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Fomalhaut, Alpha Piscis Austrini, 24 Piscis Austrini, HD216956, HIP113368, HR8728

Fomalhaut (Alpha Piscis Austrini) Location in Piscis Austrinus

Fomalhaut (Alpha Piscis Austrini) is a blue main sequence dwarf star that can be located in the constellation of Piscis Austrinus. The description is based on the spectral class. Fomalhaut is a main star of the constellation.

Fomalhaut is the 18th brightest star in the night sky and is the brightest star in Piscis Austrinus based on the Hipparcos 2007 apparent magnitude. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it. It is calculated at being .440 Billion Years old. This information comes from ExoPlanet. Fomalhaut has at least 1 Extrasolar Planets believed to be in orbit around the star.

Orbiting Extrasolar Planets and Kuiper Belt

Fomalhaut was one of the first stars to have been discovered to have an exoplanet in orbit round it, it wasn`t the first, the first was Helvetios which at the time was first referred to as plain old 51 Pegasi. The planet orbits outside the goldilocks zone, the area which scientists believe where the temperature for life is right, not too cold and not too hot. The picture at the bottom shows the white line as the orbit, the green as the goldilocks zone. The orbit is too far away from the star to get everything in the picture but it would be at the centre of the green circle. The planet was given the name Dagon in a competition by the International Astronomical Union

In addition to having a planet, it also has a Kuiper Belt in orbit round the planet. Whereas the Kuiper Belt in our solar system is about 50 A.U., thats fifty times the distance from the Earth to the Sun, the Fomalhaut Kuiper Belt is about 133 - 158 A.U. There could be more planets in orbit round the planet but we`ve not yet discovered them.

Fomalhaut's Alternative Names

Alpha Piscis Austrini (Alf Psa) is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR8728. HIP113368 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD216956. The Gliese ID of the star is GL 881. The star was part of the original catalogue devised by German Astronomer Wilheim Gliese of stars located within 20 parsecs of Earth. Star Names

Fomalhaut has alternative name(s) :- alf PsA A. In Arabic, it is known as Fam al-Hut.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John numbered the stars in the constellation with a number and the latin name, this star's Flamsteed designation is 24 Piscis Austrini with it shortened to 24 PsA.

More details on star alternative names can be found at Star Names .

Location of Fomalhaut

The location of the star in the night sky is determined by the Right Ascension (R.A.) and Declination (Dec.), these are equivalent to the Longitude and Latitude on the Earth. The Right Ascension is how far expressed in time (hh:mm:ss) the star is along the celestial equator. If the R.A. is positive then its eastwards. The Declination is how far north or south the star is compared to the celestial equator and is expressed in degrees. For Fomalhaut, the location is 22h 57m 38.83 and -29° 37` 18.6 .

Radial Velocity and Proper Motion of Fomalhaut

All stars like planets orbit round a central spot, in the case of planets, its the central star such as the Sun. In the case of a star, its the galactic centre. The constellations that we see today will be different than they were 50,000 years ago or 50,000 years from now. Proper Motion details the movements of these stars and are measured in milliarcseconds. The star is moving -164.67 ± 0.30 miliarcseconds/year towards the north and 328.95 ± 0.47 miliarcseconds/year east if we saw them in the horizon.

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is 6.50 km/s with an error of about 0.50 km/s . When the value is negative then the star and the Sun are getting closer to one another, likewise, a positive number means that two stars are moving away. Its nothing to fear as the stars are so far apart, they won't collide in our life-time, if ever.

Fomalhaut Luminosity

Luminosity is the amount of energy that a star pumps out and its relative to the amount that our star, the Sun gives out. The figure of 16.93 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature, Age, Mass) of Fomalhaut

Fomalhaut has a spectral type of A3V. This means the star is a blue main sequence dwarf star. The star is 7,397.00 Parsecs from the Galactic Centre or terms of Light Years is 24,126.30 s. The star has a B-V Colour Index of 0.14 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 8,153 Kelvin.

