Physically, Stellio is a main sequence star and, like most stars (including the Sun), generates energy through the fusion of hydrogen into helium. It is, however, about ten times as massive as the Sun, and consequently much more luminous. It has a high surface temperature of about ten thousand Kelvin, and so shines with a fierce white light. Stellio has an optical companion, which is much fainter than the primarystar at magnitude +11.8.
From Earth, Stellio lies in the northern part of its home constellation of Lacerta, against the backdrop of the Milky Way. It can prove difficult to pick out, since it is not noticeably brighter than many of its neighbouring stars; it forms the second point in the descending 'zig-zag' that forms the backbone of the Lizard. Lacerta itself occupies the faint space between Andromeda and Cygnus, and is best observed in August and September.
Until relatively recently, this star was generally known simply as 'Alpha Lacertae', but the proper name of Stellio for the star was formally recognised by the IAU in 2024. The name dates back to the star catalogue of Johannes Hevelius published in 1690, in which Hevelius named the constellation of the Lizard as Lacerta sive Stellio ('the Lizard, or Stellion'). A 'stellion' or is a particular species of lizard, Laudakia stellio, named for the star-shaped spots that run down its back (for which reason it is also known as a 'starred agama'). Hence the Latin Stellio literally refers to a 'star lizard', an appropriate choice for the constellation of the Lizard, and for its brighteststar.
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