Telescopium
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Telescopium is a minor constellation in the southern celestial hemisphere, one of twelve named in the 18th century by French astronomer Nicolas-Louis de Lacaille and one of several depicting scientific instruments. Its name is a Latinized form of the Greek word for telescope. Telescopium was later much reduced in size by Francis Baily and Benjamin Gould.
The brightest star in the constellation is Alpha Telescopii, a blue-white subgiant with an apparent magnitude of 3.5, followed by the orange giant star Zeta Telescopii at magnitude 4.1. Eta and PZ Telescopii are two young star systems with debris disks and brown dwarf companions. Telescopium hosts two unusual stars with very little hydrogen that are likely to be the result of two merged white dwarfs: PV Telescopii, also known as HD 168476, is a hot blue extreme helium star, while RS Telescopii is an R Coronae Borealis variable. RR Telescopii is a cataclysmic variable that brightened as a nova to 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.
HistoryEdit
Telescopium was introduced in 1751–52 by Nicolas-Louis de Lacaille with the French name le Telescope,Template:Sfn depicting an aerial telescope,Template:Sfn after he had observed and catalogued 10,000 southern stars during a two-year stay at the Cape of Good Hope. He devised 14 new constellations in uncharted regions of the Southern Celestial Hemisphere not visible from Europe. All but one honored instruments that symbolised the Age of Enlightenment.Template:Sfn Covering 40 degrees of the night sky,Template:Sfn the telescope stretched out northwards between Sagittarius and Scorpius.Template:Sfn Lacaille had Latinised its name to Telescopium by 1763.Template:Sfn
The constellation was known by other names. It was called Tubus Astronomicus in the eighteenth century, during which time three constellations depicting telescopes were recognised—Tubus Herschelii Major between Gemini and Auriga and Tubus Herschelii Minor between Taurus and Orion, both of which had fallen out of use by the nineteenth century.Template:Sfn Johann Bode called it the Astronomische Fernrohr in his 1805 Gestirne and kept its size, but later astronomers Francis Baily and Benjamin Gould subsequently shrank its boundaries.Template:Sfn The much-reduced constellation lost several brighter stars to neighbouring constellations: Beta Telescopii became Eta Sagittarii, which it had been before Lacaille placed it in Telescopium,Template:Sfn Gamma was placed in Scorpius and renamed G Scorpii by Gould,Template:Sfn Theta Telescopii reverted to its old appellation of d Ophiuchi,Template:Sfn and Sigma Telescopii was placed in Corona Australis. Initially uncatalogued, the latter is now known as HR 6875.Template:Sfn The original object Lacaille had named Eta Telescopii—the open cluster Messier 7—was in what is now Scorpius, and Gould used the Bayer designation for a magnitude 5 star, which he felt warranted a letter.Template:Sfn
CharacteristicsEdit
A small constellation, Telescopium is bordered by Sagittarius and Corona Australis to the north, Ara to the west, Pavo to the south, and Indus to the east, cornering on Microscopium to the northeast. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is "Tel".Template:Sfn The official constellation boundaries, as set by Belgian astronomer Eugène Delporte in 1930, are defined by a quadrilateral. In the equatorial coordinate system, the right ascension coordinates of these borders lie between Template:RA and Template:RA, while the declination coordinates are between −45.09° and −56.98°.Template:Sfn The whole constellation is visible to observers south of latitude 33°N.Template:SfnTemplate:Efn
FeaturesEdit
StarsEdit
Template:See also Within the constellation's borders, there are 57 stars brighter than or equal to apparent magnitude 6.5.Template:EfnTemplate:Sfn With a magnitude of 3.5, Alpha Telescopii is the brightest star in the constellation. It is a blue-white subgiant of spectral type B3IV which lies around 250 light-years away.Template:Sfn It is radiating nearly 800 times the Sun'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.Template:Sfn Close by Alpha Telescopii are the two blue-white stars sharing the designation of Delta Telescopii. Delta¹ Telescopii is of spectral type B6IV and apparent magnitude 4.9,Template:Sfn while Delta² Telescopii is of spectral type B3III and magnitude 5.1.Template:Sfn They form an optical double,Template:Sfn as the stars are estimated to be around 710 and 1190 light-years away respectively.Template:Sfn The faint (magnitude 12.23) Gliese 754, a red dwarf of spectral type M4.5V, is one of the nearest 100 stars to Earth at 19.3 light-years distant.Template:Sfn Its eccentric orbit around the Galaxy indicates that it may have originated in the Milky Way's thick disk.Template:Sfn
At least four of the fifteen stars visible to the unaided eye are orange giants of spectral class K.Template:Sfn The second brightest star in the constellation—at apparent magnitude 4.1—is Zeta Telescopii, an orange subgiant of spectral type K1III-IV.Template:Sfn Around 1.53 times as massive as the Sun, it shines with 512 times its luminosity.Template:Sfn Located 127 light years away from Earth, it has been described as yellowTemplate:Sfn or reddish in appearance.Template:Sfn Epsilon Telescopii is a binary star system:Template:Sfn the brighter component, Epsilon Telescopii A, is an orange giant of spectral type K0III with an apparent magnitude of +4.52,Template:Sfn while the 13th magnitude companion, Epsilon Telescopii B, is 21 arcseconds away from the primary, and just visible with a 15 cm aperture telescope on a dark night.Template:Sfn The system is 417 light-years away.Template:Sfn Iota Telescopii and HD 169405—magnitude 5 orange giants of spectral types K0III and K0.5III respectivelyTemplate:SfnTemplate:Sfn—make up the quartet.Template:Sfn They are around 370 and 497 light-years away from the Sun respectively.Template:Sfn Another ageing star, Kappa Telescopii is a yellow giant with a spectral type G9III and apparent magnitude of 5.18.Template:Sfn Around 1.87 billion years old, this star of around 1.6 solar masses has swollen to 11 times the Sun's diameter.Template:Sfn It is approximately 293 light-years from Earth, and is another optical double.Template:Sfn
