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Boötes

This article is about the Northern constellation. For the astronomical observatory, seeBOOTES.For cosmic void, seeBoötes void.

Boötes(/boʊˈoʊtiːz/boh-OH-teez) is aconstellationin thenorthern sky,located between 0° and +60°declination,and 13 and 16 hours ofright ascensionon thecelestial sphere.The name comes fromLatin:Boōtēs,which comes from‹See Tfd›Greek:Βοώτης,translit.Boṓtēs'herdsman' or 'plowman' (literally, 'ox-driver'; fromβοῦςboûs'cow').

Boötes
Constellation
Boötes
List of stars in Boötes
AbbreviationBoo
GenitiveBoötis
Pronunciation/boʊˈoʊtiːz/,genitive/boʊˈoʊtɪs/[1]
SymbolismThe Herdsman
Right ascension13h36.1mto15h49.3m[2]
Declination+7.36° to +55.1°[2]
Area907 sq. deg. (13th)
Main stars7, 15
Bayer/Flamsteed
stars		59
Stars withplanets10
Stars brighter than 3.00m3
Stars within 10.00 pc (32.62 ly)3
Brightest starArcturus(α Boo) (−0.04m)
Messier objects0
Meteor showers
Bordering
constellations
Visible at latitudes between +90° and −50°.
Best visible at 21:00 (9 p.m.) during the month ofJune.
Other designations:Arctophylax

One of the 48 constellations described by the 2nd-century astronomerPtolemy,Boötes is now one of the 88modern constellations.It contains thefourth-brightest starin the night sky, theorange giantArcturus.Epsilon Boötis, or Izar, is a colourfulmultiple starpopular withamateur astronomers.Boötes is home to many other brightstars,including eight above the fourth magnitude and an additional 21 above the fifth magnitude, making a total of 29 stars easily visible to thenaked eye.

History and mythology

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Inancient Babylon,the stars of Boötes were known as SHU.PA. They were apparently depicted as the godEnlil,who was the leader of theBabylonian pantheonand special patron of farmers.[3]Boötes may have been represented by the animal foreleg constellation in ancient Egypt, resembling that of an ox sufficiently to have been originally proposed as the "foreleg of ox"by Berio.[4]

The constellation of Boötes overlaid on the ancient Egyptian foreleg constellation

Homermentions Boötes in theOdysseyas a celestial reference fornavigation,[5]describing it as "late-setting" or "slow to set".[6]Exactly whom Boötes is supposed to represent inGreek mythologyis not clear. According to one version, he was a son ofDemeter,[7]Philomenus,twin brother ofPlutus,a plowman who drove the oxen in the constellationUrsa Major.[8]This agrees with the constellation's name.[9]The ancient Greeks saw theasterismnow called the "Big Dipper"or" Plough "as a cart with oxen.[1][10]Some myths say that Boötes invented theplowand was memorialized for his ingenuity as a constellation.[11]

Another myth associated with Boötes byHyginusis that ofIcarius,who wasschooledas agrape farmerandwinemakerbyDionysus.Icarius made wine so strong that those who drank it appearedpoisoned,which causedshepherdsto avenge their supposedly poisoned friends by killing Icarius.Maera,Icarius' dog, brought his daughterErigoneto her father's body, whereupon both she and the dog committedsuicide.Zeus then chose to honor all three by placing them in the sky as constellations: Icarius as Boötes, Erigone asVirgo,and Maera asCanis MajororCanis Minor.[10]

Following another reading, the constellation is identified withArcasand also referred to as Arcas and Arcturus, son ofZeusandCallisto.Arcas was brought up by his maternal grandfatherLycaon,to whom one day Zeus went and had a meal. To verify that the guest was really the king of the gods, Lycaon killed his grandson and prepared a meal made from his flesh. Zeus noticed and became very angry, transforming Lycaon into awolfandgiving life backto his son. In the meantime Callisto had been transformed into a she-bearby Zeus's wifeHera,who was angry at Zeus'sinfidelity.[8][10]This is corroborated by the Greek name for Boötes,Arctophylax,which means "Bear Watcher".[10]

Callisto, in the form of a bear was almost killed by her son, who was out hunting. Zeus rescued her, taking her into the sky where she became Ursa Major, "the Great Bear". Arcturus, the name of the constellation's brightest star, comes from the Greek word meaning "guardian of the bear". Sometimes Arcturus is depicted as leading thehunting dogsof nearbyCanes Venaticiand driving the bears of Ursa Major andUrsa Minor.[12]

Boötes as depicted inUrania's Mirror,a set of constellation cards published in Londonc. 1825.In his left hand he holds his hunting dogs, Canes Venatici. Below them is the constellation Coma Berenices. Above the head of Boötes isQuadrans Muralis,now obsolete, but which lives on as the name of the early JanuaryQuadrantidmeteor shower.Mons Mænaluscan be seen at his feet.

