The Markab Star– Facts in brief:
What is it?
The luminous Fixed Star named Markab (or Marchab, 54 Pegasi its Flamsteed designation) from the Arabic language is a main star forming the outline of the well-known Constellation of Pegasus.
It is sometimes referred to as the white star on the wing of the mythical flying winged horse.
Markab, is a mature main sequence star that can be described in two ways:
- a giant star, with spectral type B9III
- a subgiant star , spectral type AO IV
It is a suspected variable blue subgiant star, located in the Constellation Pegasus, which is located in the Northern Hemisphere.
Markab is located close to the celestial equator and it therefore partly visible from both the northern Hemisphere and the Southern Hemisphere, in the night sky, at certain times of year.
It is also prominent as one of the four bright stars that make up one of the easiest to recognize prominent Northern asterisms known as ‘The Great Square of Pegasus’. It is best seen in summer months in the Northern Hemisphere. The luminosity of all these bright stars is within the second magnitude category but each star has distinct features.
Three of these fixed stars are located within the Constellation Pegasus and one in the neighboring Constellation of Andromeda.
The star names in the asterism often referred to as ‘The Great Square of Pegasus’ include:
- Markab, from Arabic,(Alpha Pegasi), a blue subgiant, with a magnitude of 2.49, located 133 light years distant from Earth
- Scheat (Beta Pegasi), a red giant star, a semi-regular variable star located 196 light years from the Sun (60 Parsecs)
- Algenib, from Arabic,(Gamma Pegasi) is located 390 light years distant, (120 Parsecs). Algenib is the faintest of the four stars in the asterism with an apparent magnitude of 2.84
- Alpheratz, from Arabic,(Alpha Andromedae), a white-purple binary star, with a magnitude of 2.1, located 97 light years from the Sun
Markab in Pegasus
Markab (a Peg) is an A-type subgiant star.
It is the third brightest star in Pegasus, after two other bright stars that also have a second magnitude rating:
- Enif, Epsilon Pegasi, the brightest star in Pegasus, with an apparent magnitude of 2.38 and visible by naked eye in the night sky
- Scheat, Beta Pegasi, is the second brightest star in Pegasus with an apparent magnitude of 2.44, and visible by naked eye
The Constellation of Pegasus is the 7th largest Constellation in the Northern Sky and borders several other well known, and easy to identify Constellations – Andromeda, Lacerta and Pisces.
The Markab star is a luminous second magnitude star, with an apparent magnitude of 2.49.
It is classified as a giant AO IV rated star in the stellar classification color chart with a spectrum classification of B9V, B9.5lll. This suggests that it is an A-type subgiant star that has exhausted all of the hydrogen at its core and has therefore evolved beyond the main sequence stage.
This is a hot star that has expanded over time and now is estimated to have 5 times the radius of the Sun and emits around 165 times as much energy. It ranks as the 91st brightest star overall in the night sky.
At this luminosity it is easily located in the night sky and is one of 58 bright stars commonly used for celestial navigation and marking our position.
FACT: The Navigational stars are some of the brightest and most easily recognized stars in the night sky. They were used by many ancient civilizations during sea voyages and from land points to mark time, locate their position and plan directions for journeys.
Today time is regulated by the Coordinated Universal Time (UTC) around the world, which is a 24-hour clock centered at zero in the Greenwich Meridian in London, England.
The 58 recognized celestial navigational stars include 19 first magnitude stars and 38 second-magnitude stars. Markab, Enif and Polaris are among these 58 recognized stars.
Markab is at its highest in the sky in the evening sky in September to October.
The age of Markab
It is estimated to be around 200 million years in age but it is not known how long its lifespan will be. Markab is thought to already be through its main sequence stage, and is losing its supply of oxygen at its core and expanded to a radius of 4.72 solar radii.
It is possible that it will continue to expand and evolve into an orange giant star and possibly end life in a supernova explosion.
The ‘Markab’ star names recorded as myths
The proper star name, approved by the International Astronomical Union (IAU), of this giant bright star is Markab, from the Arabic ‘Markab’, which means ‘the saddle of the horse’.
Or, it could possibly come from the Arabic word Mankib, from the phrase ‘Mankib al-faras’, which means‘the shoulder of the horse’, or Matn al faras, meaning ‘the horse’s shoulder’ (or withers).
This Arabic word can refer to any object that can be ridden on, such as a saddle, type of vehicle, or even a ship.
