Octans

Last updated
Octans
Constellation
Octans IAU.svg
AbbreviationOct [1]
Genitive Octantis
Pronunciation /ˈɒktænz/ , genitive /ɒkˈtæntɪs/
Symbolismthe Octant
Right ascension 00h to 24h [1]
Declination −74.30° to −90° [1]
QuadrantSQ4
Area 291 sq. deg. (50th)
Main stars 3
Bayer/Flamsteed
stars
27
Stars with planets 3
Stars brighter than 3.00m0
Stars within 10.00 pc (32.62 ly)1
Brightest star ν Oct  (3.73 m )
Messier objects 0
Meteor showers 0
Bordering
constellations
Tucana
Indus
Pavo
Apus
Chamaeleon
Mensa
Hydrus
Visible at latitudes between +0° and −90°.
Best visible at 21:00 (9 p.m.) during the month of October.
Circumpolar

Octans is a faint constellation located in the deep Southern Sky. Its name is Latin for the eighth part of a circle, but it is named after the octant, a navigational instrument. Devised by French astronomer Nicolas Louis de Lacaille in 1752, Octans remains one of the 88 modern constellations. The southern celestial pole is located within the boundaries of Octans.

Contents

History and mythology

Octans was one of 14 constellations created by French astronomer Nicolas Louis de Lacaille during his expedition to the Cape of Good Hope, and was originally named l’Octans de Reflexion (“the reflecting octant”) in 1752, after he had observed and catalogued almost 10,000 southern stars during a two-year stay at the Cape of Good Hope. He devised fourteen new constellations in uncharted regions of the Southern Celestial Hemisphere not visible from Europe. All but one honoured instruments that symbolised the Age of Enlightenment. [lower-alpha 1] [2]

It was part of his catalogue of the southern sky, the Coelum Australe Stelliferum, which was published posthumously in 1763. In Europe, it became more widely known as Octans Hadleianus, in honor of English mathematician John Hadley, who invented the octant in 1730. There is no real mythology related to Octans, partially due to its faintness and relative recentness, but mostly because of its extreme southerly latitude. [3]

Notable features

Stars

The constellation Octans as it can be seen by the naked eye. Constellation Octans.jpg
The constellation Octans as it can be seen by the naked eye.

Octans is a generally inconspicuous constellation with only one star brighter than magnitude 4; its brightest member is Nu Octantis, a spectral class K1 III giant star with an apparent magnitude  3.73. It is 63.3 ± 0.8 light-years distant from Earth. [4]

Beta Octantis is the second brightest star in the constellation.

Polaris Australis (Sigma Octantis), the southern pole star, is a magnitude 5.4 star just over 1 degree away from the true south celestial pole. Its relative faintness means that it is not practical for navigation. [5]

BQ Octantis is a fainter, magnitude 6.82 star located much closer to the South Pole (at less than a degree) than Sigma.

In addition to having the current southern pole star of Earth, Octans also contains the southern pole star of the planet Saturn, which is the magnitude 4.3 Delta Octantis.

The Astronomical Society of Southern Africa in 2003 reported that observations of the Mira variable stars R and T Octantis were urgently needed. [6]

Four star systems are known to have planets. Mu2 Octantis is a binary star system, the brighter component of which has a planet. Nu Octantis A also has a planet orbiting. HD 142022 is a binary system, a component of which is a sunlike star with a massive planet with an orbital period of 1928 ± 46 days. HD 212301 is a yellow-white main sequence star with a hot jupiter that completes an orbit every 2.2 days.

Deep sky objects

NGC 7098 NGC 7098 ESO.jpg
NGC 7098

NGC 2573 (also known as Polarissima Australis) is a faint barred spiral galaxy that happens to be the closest NGC object to the south celestial pole. NGC 7095 and NGC 7098 are two barred spiral galaxies that are 115 million and 95 million light-years distant from Earth respectively. The sparse open cluster Collinder 411 is also located in the constellation.

Namesakes

USS Octans (AF-26) was a stores ship used by the United States Navy during World War II.

See also

Notes

  1. The exception is Mensa, named for the Table Mountain. The other thirteen (alongside Horologium) are Antlia, Caelum, Circinus, Fornax, Horologium, Microscopium, Norma, Pictor, Pyxis, Reticulum, Sculptor and Telescopium. [2]

Related Research Articles

<span class="mw-page-title-main">Antlia</span> Constellation in the Southern Celestial Hemisphere

Antlia is a constellation in the Southern Celestial Hemisphere. Its name means "pump" in Latin and Greek; it represents an air pump. Originally Antlia Pneumatica, the constellation was established by Nicolas-Louis de Lacaille in the 18th century. Its non-specific (single-word) name, already in limited use, was preferred by John Herschel then welcomed by the astronomic community which officially accepted this. North of stars forming some of the sails of the ship Argo Navis, Antlia is completely visible from latitudes south of 49 degrees north.

