Star Constellation Facts: Microscopium

Microscopium Constellation
Image Credit: IAU and Sky&Telescope magazine

Microscopium (“microscope”) is a small southern hemisphere constellation that was created by French astronomer Nicolas Louis de Lacaille in the 1750s after visiting South Africa. Its brightest star, Gamma Microscopii, is a yellow giant situated 229 light years from Earth with a visual magnitude of just +4.68. There is one minor meteor showers associated with the constellation, namely the Microscopids that occur from June to mid-July, with no discernible activity peak yet discovered.


Microscopium is the 66th largest constellation, taking up an area of 210 square degrees of the southern celestial hemisphere. It can be seen by observers located between +45° and -90° of latitude, although best seen from July to September. Bordering Microscopium is Sagittarius to its east, Piscis Austrinus and Grus to its west, Capricornus to its north, and Indus to its south.

Lacaille Constellation Family

Microscopium belongs to the Lacaille family of constellations, along with Antlia, Caelum, Circinus, Fornax, Horologium, Mensa, Norma, Octans, Pictor, Reticulum, Sculptor and Telescopium.


In the late 16th century, Dutch astronomer Petrus Plancius created 12 new southern sky constellations, while in the mid-18th century French astronomer Nicolas-Louis de Lacaille added a further 14 new constellations to the list of 32 southern sky constellations, including Microscopium. He created it to honor the compound microscope, or one that employs more than a single lens, and imagined the constellation as “a tube above a square box”.

Principal Stars

Image Credit: Torsten Bronger

– Gamma Microscopii, the constellation’s brightest star, is a yellow giant (G6 III) found 229 light years from our solar system with an apparent visual magnitude of 4.68. It is around 10 times bigger than the Sun, with 2.5 times its mass, and 64 times its luminosity. Gamma Microscopii has a visual line of sight companion called CCDM J21013-3215B, which has an apparent magnitude of 13.7

– Epsilon Microscopii, the second brightest star in Microscopium, is a white dwarf (A1V) situated 165 light years away that shines with a visual magnitude of 4.72. It has around twice the Sun’s size and mass, but with 35.62 times its luminosity. Epsilon Microscopii also has a rotational velocity of 127 km/s, compared to 1.9 km/s for our sun.

– Theta Microscopii, the constellation’s third brightest star, is a wide double star system with an overall visual magnitude of 4.81. Its brightest component, Theta-1 Microscopii, is a bluish-white variable star situated 197 light years away whose luminosity ranges from 4.77 to 4.87 over a 2.125 day period. The second component, Theta-2 Microscopii, is a white giant (A0III) found 390 light years from Earth apparent with a visual magnitude of 5.76.

Other stars of interest in Microscopium includes Alpha Microscopii, a yellow giant (G7III) variable star 380 light years distant of magnitude 4.88 to 4.94; Lacaille 8760, a flare star found a mere 12.87 light years from the Sun of magnitude 6.67; WASP-7, a yellow-white dwarf (F5V) with an extrasolar planet called WASP-7b; and the red dwarf variable star AU Microscopii, a 32.3 light years distant with a luminosity just 9% that of the Sun.

Notable Deep-Sky Objects

There are no Messier objects in Microscopium, and just a few notable deep-sky objects.

– Microscopium Supercluster is a large group of galaxies that was discovered in he early 1990s. Amongst the members of this little studied supercluster is Abell 3695 and 3696, while its relationship with Abell clusters 3693 and 3705 has yet to be determined.

– NGC 6925 is an unbarred spiral galaxy located 99,000 light years away with a visual magnitude of 11.3. It can be found west-northwest of the star Alpha Microscopii, and appears as a large elongated lens-shape on account of it lying almost edge to Earth. In July 2011 a supernova explosion, SN 2011ei, was observed in NGC 6925.

Other objects of interest in Microscopium includes the spiral galaxies NGC 6923, NGC 6958, and IC 5105; and the Microscopium Void, a vast area of spaces defined by its low average density of matter, and an absence of galaxies and clusters.

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