Severalformer constellationswere formed from stars now included in Boötes.Quadrans Muralis,the Quadrant, was a constellation created nearBeta Boötisfrom faint stars.[13]It was designated in 1795 byJérôme Lalande,an astronomer who used aquadrantto perform detailedastronometric measurements.Lalande worked withNicole-Reine Lepauteand others to predict the 1758 return ofHalley's Comet.Quadrans Muralis was formed from the stars of eastern Boötes, westernHerculesandDraco.[14]It was originally calledLe MuralbyJean Fortinin his 1795Atlas Céleste;it was not given the nameQuadrans MuralisuntilJohann Bode's 1801Uranographia.The constellation was quite faint, with its brightest stars reaching the 5th magnitude.[15]Mons Maenalus,representing theMaenalusmountains, was created byJohannes Heveliusin 1687 at the foot of the constellation's figure. The mountain was named for the son of Lycaon,Maenalus.The mountain, one ofDiana'shuntinggrounds, was also holy toPan.[16]

Non-Western astronomy

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The stars of Boötes were incorporated into many differentChinese constellations.Arcturus was part of the most prominent of these, variously designated as the celestial king's throne (Tian Wang) or theBlue Dragon's horn (Daijiao); the nameDaijiao,meaning "great horn", is more common. Arcturus was given such importance in Chinese celestial mythology because of its status marking the beginning of thelunar calendar,as well as its status as the brightest star in the northern night sky.[citation needed]

Two constellations flankedDaijiao:Youshetito the right andZuoshetito the left; they represented companions that orchestrated the seasons.Zuoshetiwas formed from modernZeta,OmicronandPi Boötis,whileYoushetiwas formed from modernEta,TauandUpsilon Boötis.Dixi,the Emperor's ceremonial banquet mat, was north of Arcturus, consisting of the stars12,11and9 Boötis.Another northern constellation wasQigong,theSeven Dukes,which mostly straddled the Boötes-Hercules border. It included eitherDelta BoötisorBeta Boötisas its terminus.[10]

The other Chinese constellations made up of the stars of Boötes existed in the modern constellation's north; they are all representations of weapons.Tianqiang,thespear,was formed fromIota,KappaandTheta Boötis;Genghe,variously representing alanceorshield,was formed fromEpsilon,RhoandSigma Boötis.

There were also two weapons made up of a singular star.Xuange,thehalberd,was represented byLambda Boötis,andZhaoyao,either theswordor the spear, was represented byGamma Boötis.[10]

Two Chinese constellations have an uncertain placement in Boötes.Kangchi,the lake, was placed south of Arcturus, though its specific location is disputed. It may have been placed entirely in Boötes, on either side of the Boötes-Virgo border, or on either side of the Virgo-Libra border. The constellationZhouding,a bronzetripod-mounted container used for food, was sometimes cited as the stars1,2and6 Boötis.However, it has also been associated with three stars inComa Berenices.[10]

Boötes is also known toNative American cultures.InYup'ik language,Boötes isTaluyaq,literally "fish trap,"and the funnel-shaped part of the fish trap is known asIlulirat.[17]

Characteristics

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Boötes is a constellation bordered by Virgo to the south, Coma Berenices and Canes Venatici to the west, Ursa Major to the northwest, Draco to the northeast, and Hercules,Corona BorealisandSerpens Caputto the east. The three-letter abbreviation for the constellation, as adopted by theInternational Astronomical Unionin 1922, is "Boo".[18]The official constellation boundaries, as set by Belgian astronomerEugène Delportein 1930, are defined by a polygon of 16 segments. In theequatorial coordinate system,theright ascensioncoordinates of these borders lie between13h36.1mand15h49.3m,while thedeclinationcoordinates stretch from +7.36° to +55.1°.[2]Covering 907 square degrees, Boötesculminatesat midnight around 2 May and ranks 13th in area.[19]

Colloquially, its pattern of stars has been likened to a kite or ice cream cone.[19][20]However, depictions of Boötes have varied historically.Aratusdescribed him circling the north pole, herding the two bears. Later ancient Greek depictions, described by Ptolemy, have him holding the reins of his hunting dogs (Canes Venatici) in his left hand, with a spear, club, or staff in his right hand.[10]After Hevelius introduced Mons Maenalus in 1681, Boötes was often depicted standing on thePeloponnesemountain.[16]By 1801, when Johann Bode published hisUranographia,Boötes had acquired a sickle, which was also held in his left hand.[10]

The placement of Arcturus has also been mutable through the centuries. Traditionally, Arcturus lay between his thighs, as Ptolemy depicted him. However,Germanicus Caesardeviated from this tradition by placing Arcturus "where his garment is fastened by a knot".[10]

Features

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The constellation Boötes as it can be seen by the naked eye

Stars

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See also:List of stars in Boötes