Arabic Astrology – The Arabic Moon Mansion (the 24th Manzil) is composed of the fixed stars Markab (alpha Pegasi) and Scheat (beta Pegasi), which is associated with poor health, destruction and captivity.
Bayer, the 17th Century German Astronomer referred to the Horse’s Hand (Yed Alpheras) and the Forearm (the Arabian Yad) in connection with the bright star Markab.
In some cultures, there is an association with The Lunar Mansions:
This star is regarded as ‘the first star of encampment’. Encampment is one of the seven mansions of the Black Tortoise.
Along with its fellow Great Square of Pegasus star, Scheat, it forms the Chinese Encampment Mansion.
It was referred to as the junction star of the Hindu Moon Mansion, and considered a double union, although it is unclear which two of the four stars in this asterism are being referred to specifically.
In the Hindu lunar zodiac, the Great Square of Pegasus is the large asterism that constituted Nakshatra – the Mansion of the Moon, composed of Algenib, Alpheratz, Markab and Scheat.
Pegasus, the mythical winged horse according to the Greek myth, was born from of the blood from Medusa (the Gorgon), when Perseus cut off her head.
Characteristics of this supergiant star
Markab can be categorized in two ways, as a giant star with spectral type B9lll la or as a subgiant star with spectral type AO lV.
The brightness of Markab has been used as the guide point for several other Constellations, asterisms or stars, asterism for luminosity by which other stars are categorized.
Markab (alpha Pegasi) is a suspected variable blue star, with an absolute magnitude of 2.48 and a surface temperature of around 9,765K, at the latest estimate, making it around 200 times more luminous than the Sun. It is visible by naked eye.
Variable means its brightness can vary or fluctuate over time.
Markab is regarded as one of the Navigation stars used for celestial navigation because of its luminosity and the fact that it is easy to identify as a part of a familiar asterism in the sky
The latest Hipparcos distance estimate in 2007 for this bright blue giant star locates it around 133.35 light years from Earth (around 40.9 parsecs). Its exact distance is not certain.
FACT: 1 light year equals 0.3066 parsecs
However we now know that everything moves around in space, the planets orbit stars and the stars orbit the galactic center.
Markab‘s Galacto-Centric distance is 24,132.83 light years (7,399.00 parsecs). Markab is now located about 8,432,046.52 Astronomical Units from the Earth/Sun, according to the 2007 Hipparcos distance data. The movement of stars away from/to the Sun, is measured in milliarcseconds.
If the Radial Velocity measure is negative it means the star is moving closer to the Sun, and if the number is positive it means the star is moving away from the Sun. Markab is moving 60.40 milliarcseconds east (away from the Sun) and -41.30 milliarcseconds north (towards the Sun). It is regarded as a rapid spinner and has a projected spinning velocity of 125km/s.
Who named the stars?
In 1603, the German Astronomer – Johann Bayer, systematically assigned names to the brightest stars in each constellation and cataloged them in his Star atlas – ‘Uranometria Omnium Asterismorum’.
The Bayer designations are stellar designations where the stars within Constellations such as the Constellations Pegasus, or Perseus, are initially identified by a name or a letter from the Greek Alphabet from Alpha through Omega (in order of brightness).
1. The names of the Stars begin with a letter of the Greek alphabet starting with– Alpha, then beta, gamma, etc.
2. Followed by the genitive form of their Pegasus parent constellation’s Latin name – ‘Pegasi’, sometimes abbreviated to ‘Peg’.
The main sequence stars of Pegasus are listed by their apparent magnitude (luminosity) from Earth, listed from the brightest to faintest star in decreasing order:
1. Enif, Fum al-faras, (epsilon Pegasi) is a red supergiant star and the most luminous star in Pegasus, with a luminous apparent magnitude of 2.38, representing the Nose of the horse
2. Scheat, (beta Pegasi), is a red giant star and the second brightest star in Pegasus with a visual/apparent magnitude of 2.44
3. Markab, Marchab, (name from Arabic), an A-type giant star and third brightest Star with a visual/apparent magnitudeof 2.49
4. Algenib (gamma Pegasi)– the fourth brightest star with a variable magnitude of 2.83
5. Matar (eta Pegasi) – the fifth brightest and is a binary star system, with a visual magnitude of 2.95
Where is it in the shape of Pegasus?
The outline of the Constellation of Pegasus is in the shape of a majestic flying winged horse, representing the body of Pegasus from Greek Mythology.
