: The event sufficiently for it to go unnoticed. The situation for Cassiopeia A is less clear; infrared light echoes have been detected showing that it was not in a region of especially high extinction. SN's identification With the development of the astronomical telescope , observation and discovery of fainter and more distant supernovae became possible. The first such observation was of SN 1885A in
10160-558: The extra mass is supported by differential rotation . There is no formal sub-classification for non-standard type Ia supernovae. It has been proposed that a group of sub-luminous supernovae that occur when helium accretes onto a white dwarf should be classified as type Iax . This type of supernova may not always completely destroy the white dwarf progenitor and could leave behind a zombie star . One specific type of supernova originates from exploding white dwarfs, like type Ia, but contains hydrogen lines in their spectra, possibly because
10287-451: The first moments they begin exploding provide information that cannot be directly obtained in any other way." The James Webb Space Telescope (JWST) has significantly advanced our understanding of supernovae by identifying around 80 new instances through its JWST Advanced Deep Extragalactic Survey (JADES) program. This includes the most distant spectroscopically confirmed supernova at a redshift of 3.6, indicating its explosion occurred when
10414-405: The first studies done in astronomy where the telescope time was scheduled to observe objects not yet discovered. The survey discovered 50 supernovae between 1990 and 1993, of which 32 were Type Ia supernovae . The survey provided a uniform photometric and spectroscopic dataset of all classes of supernovae, which led to the discovery of a method of using Type Ia supernovae as standard candles ,
10541-439: The gradual change in properties or different frequencies of abnormal luminosity supernovae at high redshift, and for small variations in brightness identified by light curve shape or spectrum. There are several means by which a supernova of this type can form, but they share a common underlying mechanism. If a carbon - oxygen white dwarf accreted enough matter to reach the Chandrasekhar limit of about 1.44 solar masses (for
10668-409: The hydrogen found in the atomic form and the remaining one-third as molecular hydrogen . The mass of the Milky Way's interstellar gas is equal to between 10% and 15% of the total mass of its stars. Interstellar dust accounts for an additional 1% of the total mass of the gas. In March 2019, astronomers reported that the virial mass of the Milky Way Galaxy is 1.54 trillion solar masses within
10795-551: The increasing number of discoveries has regularly led to the additional use of three-letter designations. After zz comes aaa, then aab, aac, and so on. For example, the last supernova retained in the Asiago Supernova Catalogue ; when it was terminated on 31 December 2017 bears the designation SN 2017jzp. Astronomers classify supernovae according to their light curves and the absorption lines of different chemical elements that appear in their spectra . If
10922-527: The infant Heracles , on Hera 's breast while she is asleep so the baby will drink her divine milk and become immortal. Hera wakes up while breastfeeding and then realizes she is nursing an unknown baby: she pushes the baby away, some of her milk spills, and it produces the band of light known as the Milky Way. In another Greek story, the abandoned Heracles is given by Athena to Hera for feeding, but Heracles' forcefulness causes Hera to rip him from her breast in pain. Llys Dôn (literally "The Court of Dôn ")
11049-436: The isophotal diameter is not well understood. It is estimated that the significant bulk of stars in the galaxy lies within the 26 kiloparsecs (80,000 light-years) diameter, and that the number of stars beyond the outermost disc dramatically reduces to a very low number, with respect to an extrapolation of the exponential disk with the scale length of the inner disc. There are several methods being used in astronomy in defining
11176-431: The life of the decline are classified on the basis of their light curves. The most common type shows a distinctive "plateau" in the light curve shortly after peak brightness where the visual luminosity stays relatively constant for several months before the decline resumes. These are called type II-P referring to the plateau. Less common are type II-L supernovae that lack a distinct plateau. The "L" signifies "linear" although
11303-437: The light curve is extremely consistent across normal type Ia supernovae, having a maximum absolute magnitude of about −19.3. This is because typical type Ia supernovae arise from a consistent type of progenitor star by gradual mass acquisition, and explode when they acquire a consistent typical mass, giving rise to very similar supernova conditions and behaviour. This allows them to be used as a secondary standard candle to measure
11430-487: The light curve is not actually a straight line. Supernovae that do not fit into the normal classifications are designated peculiar, or "pec". Zwicky defined additional supernovae types based on a very few examples that did not cleanly fit the parameters for type I or type II supernovae. SN 1961i in NGC 4303 was the prototype and only member of the type III supernova class, noted for its broad light curve maximum and broad hydrogen Balmer lines that were slow to develop in