In hisUranometria,Johann Bayerused theGreek lettersalphathrough toomegaand then A to k to label what he saw as the most prominent 35 stars in the constellation, with subsequent astronomers splitting Kappa, Mu, Nu and Pi as two stars each. Nu is also the same star as Psi Herculis.[21]John Flamsteednumbered 54 stars for the constellation.[22]

Located 36.7light-yearsfrom Earth, Arcturus, or Alpha Boötis, is the brightest star in Boötes and the fourth-brightest star in the sky at anapparent magnitudeof −0.05;[23]It is also the brightest star north of thecelestial equator,just shading outVegaandCapella.[13][24]Its name comes from the Greek for "bear-keeper". Anorange giantofspectral classK1.5III,[23]Arcturus is an ageing star that has exhausted its core supply of hydrogen and cooled and expanded to a diameter of 27solar diameters,[8]equivalent to approximately 32 million kilometers.[13]Though its mass is approximately onesolar mass(M☉),[8]Arcturus shines with 133 times theluminosity of the Sun(L☉).[25]

Bayer located Arcturus above the Herdman's left knee in hisUranometria.NearbyEta Boötis,or Muphrid, is the uppermost star denoting the left leg.[26]It is a 2.68-magnitude star 37 light-years distant with a spectral class of G0IV,[27]indicating it has just exhausted its core hydrogen and is beginning to expand and cool. It is 9 times as luminous as the Sun and has 2.7 times its diameter. Analysis of itsspectrumreveals that it is aspectroscopic binary.[28]Muphrid and Arcturus lie only 3.3 light-years away from each other. Viewed from Arcturus, Muphrid would have a visual magnitude of −2½, while Arcturus would be around visual magnitude −4½ when seen from Muphrid.[29]

Marking the herdsman's head is Beta Boötis,[26]or Nekkar, ayellow giantof magnitude 3.5 and spectral type G8IIIa.[30]Like Arcturus, it has expanded and cooled off themain sequence—likely to have lived most of its stellar life as a blue-whiteB-type main sequence star.[31]Its common name comes from the Arabic phrase for "ox-driver". It is 219 light-years away[8]and has a luminosity of 58L☉.[13]

Located 86 light-years distant,Gamma Boötis,or Seginus, is a white giant star of spectral class A7III,[32]with a luminosity 34 times and diameter 3.5 times that of the Sun.[33]It is aDelta Scuti variable,ranging between magnitudes 3.02 and 3.07 every 7 hours.[34]These stars are short period (six hours at most) pulsating stars that have been used asstandard candlesand as subjects to studyasteroseismology.[35]

Delta Boötisis a wide double star with a primary of magnitude 3.5 and a secondary of magnitude 7.8. The primary is a yellow giant that has cooled and expanded to 10.4 times the diameter of the Sun.[36]Of spectral class G8IV, it is around 121 light-years away,[37]while the secondary is a yellow main sequence star of spectral type G0V.[38]The two are thought to take 120,000 years to orbit each other.[36]

Mu Boötis,known asAlkalurops,is a triple star popular with amateur astronomers. It has an overall magnitude of 4.3 and is 121 light-years away. Its name is from the Arabic phrase for "club" or "staff". The primary appears to be of magnitude 4.3 and is blue-white. The secondary appears to be of magnitude 6.5, but is actually a close double star itself with a primary of magnitude 7.0 and a secondary of magnitude 7.6. The secondary and tertiary stars have an orbital period of 260 years.[8]The primary has an absolute magnitude of 2.6 and is of spectral class F0.[13]The secondary and tertiary stars are separated by 2 arcseconds; the primary and secondary are separated by 109.1 arcseconds at an angle of 171 degrees.[39]

Nu Boötisis an optical double star. The primary is an orange giant of magnitude 5.0 and the secondary is a white star of magnitude 5.0. The primary is 870 light-years away and the secondary is 430 light-years.

Epsilon Boötis,also known asIzarorPulcherrima,is a close triple star popular with amateur astronomers and the most prominent binary star in Boötes. The primary is a yellow-[40]or orange-hued magnitude 2.5 giant star, the secondary is a magnitude 4.6 blue-huedmain-sequence star,[8]and the tertiary is a magnitude 12.0 star.[40]The system is 210 light-years away. The name "Izar" comes from the Arabic word for "girdle" or "loincloth", referring to its location in the constellation. The name "Pulcherrima" comes from the Latin phrase for "most beautiful", referring to its contrasting colors in a telescope.[8]The primary and secondary stars are separated by 2.9arcsecondsat an angle of 341 degrees; the primary's spectral class is K0 and it has a luminosity of 200L☉.[13][40]To the naked eye, Izar has a magnitude of 2.37.[13]

