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Telescopium

Coordinates:Sky map19h00m00s,−50° 00′ 00″
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For the snail, seeTelescopium telescopium.

Telescopium
Constellation
Telescopium
List of stars in Telescopium
AbbreviationTel
GenitiveTelescopii
Pronunciation/ˌtɛlɪˈskoʊpiəm/,
genitive/ˌtɛlɪˈskoʊpi.aɪ/
SymbolismtheTelescope
Right ascension19h
Declination−50°
QuadrantSQ4
Area252 sq. deg. (57th)
Main stars2
Bayer/Flamsteed
stars		13
Stars withplanets0
Stars brighter than 3.00m0
Stars within 10.00 pc (32.62 ly)2
Brightest starα Tel(3.49m)
Messier objects0
Bordering
constellations
Visible at latitudes between +40° and −90°.
Best visible at 21:00 (9 p.m.) during the month ofAugust.

Telescopiumis a minorconstellationin the southerncelestial hemisphere,one of twelve named in the 18th century by FrenchastronomerNicolas-Louis de Lacailleand one of several depicting scientific instruments. Its name is aLatinizedform of theGreekword fortelescope.Telescopium was later much reduced in size byFrancis BailyandBenjamin Gould.

The brightest star in the constellation isAlpha Telescopii,a blue-whitesubgiantwith anapparent magnitudeof 3.5, followed by the orange giant starZeta Telescopiiat magnitude 4.1.EtaandPZ Telescopiiare two young star systems withdebris disksandbrown dwarfcompanions. Telescopium hosts two unusual stars with very little hydrogen that are likely to be the result of two mergedwhite dwarfs:PV Telescopii,also known as HD 168476, is a hot blueextreme helium star,whileRS Telescopiiis anR Coronae Borealis variable.RR Telescopiiis acataclysmic variablethat brightened as anovato magnitude 6 in 1948.

It had been hypothesized in 2020 that Telescopium would also host the first known visible star system with a black hole,QV Telescopii (HR 6819),however observations in 2022 indicated that this is a binary system of two main-sequence stars without a black hole instead.

History[edit]

Seen in the 1824 star chart setUrania's Mirror(in the lower right)

Telescopium was introduced in 1751–52 byNicolas-Louis de Lacaillewith the French namele Telescope,[1]depicting anaerial telescope,[2]after he had observed and catalogued 10,000 southern stars during a two-year stay at theCape of Good Hope.He devised 14 new constellations in uncharted regions of theSouthern Celestial Hemispherenot visible from Europe. All but one honored instruments that symbolised theAge of Enlightenment.[3]Covering 40 degrees of the night sky,[2]the telescope stretched out northwards between Sagittarius and Scorpius.[4]Lacaille had Latinised its name toTelescopiumby 1763.[1]

The constellation was known by other names. It was calledTubus Astronomicusin the eighteenth century, during which time three constellations depicting telescopes were recognised—Tubus Herschelii Majorbetween Gemini and Auriga andTubus Herschelii Minorbetween Taurus and Orion, both of which had fallen out of use by the nineteenth century.[5]Johann Bodecalled it theAstronomische Fernrohrin his 1805Gestirneand kept its size, but later astronomersFrancis BailyandBenjamin Gouldsubsequently shrank its boundaries.[6]The much-reduced constellation lost several brighter stars to neighbouring constellations: Beta Telescopii becameEta Sagittarii,which it had been before Lacaille placed it in Telescopium,[7]Gamma was placed in Scorpius and renamedG Scorpiiby Gould,[7]Theta Telescopii reverted to its old appellation ofd Ophiuchi,[7]and Sigma Telescopii was placed in Corona Australis. Initially uncatalogued, the latter is now known asHR 6875.[7]The original object Lacaille had named Eta Telescopii—the open clusterMessier 7—was in what is now Scorpius, and Gould used the Bayer designation for a magnitude 5 star, which he felt warranted a letter.[7]

Characteristics[edit]