<span class="mw-page-title-main">Ara (constellation)</span> Constellation in the southern celestial hemisphere

Ara is a southern constellation between Scorpius, Telescopium, Triangulum Australe, and Norma. It was one of the Greek bulk described by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations designated by the International Astronomical Union.

<span class="mw-page-title-main">Apus</span> Constellation in the southern celestial hemisphere

Apus is a small constellation in the southern sky. It represents a bird-of-paradise, and its name means "without feet" in Greek because the bird-of-paradise was once wrongly believed to lack feet. First depicted on a celestial globe by Petrus Plancius in 1598, it was charted on a star atlas by Johann Bayer in his 1603 Uranometria. The French explorer and astronomer Nicolas Louis de Lacaille charted and gave the brighter stars their Bayer designations in 1756.

<span class="mw-page-title-main">Carina (constellation)</span> Constellation in the southern celestial hemisphere

Carina is a constellation in the southern sky. Its name is Latin for the keel of a ship, and it was the southern foundation of the larger constellation of Argo Navis until it was divided into three pieces, the other two being Puppis, and Vela.

<span class="mw-page-title-main">Fornax</span> Constellation in the southern celestial hemisphere

Fornax is a constellation in the southern celestial hemisphere, partly ringed by the celestial river Eridanus. Its name is Latin for furnace. It was named by French astronomer Nicolas Louis de Lacaille in 1756. Fornax is one of the 88 modern constellations.

<span class="mw-page-title-main">Hydrus</span> Constellation in the southern celestial hemisphere

Hydrus is a small constellation in the deep southern sky. It was one of twelve constellations created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman and it first appeared on a 35-cm (14 in) diameter celestial globe published in late 1597 in Amsterdam by Plancius and Jodocus Hondius. The first depiction of this constellation in a celestial atlas was in Johann Bayer's Uranometria of 1603. The French explorer and astronomer Nicolas Louis de Lacaille charted the brighter stars and gave their Bayer designations in 1756. Its name means "male water snake", as opposed to Hydra, a much larger constellation that represents a female water snake. It remains below the horizon for most Northern Hemisphere observers.

<span class="mw-page-title-main">Microscopium</span> Minor constellation in the southern celestial hemisphere

Microscopium is a minor constellation in the southern celestial hemisphere, one of twelve created in the 18th century by French astronomer Nicolas-Louis de Lacaille and one of several depicting scientific instruments. The name is a Latinised form of the Greek word for microscope. Its stars are faint and hardly visible from most of the non-tropical Northern Hemisphere.

<span class="mw-page-title-main">Pyxis</span> Constellation in the southern celestial hemisphere

Pyxis is a small and faint constellation in the southern sky. Abbreviated from Pyxis Nautica, its name is Latin for a mariner's compass. Pyxis was introduced by Nicolas-Louis de Lacaille in the 18th century, and is counted among the 88 modern constellations.

<span class="mw-page-title-main">Puppis</span> Constellation in the southern celestial hemisphere

Puppis ("stern") is a constellation in the southern sky. It was originally part of the traditional constellation of Argo Navis, which was divided into three parts, the other two being Carina, and Vela. Puppis is the largest of the three constellations in square degrees. It is one of the 88 modern constellations recognized by the International Astronomical Union.

<span class="mw-page-title-main">Piscis Austrinus</span> Constellation in the southern celestial hemisphere

Piscis Austrinus is a constellation in the southern celestial hemisphere. The name is Latin for "the southern fish", in contrast with the larger constellation Pisces, which represents a pair of fish. Before the 20th century, it was also known as Piscis Notius. Piscis Austrinus was one of the 48 constellations listed by the 2nd-century astronomer Ptolemy, and it remains one of the 88 modern constellations. The stars of the modern constellation Grus once formed the "tail" of Piscis Austrinus. In 1597, Petrus Plancius carved out a separate constellation and named it after the crane.

<span class="mw-page-title-main">Sextans</span> Constellation on the celestial equator

Sextans is a faint, minor constellation on the celestial equator which was introduced in 1687 by Polish astronomer Johannes Hevelius. Its name is Latin for the astronomical sextant, an instrument that Hevelius made frequent use of in his observations.

<span class="mw-page-title-main">Tucana</span> Constellation in the southern celestial hemisphere

Tucana is a constellation in the southern sky, named after the toucan, a South American bird. It is one of twelve constellations conceived in the late sixteenth century by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman. Tucana first appeared on a 35-centimetre-diameter (14 in) celestial globe published in 1598 in Amsterdam by Plancius and Jodocus Hondius and was depicted in Johann Bayer's star atlas Uranometria of 1603. French explorer and astronomer Nicolas Louis de Lacaille gave its stars Bayer designations in 1756. The constellations Tucana, Grus, Phoenix and Pavo are collectively known as the "Southern Birds".