11557-411: The low-distance end of the Hubble curve , which is a plot of distance versus redshift for visible galaxies. As survey programmes rapidly increase the number of detected supernovae, collated collections of observations (light decay curves, astrometry, pre-supernova observations, spectroscopy) have been assembled. The Pantheon data set, assembled in 2018, detailed 1048 supernovae. In 2021, this data set
11684-492: The main sequence to form a red giant. Matter from the giant is accreted by the white dwarf, causing the latter to increase in mass. The exact details of initiation and of the heavy elements produced in the catastrophic event remain unclear. Type Ia supernovae produce a characteristic light curve—the graph of luminosity as a function of time—after the event. This luminosity is generated by the radioactive decay of nickel -56 through cobalt -56 to iron -56. The peak luminosity of
11811-526: The measurable volume of space by a factor of 100 in radius and a factor of 1,000 in precision. A study in 2020 concluded that Gaia detected a wobbling motion of the galaxy, which might be caused by " torques from a misalignment of the disc's rotation axis with respect to the principal axis of a non-spherical halo, or from accreted matter in the halo acquired during late infall, or from nearby, interacting satellite galaxies and their consequent tides". In April 2024, initial studies (and related maps) involving
11938-518: The milky appearance of the Milky Way Galaxy is due to the refraction of the Earth's atmosphere. The Neoplatonist philosopher Olympiodorus the Younger ( c. 495 –570 AD) criticized this view, arguing that if the Milky Way were sublunary , it should appear different at different times and places on Earth, and that it should have parallax , which it does not. In his view, the Milky Way
12065-463: The most distant supernovae observed in 2003 appeared dimmer than expected. This supports the view that the expansion of the universe is accelerating . Techniques were developed for reconstructing supernovae events that have no written records of being observed. The date of the Cassiopeia A supernova event was determined from light echoes off nebulae , while the age of supernova remnant RX J0852.0-4622
12192-503: The naked eye, had a notable influence on the development of astronomy in Europe because they were used to argue against the Aristotelian idea that the universe beyond the Moon and planets was static and unchanging. Johannes Kepler began observing SN 1604 at its peak on 17 October 1604, and continued to make estimates of its brightness until it faded from naked eye view a year later. It was
12319-573: The nature of the Milky Way, spiral nebulae, and the dimensions of the Universe. To support his claim that the Great Andromeda Nebula is an external galaxy, Curtis noted the appearance of dark lanes resembling the dust clouds in the Milky Way, as well as the significant Doppler shift . The controversy was conclusively settled by Edwin Hubble in the early 1920s using the Mount Wilson observatory 2.5 m (100 in) Hooker telescope . With
12446-571: The newly ejected material. Milky Way The Milky Way is the galaxy that includes the Solar System , with the name describing the galaxy's appearance from Earth : a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye . The Milky Way is a barred spiral galaxy with a D 25 isophotal diameter estimated at 26.8 ± 1.1 kiloparsecs (87,400 ± 3,600 light-years ), but only about 1,000 light-years thick at
12573-405: The number of very-low-mass stars, which are difficult to detect, especially at distances of more than 300 ly (90 pc) from the Sun. As a comparison, the neighboring Andromeda Galaxy contains an estimated one trillion (10 ) stars. The Milky Way may contain ten billion white dwarfs , a billion neutron stars , and a hundred million stellar black holes . Filling the space between the stars
12700-433: The old population of the galactic halo. A 2020 study predicted the edge of the Milky Way's dark matter halo being around 292 ± 61 kpc (952,000 ± 199,000 ly ), which translates to a diameter of 584 ± 122 kpc (1.905 ± 0.3979 Mly ). The Milky Way's stellar disk is also estimated to be approximately up to 1.35 kpc (4,000 ly) thick. The Milky Way
12827-499: The ones in the Milky Way, and modelling the relationship to their surface brightnesses. This gave an isophotal diameter for the Milky Way at 26.8 ± 1.1 kiloparsecs (87,400 ± 3,600 light-years), by assuming that the galactic disc is well represented by an exponential disc and adopting a central surface brightness of the galaxy (μ 0 ) of 22.1 ± 0.3 B -mag/arcsec and a disk scale length ( h ) of 5.0 ± 0.5 kpc (16,300 ± 1,600 ly). This
12954-522: The photographic record, he found 11 more novae . Curtis noticed that these novae were, on average, 10 magnitudes fainter than those that occurred within the Milky Way. As a result, he was able to come up with a distance estimate of 150,000 parsecs. He became a proponent of the "island universes" hypothesis, which held that the spiral nebulae were independent galaxies. In 1920 the Great Debate took place between Harlow Shapley and Heber Curtis, concerning
13081-635: The precise measurements of the Hubble Constant H 0 and the deceleration parameter q 0 , the latter indicating the presence of a dark energy or cosmological constant dominating the mass/energy of the Universe . The Calán/Tololo data of nearby Type Ia supernovae were used as the anchors for the Hubble flow measurements both by the High-Z Supernova Search Team and the Supernova Cosmology Project . Their pioneering work
