Sextans the Sextant

Constellation Sextans the Sextant

Sextans the Sextant  is a small faint constellation south of Leo visible in the Northern Sky in  Autumn.  Sextans was formed by the Polish astronomer Johannes Hevelius in the 17 the century, to  honour the observatory instrument he used to measure star positions. (Not to be mistaken for the nautical sextant invented by Hadley in 1730).

The three brightest stars are faint from magnitude 4.5 to 5.

Alpha Sextantis: Located approximately 12°59’ south of Regulus in Leo, is the brightest star at mag. 4.5. A blue giant, 287 l.y. away.

Beta Sextanis: mag. 5.1 blue-white star 345 l.y. away.

Gamma Sextanis: mag. 5.1 is a difficult binary discovered in 1854 by Alvan Clark with 12 cm aperture. The companions were closest in 1960 and had maximum separation in 1994 when they could be separated with 25 cm aperture.

35 Sextans  (RA 10h 43.3 Dec +04° 45) is an orange tinted binary of magnitude 6.3 and 7.4 with 6.8 arc minutes of separation. These can be separated with a small telescope.

NGC 3115 “The Spindle Galaxy” (RA 10h o5m 14s, Dec. –7° 43’ 09”). A magnitude 9.2 edge-on lenticular galaxy (a type of galaxy which falls between spiral and elliptical types. They have the flattened form of spirals without the arms, and appear lens shaped.), 14million ly away. It has high surface brightness allowing the central region to be visible with a 7.5 cm telescope and with 15 cm the bright  elongated spindle shape should be visible.

NGC 3166/3169 (RA 10h 13m 48s, Dec +03 °26’00”) A pair of magnitude 10, edge on spiral galaxies approximately 5.20’ in size, 60 million l.y. distant and 8 arc minutes apart. Both galaxies should be visible in the same field of view with a 15 cm telescope.

Sources: Malin, D. & Frew D., 1995, Hartung’s Astronomical Objects for Southern Telescopes, 2nd edn, Melbourne University Press, Burwood. Burnham, R., 1966, Burnham’s Celestial Handbook,Volume 3, Dover Publications, New York. Ridpath, I. & Tirion, W., 2000, Collins Stars and Planets, 3rd edn., Harper Collins Publishers, London. Massey, S. & Quirk, S., 2007, Atlas of the Southern Night Sky, New Holland Publishers, Sydney. Woodruff, J. & Ridpath, I., 1999, Philip’s Astronomy Dictionary, George Philip Ltd., London. SKYlab Astronomy Software, 2005, Star Atlas Pro Version 6.2, Wallsend. Photos from Digital Sky Survey