Lacerta (the Lizard) is a small, faint constellation in the northern sky, situated between Cygnus and Andromeda. Introduced by astronomer Johannes Hevelius in the 17th century, its stars form a loose zigzag pattern sometimes nicknamed Little Cassiopeia.
Although Lacerta has no particularly bright stars or Messier objects, it contains several attractive open star clusters and one remarkable object: BL Lacertae, a distant active galaxy that gave its name to an entire class of powerful cosmic sources.
Where Is Lacerta and When Can You See It?
Lacerta is the 68th-largest constellation, covering approximately 201 square degrees of the northern sky. It lies between Cygnus and Andromeda, with Cepheus and Cassiopeia nearby.
The best time to observe Lacerta is September through November, particularly October, when it is high in the evening sky for Northern Hemisphere observers. From Britain, it is visible for much of the year.
To find it, locate the bright star Deneb in Cygnus and look eastward toward the Great Square of Pegasus. Lacerta occupies the relatively faint region between these landmarks.
Its principal stars form a small zigzag resembling a stretched-out W, although they are considerably fainter than the stars of Cassiopeia. Dark skies make the pattern much easier to recognize.
History of Lacerta
Unlike many familiar constellations, Lacerta has no ancient Greek mythology associated with it.
It was introduced by the Polish astronomer Johannes Hevelius, who included it in his constellation atlas published posthumously in 1690. Hevelius had devised the constellation in the late 17th century, using stars in a region of sky that had not previously been assigned a widely recognized constellation figure. The name Lacerta is Latin for lizard. Its small, winding star pattern makes the animal a fitting choice, although the constellation is not especially easy to visualize without a star chart.
Lacerta is one of several constellations introduced by Hevelius that remain among the 88 officially recognized constellations today.
Notable Stars in Lacerta
- Alpha Lacertae – The brightest star in Lacerta, a white A-type main-sequence star approximately 100 light-years away, shining at magnitude 3.8. It is considerably hotter and more luminous than the Sun. A faint star visible nearby is an optical companion, meaning the two appear close together from Earth but are not physically associated.
- 1 Lacertae – An evolved orange star approximately 600 light-years away, with an apparent magnitude around 4.2. It lies toward the southern end of the constellation, near the border with Pegasus.
- 5 Lacertae – A luminous, evolved star approximately 1,000 light-years away, shining near magnitude 4.4. It is a variable star whose brightness changes slowly and irregularly.
- Beta Lacertae – A yellow giant with an apparent magnitude around 4.4, making it one of the brighter stars in Lacerta’s faint zigzag pattern.
- EV Lacertae – A nearby red dwarf approximately 16 light-years away. Despite being invisible to the naked eye, it is notable for producing powerful stellar flares. In 2008, astronomers detected an exceptionally energetic flare from this otherwise faint star.
Most of Lacerta’s principal stars are only fourth magnitude or fainter, which explains why the constellation is easily overlooked from light-polluted locations.
Notable Deep-Sky Objects in Lacerta
Lacerta lies along the Milky Way, giving it several open star clusters that are particularly attractive through binoculars and small telescopes. It contains no Messier objects.
NGC 7243 — Caldwell 16
NGC 7243 is an open star cluster approximately 2,800 light-years away, with an apparent magnitude around 6.4. It contains a loose grouping of young, predominantly blue-white stars spread across an area roughly half the apparent diameter of the full Moon.
Under dark skies, binoculars reveal a faint scattering of stars, while a small telescope resolves many of its brighter members. The cluster’s relatively open arrangement makes it a pleasant target at low magnification.
NGC 7209 — An Open Cluster
NGC 7209 is another open cluster in Lacerta, approximately 3,000 light-years away, with an apparent magnitude around 6.7. Its stars are spread across a broad area, giving the cluster a loose, irregular appearance. Binoculars may show it as a faint glow, while telescopes reveal a richer scattering of individual stars.
Lacerta also contains NGC 7245, a smaller and more compact open cluster that benefits from a telescope with moderate aperture.
BL Lacertae — A Galaxy With a Jet Pointed Toward Earth
BL Lacertae is the most extraordinary object associated with the constellation.
When first identified, it appeared to be an unusual variable star whose brightness changed unpredictably. However, observations revealed a powerful radio source, and astronomers eventually established that it was not a star at all. BL Lacertae is the active nucleus of a distant galaxy, powered by matter falling toward a supermassive black hole.
As material spirals inward, some of it is accelerated into narrow jets of energetic particles and radiation. One of these jets points almost directly toward Earth, making the galaxy appear exceptionally bright and variable. Objects of this kind are known as blazars, and BL Lacertae became the prototype for a subclass called BL Lacertae objects.
BL Lacertae lies roughly 900 million light-years away. Its brightness varies substantially, generally placing it far beyond naked-eye visibility.
Unlike Lacerta’s open clusters, BL Lacertae is not a conventional visual showpiece. Its importance lies in what it reveals about supermassive black holes, relativistic jets, and the extraordinary energy produced in the centers of active galaxies.