13208-400: The relative physical scale of the Milky Way, if the Solar System out to Neptune were the size of a US quarter (24.3 mm (0.955 in)), the Milky Way would be approximately at least the greatest north–south line of the contiguous United States . An even older study from 1978 gave a lower diameter for Milky Way about 23 kpc (75,000 ly). A 2015 paper discovered that there
13335-574: The root of "galaxy", the name for our, and later all such, collections of stars. The Milky Way, or "milk circle", was just one of 11 "circles" the Greeks identified in the sky, others being the zodiac , the meridian , the horizon , the equator , the tropics of Cancer and Capricorn , the Arctic Circle and the Antarctic Circle , and two colure circles passing through both poles. The Milky Way
13462-485: The second supernova to be observed in a generation, after Tycho Brahe observed SN 1572 in Cassiopeia . There is some evidence that the youngest known supernova in our galaxy, G1.9+0.3 , occurred in the late 19th century, considerably more recently than Cassiopeia A from around 1680. Neither was noted at the time. In the case of G1.9+0.3, high extinction from dust along the plane of the galactic disk could have dimmed
13589-512: The size of a galaxy, and each of them can yield different results with respect to one another. The most commonly employed method is the D 25 standard – the isophote where the photometric brightness of a galaxy in the B-band (445 nm wavelength of light, in the blue part of the visible spectrum ) reaches 25 mag/arcsec . An estimate from 1997 by Goodwin and others compared the distribution of Cepheid variable stars in 17 other spiral galaxies to
13716-538: The south galactic pole is near α Sculptoris . Because of this high inclination, depending on the time of night and year, the Milky Way arch may appear relatively low or relatively high in the sky. For observers from latitudes approximately 65° north to 65° south, the Milky Way passes directly overhead twice a day. In Meteorologica , Aristotle (384–322 BC) states that the Greek philosophers Anaxagoras ( c. 500 –428 BC) and Democritus (460–370 BC) proposed that
13843-452: The spectrum. SN 1961f in NGC 3003 was the prototype and only member of the type IV class, with a light curve similar to a type II-P supernova, with hydrogen absorption lines but weak hydrogen emission lines . The type V class was coined for SN 1961V in NGC 1058 , an unusual faint supernova or supernova impostor with a slow rise to brightness, a maximum lasting many months, and an unusual emission spectrum. The similarity of SN 1961V to
13970-527: The spiral arms (more at the bulge). Recent simulations suggest that a dark matter area, also containing some visible stars, may extend up to a diameter of almost 2 million light-years (613 kpc). The Milky Way has several satellite galaxies and is part of the Local Group of galaxies, which form part of the Virgo Supercluster , which is itself a component of the Laniakea Supercluster . It
14097-514: The star prior to the supernova event, given in multiples of the Sun's mass, although the mass at the time of the supernova may be much lower. Type IIn supernovae are not listed in the table. They can be produced by various types of core collapse in different progenitor stars, possibly even by type Ia white dwarf ignitions, although it seems that most will be from iron core collapse in luminous supergiants or hypergiants (including LBVs). The narrow spectral lines for which they are named occur because
14224-512: The stellar disk larger by increasing to this size. A more recent 2018 paper later somewhat ruled out this hypothesis, and supported a conclusion that the Monoceros Ring, A13 and TriAnd Ring were stellar overdensities rather kicked out from the main stellar disk, with the velocity dispersion of the RR Lyrae stars found to be higher and consistent with halo membership. Another 2018 study revealed
14351-462: The supernova is expanding into a small dense cloud of circumstellar material. It appears that a significant proportion of supposed type IIn supernovae are supernova impostors, massive eruptions of LBV-like stars similar to the Great Eruption of Eta Carinae . In these events, material previously ejected from the star creates the narrow absorption lines and causes a shock wave through interaction with
14478-422: The surrounding interstellar medium , sweeping up an expanding shell of gas and dust observed as a supernova remnant. Supernovae are a major source of elements in the interstellar medium from oxygen to rubidium . The expanding shock waves of supernovae can trigger the formation of new stars . Supernovae are a major source of cosmic rays . They might also produce gravitational waves . The word supernova has
14605-409: The table above, are taxonomic : the type number is based on the light observed from the supernova, not necessarily its cause. For example, type Ia supernovae are produced by runaway fusion ignited on degenerate white dwarf progenitors, while the spectrally similar type Ib/c are produced from massive stripped progenitor stars by core collapse. A white dwarf star may accumulate sufficient material from