NearbyRhoandSigma Boötisdenote the herdsman's waist.[26]Rho is an orange giant of spectral type K3III located around 160 light-years from Earth.[41]It is ever so slightly variable, wavering by 0.003 of a magnitude from its average of 3.57.[42]Sigma, ayellow-white main-sequence starof spectral type F3V, is suspected of varying in brightness from 4.45 to 4.49.[42]It is around 52 light-years distant.[43]

Traditionally known asAulād al Dhiʼbah(أولاد الضباع–aulād al dhiʼb), "the Whelps of the Hyenas",Theta,Iota,KappaandLambda Boötis(or Xuange[44]) are a small group of stars in the far north of the constellation. The magnitude 4.05 Theta Boötis has a spectral type of F7 and an absolute magnitude of 3.8. Iota Boötis is a triple star with a primary of magnitude 4.8 and spectral class of A7,[13]a secondary of magnitude 7.5,[8]and a tertiary of magnitude 12.6.[40]The primary is 97 light-years away.[8]The primary and secondary stars are separated by 38.5 arcseconds, at an angle of 33 degrees.[13]The primary and tertiary stars are separated by 86.7 arcseconds at an angle of 194 degrees. Both the primary and tertiary appear white in a telescope, but the secondary appears yellow-hued.[40]

Kappa Boötis is another wide double star. The primary is 155 light-years away and has a magnitude of 4.5. The secondary is 196 light-years away and has a magnitude of 6.6.[8]The two components are separated by 13.4 arcseconds, at an angle of 236 degrees.[13]The primary, with spectral class A7, appears white and the secondary appears bluish.[40]

An apparent magnitude 4.18type A0p star,[13]Lambda Boötis is the prototype of a class of chemically peculiar stars, only some of which pulsate asDelta Scuti-type stars. The distinction between the Lambda Boötis stars as a class of stars with peculiar spectra, and the Delta Scuti stars whose class describes pulsation in low-overtone pressure modes, is an important one. While many Lambda Boötis stars pulsate and are Delta Scuti stars, not many Delta Scuti stars have Lambda Boötis peculiarities, since the Lambda Boötis stars are a much rarer class whose members can be found both inside and outside the Delta Scuti instability strip. Lambda Boötis stars aredwarf starsthat can be either spectral class A or F.[45]Like BL Boötis-type stars they are metal-poor.[46]Scientists have had difficulty explaining the characteristics of Lambda Boötis stars, partly because only around 60 confirmed members exist, but also due to heterogeneity in the literature. Lambda has an absolute magnitude of 1.8.[13]

There are two dimmerF-type stars,magnitude 4.8312 Boötis,class F8; and magnitude 4.9345 Boötis,class F5.[13]Xi Boötisis a G8 yellow dwarf of magnitude 4.55, and absolute magnitude is 5.5. Two dimmer G-type stars are magnitude 4.8631 Boötis,class G8, and magnitude 4.7644 Boötis,class G0.[13]

Of apparent magnitude 4.06,Upsilon Boötishas a spectral class of K5 and an absolute magnitude of −0.3. Dimmer than Upsilon Boötis is magnitude 4.54Phi Boötis,with a spectral class of K2 and an absolute magnitude of −0.1. Just slightly dimmer than Phi at magnitude 4.60 isO Boötis,which, like Izar, has a spectral class of K0. O Boötis has an absolute magnitude of 0.2. The other four dim stars are magnitude 4.916 Boötis,class K4; magnitude 4.8620 Boötis,class K3; magnitude 4.81Omega Boötis,class K4; and magnitude 4.83A Boötis,class K1.[13]

There is one bright B-class star in Boötes; magnitude 4.93Pi1Boötis,also called Alazal. It has a spectral class of B9 and is 40 parsecs from Earth. There is also one M-type star, magnitude 4.8134 Boötis.It is of class gM0.[13]

Multiple stars

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Besides Pulcherrima and Alkalurops, there are several other binary stars in Boötes:

  • Xi Boötisis a quadruple star popular with amateur astronomers. The primary is a yellow star of magnitude 4.7 and the secondary is an orange star of magnitude 6.8. The system is 22 light-years away and has an orbital period of 150 years.[8]The primary and secondary have a separation of 6.7 arcseconds at an angle of 319 degrees.[13]The tertiary is a magnitude 12.6 star (though it may be observed to be brighter) and the quaternary is a magnitude 13.6 star.[40]
  • Pi Boötisis a close triple star. The primary is a blue-white star of magnitude 4.9, the secondary is a blue-white star of magnitude 5.8,[8]and the tertiary is a star of magnitude 10.4.[40]The primary and secondary components are separated by 5.6 arcseconds at an angle of 108 degrees;[13]the primary and tertiary components are separated by 128 arcseconds at an angle of 128 degrees.[40]
  • Zeta Boötisis a triple star that consists of aphysical binarypair with anopticalcompanion. Lying 205 light-years away from Earth, The physical pair has a period of 123.3 years and consists of a magnitude 4.5 and a magnitude 4.6 star. The two components are separated by 1.0 arcseconds at an angle of 303 degrees. The optical companion is of magnitude 10.9, separated by 99.3 arcseconds at an angle of 259 degrees.44 Boötisis an eclipsing variable star. The primary is of variable magnitude and the secondary is of magnitude 6.2; they have an orbital period of 225 years. The components are separated by 1.0 arcsecond at an angle of 40 degrees.[13]