<span class="mw-page-title-main">Triangulum Australe</span> Constellation in the southern celestial hemisphere

Triangulum Australe is a small constellation in the far Southern Celestial Hemisphere. Its name is Latin for "the southern triangle", which distinguishes it from Triangulum in the northern sky and is derived from the acute, almost equilateral pattern of its three brightest stars. It was first depicted on a celestial globe as Triangulus Antarcticus by Petrus Plancius in 1589, and later with more accuracy and its current name by Johann Bayer in his 1603 Uranometria. The French explorer and astronomer Nicolas Louis de Lacaille charted and gave the brighter stars their Bayer designations in 1756.

<span class="mw-page-title-main">Celestial pole</span> Imaginary sky rotation points

The north and south celestial poles are the two points in the sky where Earth's axis of rotation, indefinitely extended, intersects the celestial sphere. The north and south celestial poles appear permanently directly overhead to observers at Earth's North Pole and South Pole, respectively. As Earth spins on its axis, the two celestial poles remain fixed in the sky, and all other celestial points appear to rotate around them, completing one circuit per day.

<span class="mw-page-title-main">Sculptor (constellation)</span> Constellation in the southern celestial hemisphere

Sculptor is a faint constellation in the southern sky. It represents a sculptor. It was introduced by Nicolas Louis de Lacaille in the 18th century. He originally named it Apparatus Sculptoris, but the name was later shortened.

<span class="mw-page-title-main">Volans</span> Constellation in the southern celestial hemisphere

Volans is a constellation in the southern sky. It represents a flying fish; its name is a shortened form of its original name, Piscis Volans. Volans was one of twelve constellations created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman and it first appeared on a 35-cm (14") diameter celestial globe published in 1597 in Amsterdam by Plancius with Jodocus Hondius. The first depiction of this constellation in a celestial atlas was in Johann Bayer's Uranometria of 1603.

<span class="mw-page-title-main">Musca</span> Constellation in the southern celestial hemisphere

Musca is a small constellation in the deep southern sky. It was one of 12 constellations created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman, and it first appeared on a celestial globe 35 cm (14 in) in diameter published in 1597 in Amsterdam by Plancius and Jodocus Hondius. The first depiction of this constellation in a celestial atlas was in Johann Bayer's Uranometria of 1603. It was also known as Apis for 200 years. Musca remains below the horizon for most Northern Hemisphere observers.

<span class="mw-page-title-main">Horologium (constellation)</span> Constellation in the southern celestial hemisphere

Horologium is a constellation of six stars faintly visible in the southern celestial hemisphere. It was first described by the French astronomer Nicolas-Louis de Lacaille in 1756 and visualized by him as a clock with a pendulum and a second hand. In 1922 the constellation was redefined by the International Astronomical Union (IAU) as a region of the celestial sphere containing Lacaille's stars, and has since been an IAU designated constellation. Horologium's associated region is wholly visible to observers south of 23°N.

<span class="mw-page-title-main">Sigma Octantis</span> Star in the constellation Octans

Sigma Octantis is a solitary star in the Octans constellation that forms the pole star of the Southern Hemisphere. Its name is also written as σ Octantis, abbreviated as Sigma Oct or σ Oct, and it is officially named Polaris Australis. The star is positioned one degree away from the southern celestial pole of the Southern Hemisphere, lying in nearly opposite direction to the North Star on the celestial sphere.

<span class="mw-page-title-main">Alpha Octantis</span> Binary star system in the constellation Octans

Alpha Octantis is a binary star system in the constellation of Octans. The name is Latinized from α Octantis. Despite being labeled the "alpha" star by Lacaille, it is not the brightest star in the constellation—that title belongs to Nu Octantis. It is visible to the naked eye as a faint, yellow-white-hued point of light with an overall apparent visual magnitude of approximately 5.13. The system is located approximately 148 light-years away from the Sun based on parallax.

References

Citations
  1. 1 2 3 "Octans, Constellation Boundary". The Constellations. International Astronomical Union. Retrieved 10 Mar 2023.
  2. 1 2 Wagman, Morton (2003). Lost Stars: Lost, Missing and Troublesome Stars from the Catalogues of Johannes Bayer, Nicholas Louis de Lacaille, John Flamsteed, and Sundry Others. Blacksburg, Virginia: The McDonald & Woodward Publishing Company. pp. 6–7. ISBN   978-0-939923-78-6.
  3. Staal 1988, p. 257.
  4. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics . 616. A1. arXiv: 1804.09365 . Bibcode: 2018A&A...616A...1G . doi: 10.1051/0004-6361/201833051 . Gaia DR2 record for this source at VizieR .
  5. Staal 1988, p. 258.
  6. Cooper, Tim (2003). "Presidential address: Amateur Observations – Successes and Opportunities". Monthly Notes of the Astronomical Society of Southern Africa. 62: 234–240. Bibcode:2003MNSSA..62..234C.
References