Polish astronomerJohannes Hevelius formed the constellation in 1687 from 19 faint stars between the constellationsUrsa Major andAuriga that earlier had been part of the obsolete constellationJordanus Fluvius. Naming it Lynx because of its faintness, he challenged future stargazers to see it, declaring that only the lynx-eyed (those with good sight) would have been able to recognize it. Hevelius also used the name Tigris (Tiger) in his catalog but kept the former name only in his atlas. English astronomerJohn Flamsteed adopted the constellation in his catalog, published in 1712, and his subsequent atlas.[1] According to 19th-century amateur astronomerRichard Hinckley Allen, the chief stars in Lynx "might well have been utilized by the modern constructor, whoever he was, of our Ursa Major to complete the quartette of feet."[2]
The constellation of Lynx as it can be seen by the naked eye
Lynx is bordered byCamelopardalis to the north, Auriga to the west,Gemini to the southwest,Cancer to the south,Leo to the east andUrsa Major to the northeast. Covering 545.4 square degrees and 1.322% of the night sky, it ranks28th of the 88 constellations in size,[3] surpassing better known constellations such as Gemini.[4] The three-letter abbreviation for the constellation, as adopted by theInternational Astronomical Union in 1922, is "Lyn".[5] The official constellation boundaries, as set by Belgian astronomerEugène Delporte in 1930,[a] are defined by a polygon of 20 segments (illustrated in infobox). In theequatorial coordinate system, theright ascension coordinates of these borders lie between06h 16m 13.76s and09h 42m 50.22s, and thedeclination coordinates are between +32.97° and +61.96°.[7] On dark nights, the brighter stars can be seen as a crooked line extending roughly between Camelopardalis and Leo,[8] and north of the bright starCastor.[2] Lynx is most readily observed from the late winter to late summer to northern hemisphere observers, with midnightculmination occurring on 20 January.[8] The whole constellation is visible to observers north of latitude28°S.[b]
English astronomerFrancis Baily gave a single star aBayer designation—Alpha Lyncis—while Flamsteed numbered 44 stars, though several lie across the boundary in Ursa Major.[9] Overall, there are 97 stars within the constellation's borders brighter than or equal toapparent magnitude 6.5.[c][3]
The brightest star in this constellation is Alpha Lyncis, with anapparent (visual) magnitude of 3.14.[11] It is anorangegiant ofspectral type K7III located 203 ± 2light-years distant from Earth.[12] Around twice as massive as theSun,[13] it has exhausted thehydrogen at itscore and hasevolved away from themain sequence. The star has swollen to about 55 times theSun's radius and is emitting roughly 673 times theluminosity of the Sun. Thestellar atmosphere has cooled, giving it a surface temperature of 3,880 K.[14] The only star with aproper name isAlsciaukat (from theArabic for thorn), also known as 31 Lyncis, located 380 ± 10 light-years from Earth.[12] This star is also an evolved giant with around twice the Sun's mass that has swollen and cooled since exhausting its core hydrogen. It is anywhere from 59 to 75 times as wide as the Sun, and 740 times as luminous.[13] Alsciaukat is also a variable star, ranging in brightness by 0.05 magnitude over 25 to 30 days from its baseline magnitude of 4.25.[15]
Lynx is rich indouble stars.[2] The second brightest star in the constellation is38 Lyncis at magnitude 3.8. When viewed through a moderate telescope, the two components—a brighter blue-white star of magnitude 3.9 and a fainter star of magnitude 6.1 that has been described as lilac as well as blue-white—can be seen.[16]15 Lyncis is another star that is found to be a double system when viewed through a telescope, separating into two yellowish stars of magnitudes 4.7 and 5.8 that are 0.9 arcseconds apart.[16] The components are a yellow giant of spectral type G8III that is around 4.01 times as massive as the Sun, and ayellow-white main sequence star of spectral type F8V that is around 3.73 times as massive as the Sun. Orbiting each other every 262 years,[17] the stars are 178 ± 2 light years distant from Earth.[12]12 Lyncis has a combined apparent magnitude of 4.87. When seen through a telescope, it can be separated into three stars: two components with magnitudes 5.4 and 6.0 that lie at anangular separation by 1.8″ (as of 1992[update]) and a yellow-hued star of magnitude 7.2 at a separation of 8.6″ (as of 1990).[16][18] The two brighter stars are estimated to orbit each other with a period that is poorly known but estimated to be roughly 700 to 900 years.[17] The 12 Lyncis system is 210 ± 10 light years distant from Earth.[12]
