Stars French astronomer
Nicolas-Louis de 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.
Francis Baily considered Gamma and Epsilon Microscopii to belong to the neighbouring constellation Piscis Austrinus, but subsequent cartographers did not follow this. In his 1725
Catalogus Britannicus, John Flamsteed labelled the stars 1, 2, 3 and 4 Piscis Austrini, which became Gamma Microscopii,
HR 8076,
HR 8110 and Epsilon Microscopii respectively. Within the constellation's borders, there are 43 stars brighter than or equal to
apparent magnitude 6.5. which—at magnitude of 4.68—is the brightest star in the constellation. Having spent much of its 620-million-year lifespan as a blue-white
main sequence star, it has swollen and cooled to become a yellow
giant of
spectral type G6III, with a diameter ten times that of the Sun. Measurement of its parallax yields a distance of 223 ± 8 light years from Earth. It likely passed within 1.14 and 3.45 light-years of the Sun some 3.9 million years ago, at around 2.5 times the mass of the Sun, it is possibly massive enough and close enough to disturb the
Oort cloud.
Alpha Microscopii is also an ageing yellow giant star of spectral type G7III with an apparent magnitude of 4.90. Located 400 ± 30 light-years away from Earth, it has swollen to 17.5 times the diameter of the Sun. Alpha has a 10th magnitude companion, visible in 7.5 cm telescopes, though this is a coincidental closeness rather than a true binary system. and is a white star of apparent magnitude 4.7,
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.
BO Microscopii is a rapidly rotating star that has 80% the diameter of the Sun. Nicknamed "Speedy Mic", it has a rotation period of 9 hours 7 minutes. An active star, it has prominent
stellar flares that average 100 times stronger than those of the Sun, and are emitting energy mainly in the X-ray and ultraviolet bands of the spectrum. It lies 218 ± 4 light-years away from the Sun.
AT Microscopii is a binary star system, both members of which are flare star red dwarfs. The system lies close to and may form a very wide triple system with
AU Microscopii, a young star which has a
planetary system in the making with a
debris disk. The three stars are candidate members of the
Beta Pictoris moving group, one of the nearest
associations of stars that share a common motion through space. The
Astronomical Society of Southern Africa in 2003 reported that observations of four of the
Mira variables in Microscopium were very urgently needed as data on their light curves was incomplete. Two of them—
R and
S Microscopii—are challenging stars for novice amateur astronomers, and the other two,
U and
RY Microscopii, are more difficult still. Of apparent magnitude 11,
DD Microscopii is a
symbiotic star system composed of an orange giant of spectral type K2III and
white dwarf in close orbit, with the smaller star ionizing the stellar wind of the larger star. The system has a low
metallicity. Combined with its high galactic latitude, this indicates that the star system has its origin in the
galactic halo of the
Milky Way.
HD 205739 is a yellow-white main sequence star of spectral type F7V that is around 1.22 times as massive and 2.3 times as luminous as the Sun. It has a Jupiter-sized planet with an orbital period of 280 days that was discovered by the
radial velocity method.
WASP-7 is a star of spectral type F5V with an apparent magnitude of 9.54, about 1.28 times as massive as the Sun. Its
hot Jupiter planet—
WASP-7b—was discovered by
transit method and found to orbit the star every 4.95 days.
HD 202628 is a sunlike star of spectral type G2V with a debris disk that ranges from 158 to 220 AU distant. Its inner edge is sharply defined, indicating a probable planet orbiting between 86 and 158 AU from the star.
Deep-sky objects taken by Hubble. Describing Microscopium as "totally unremarkable", astronomer
Patrick Moore concluded there was nothing of interest for amateur observers.
NGC 6925 is a
barred spiral galaxy of apparent magnitude 11.3 which is lens-shaped, as it lies almost edge-on to observers on Earth, 3.7 degrees west-northwest of Alpha Microscopii.
SN 2011ei, a
Type II Supernova in NGC 6925, was discovered by Stu Parker in New Zealand in July 2011.
NGC 6923 lies nearby and is a magnitude fainter still. The
Microscopium Void is a roughly rectangular region of relatively empty space, bounded by incomplete sheets of galaxies from other voids. The
Microscopium Supercluster is an overdensity of galaxy clusters that was first noticed in the early 1990s. The component Abell clusters
3695 and
3696 are likely to be gravitationally bound, while the relations of Abell clusters
3693 and
3705 in the same field are unclear.
Meteor showers '' (in the lower left) The
Microscopids are a minor
meteor shower that appear from June to mid-July. ==History==