Xi Telescopii is an irregular variable star that ranges between magnitudes 4.89 and 4.94.Template:Sfn Located 1079 light-years distant, it is a red giant of spectral type M2III that has a diameter around 5.6 times the Sun's,Template:Sfn and a luminosity around 2973 times that of the Sun.Template:Sfn Another irregular variable, RX Telescopii is a red supergiant that varies between magnitudes 6.45 and 7.47,Template:Sfn just visible to the unaided eye under good viewing conditions. BL Telescopii is an Algol-like eclipsing binary system that varies between apparent magnitudes 7.09 and 9.08 over a period of just over 778 days (2 years 48 days).Template:Sfn The primary is a yellow supergiant that is itself intrinsically variable.Template:Sfn Dipping from its baseline magnitude of 9.6 to 16.5,Template:Sfn RS Telescopii is a rare R Coronae Borealis variable—an extremely hydrogen-deficient supergiant thought to have arisen as the result of the merger of two white dwarfs; fewer than 100 have been discovered as of 2012.Template:Sfn The dimming is thought to be caused by carbon dust expelled by the star. As of 2012, four dimmings have been observed.Template:Sfn PV Telescopii is a class B-type (blue) extreme helium star that is the prototype of a class of variables known as PV 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 the Chandrasekhar 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.Template:Sfn
While RR Telescopii, also designated Nova Telescopii 1948, is often called a slow nova, it is now classified as a symbiotic nova system composed of an M5III pulsating red giant and a white dwarf; between 1944 and 1948 it brightened by about 7 magnitudes before being noticed at apparent magnitude 6.0 in mid-1948.Template:Sfn It has since faded slowly to about apparent magnitude 12.Template:Sfn QS Telescopii is a binary system composed of a white dwarf and main sequence donor star, in this case the two are close enough to be tidally locked, facing one another. Known as polars, material from the donor star does not form an accretion disk around the white dwarf, but rather streams directly onto it.Template:Sfn This is due to the presence of the white dwarf's strong magnetic field.Template:Sfn
Although no star systems in Telescopium have confirmed planets, several have been found to have brown dwarf companions. A member of the 12-million-year-old Beta Pictoris moving group of stars that share a common proper motion through space,Template:Sfn Eta Telescopii is a young white main sequence star of magnitude 5.0 and spectral type A0V.Template:Sfn It has a debris disk and brown dwarf companion of spectral type M7V or M8V that is between 20 and 50 times as massive as Jupiter.Template:Sfn The system is complex, as it has a common proper motion with (and is gravitationally bound to) the star HD 181327, which has its own debris disk.Template:Sfn This latter star is a yellow-white main sequence star of spectral type F6V of magnitude 7.0.Template:Sfn PZ Telescopii is 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.Template:Sfn HD 191760 is a yellow subgiant—a star that is cooling and expanding off the main 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 the High Accuracy Radial Velocity Planet Searcher (HARPS) instrument on the ESO 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 the brown-dwarf desert.Template:Sfn
Deep sky objectsEdit
The Telescopium group is a group of twelve galaxies spanning three degrees in the northeastern part of the constellation, lying around 37 megaparsecs (120 million light-years) from our own galaxy.Template:Sfn The brightest member is the elliptical galaxy NGC 6868,Template:Sfn and to the west lies the spiral galaxy (or, perhaps, lenticular galaxy) NGC 6861.Template:Sfn These are the brightest members of two respective subgroups within the galaxy group, and are heading toward a merger in the future.Template:Sfn
The globular cluster NGC 6584 lies near Theta Arae and is 45,000 light-years distant from Earth.Template:Sfn It is an Oosterhoff type I cluster, and contains at least 69 variable stars, most of which are RR Lyrae variables.Template:Sfn The planetary nebula IC 4699 is of 13th magnitude and lies midway between Alpha and Epsilon Telescopii.Template:Sfn IC 4889 is an elliptical galaxy of apparent magnitude 11.3, which can be found 2 degrees north-north-west of 5.3-magnitude Nu Telescopii. Observing it through a 40 cm telescope will reveal its central region and halo.Template:Sfn
Occupying an area of around 4' × 2', NGC 6845 is an interacting system of four galaxies—two spiral and two lenticular galaxies—that is estimated to be around 88 megaparsecs (287 million light-years) distant.Template:Sfn SN 2008da was a type II supernova observed in one of the spiral galaxies, NGC 6845A, in June 2008.Template:Sfn SN 1998bw was a luminous supernova observed in the spiral arm of the galaxy ESO184-G82 in April 1998, and is notable in that it is highly likely to be the source of the gamma-ray burst GRB 980425.Template:Efn Template:Sfn
See alsoEdit
NotesEdit
ReferencesEdit
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