10 Ursae Majoris is the third-brightest star in Lynx. Originally in the neighbouring constellation Ursa Major, it became part of Lynx with the official establishment of the constellation's borders.[19] Appearing to be of magnitude 3.97, a telescope reveals a yellow-white main sequence star of spectral type F4V of magnitude 4.11 and a star very similar to the Sun of spectral type G5V and magnitude 6.18. The two are 10.6 astronomical units (au)[d] apart and orbit each other every 21.78 years.[20] The system is 52.4 ± 0.6 light-years distant from Earth.[12] Likewise16 Lyncis was originally known as Psi10 Aurigae and conversely,37,39,41 and44 Lyncis became part of Ursa Major.[9]
Y Lyncis is a popular target among amateur astronomers, as it is asemiregular variable ranging in brightness from magnitude 6.2 to 8.9.[21] These shifts in brightness are complex, with a shorter period of 110 days due to the star's pulsations, and a longer period of 1400 days possibly due to the star's rotation or regular cycles in itsconvection.[22] Ared supergiant, it has an estimated diameter around 580 times that of the Sun, is around 1.5 to 2 times as massive, and has aluminosity around 25,000 times that of the Sun.[21]1 Lyncis andUX Lyncis arered giants that are also semiregular variables with complex fluctuations in brightness.[22]
Six star systems have been found to containexoplanets, of which two were discovered by theDoppler method and four by the transit method.6 Lyncis, an orange subgiant that spent much of its life as an A-type or F-type main sequence star, is orbited by a planet with aminimum mass of 2.4Jupiter masses and anorbital period of 899 days.[23]HD 75898 is a 3.8 ± 0.8 billion-year-old yellow star of spectral type G0V that has just begun expanding and cooling off the main sequence. It has a planet at least 2.51 times as massive as Jupiter orbiting with a period of around 418 days. The centre of mass of the system is accelerating, indicating there is a third, more distant, component at least the size of Jupiter.[24] Three star systems were found to have planets that were observed by theXO Telescope in Hawaii as theypassed in front of them.XO-2 is abinary star system, both the stars of which are slightly less massive and cooler than the Sun and have planetary companions: XO-2S has aSaturn-mass planet at 0.13 au distance with a period of around 18 days, and one a little more massive thanJupiter at a distance of 0.48 au and with a period of around 120 days,[25] and XO-2N has ahot Jupiter with around half Jupiter's mass that has an orbit of only 2.6 days.[26]XO-4 is an F-type main sequence star that is a little hotter and more massive than the Sun that has a hot Jupiter orbiting with a period of around 4.1 days.[27]XO-5 is a Sun-like star with a hot Jupiter about as massive as Jupiter that takes around 4.2 days to complete an orbit.[28]WASP-13, a Sun-like star that has begun to swell and cool off the main sequence, had a transiting planet discovered by theSuperWASP program in 2009. The planet is around half as massive as Jupiter and takes 4.35 days to complete a revolution.[29]
NGC 2419 (Credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona)
Lynx's most notabledeep sky object isNGC 2419, also called the "Intergalactic Wanderer" as it was assumed to lie outside theMilky Way. At a distance of between 275,000 and 300,000 light-years from Earth,[30] it is one of the most distant knownglobular clusters within our galaxy. NGC 2419 is likely in a highly elliptical orbit around the Milky Way.[31] It has a magnitude of +9.06 and is aShapley class VII cluster.[32] Originally thought to be a star, NGC 2419 was discovered to be a globular cluster by American astronomerCarl Lampland.[33]