14732-820: The universe was merely 1.8 billion years old. These findings offer crucial insights into the early universe's stellar evolution and the frequency of supernovae during its formative years. Because supernovae are relatively rare events within a galaxy, occurring about three times a century in the Milky Way, obtaining a good sample of supernovae to study requires regular monitoring of many galaxies. Today, amateur and professional astronomers are finding several hundred every year, some when near maximum brightness, others on old astronomical photographs or plates. Supernovae in other galaxies cannot be predicted with any meaningful accuracy. Normally, when they are discovered, they are already in progress. To use supernovae as standard candles for measuring distance, observation of their peak luminosity
14859-456: The universe, the Milky Way galaxy has a below average amount of neutrino luminosity making our galaxy a " neutrino desert ". The Milky Way consists of a bar-shaped core region surrounded by a warped disk of gas, dust and stars. The mass distribution within the Milky Way closely resembles the type Sbc in the Hubble classification , which represents spiral galaxies with relatively loosely wound arms. Astronomers first began to conjecture that
14986-399: The very probable presence of disk stars at 26–31.5 kpc (84,800–103,000 ly) from the Galactic Center or perhaps even farther, significantly beyond approximately 13–20 kpc (40,000–70,000 ly), in which it was once believed to be the abrupt drop-off of the stellar density of the disk, meaning that few or no stars were expected to be above this limit, save for stars that belong to
15113-478: The visible sky. He produced a diagram of the shape of the Milky Way with the Solar System close to the center. In 1845, Lord Rosse constructed a new telescope and was able to distinguish between elliptical and spiral-shaped nebulae. He also managed to make out individual point sources in some of these nebulae, lending credence to Kant's earlier conjecture. In 1904, studying the proper motions of stars, Jacobus Kapteyn reported that these were not random, as it
15240-480: The white dwarf is surrounded by an envelope of hydrogen-rich circumstellar material . These supernovae have been dubbed type Ia/IIn , type Ian , type IIa and type IIan . The quadruple star HD 74438 , belonging to the open cluster IC 2391 the Vela constellation , has been predicted to become a non-standard type Ia supernova. Very massive stars can undergo core collapse when nuclear fusion becomes unable to sustain
15367-460: The year they occurred: SN 185, SN 1006, SN 1054, SN 1572 (called Tycho's Nova ) and SN 1604 ( Kepler's Star ). Since 1885 the additional letter notation has been used, even if there was only one supernova discovered that year (for example, SN 1885A, SN 1907A, etc.); this last happened with SN 1947A. SN , for SuperNova, is a standard prefix. Until 1987, two-letter designations were rarely needed; since 1988, they have been needed every year. Since 2016,
15494-505: Was believed in that time; stars could be divided into two streams, moving in nearly opposite directions. It was later realized that Kapteyn's data had been the first evidence of the rotation of our galaxy, which ultimately led to the finding of galactic rotation by Bertil Lindblad and Jan Oort . In 1917, Heber Doust Curtis had observed the nova S Andromedae within the Great Andromeda Nebula ( Messier object 31). Searching
15621-459: Was cited in the award of the 2011 Nobel Prize in Physics Supernova A supernova ( pl. : supernovae or supernovas ) is a powerful and luminous explosion of a star . A supernova occurs during the last evolutionary stages of a massive star , or when a white dwarf is triggered into runaway nuclear fusion . The original object, called the progenitor , either collapses to
15748-548: Was documented by Chinese astronomers in 185 AD. The brightest recorded supernova was SN 1006 , which was observed in AD 1006 in the constellation of Lupus . This event was described by observers in China, Japan, Iraq, Egypt and Europe. The widely observed supernova SN 1054 produced the Crab Nebula . Supernovae SN 1572 and SN 1604 , the latest Milky Way supernovae to be observed with
15875-460: Was estimated from temperature measurements and the gamma ray emissions from the radioactive decay of titanium-44 . The most luminous supernova ever recorded is ASASSN-15lh , at a distance of 3.82 gigalight-years . It was first detected in June 2015 and peaked at 570 billion L ☉ , which is twice the bolometric luminosity of any other known supernova. The nature of this supernova
16002-482: Was expanded to 1701 light curves for 1550 supernovae taken from 18 different surveys, a 50% increase in under 3 years. Supernova discoveries are reported to the International Astronomical Union 's Central Bureau for Astronomical Telegrams , which sends out a circular with the name it assigns to that supernova. The name is formed from the prefix SN , followed by the year of discovery, suffixed with
16129-503: Was used, as "super-Novae", in a journal paper published by Knut Lundmark in 1933, and in a 1934 paper by Baade and Zwicky. By 1938, the hyphen was no longer used and the modern name was in use. American astronomers Rudolph Minkowski and Fritz Zwicky developed the modern supernova classification scheme beginning in 1941. During the 1960s, astronomers found that the maximum intensities of supernovae could be used as standard candles , hence indicators of astronomical distances. Some of
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