Different neighboring stars within Pegasus form part of the body shape:
- Markab, Scheat, Algenib and Alpheratz (actually from the Constellation of Andromeda) – represent the body of the Horse
- Enif (epsilon) – represents the nose of the horse
- Homam (zeta Pegasi)- represents the neck of the horse
- Baham (theta Pegasi) – represents the head of the horse
- Matar (eta Pegasi)– represents the upper leg of the horse
The traditional name ‘Markab’, of the star alpha Pegasi, has been officially recognized by the International Astronomical Union (IAU).
The Constellation of Pegasus has a total of 15 formally named stars, which are approved by the IAU, including:
- Algenib, Alkarab, Anadolu, Biham, Enif, Helvetios, Homam, Markab, Matar, Morava, Sadalbari, Salm, Scheat, Solaris and Tangra
Properties of the Markab Star
Markab is a massive star, classified as a bright blue giant star, and It is located approximately 133.35 light years distant from Earth.
Markab is located in Constellation Pegasus-
- South of the Constellations Andromeda, Lacerta and Cygnus
- North of the Constellations Pisces, Aquarius and Equuleus
Generally the rate at which stars evolve depends on their mass. The greater the mass the quicker the star evolves from the main sequence. Mass of the sun, referred to as its stellar mass, and enumerated as the Sun’s mass as a proportion of solar mass. The Markab star has strong stellar winds which means it can lose mass quickly
The Markab Star has a solar radius of 4.72 times that of the Sun, referred to as 4.72 solar radii.
How bright is this Star
Markab, the blue giant star, has a variable brightness that ranks it as the 91st most luminous star of all the known stars viewed from Earth. Its luminosity is the amount of energy emitted from this giant star relative to the Sun. It is estimated to be over 200 times brighter than the Sun.
The brightness of a star as seen from earth is measured by its magnitude of which there are three classifications: Apparent Magnitude, Visual Magnitude and Absolute Magnitude.
The measurements for the brightness of Markab are:
- An apparent magnitude (also referred to as its visual magnitude) of +2.48/2.49 variable
- An absolute magnitude of -0.67
FACT: The Apparent Magnitude is how bright we see a Star from Earth, and the Absolute Magnitude is the Apparent Magnitude of that star from a 10 parsecs distance (32.6 light years), assuming there are no molecular clouds, or dust in the line of sight.
The lower the number of magnitude the brighter the Star.
The color of the Markab Star
The Markab Star is classified as either a giant star or a subgiant Star, which according to its spectral type is a blue coloured star.
The surface temperature of this blue giant star
Based on the spectral type of this Star it is estimated to have a surface temperature of at least 9,765 degrees Kelvin. This makes it one of the hotter Stars in the Universe.
Where is it located? –
The distances vary depending on how it’s measured and there are certainly margins of error.
According the latest 2007 Hipparcos measurement the parallax data gave an uncertain result. The Markab Star is estimated to be around 133 light years (40.9 parsecs) from Earth.
FACT: A parallax is a difference in the apparent position of a star or any solar system object viewed from two different lines of sight. The parallax is measured by the angle between the two lines of sight.
The distance between the Earth and the Sun is known as an Astronomical Unit (AU).
The figure of A.U. is calculated as the number of times that Star is from Earth, in relation to the Sun. It is estimated that the Markab Star is approximately 8,432,046.52A.U. from Earth to Sun in distance.
FACT: All Stars and Planets orbit round a central point, the planets orbit the Sun and the Stars orbit the Galactic Centre.
The Star Markab is located approximately 24,132.83 lightyears (7,399.00 parsecs) from the Galactic Center, the center of the galaxy we call the Milky Way.
The Galacto-Centric distance is measured as the distance from that Star to the center of the Galaxy (Sagittarius A).
FACT: The Galactic Center, is a supermassive black hole and the rotational center of our Milky Way galaxy. It is not possible to view it at visible, ultraviolet, or even soft or low-energy X-ray wavelengths because of the molecular clouds of interstellar dust along its line of sight.
Where can it be seen?
The Markab Star is one of the main Stars in the outline of the Constellation Pegasus and a bright star you can see by the naked eye.
The luminous Markab Star is of great interest to amateur astronomers as it is visible as part of the Great Square of Pegasus, and points towards the large W-shape of the Constellation Cassiopeia.
Co-ordinates of a right ascension, or left ascension and their declination are used to locate all of the notable objects in the sky
The Markab Star lies at a 23 hours 04 minute right ascension, and a declination of +15 degrees.
The right ascension – is the angular distance of any sky object along the celestial equator from the March (Spring) equinox.
- If it has a positive number it is east of the March equinox.
