Star Markab (Alpha (α) Pegasi) is one of the four corner stars of the Great Square of Pegasus, the one that marks the southwest corner to be precise.
It’s the third brightest in the Square asterism, shining at mag. +2.5.
Magnitude +2.1 Alpheratz (Alpha (α) Andromedae) in the northeast and mag. +2.4 Scheat (Beta (β) Pegasi) in the northwest are a little brighter
Mag. +2.8 Algenib (Gamma (γ) Pegasi) in the southeast is the faintest.
Star Markab's name
The name Markab derives from the Arabic for ‘saddle of the horse’.
In Chinese culture it forms an asterism with Scheat called the encampment, Markab being the ‘first star of the encampment’.
The Square stars are white with the exception of Scheat, which appears orange.
For more info, read our guides to Arabian astronomy and Chinese astronomy
Facts about star Markab
Star Markab is an evolved subgiant star of spectral classification A0 IV.
This means its core hydrogen has run out and the fusion of this element has stopped, or is in the process of stopping.
Just to show how close to the tipping point Markab is, its spectrum is sometimes given as B9 V or B9.5 III – that’s a hot blue-white dwarf or giant.
Find out more about this in our guide to stellar spectral classifications.
Markab is estimated to be 133 lightyears away and has a mass 3.5 times, radius 4.6 times and luminosity 165 times larger than our own Sun.
It’s a fast rotator too, at 130 km/s.
The star is remarkable for not being remarkable, a normal star with no real deviations from what you’d expect from it.
As a consequence, it has been cited many times as a standard against which other stars are measured.
This guide appeared in the October 2023 issue of BBC Sky at Night Magazine.