44 Boötis (i Boötis) is a double variable star 42 light-years away. It has an overall magnitude of 4.8 and appears yellow to the naked eye. The primary is of magnitude 5.3 and the secondary is of magnitude 6.1; their orbital period is 220 years. The secondary is itself an eclipsing variable star with a range of 0.6 magnitudes; its orbital period is 6.4 hours.[8]It is aW Ursae Majoris variablethat ranges in magnitude from a minimum of 7.1 to a maximum of 6.5 every 0.27 days. Both stars are G-type stars. Another eclipsing binary star isZZ Boötis,which has two F2-type components of almost equal mass,[47]and ranges in magnitude from a minimum of 6.79 to a maximum of 7.44 over a period of 5.0 days.[48]

Variable stars

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Two of the brighter Mira-type variable stars in the constellation areRandS Boötis.Both are red giants that range greatly in magnitude—from 6.2 to 13.1 over 223.4 days,[49][13]and 7.8 to 13.8 over a period of 270.7 days, respectively.[13]Also red giants,VandW Boötisaresemi-regular variable starsthat range in magnitude from 7.0 to 12.0 over a period of 258 days, and magnitude 4.7 to 5.4 over 450 days, respectively.[13]

BL Boötisis the prototype of its class of pulsating variable stars,[50]theanomalous Cepheids.These stars are somewhat similar toCepheid variables,but they do not have the same relationship between their period and luminosity.[51]Their periods are similar toRRAB variables;however, they are far brighter than these stars.[52]BL Boötis is a member of the clusterNGC 5466.Anomalous Cepheids aremetal poorand have masses not much larger than the Sun's, on average, 1.5M☉.BL Boötis type stars are a subtype ofRR Lyraevariables.[53]

T Boötiswas anovaobserved in April 1860 at a magnitude of 9.7. It has never been observed since, but that does not preclude the possibility of it being a highly irregularvariable staror arecurrent nova.[24]

Stars with planetary systems

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A digital rendering of Tau Boötis b

Extrasolar planetshave been discovered encircling ten stars in Boötes as of 2012.Tau Boötisis orbited by a large planet, discovered in 1999. The host star itself is a magnitude 4.5 star of type F7V, 15.6parsecsfrom Earth. It has a mass of 1.3M☉and a radius of 1.331solar radii(R☉); a companion,GJ527B,orbits at a distance of 240 AU.Tau Boötis b,the sole planet discovered in the system, orbits at a distance of 0.046 AU every 3.31 days. Discovered throughradial velocitymeasurements, it has a mass of 5.95Jupiter masses(MJ).[54]This makes it ahot Jupiter.[55]The host star and planet aretidally locked,meaning that the planet's orbit and the star's particularly high rotation are synchronized.[56][57]Furthermore, a slight variability in the host star's light may be caused by magnetic interactions with the planet.[57]Carbon monoxideis present in the planet's atmosphere. Tau Boötis b does nottransitits star, rather, its orbit is inclined 46 degrees.[55]

Like Tau Boötis b,HAT-P-4bis also a hot Jupiter. It is noted for orbiting a particularlymetal-richhost star and being of low density.[58]Discovered in 2007, HAT-P-4 b has a mass of0.68MJand a radius of1.27RJ.It orbits every 3.05 days at a distance of 0.04 AU.HAT-P-4,the host star, is an F-type star of magnitude 11.2, 310 parsecs from Earth. It is larger than the Sun, with a mass of 1.26M☉and a radius of 1.59R☉.[59]

Evolution of the HD 128311 system over time

Boötes is also home to multiple-planet systems.HD 128311is the host star for a two-planet system, consisting ofHD 128311 bandHD 128311 c,discovered in 2002 and 2005, respectively.[60][61]HD 128311 b is the smaller planet, with a mass of2.18MJ;it was discovered throughradial velocityobservations. It orbits at almost the same distance as Earth, at 1.099 AU; however, its orbital period is significantly longer at 448.6 days.[60]

The larger of the two, HD 128311 c, has a mass of3.21MJand was discovered in the same manner. It orbits every 919 days inclined at 50°, and is 1.76 AU from the host star.[61]The host star, HD 128311, is a K0V-type star located 16.6 parsecs from Earth. It is smaller than the Sun, with a mass of 0.84M☉and a radius of 0.73R☉;it also appears below the threshold of naked-eye visibility at an apparent magnitude of 7.51.[60]