The declination – is the angle of the sky object from the celestial equator.
- If it has a positive number it indicates it is located in the Northern Hemisphere
Markab is located close to the celestial equator and is therefore partly visible from both the northern hemisphere and the southern hemisphere at certain times of year.
The age of the Markab Star
It is not certain what age the Star Markab is or how long it is likely to continue to survive.
One estimate of the age of this Star is that it is still young and possibly only 200 million years old. (The Sun is estimated to be 4.6 billion years)
How can you identify the Markab Star?
The simplest method for spotting any particular Star from Earth is to first of all locate an easy to recognize neighboring Constellation or object in the night sky.
Pegasus is probably one of the easiest to spot as it is formed from some very bright stars in a distinctive pattern. The Constellation of Pegasus is located near the celestial equator and that means it is visible in most of the world.
The best time of year to spot the bright star Markab is in the evening sky is
- July to January – Northern Hemisphere
- August to December – Southern Hemisphere.
Like all stars, Markab is constantly on the move, and when viewed from the Southern Hemisphere the outline of Pegasus will appear upside down!
How do we obtain the images and measurements of Stars from Space?
Images of the different Stars and nebulae have been captured using a professional large telescope, such as the NASA Spitzer Space Telescope, with a near infrared camera and multi-object spectrometer, all covered by Wikipedia sources.
The standard measurement of distance for Stars for decades has been using the ESA Earth-orbiting Hipparcos satellite, which replaced the ESA Gaia mission to chart a three dimensional map of the Milky Way Galaxy.
ESA Gaia measured the positions and radical velocities of around one billion stars in our galaxy.
A supernova remnant is the structure that’s left after a star explodes in a supernova. There are 3 types of supernova remnants: shell-like, composite and mixed-morphology (or thermal composite). It is anticipated that Markab is not massive enough to end in a supernova, but as a white dwarf instead.
The celestial pole
The celestial pole defines the poles of the celestial equatorial coordinate system.
An object at the Celestial pole has a declination of 0 degrees.
- The declinations for the north celestial pole is +90 degrees
- The declinations for the south celestial pole is -90 degrees
The celestial poles are not permanently in a fixed position against the background of the stars as everything moves in Space.
The Markab Star is located in the Northern celestial sky at a +15, 12 degrees declination, and an average 23 hours, 04 min right ascension.
Fun Facts about Stars – Did you know that?
- Markab is sometimes referred to as SAO 108378
- It is listed as HIP 113963 in the Hipparcos Star Catalogue
- After the Sun, Sirius is the brightest star in the sky with an apparent magnitude of -1.46
- The Star we call The Sun does not belong to any constellation
- The planet Jupiter is often cited when making size comparisons between planets or stars. The Jupiter mass is a unit of mass equal to the total mass of planet Jupiter
- The rate of formation of stars in a starburst galaxy is more than 10 times faster than the star formation in the Milky Way galaxy
- The center of a Galaxy does not contain a Giant Star it contains a Supermassive Black Hole.
- A Red Dwarf is not a Dwarf Planet it is a Star. Most common Stars are Red Dwarf (cool Stars)
Commonly Asked Questions
Q. What prevents us seeing the Stars in the night sky?
A. Light pollution, fog, city lights and artificial lights all limit our visibility of the objects in the sky at night.
Q. Will the locations of Stars change over time?
A. Stars are continually on the move.
The images we form in our imagination to make objects, shapes and patterns out of the constellations have already shifted over time.
As we view the night skies from Earth they are likely to continue to shift and possibly in time the images may look very different.
- Markab (Alpha Pegasi), image: Wikisky – https://www.star-facts.com/wp-content/uploads/2020/04/Markab.jpg?189db0&189db0
- Markab in pegasus – https://www.astronomytrek.com/wp-content/uploads/2015/02/Pegasus-678×381.gif
- Johann Bayer – https://laexuberanciadehades.files.wordpress.com/2012/10/johann-bayer.jpg
- Nebula – By Credit: NASA, Jeff Hester, and Paul Scowen (Arizona State University) – Public Domain, https://commons.wikimedia.org/w/index.php?curid=129538
- Supernova Remnant – Cassiopeia A. Credit: NASA/CXC/SAO – https://scitechdaily.com/lonely-origin-of-cassiopeia-a-revealed-one-of-the-most-famous-supernova-remnants
- Milky way – Source: Nick Risinger – https://sedsvit.medium.com/just-us-d4ab577099a2
- Celestial Pole – By I, Dennis Nilsson, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=3262268