The constellation of Telescopium, the telescope, as it can be seen by the naked eye

A small constellation, Telescopium is bordered bySagittariusandCorona Australisto the north,Arato the west,Pavoto the south, andIndusto the east, cornering onMicroscopiumto the northeast. The three-letter abbreviation for the constellation, as adopted by theInternational Astronomical Unionin 1922, is "Tel".[8]The official constellation boundaries, as set by Belgian astronomerEugène Delportein 1930, are defined by aquadrilateral.In theequatorial coordinate system,theright ascensioncoordinates of these borders lie between18h09.1mand20h29.5m,while thedeclinationcoordinates are between −45.09° and −56.98°.[9]The whole constellation is visible to observers south of latitude33°N.[10][a]

Features[edit]

Stars[edit]

See also:List of stars in Telescopium

Within the constellation's borders, there are 57 stars brighter than or equal toapparent magnitude6.5.[b][10]With a magnitude of 3.5,Alpha Telescopiiis the brightest star in the constellation. It is a blue-whitesubgiantofspectral typeB3IV which lies around 250light-yearsaway.[12]It is radiating nearly 800 times theSun's luminosity,and is estimated to be 5.2±0.4 times as massive and have 3.3±0.5 times the Sun's radius.[13]Close by Alpha Telescopii are the two blue-white stars sharing the designation ofDelta Telescopii.Delta¹ Telescopii is of spectral type B6IV and apparent magnitude 4.9,[14]while Delta² Telescopii is of spectral type B3III and magnitude 5.1.[15]They form anoptical double,[16]as the stars are estimated to be around 710 and 1190 light-years away respectively.[17]The faint (magnitude 12.23)Gliese 754,ared dwarfof spectral type M4.5V, is one of the nearest 100 stars to Earth at 19.3 light-years distant.[18]Itseccentric orbitaround the Galaxy indicates that it may have originated in the Milky Way'sthick disk.[19]

At least four of the fifteen stars visible to the unaided eye areorange giantsofspectral class K.[20]The second brightest star in the constellation—at apparent magnitude 4.1—isZeta Telescopii,an orange subgiant of spectral type K1III-IV.[21]Around 1.53 times as massive as the Sun, it shines with 512 times itsluminosity.[22]Located 127 light years away from Earth, it has been described as yellow[16]or reddish in appearance.[23]Epsilon Telescopiiis abinary starsystem:[24]the brighter component, Epsilon Telescopii A, is an orangegiantof spectral type K0III with anapparent magnitudeof +4.52,[25]while the 13th magnitude companion, Epsilon Telescopii B, is 21arcsecondsaway from the primary, and just visible with a 15 cmaperturetelescope on a dark night.[24]The system is 417 light-years away.[26]Iota TelescopiiandHD 169405—magnitude 5 orange giants of spectral types K0III and K0.5III respectively[27][28]—make up the quartet.[20]They are around 370 and 497 light-years away from the Sun respectively.[26]Another ageing star,Kappa Telescopiiis ayellow giantwith a spectral type G9III and apparent magnitude of 5.18.[29]Around 1.87 billion years old, this star of around 1.6 solar masses has swollen to 11 times the Sun's diameter.[30]It is approximately 293 light-years from Earth, and is another optical double.[24]

