Lacerta (“the lizard”) is a small, faint constellation of the northern skies that was created by Polish astronomer Johannes Hevelius in 1687. Its brightest star is Alpha Lacertae, a blue dwarf situated 102 light years from Earth with an apparent visual magnitude of just +3.77.
Lacerta is the 68th biggest constellation, taking up an area of 201 square degrees of the northern celestial hemisphere. It can be seen by observers located between +90° and -40° of latitude, although best viewed during the month of October. The constellation forms a small W shape, earning it the nickname “Little Cassiopeia”, and can be found nestled between Cygnus and Andromeda, with Cepheus and Cassiopeia to its north, and Perseus to its south.
Perseus Constellation Family
Lacerta is a member of the Perseus family of constellations, together with Andromeda, Auriga, Cassiopeia, Cepheus, Cetus, Pegasus, Perseus and Triangulum.
– Alpha Lacertae, the constellation’s brightest star, is a blue dwarf (A1 V) that is located 102 light years away with a visual magnitude of 3.77. This 400 million year old star has twice the size and mass as the Sun, with 27 times its brightness. Alpha Lacertae also has an optical companion located around 2,700 light years distant with an apparent magnitude of 11.8.
– 1 Lacertae, the second brightest star in Lacerta, is an orange giant (K3II-III) situated 627 light years from our solar system that shines with an apparent magnitude of 4.15. It is 53 times bigger than the Sun, and can be found at the southern tip of the constellation near Pegasus.
– 5 Lacertae, the constellation’s third brightest star, is a red giant (B-V) found 1,164 light years from Earth with a visual magnitude of 4.34. It is around 118 times bigger than our sun, and is also a slow irregular variable.
Other stars of interest in Lacerta includes the blue-white dwarf 2 Lacertae; the blue-white supergiant 4 Lacertae; the yellow giant Beta Lacertae of magnitude 4.40; the red dwarf EV Lacertae; and the multiple star system Roe 47.
Notable Deep-Sky Objects
Lacerta lies in the direction of the Milky Way, and while it has no Messier objects, it does contain several open clusters, as well as a variable star which turned out to be a blazing quasi-stellar object that has since spawned its own class of deep-sky object called BL Lacertae or BL Lac.
– NGC 7243 (Caldwell 16) is an open cluster that is 17 light years across and situated 2,800 light-years from the Sun. It is around 100 million years old, and as such contains mostly young blue and white stars. NGC 7243 has an apparent magnitude of 6.4, and with a 4-inch refractor the cluster is fully resolvable into two distinct groups of around 40 stars.
Other open clusters in Lacerta includes NGC 7245 consisting of around 50 stars, and NGC 7209, which has about 100 blue and white stars.
– BL Lacertae was thought to be a variable star up until 1969 when the discovery of its bright radio source saw it promoted to the realm of quasar, which are active galactic nucleus powered by supermassive black holes. In the case of BL Lacertae objects, however, they are a further sub class of very compact quasars, known as blazar, whose jets of high-energy photons emitted are pointed almost straight at the Earth. The actual object BL Lacertae in the constellation of Lacerta lies 900 million light years distant with an apparent magnitude of between 14 and 17.