There are several single-planet systems in Boötes.HD 132406is a Sun-like star of spectral type G0V with an apparent magnitude of 8.45, 231.5 light-years from Earth.[62]It has a mass of 1.09M☉and a radius of 1R☉.[63]The star is orbited by a gas giant,HD 132406 b,discovered in 2007.[62]HD 132406 orbits 1.98 AU from its host star with a period of 974 days and has a mass of5.61MJ.The planet was discovered by the radial velocity method.[63]

WASP-23is a star with one orbiting planet,WASP-23 b.The planet, discovered by thetransit methodin 2010, orbits every 2.944 days very close to its Sun, at 0.0376 AU. It is smaller than Jupiter, at0.884MJand0.962RJ.Its star is a K1V-type star of apparent magnitude 12.7, far below naked-eye visibility, and smaller than the Sun at 0.78M☉and 0.765R☉.[64]

HD 131496is also encircled by one planet,HD 131496 b.The star is of type K0 and is located 110 parsecs from Earth; it appears at a visual magnitude of 7.96. It is significantly larger than the Sun, with a mass of 1.61M☉and a radius of 4.6 solar radii. Its one planet, discovered in 2011 by theradial velocity method,has a mass of2.2MJ;its radius is as yet undetermined. HD 131496 b orbits at a distance of 2.09 AU with a period of 883 days.[65]

Another single planetary system in Boötes is theHD 132563system, atriple starsystem. The parent star, technicallyHD 132563B,is a star of magnitude 9.47, 96 parsecs from Earth. It is almost exactly the size of the Sun, with the same radius and a mass only 1% greater. Its planet,HD 132563B b,was discovered in 2011 by the radial velocity method.1.49MJ,it orbits 2.62 AU from its star with a period of 1544 days.[66]Its orbit is somewhat elliptical, with aneccentricityof 0.22. HD 132563B b is one of very few planets found in triple star systems; it orbits the isolated member of the system, which is separated from the other components, aspectroscopic binary,by 400 AU.[67]

Also discovered through the radial velocity method, albeit a year earlier, isHD 136418 b,a two-Jupiter-mass planet that orbits the starHD 136418at a distance of 1.32 AU with a period of 464.3 days. Its host star is a magnitude 7.88 G5-type star, 98.2 parsecs from Earth. It has a radius of 3.4R☉and a mass of 1.33M☉.[68]

WASP-14 bis one of the most massive and dense exoplanets known,[69]with a mass of7.341MJand a radius of1.281RJ.Discovered via the transit method, it orbits 0.036 AU from its host star with a period of 2.24 days.[70]WASP-14 b has a density of 4.6 grams per cubic centimeter, making it one of the densest exoplanets known.[69]Its host star,WASP-14,is an F5V-type star of magnitude 9.75, 160 parsecs from Earth. It has a radius of 1.306R☉and a mass of 1.211M☉.[70]It also has a very high proportion oflithium.[69]

Deep-sky objects

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Hubble Space Telescopeimage of SDSSCGB 10189, three colliding galaxies

Boötes is in a part of thecelestial spherefacing away from the plane of our homeMilky Waygalaxy,and so does not have open clusters or nebulae. Instead, it has one brightglobular clusterand many faint galaxies.[1]The globular clusterNGC 5466has an overall magnitude of 9.1 and a diameter of 11arcminutes.[13]It is a very loose globular cluster with fairly few stars and may appear as a rich, concentratedopen clusterin a telescope. NGC 5466 is classified as aShapley–Sawyer Concentration Class12 cluster, reflecting its sparsity.[71]Its fairly large diameter means that it has a lowsurface brightness,so it appears far dimmer than the catalogued magnitude of 9.1 and requires a large amateur telescope to view. Only approximately 12 stars are resolved by an amateur instrument.[72]

Boötes has two bright galaxies.NGC 5248(Caldwell45) is atype Sc galaxy(a variety ofspiral galaxy) of magnitude 10.2. It measures 6.5 by 4.9 arcminutes.[13]Fifty million light-years from Earth, NGC 5248 is a member of theVirgo Clusterof galaxies; it has dim outer arms and obviousH II regions,dust lanesand youngstar clusters.[73]NGC 5676is another type Sc galaxy of magnitude 10.9. It measures 3.9 by 2.0 arcminutes.[13]Other galaxies includeNGC 5008,a type Scemission-line galaxy,[74]NGC 5548,a type SSeyfert galaxy,[75]NGC 5653,a type SHII galaxy,[76]NGC 5778(also classified as NGC 5825),[77]a type E galaxy that is the brightest of its cluster,[78]NGC 5886,[79]andNGC 5888,a type SBb galaxy.[80]NGC 5698is a barred spiral galaxy, notable for being the host of the 2005 supernovaSN 2005bc,which peaked at magnitude 15.3.

