The Lacerta Constellation

Lacerta is one of the 88 modern constellations defined by the International Astronomical Union. Its name is Latin for the lizard. A small, faint constellation, it was defined in 1687 by the astronomer Johannes Hevelius. Its brightest stars form a “W” shape similar to that of Cassiopeia, and it is thus sometimes referred to as ‘Little Cassiopeia.’ Lacerta is the 68th constellation in size, occupying an area of 201 square degrees. It is located in the fourth quadrant of the northern hemisphere (NQ4) and can be seen at latitudes between +90° and -40°. The neighbouring constellations are Andromeda, Cassiopeia, Cepheus, Cygnus and Pegasus in the northern celestial sphere. The northern part lies on the Milky Way. Lacerta belongs to the Perseus family of constellations, along with Andromeda, Auriga,  Cassiopeia, Cepheus, Cetus, Pegasus, Perseus and Triangulum.

Alpha Lacertae is a blue-white hued main-sequence star of magnitude 3.8, 102 light-years from Earth. It has a spectral type of A1 V and is an optical double star. Beta Lacertae is far dimmer, a yellow giant of magnitude 4.4, 170 light-years from Earth. Roe 47 is multiple stars consisting of five components (magnitudes 5.8, 9.8, 10.1, 9.4, 9.8). EV Lacertae is a rapidly spinning magnitude 10 red dwarf with a strong magnetic field. It is a flare star that can emit powerful flares, thousands of times more energetic than any from Earth’s sun. ADS 16402 is a binary star system in Lacerta, around which a planet orbits with some unusual properties. The Jupiter-sized planet exhibits an unexpectedly low density, about the same as cork. This planet is dubbed HAT P-1.

Lacerta is typical of Milky Way constellations: no bright galaxies, nor globular clusters, but instead open clusters, for example, NGC 7243, the faint planetary nebula IC 5217 and quite a few double stars. It also contains the prototypic blazar BL Lacertae. Lacerta contains no Messier objects. NGC 7243 is an open cluster 2500 light-years from Earth. It has a few dozens “scattered” stars, the brightest of which are of the 8th magnitude. IC 5217 was discovered in 1904 by Williamina Fleming of Harvard College Observatory. It was nearly 100 years later before planet’s bipolar structure was confirmed: it has a very bright equatorial ring and open bipolar lobes. IC 5217 is located pretty much on a straight line midway between the stars 4 and Beta Lacertae. Like any other bright 11th magnitude star, a slight green tinge might be detectable. The central star at a magnitude of 15.5 is difficult, if not impossible to observe visually, due to the high surface brightness of the planetary nebula overwhelming the faint central star. BL Lacertae is the prototype of the BL Lacertae objects, which appear to be dim variable stars but are actually the variable nuclei of elliptical galaxies; they are similar to quasars. It lent its name to a whole type of celestial objects, the BL Lacertae objects (a subtype of blazar). The object varies irregularly between magnitudes 14 and 17 over a few days. Credits: Constellation Guide, Deep Sky Forum, Wikipedia.