Xi Telescopiiis anirregular variablestar that ranges between magnitudes 4.89 and 4.94.[31]Located 1079 light-years distant, it is ared giantof spectral type M2III that has a diameter around 5.6 times the Sun's,[32]and a luminosity around 2973 times that of the Sun.[26]Another irregular variable,RX Telescopiiis ared supergiantthat varies between magnitudes 6.45 and 7.47,[33]just visible to the unaided eye under good viewing conditions.BL Telescopiiis anAlgol-likeeclipsing binarysystem that varies betweenapparent magnitudes7.09 and 9.08 over a period of just over 778 days (2 years 48 days).[34]The primary is ayellow supergiantthat is itself intrinsically variable.[35]Dipping from its baseline magnitude of 9.6 to 16.5,[36]RS Telescopiiis a rareR Coronae Borealis variable—an extremely hydrogen-deficientsupergiantthought to have arisen as the result of the merger of twowhite dwarfs;fewer than 100 have been discovered as of 2012.[37]The dimming is thought to be caused by carbon dust expelled by the star. As of 2012, four dimmings have been observed.[37]PV Telescopiiis a class B-type (blue)extreme helium starthat is the prototype of a class of variables known asPV Telescopii variables.First discovered in 1952, it was found to have a very low level of hydrogen. One theory of its origin is that it is the result of a merger between a helium- and a carbon-oxygen white dwarf. If the combined mass does not exceed theChandrasekhar limit,the former will accrete onto the latter star and ignite to form a supergiant. Later this will become an extreme helium star before cooling to become a white dwarf.[38]

An artist's depiction of the orbits of the hierarchical triple star systemHR 6819,with the inferred black hole (red orbit) in the inner binary

WhileRR Telescopii,also designatedNova Telescopii 1948,is often called aslow nova,it is now classified as asymbiotic novasystem composed of an M5III pulsatingred giantand a white dwarf; between 1944 and 1948 it brightened by about 7 magnitudes before being noticed at apparent magnitude 6.0 in mid-1948.[39]It has since faded slowly to about apparent magnitude 12.[40]QS Telescopiiis a binary system composed of a white dwarf andmain sequencedonor star, in this case the two are close enough to betidally locked,facing one another. Known aspolars,material from the donor star does not form anaccretion diskaround the white dwarf, but rather streams directly onto it.[41]This is due to the presence of the white dwarf's strongmagnetic field.[42]

Although no star systems in Telescopium have confirmed planets, several have been found to havebrown dwarfcompanions. A member of the 12-million-year-oldBeta Pictoris moving groupof stars that share acommon proper motionthrough space,[43]Eta Telescopiiis a youngwhite main sequence starof magnitude 5.0 and spectral type A0V.[44]It has adebris diskand brown dwarf companion of spectral type M7V or M8V that is between 20 and 50 times as massive as Jupiter.[43]The system is complex, as it has a common proper motion with (and is gravitationally bound to) the starHD 181327,which has its own debris disk.[45]This latter star is ayellow-white main sequence starof spectral type F6V of magnitude 7.0.[46]PZ Telescopiiis another young star with a debris disk and substellar brown dwarf companion, though at 24 million years of age appears too old to be part of the Beta Pictoris moving group.[47]HD 191760is a yellow subgiant—a star that is cooling and expanding off themain sequence—of spectral type G3IV/V. Estimated to be just over four billion years old, it is slightly (1.1 to 1.3 times) more massive as the Sun, 2.69 times as luminous, and has around 1.62 times its radius. Using theHigh Accuracy Radial Velocity Planet Searcher(HARPS) instrument on theESO 3.6 m Telescope,it was found to have a brown dwarf around 38 times as massive as Jupiter orbiting at an average distance of 1.35 AU with a period of 505 days. This is an unusually close distance from the star, within a range that has been termed thebrown-dwarf desert.[48]

Deep sky objects[edit]

TheTelescopium groupis group of twelve galaxies spanning three degrees in the northeastern part of the constellation, lying around 37megaparsecs(120 million light-years) from our own galaxy.[23]The brightest member is the elliptical galaxyNGC 6868,[49]and to the west lies thespiral galaxy(or, perhaps,lenticular galaxy)NGC 6861.[23]These are the brightest members of two respective subgroups within the galaxy group, and are heading toward a merger in the future.[49]

The globular clusterNGC 6584,as observed with theHubble Space Telescope

Theglobular clusterNGC 6584lies nearTheta Araeand is 45,000 light-years distant from Earth.[23]It is anOosterhoff type Icluster, and contains at least 69 variable stars, most of which areRR Lyrae variables.[50]Theplanetary nebulaIC 4699is of 13th magnitude and lies midway between Alpha and Epsilon Telescopii.[23]IC 4889is anelliptical galaxyof apparent magnitude 11.3, which can be found 2 degrees north-north-west of 5.3-magnitudeNu Telescopii.Observing it through a 40 cm telescope will reveal its central region and halo.[51]