Further away lies the 250-million-light-year-diameterBoötes void,a huge space largely empty of galaxies. Discovered byRobert Kirshnerand colleagues in 1981, it is roughly 700 million light-years from Earth.[81]Beyond it and within the bounds of the constellation, lie twosuperclustersat around 830 million and 1 billion light-years distant.

TheHercules–Corona Borealis Great Wall,the largest-known structure in the Universe, covers a significant part of Boötes.[82]

Meteor showers

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A Quadrantid captured by an all-sky camera during a 4-second exposure

Boötes is home to theQuadrantidmeteor shower,the most prolific annual meteor shower. It was discovered in January 1835 and named in 1864 by Alexander Herschel.[83]Theradiantis located in northern Boötes near Kappa Boötis,[84]in its namesake former constellation of Quadrans Muralis. Quadrantid meteors are dim, but have a peak visible hourly rate of approximately 100 per hour on January 3–4.[8][24]Thezenithal hourly rateof the Quadrantids is approximately 130 meteors per hour at their peak; it is also a very narrow shower.

The Quadrantids are notoriously difficult to observe because of a low radiant and often inclement weather. The parent body of the meteor shower has been disputed for decades;[83]however,Peter Jenniskenshas proposed2003 EH1,a minor planet, as the parent.[85]2003 EH1may be linked toC/1490 Y1,a comet previously thought to be a potential parent body for the Quadrantids.[86][87]

2003 EH1is ashort-period cometof theJupiter family;500 years ago, it experienced a catastrophic breakup event. It is now dormant.[88]The Quadrantids had notable displays in 1982, 1985 and 2004.[89]Meteors from this shower often appear to have a blue hue and travel at a moderate speed of 41.5–43 kilometers per second.[90]

On April 28, 1984, a remarkable outburst of the normally placidAlpha Bootidswas observed by visual observer Frank Witte from 00:00 to 2:30 UTC. In a 6 cm telescope, he observed 433 meteors in a field of view near Arcturus with a diameter of less than 1°.Peter Jenniskenscomments that this outburst resembled a "typical dust trail crossing".[91]The Alpha Bootids normally begin on April 14, peaking on April 27 and 28, and finishing on May 12.[92]Its meteors are slow-moving, with a velocity of 20.9 kilometers per second.[93]They may be related to Comet73P/Schwassmann–Wachmann3, but this connection is only theorized.[92]

A bright Quadrantid observed at twilight

TheJune Bootids,also known as the Iota Draconids, is a meteor shower associated with the comet7P/Pons–Winnecke,first recognized on May 27, 1916, by William F. Denning.[94]The shower, with its slow meteors, was not observed prior to 1916 because Earth did not cross the comet's dust trail until Jupiter perturbed Pons–Winnecke's orbit, causing it to come within 0.03AU(4.5 million km; 2.8 million mi) of Earth's orbit the first year the June Bootids were observed.

In 1982, E. A. Reznikov discovered that the 1916 outburst was caused by material released from the comet in 1819.[95]Another outburst of the June Bootids was not observed until 1998, because Comet Pons–Winnecke's orbit was not in a favorable position. However, on June 27, 1998, an outburst of meteors radiating from Boötes, later confirmed to be associated with Pons-Winnecke, was observed. They were incredibly long-lived, with trails of the brightest meteors lasting several seconds at times. Manyfireballs,green-hued trails, and even some meteors that cast shadows were observed throughout the outburst, which had a maximum zenithal hourly rate of 200–300 meteors per hour.[96]

Two Russian astronomers determined in 2002 that material ejected from the comet in 1825 was responsible for the 1998 outburst.[97]Ejectafrom the comet dating to 1819, 1825 and 1830 was predicted to enter Earth's atmosphere on June 23, 2004. The predictions of a shower less spectacular than the 1998 showing were borne out in a display that had a maximum zenithal hourly rate of 16–20 meteors per hour that night. The June Bootids are not expected to have another outburst in the next 50 years.[98]

Typically, only 1–2 dim, very slow meteors are visible per hour; the average June Bootid has a magnitude of 5.0. It is related to theAlpha Draconidsand theBootids-Draconids.The shower lasts from June 27 to July 5, with a peak on the night of June 28.[99]The June Bootids are classified as a class III shower (variable),[100]and has an average entry velocity of 18 kilometers per second. Its radiant is located 7 degrees north of Beta Boötis.[101]

TheBeta Bootidsis a weak shower that begins on January 5, peaks on January 16, and ends on January 18. Its meteors travel at 43 km/s.[102]TheJanuary Bootidsis a short, young meteor shower that begins on January 9, peaks from January 16 to January 18, and ends on January 18.[103]

ThePhi Bootidsis another weak shower radiating from Boötes. It begins on April 16, peaks on April 30 and May 1, and ends on May 12.[92]Its meteors are slow-moving, with a velocity of 15.1 km/s. They were discovered in 2006.[104]The shower's peak hourly rate can be as high as six meteors per hour. Though named for a star in Boötes, the Phi Bootid radiant has moved into Hercules.[105]The meteor stream is associated with three different asteroids:1620 Geographos,2062 Atenand1978 CA.[106]

