Abbreviation Mic
Genitive Microscopii
Pronunciation , genitive
Symbolism the Microscope
Right ascension 21
Declination −36
Family La Caille
Quadrant SQ4
Area 210 sq. deg. (66th)
Main stars 5
Stars with planets 2
Stars brighter than 3.00m 0
Stars within 10.00 pc (32.62 ly) 2
Brightest star γ Mic (4.67m)
Nearest star Lacaille 8760
(12.87 ly, 3.95 pc)
Messier objects none
Meteor showers ?????
Telescopium (corner)
Piscis Austrinus
Visible at latitudes between +45° and −90°.
Best visible at 21:00 (9 p.m.) during the month of September.

Microscopium is a small constellation in the southern sky, defined in the 18th century by Nicolas Louis de Lacaille. Its brightest star is Gamma Microscopii of apparent magnitude 4.68, actually a yellow giant located around 381 light-years distant. Two star systems—WASP-7 and HD 205739—have been found to have planets, while another—AU Microscopii—has a debris disk.


Seen in the 1824 star chart set Urania's Mirror (in the lower left)

The stars that now comprise Microscopium may formerly have belonged to the hind feet of Sagittarius.[1] However, this is uncertain as, while its stars seem to be referred to by Al-Sufi as having been seen by Ptolemy, Al-Sufi does not specify their exact positions.[2]

Its name is Latin for microscope; it was invented by Lacaille to commemorate the compound microscope.[3] Its stars are very faint and hardly visible from most of the non-tropical northern hemisphere.


The constellation Microscopium as it can be seen by the naked eye.

Microscopium is a small constellation bordered by Capricornus to the north, Piscis Austrinus and Grus to the west, Sagittarius to the east, Indus to the south, and touching on Telescopium to the southeast. The recommended three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is 'Mic'.[4] The official constellation boundaries, as set by Eugène Delporte in 1930, are defined by a polygon of four segments (illustrated in infobox). In the equatorial coordinate system, the right ascension coordinates of these borders lie between 20h 27.3m and 21h 28.4m, while the declination coordinates are between −27.45° and −45.09°.[5] The whole constellation is visible to observers south of latitude 45°N.[6][1] Given that its brightest stars are of fifth magnitude, the constellation is invisible to the naked eye in areas with polluted skies.[7]

Notable features

Lacaille charted and designated ten stars with the Bayer designations Alpha through to Iota in 1756. A star in neighbouring Indus that Lacaille had labelled Nu Indi turned out to be in Microscopium, so Gould renamed it Nu Microscopii.[8] Within the constellation's borders, there are 43 stars brighter than or equal to apparent magnitude 6.5[2].[6]

The brightest star is Gamma Microscopii, which has an apparent (visual) magnitude of 4.68. It is a yellow giant of spectral type G6III.[10] Lying 381 light years away,[11] It depicts the eyepiece of the microscope.[12] Alpha Microscopii is also a yellow giant, though in this case a variable star, which ranges between apparent magnitudes 4.88 and 4.94. It is of spectral type G7III.[13] Alpha has a 10th magnitude companion, visible in small telescopes.[11] Epsilon Microscopii lies 165 light years away, and is a blue-white main sequence star of apparent magnitude 4.7,[11] and spectral type A1V.[14] Theta1 and Theta2 Microscopii make up a wide double whose components are splittable to the naked eye. Both are white A-class magnetic spectrum variable stars with strong metallic lines, similar to Cor Caroli. They mark the constellation's specimen slide.[12]

Many notable objects are too faint to be seen with the naked eye. AX Microscopii, better known as Lacaille 8760, is a red dwarf which lies only 12.9 light years from our solar system.[15] HD 205739 has a jupiter-sized planet. WASP-7 is a star of magnitude 9.54 which has been discovered to have an exoplanet WASP-7b, while AU Microscopii is a young star which appears to be a solar system in the making with a debris disk. BO Microscopii is a rapidly rotating star, and PSR J2144-3933 is an unusual pulsar with an unusually long rotation period.

NGC 6925 is a barred spiral galaxy of apparent magnitude 11.3 which is lens-shaped as it lies almost edge on to us. It lies 3.7 degrees westnorthwest of Alpha Microscopii.[16] NGC 6923 lies nearby and is a magnitude fainter still.[17]


  1. ^ While parts of the constellation technically rise above the horizon to observers between 45°N and 62°N, stars within a few degrees of the horizon are to all intents and purposes unobservable.[6]
  2. ^ Objects of magnitude 6.5 are among the faintest visible to the unaided eye in suburban-rural transition night skies.[9]


  1. ^ G. Rubie (1830) The British Celestial Atlas, p. 37 (ebook available at https://play.google.com/store/books/details?id=KDEAAAAAQAAJ&rdid=book-KDEAAAAAQAAJ&rdot=1).
  2. ^ J. Ellard Gore, Astronomical Curiosities:Facts and Fallacies (Google e-Book) (ISBN 1465524428, 9781465524423).
  3. ^ Lacaille, N. L. (1756), Mémoires de l'Académie Royale des Sciences, p.589 http://gallica.bnf.fr/ark:/12148/bpt6k35505/f787.image
  4. ^  
  5. ^ "Microscopium, constellation boundary". The Constellations (International Astronomical Union). Retrieved 13 July 2012. 
  6. ^ a b c  
  7. ^ Kambič, Bojan (2009). Viewing the Constellations with Binoculars. Springer. p. 341.  
  8. ^ 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. 181, 210.  
  9. ^ Bortle, John E. (February 2001). "The Bortle Dark-Sky Scale".  
  10. ^ Kaler, James B. (Jim). "Gamma Mic". Stars. Retrieved 13 July 2012. 
  11. ^ a b c Ridpath, Ian; Tirion, Wil (2007). Stars and Planets Guide. Princeton: Princeton University Press. pp. 184–85.  
  12. ^ a b Motz, Lloyd; Nathanson, Carol (1991). The Constellations: An Enthusiast's Guide to the Night Sky. London, United Kingdom: Aurum Press. pp. 369–70.  
  13. ^ "Alpha MicroscopiI". SIMBAD. Retrieved 15 July 2012. 
  14. ^ "Epsilon Microscopii". SIMBAD. Retrieved 15 July 2012. 
  15. ^ Croswell, Ken (July 2003). "The Brightest Red Dwarf". Sky & Telescope. p. 32. Retrieved 15 July 2012. 
  16. ^ Bakich, Michael E. (2010). 1001 Celestial Wonders to See Before You Die: The Best Sky Objects for Star Gazers. Patrick Moore's Practical Astronomy Series. Springer. p. 289.  
  17. ^ Moore, Patrick; Tirion, Wil (1997). Cambridge Guide to Stars and Planets. Cambridge, United Kingdom: Cambridge University Press. p. 210.  

External links

  • Star Tales – Microscopium