The interacting galaxy systemNGC 6845,as observed withGALEX

Occupying an area of around 4'× 2',NGC 6845is an interacting system of four galaxies—two spiral and twolenticular galaxies—that is estimated to be around 88 megaparsecs (287 million light-years) distant.[52]SN 2008da was atype II supernovaobserved in one of the spiral galaxies,NGC 6845A,in June 2008.[53]SN 1998bwwas a luminous supernova observed in the spiral arm of the galaxyESO184-G82in April 1998, and is notable in that it is highly likely to be the source of thegamma-ray burstGRB 980425.[c][54]

See also[edit]

Wikimedia Commons has media related toTelescopium (constellation).

Notes[edit]

  1. ^While parts of the constellation technically rise above the horizon to observers between 33°N and44°N,stars within a few degrees of the horizon are to all intents and purposes unobservable.[10]
  2. ^Objects of magnitude 6.5 are among the faintest visible to the unaided eye in suburban-rural transition night skies.[11]
  3. ^chances of signals being unrelated is around 1 in 10,000.[54]

References[edit]

Citations

  1. ^abRidpath,Star TalesLacaille.
  2. ^abWagman 2003,p. 299.
  3. ^Wagman 2003,pp. 6–7.
  4. ^Ridpath,Star TalesTelescopium.
  5. ^Ellis 1997.
  6. ^Allen 1963,p. 414.
  7. ^abcdeWagman 2003,p. 300.
  8. ^Russell 1922,p. 469.
  9. ^IAU,The Constellations,Telescopium.
  10. ^abcRidpath, Constellations – 2.
  11. ^The Bortle Dark-Sky Scale.
  12. ^Kaler,Alpha Telescopii.
  13. ^Hubrig et al. 2009.
  14. ^SIMBAD HR 6934.
  15. ^SIMBAD HR 6938.
  16. ^abRidpath & Tirion 2007,pp. 242–43.
  17. ^van Leeuwen 2007.
  18. ^SIMBAD LHS 60.
  19. ^Innanen & Flynn 2010.
  20. ^abBagnall 2012,pp. 434–35.
  21. ^Gray et al. 2006.
  22. ^Liu et al. 2007.
  23. ^abcdeStreicher 2009,pp. 168–71.
  24. ^abcFerreira 2009,pp. 166–67.
  25. ^SIMBAD Epsilon Telescopii.
  26. ^abcMcDonald et al. 2012.
  27. ^SIMBAD Iota Telescopii.
  28. ^SIMBAD HD 169405.
  29. ^SIMBAD Kappa Telescopii.
  30. ^da Silva et al. 2006.
  31. ^AAVSO NSV 12783.
  32. ^Pasinetti Fracassini et al. 2001.
  33. ^AAVSO RX Telescopii.
  34. ^AAVSO BL Telescopii.
  35. ^Zsoldos 1994.
  36. ^AAVSO RS Telescopii.
  37. ^abTisserand 2012.
  38. ^Pandey 2006.
  39. ^Robinson 1975.
  40. ^Light Curve Generator.
  41. ^Gerke 2006.
  42. ^Traulsen 2011.
  43. ^abSmith 2009.
  44. ^SIMBAD Eta Telescopii.
  45. ^Neuhäuser 2011.
  46. ^SIMBAD HD 181327.
  47. ^Jenkins 2012.
  48. ^Jenkins 2009.
  49. ^abMachacek et al. 2010.
  50. ^Toddy et al. 2012,pp. 63–71.
  51. ^Bakich 2010,p. 277.
  52. ^Gordon 2003.
  53. ^Morrell 2008.
  54. ^abgalama 1998.

Sources

Online sources

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