Lacerta

Lacerta (genitive Lacertae), the lizard, is one of the 88 constellations recognized by the International Astronomical Union. It is located about 20 degrees east of Deneb (α Cygni). The lizard's body goes in a north-south direction. It was recorded in Hevelius's atlas in 1690.

Observation

Its shape is quite small, but its constituent stars are faint. Therefore, it is necessary to have good visibility conditions to discover it.

• The constellation is south of Cygni's Casiopea-Deneb axis.
• The constellation is in the prolongation of the Andromeda chain, and the limit between these two groups is not very easy to establish.

Notable features

Constellation of Lacerta

Only one star in the constellation, α Lacertae, has visual magnitude less than 4. This is a white main-sequence star of type A1V, significantly hotter than the Sun, as its surface temperature is 9050 K. It is almost identical to Sirius, but it is twelve times farther than it, since α Lacertae is 102 light years away.

The second brightest star in Lacerta has no Bayer designation. Known by its name of Flamsteed, 1 Lacertae is a distant orange giant of type K3 with a luminosity 1453 times greater than the solar luminosity, for which reason it is also classified as a possible luminous giant. It has a radius 69 times greater than that of the Sun.

Next in brightness is 5 Lacertae, a spectroscopic binary with a long period —41.95 years— that has been resolved by speckle interferometry. The system is composed of a cool red giant of spectral type K9Ia and a hot main sequence star of type B2V. For its part, β Lacertae is a yellow giant of spectral type G9III with an effective temperature of 4710 K.

Among the constellation's variables is EW Lacertae, one of the most complex and most observed Be stars. Spectral type B3IIIpe, it is an eruptive variable of the Gamma Cassiopeiae type that experiences mass loss from its equatorial zone, as a consequence of its very high rotation speed. Another variable of interest is GL Lacertae, also called Babcock's Star, an A0p-type star that has the largest known stellar magnetic field (34,000 gauss). Very different is EV Lacertae, a red dwarf at 16.5 light years and one of the most studied flare stars, since it is extraordinarily active. In 2008, NASA astronomers detected through the Swift satellite an enormous flare on this star; said flare was thousands of times more powerful than the largest observed so far on the Sun.

In Lacerta you can see the open clusters NGC 7209 and NGC 7243. The former consists of about 150 stars, including the eclipsing binary SS Lacertae. The second is a young cluster—approximately 250 million years old—located 2,230 light-years from Earth.

IC 5217 is a double-layered planetary nebula, symmetric about a single point with a very narrow waist; consists of a bright equatorial ring and open bipolar lobes. IRAS 22272+5435 is a planetary protonebula, one of the coldest within its class, associated with the supergiant of type G5 V354 Lacertae; it has excess carbon and s-process elements in its atmosphere.

On the other hand, BL Lacertae is the prototype of BL Lacertae objects, which are variable nuclei of quasar-like elliptical galaxies. They are characterized by rapid and large-amplitude variability, as well as significant optical polarization. Due to these properties, BL Lacertae was originally classified as a variable star.

Main Stars

Artistic impression of the enormous call that took place in 2008 in EV Lacertae.

• α Lacertae, the brightest star of magnitude +3.8 and white, 102 light years away.
• β Lacertae, at the top of the lizard, only the fourth brightest star, of magnitude 4.4 and yellow-orange color.
• 1 Lacertae, at the lower end of the figure, the second brightest star with magnitude 4,1.
• 2 Lacertae, rotating ellipsoidal variable of magnitude 4,55.
• 5 Lacertae (V412 Lacertae), a distant star system composed of a red giant and a hot star. Of magnitude 4,34 is the third brightest star of the constellation.
• 9 Lacertae, a white subject of magnitude 4,65.
• 10 Lacertae, of magnitude 4,88, blue star 26 800 times brighter than the Sun that is about 1000 light years.
• 12 Lacertae (DD Lacertae), variable star Beta Cephei of average magnitude 5.25.
• Z Lacertae and RR Lacertae, both strained variables; the brightness of the first varies between +7.88 and +8.93 over a period of 10,8856 days.
• RW Lacertae, an eclipsing binary formed by two stars similar to the Sun.
• AR Lacertae, of magnitude 6,09, is one of the most brilliant RS Canum Venaticorum variables in the sky.
• CM Lacertae, binaria eclipsante of magnitude 8,18.
• EV Lacertae, red dwarf and shining star at 16.5 light years of the solar system.
• EW Lacertae, one of the most complex and best studied Be stars, located about 1100 light years.
• Babcock Star (GL Lacertae), star with the best known magnetic field.
• V364 Lacertae, an eclipsing binary formed by two Am stars.
• V424 Lacertae, red supergigante and irregular variable.
• ADS 16402, binary star, whose secondary component has an extrasolar planet (HAT-P-1b).

Galaxy NGC 7250 (right) and star TYC 3203-450-1 (left)

Deep Sky Objects

• Galaxy BL Lacertae, of magnitude 13, prototype of a type of galaxies (BL Lac objects) that emit a lot of energy.
• Open volume NGC 7209, of magnitude 6.7 to 2900 light years of us, is about 300 million years old.
• Open Cluster NGC 7243, with an extension of 20 arcmin and magnitude 6,4 is 2900 light years.
• NGC 7250, irregular galaxy.
• NGC 7265, elliptical galaxy of magnitude 12.2, 2nd to the southeast of 1 Lacertae; it is the brightest of a triplet of galaxies.

History

Before Johannes Hevelius adopted the name Lacerta, other names were proposed for this part of the sky. Among them Sceptrum et Manus Iustitiae (Scepter and Hand of Justice) and Frederick's Honors, alluding to Frederick the Great of Prussia. The other names have decayed and Lacerta is the one that has survived. Being a modern constellation, it is not associated with any ancient legend.

You can see the constellation Lacerta on the left of this map of the 1825 stars that appears on Urania's Mirror

Equivalents

Although not included in the ancient star maps of Europe and the Near East, the stars of Lacerta, along with some of the eastern portion of Cygnus, were coincidentally combined by early Chinese astronomers in their "Flying Serpent" 34;.

Further reading

• Allen, Richard H. (1899). Star-names and their meaning (in English). New York: Stechert.
• Ridpath, Ian; Tirion, Wil (2008). Stars and Planets: The Most Complete Guide to the Stars, Planets, Galaxies, and the Solar System. Princeton Field Guides (in English) (2nd edition). Princeton UP. ISBN 978-0691135564.
• Bakich, Michael E. (1995). The Cambridge Guide to the Constellations. Princeton Field Guides (in English). Cambridge University Press.
• European Space Agency (1997). «The Hipparcos and Tycho Catalogues». Consultation on 26 December 2006.
• Natalia Dimitrievna Kostyuk (2002). «HD-DM-GC-HR-HIP-Bayer-Flamsteed Cross Index». Consultation on 26 December 2006.
• Nancy Roman (1987). « Identification of a Constellation from a Position». Consultation on 26 December 2006.
• "SMBAD Astronomical Database". Centre de données astronomiques de Strasbourg. Consultation on 26 December 2006.