NGC 2537, known as the Bear's Paw Galaxy, lies about 3 degrees north-northwest of 31 Lyncis.[34] It is ablue compact dwarf galaxy that is somewhere between 17 and 30 million light-years away from Earth. Close by isIC 2233, a very flat and thin spiral galaxy that is between 26 and 40 million light-years away from Earth. A comparatively quiet galaxy with a low rate of star formation (less than one solar mass every twenty years), it was long suspected to be interacting with the Bear's Paw galaxy. This is now considered highly unlikely as observations with theVery Large Array showed the two galaxies lie at different distances.[35]
TheNGC 2841 group is agroup of galaxies that lie both in Lynx and neighbouring Ursa Major. It includes the loose tripletNGC 2541,NGC 2500, andNGC 2552 within Lynx. Using cepheids of NGC 2541 asstandard candles, the distance to that galaxy (and the group) has been estimated at around 40 million light–years.[36]NGC 2841 itself lies in Ursa Major.[37]
NGC 2770 is atype SAScspiral galaxy located about 88 million light–years away that has hostedType Ib supernovae:SN 1999eh,SN 2007uy, andSN 2008D.[38] The last of these is famous for being the first supernova detected by theX-rays released very early on in its formation, rather than by the opticallight emitted during later stages, which allowed the first moments of the outburst to be observed. It is possible that NGC 2770's interactions with a suspected companion galaxy may have created the massive stars causing this activity.[39]UGC 4904 is a galaxy located about 77 million light-years from Earth. On 20 October 2004, asupernova impostor was observed by Japanese amateur astronomerKōichi Itagaki within the galaxy. Observations of its spectrum suggest that it shed massive amounts of material in a two-year period, transforming from aLBV star to aWolf–Rayet star,[40][41] before it was observed erupting ashypernovaSN 2006jc on October 11, 2006.[42]
Galaxy UGC 3855 captured by the NASA/ESA Hubble Space Telescope.
APM 08279+5255 is a very distant, broad absorption linequasar discovered in 1998 and initially considered the most luminous object yet found. It is magnified and split into multiple images by thegravitational lensing effect of a foreground galaxy through which its light passes.[43] It appears to be a giantelliptical galaxy with asupermassive black hole around 23 billion times as massive as the Sun and an associatedaccretion disk that has a diameter of 3600 light years. The galaxy possesses large regions of hot dust and molecular gas, as well as regions withstarburst activity. It has a cosmologicalredshift of 3.911.[44][e] While observing the quasar in 2008, astronomers using ESA'sXMM Newton and theLarge Binocular Telescope (LBT) in Arizona discovered the huge galaxy cluster2XMM J083026+524133.[45][46]
TheLynx Supercluster is a remotesupercluster with a redshift of 1.26–1.27.[47] It was the most distant supercluster known at the time of its discovery in 1999.[48] It is made up of two main clusters of galaxies—RX J0849+4452 or Lynx E and RX J0848+4453 or Lynx W—and several smaller clumps.[47] Further still lies theLynx Arc, located around 12 billion light years away (a redshift of 3.357). It is a distant region containing a million extremely hot, young blue stars with surface temperatures of 80,000–100,000 K that are twice as hot as similar stars in the Milky Way galaxy. Only visible through gravitational lensing produced by a closer cluster of galaxies, the Arc is a feature of the early days of the universe, when "furious firestorms of star birth" were more common.[49]
TheSeptember Lyncids are a minormeteor shower that appears around 6 September. They were historically more prominent, described as such byChinese observers in 1037 and 1063, and Korean astronomers in 1560.[50] TheAlpha Lyncids were discovered in 1971 by Malcolm Currie,[51] and appear between 10 December and 3 January.[52]
^Delporte had proposed standardising the constellation boundaries to the International Astronomical Union, who had agreed and gave him the lead role[6]
^While parts of the constellation technically rise above the horizon to observers between 28°S and57°S, stars within a few degrees of the horizon are to all intents and purposes unobservable.[3]
^Objects of magnitude 6.5 are among the faintest visible to the unaided eye in suburban-rural transition night skies.[10]
^The distance between the Earth and the Sun is one astronomical unit
^Far distant objects are measured inredshift rather than light-years. See alsoHubble's law
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