TheLambda Bootids,part of theBootid-Coronae Borealid Complex,are a weak annual shower with moderately fast meteors; 41.75 km/s.[107]The complex includes the Lambda Bootids, as well as theTheta Coronae BorealidsandXi Coronae Borealids.[108][109]All of the Bootid-Coronae Borealid showers areJupiter family cometshowers; the streams in the complex have highly inclined orbits.[88]

There are several minor showers in Boötes, some of whose existence is yet to be verified. TheRho Bootidsradiate from near the namesake star, and were hypothesized in 2010.[110]The average Rho Bootid has an entry velocity of 43 km/s.[110][111]It peaks in November and lasts for three days.

The Rho Bootid shower is part of theSMA complex,a group of meteor showers related to theTaurids,which is in turn linked to the comet2P/Encke.However, the link to the Taurid shower remains unconfirmed and may be a chance correlation.[111]Another such shower is theGamma Bootids,which were hypothesized in 2006. Gamma Bootids have an entry velocity of 50.3 km/s.[112]TheNu Bootids,hypothesized in 2012, have faster meteors, with an entry velocity of 62.8 km/s.[113]

See also

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References

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Citations

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  2. ^abcIAU,The Constellations,Boötes.
  3. ^White 2008,p. 207.
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  7. ^Levy 1996 pp=141
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  11. ^Pasachoff 2000,p. 133.
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  14. ^Levy 2008,p. 51.
  15. ^Star Tales Quadrans Muralis.
  16. ^abStar Tales Mons Maenalus.
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  20. ^Polakis 2009.
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  23. ^abSIMBAD Alpha Boötis.
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  28. ^Kaler Muphrid.
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  31. ^Kaler Nekkar.
  32. ^SIMBAD Gamma Boötis.
  33. ^Kaler Seginus.
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  35. ^AAVSO Delta Scuti Variables.
  36. ^abKaler Delta Boötis.
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  38. ^SIMBAD BD+33 2562.
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  40. ^abcdefghiThompson & Thompson 2007,p. 105.
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  42. ^abAAVSO Rho Boötis.
  43. ^SIMBAD Sigma Boötis.
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  48. ^AAVSO ZZ Boötis.
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  61. ^abExoplanet Encyclopedia HD 128311 c.
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  68. ^Exoplanet Encyclopedia HD 136418 b.
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  70. ^abExoplanet Encyclopedia WASP-14 b.
  71. ^Thompson & Thompson 2007,p. 103.
  72. ^Thompson & Thompson 2007,p. 104.
  73. ^Niksch & Block 2004.
  74. ^SIMBAD NGC 5008.
  75. ^SIMBAD NGC 5548.
  76. ^SIMBAD NGC 5653.
  77. ^SIMBAD NGC 5825.
  78. ^SIMBAD NGC 5778.
  79. ^SIMBAD NGC 5886.
  80. ^SIMBAD NGC 5888.
  81. ^Francis, Matthew R."What's 250 Million Light-Years Big, Almost Empty, and Full of Answers?".Nautilus.Archived fromthe originalon 2018-07-17.Retrieved2018-07-17.
  82. ^Horváth, István; Bagoly, Zsolt; Hakkila, Jon; Tóth, L. V. (2015-11-18)."New data support the existence of the Hercules-Corona Borealis Great Wall".Astronomy & Astrophysics.584:A48.arXiv:1510.01933.Bibcode:2015A&A...584A..48H.doi:10.1051/0004-6361/201424829.S2CID56073380.Retrieved2018-06-19.
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  85. ^Jenniskens 2006,p. 368.
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  90. ^Levy 2008,p. 104.
  91. ^Jenniskens 2006,p. 199.
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  93. ^IAU Alpha Bootids.
  94. ^Jenniskens 2006,p. 334.
  95. ^Jenniskens 2006,p. 335.
  96. ^Jenniskens 2006,p. 336–337.
  97. ^Jenniskens 2006,p. 338.
  98. ^Jenniskens 2006,p. 339–344.
  99. ^Levy 2008,p. 113.
  100. ^AMS 2012 List.
  101. ^AMS June 23.
  102. ^Levy 2008,p. 105.
  103. ^Levy 2008,p. 106.
  104. ^IAU Phi Bootids.
  105. ^Koed & Sherrod 2003,p. 52.
  106. ^Štohl & Porubčan 1993,p. 43.
  107. ^IAU Lambda Bootids.
  108. ^IAU Bootid-Coronae Borealid Complex.
  109. ^Green 2007.
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  111. ^abBrown et al. 2010.
  112. ^IAU Gamma Bootids.
  113. ^IAU Nu Bootids.

References

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