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Man must rise above the Earth, to the top of the atmosphere and beyond, for only then will he fully understand the world in which he lives.
Socrates, 469 - 399 BC

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SEXTANS

The Sextant

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Sextans - Celestial Atlas by Alexander Jamieson - 1822

Sextans is one of the seven constellations contributed by the great seventeenth century Polish astronomer, Johannes Hevelius. At a time when the first telescopes were crude and unreliable, the astronomer's most important tool was the "Sextans Uraniae", the astronomical sextant. It was essential for measuring the precise positions of celestial objects, a critical task for sailors of the day as well, and no ship left port without one. So when Hevelius saw the familiar shape of a sextant's curved triangle up there in the stars, it was only proper for him to pay homage to it.

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Plath Sextant - NOAA Photo Library - circa 1890

Sextans may very well be the faintest constellation in the sky. At first glance there doesn't seem to be anything there at all. But if the night is dark enough, and your pupils are sufficiently dilated, and you look carefully enough, you will eventually see what Hevelius saw: the very faint outline of a large triangle with a curved base - the undeniable shape of the classic sextant. And you will have a renewed appreciation for the man known as "the last of the great naked eye astronomers."

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Sextans - April 15 - 10:00 PM - Latitude 40° North, Longitude 95° West





Stars of Sextans

Alpha Sextantis (RA: 10h07m56.272s DE:-0022'18.10")

There are no named stars in Sextans, and Alpha Sextanius, with a magnitude of only 4.49, is the brightest. Located 283 light years away, just below the Celestial Equator, it is a B9III blue/white giant.

Beta Sextantis (RA: 10h30m17.441s DE:-0038'13.65")

At one end of the sextant's curved base is Beta Sextanius, taking us down to magnitude 5.08, making it visible only on a good dark night. At a distance of 402 light years, it is a B5V blue main sequence star.

Gamma Sextantis (RA: 09h52m30.379s DE:-0806'18.70")

At the other end of the sextant's curved base is Gamma Sextanius, another dim star at magnitude 5.07. It is a binary system of two A1 blue/white main sequence stars, with a third distant, faint companion, all located about 276 light years away.

Planets of Sextans

So far seven planets have been discovered in Sextans orbiting five stars. Unfortunately these stars are all beyond naked eye visibility, and the planets are all very large gas giants. For more information on these and other extrasolar planets, visit NASA's New Worlds Atlas, and The Open Exoplanets Catalogue.


Deep Skies of Sextans

COSMOS

Although the lack of bright objects in Sextans is frustrating for small telescope owners, it provides an opportunity for the largest telescopes to peer out into intergalactic space with a minimum of interfering light from nearby stars. And since Sextans also sits squarely on the Celestial Equator, making it accessible to telescopes world wide, it was chosen for the site of one of the most extensive deep field surveys ever conducted. The project was COSMOS: The Cosmic Evolution Survey, a study started in 2003 in which virtually all the large telescopes on Earth and in Space went to work analysing a two degree square of space in all electromagnetic wavelengths from X-rays to radio waves.

The ESO telescopes in the Andean mountain tops of Chile captured a 55 hour time exposure of the COSMOS field in the infrared spectrum. Below is a sampling of the 200,000 galaxies they discovered.

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COSMOS Survey Area - European Southern Observatory - March, 2012

Dark Matter

The COSMOS survey area was large enough, and the data sufficient enough for the Hubble Telescope team to put together the first detailed 3D map of some of the mysterious, invisible dark matter that composes 80 percent of the mass of the Universe, and provides the cosmological framework for the atoms of "normal matter" to cling to, and form galaxies.

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Dark Matter in COSMOS Survey Area - Hubble Space Telescope - January, 2007

NGC 3115 (RA: 10h05m 12.0s DE:-0743'00")

Outside the COSMOS survey area is the spiral galaxy NGC 3115, one of two galaxies known as the Spindle Galaxy. It is a bright lenticular galaxy seen almost edge on, with a magnitude of 8.9, located about 32 million light years away. At the centre of the galaxy is a supermassive black hole, approximately one billion times as massive as our Sun.

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NGC 3115 - Chandra X-Ray Telescope - July, 2011

NGC 3165, 3166, 3169 (RA: 10h13m 30.0s DE:+0322'00")

At a distance of about 70 million light years are three interacting galaxies: NGC 3165 (bottom right corner of image), NGC 3166 (right centre), and NGC 3169 (left centre). Thought to be separated by only about 50,000 light years, the intense gravity wells of these galaxies are starting to distort each others spiral structure, leading to their inevitable merger in the future. The grouping is faint, at magnitude 13.9.

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NGC 3165, 3166, 3169 - Interacting Spiral Galaxies - European Southern Observatory - April, 2011







Winter: Orion   Canis Major   Canis Minor   Monoceros   Lepus   Eridanus   Taurus   Auriga   Camelopardalis   Lynx   Gemini   Cancer  
Spring: Hydra   Sextans   Crater   Corvus   Leo   Leo Minor   Ursa Major   Ursa Minor   Canes Venatici   Coma Berenices   Virgo   Bootes  
Summer: Draco   Corona Borealis   Hercules   Ophiuchus   Serpens   Libra   Scorpius   Sagittarius   Scutum   Aquila   Sagitta   Vulpecula   Lyra   Cygnus  
Autumn: Andromeda   Perseus   Pegasus   Cassiopeia   Cepheus   Cetus   Lacerta   Delphinus   Equuleus   Capricornus   Aquarius   Pisces   Aries   Triangulum  
Southern Skies: Centaurus   Crux   Lupus   Corona Australis   Piscis Australis   Sculptor   Tucana   Fornax   Dorado   Columba   Puppis   Carina   Vela  

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