Mensa (constellation)

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Abbreviation Men
Genitive Mensae
Pronunciation /ˈmɛnsə/
genitive: /ˈmɛns/
Symbolism the Table Mountain
Right ascension 4 ~ 7.5
Declination −71 ~ −85.5
Family La Caille
Quadrant SQ1
Area 153 sq. deg. (75th)
Main stars 4
Stars with planets 2
Stars brighter than 3.00m none
Stars within 10.00 pc (32.62 ly) none
Brightest star α Men (5.09m)
Nearest star α Mensae
(33.10 ly, 10.15 pc)
Messier objects none
Meteor showers none
Visible at latitudes between +4° and −90°.
Best visible at 21:00 (9 p.m.) during the month of January.
The constellation Mensa as it can be seen by the naked eye.

Mensa is a constellation in the southern sky, created in the 18th century. Its name is Latin for table. It covers a keystone-shaped wedge of sky stretching from approximately 4h to 7.5h of right ascension, and −71 to −85.5 degrees of declination. Other than the south polar constellation of Octans, it is the most southerly of constellations. As a result, it is essentially unobservable from the Northern Hemisphere. Besides those already mentioned, its other neighbouring constellations are Chamaeleon, Dorado, Hydrus, and Volans.[citation needed]


Initially known as Mons Mensae, Mensa was created by Nicolas Louis de Lacaille out of dim Southern Hemisphere stars in honor of Table Mountain, a South African mountain overlooking Cape Town. He recalled that the Magellanic clouds were sometimes known as Cape clouds, and that Table Mountain was often covered in cloud when a southeasterly stormy wind blew. Hence he made a "table" in the sky under the clouds.[1] Although the stars of Mensa do not feature in any ancient mythology, the mountain it is named after has a rich mythology. Called "Tafelberg" in Dutch and German, the mesa has two neighboring mountains called "Devil's Peak" and "Lion's Head". Table Mountain features in the mythology of the Cape of Good Hope, notorious for its storms—the explorer Bartolomeu Dias saw the mesa as a mythical anvil for storms. Another myth relating to its dangers comes from Sinbad the Sailor, an Arabic folk hero who saw the mountain as a magnet pulling his ships to the bottom of the sea.[2]

Notable features[edit]


Lacaille labelled eleven stars with Bayer designations Alpha through to Lambda (excluding Kappa). Gould later added Kappa, Mu, Nu, Xi and Pi Mensae. Stars as dim as these were not generally given designations; however, Gould felt their closeness to the South Celestial Pole warranted naming.[1] Mensa contains no bright stars, with Alpha Mensae its brightest star with a barely visible apparent magnitude of 5.09,[3] making it the faintest constellation in the entire sky. Alpha Mensae is a solar-type star (class G7V) around 33 light-years from Earth.[4] An infrared excess has been detected around this star, most likely indicating the presence of a circumstellar disk at a radius of over 147 AU. The temperature of this dust is below 22 K.[5] No planetary companions have yet been discovered around it. It has a red dwarf companion star at an angular separation of 3.05 arcseconds; equivalent to a projected separation of roughly 30 AU.[3] [6] [7] Pi Mensae, on the other hand, while also solar-type (G1) and at 59 light-years, has been found to have a large gas giant in an eccentric orbit crossing the habitable zone, which would effectively rule out the existence of any habitable planets.[citation needed]

Deep-sky objects[edit]

Mensa contains part of the Large Magellanic Cloud (the rest being in Dorado).[citation needed]

The first images taken by the Chandra X-Ray Observatory were of PKS 0637-752, a quasar in Mensa with a large gas jet visible in both optical and x-ray wavelengths. [8]


  1. ^ a b 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, VA: The McDonald & Woodward Publishing Company. pp. 207–08. ISBN 978-0-939923-78-6. 
  2. ^ Staal 1988, p. 259.
  3. ^ a b "LTT 2490 -- High proper-motion star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2010-09-11. 
  4. ^ van Leeuwen, F. (2007). "Validation of the New Hipparcos Reduction". Astronomy and Astrophysics 474 (2): 653–64. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. 
  5. ^ Eiroa, C.; et al. (July 2013). "DUst around NEarby Stars. The survey observational results". Astronomy & Astrophysics 555: A11. arXiv:1305.0155. Bibcode:2013A&A...555A..11E. doi:10.1051/0004-6361/201321050. 
  6. ^ Eggenberger, A.; et al. (2007). "The impact of stellar duplicity on planet occurrence and properties. I. Observational results of a VLT/NACO search for stellar companions to 130 nearby stars with and without planets". Astronomy and Astrophysics 474 (1): 273–291. Bibcode:2007A&A...474..273E. doi:10.1051/0004-6361:20077447. 
  7. ^ "HD 43834B -- Star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2010-03-26.  (details on the stellar properties of the companion star)
  8. ^ "Chandra Discovery of a 100 kiloparsec X-Ray Jet in PKS 0637-752"
  • Ridpath, Ian; Tirion, Wil (2007), Stars and Planets Guide, Princeton University Press, ISBN 978-0-691-13556-4 
  • Staal, Julius D.W. (1988), The New Patterns in the Sky: Myths and Legends of the Stars, The McDonald and Woodward Publishing Company, ISBN 0-939923-04-1 

External links[edit]

Coordinates: Sky map 05h 00m 00s, −80° 00′ 00″