Fomalhaut Radius has been calculated as being 2.10 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,461,288.15.km. If you need the diameter of the star, you just need to multiple the radius by 2. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 2.10. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's solar mass is 1.92 times that of the Sun's. The Sun's Mass is 1,989,100,000,000,000,000,000 billion kg. which to calculate using this website is too large. To give idea of size, the Sun is 99.86% the mass of the solar system. The star's Iron Abundance is 0.20 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

The star is believed to be about 0.44 Billion years old. To put in context, the Sun is believed to be about five billion years old and the Universe is about 13.8 billion years old.

Fomalhaut Apparent and Absolute Magnitudes

Fomalhaut has an apparent magnitude of 1.17 which is how bright we see the star from Earth. Apparent Magnitude is also known as Visual Magnitude. If you used the 1997 Parallax value, you would get an absolute magnitude of 1.74 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.74. Magnitude, whether it be apparent/visual or absolute magnitude is measured by a number, the smaller the number, the brighter the Star is. Our own Sun is the brightest star and therefore has the lowest of all magnitudes, -26.74. A faint star will have a high number. }

Distance to Fomalhaut

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 130.08 which gave the calculated distance to Fomalhaut as 25.07 light years away from Earth or 7.69 parsecs. It would take a spaceship travelling at the speed of light, 25.07 years to get there. We don't have the technology or spaceship that can carry people over that distance yet.

In 2007, Hipparcos data was revised with a new parallax of 129.81 which put Fomalhaut at a distance of 25.13 light years or 7.70 parsecs. It should not be taken as though the star is moving closer or further away from us. It is purely that the distance was recalculated.

Using the 2007 distance, the star is roughly 1,588,227.94 Astronomical Units from the Earth/Sun give or take a few. An Astronomical Unit is the distance between Earth and the Sun. The number of A.U. is the number of times that the star is from the Earth compared to the Sun.

The star's Galacto-Centric Distance is 7,397.00 Parsecs or 24,126.30 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Meteor Showers Radiating from near Fomalhaut

The Piscis Austrinids Meteor Shower radiants from a point near this star. The meteor shower runs typically between 15 Jul- 10 Aug with a peak date of 28-Jul. The speed of a meteor in the shower is 44 Km/s. The amount of meteors predicted to be seen per hour (Zenith Hourly Rate) is 44.

Source of Information

The source of the information if it has a Hip I.D. is from Simbad, the Hipparcos data library based at the University at Strasbourg, France. Hipparcos was a E.S.A. satellite operation launched in 1989 for four years. The items in red are values that I've calculated so they could well be wrong. Information regarding Metallicity and/or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

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Fomalhaut Facts

Visual Facts


Primary / Proper / Traditional NameFomalhaut
Alternative NamesAlpha Piscis Austrini, Alf Psa, alf PsA A, Fam al-Hut, HD 216956, HIP 113368, HR 8728, 24 Piscis Austrini, 24 PsA, Gliese 881
Spectral TypeA3V
Constellation's Main StarYes
Multiple Star SystemNo / Unknown
Star Type main sequence Dwarf Star
Colour blue
GalaxyMilky Way
ConstellationPiscis Austrinus
Age0.44 Billion Years Old
Absolute Magnitude 1.74 / 1.74
Visual / Apparent Magnitude1.17
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)22h 57m 38.83
Declination (Dec.)-29° 37` 18.6
Galactic Latitude-64.91 degrees
Galactic Longitude20.49 degrees
1997 Distance from Earth130.08 Parallax (milliarcseconds)
 25.07 Light Years
 7.69 Parsecs
2007 Distance from Earth 129.81 Parallax (milliarcseconds)
 25.13 Light Years
 7.70 Parsecs
 1,588,227.94 Astronomical Units
Galacto-Centric Distance24,126.30 Light Years / 7,397.00 Parsecs
Proper Motion Dec.-164.67 ± 0.30 milliarcseconds/year
Proper Motion RA.328.95 ± 0.47 milliarcseconds/year
B-V Index0.14
Radial Velocity6.50 ± 0.50 km/s
Iron Abundance0.20 ± 9.99 Fe/H
Eccentricity0.07
Semi-Major Axis7871.00
Stellar Luminosity (Lsun)16.93
Brightest in Night Sky18th
Associated / Clustered StarsFomalhaut C
TW Piscis Austrini

Companions (Multi-Star and Exoplanets) Facts


Exoplanet Count1

Estimated Facts


Calculated Effective Temperature8,153 Kelvin
Mass Compared to the Sun1.92

Sources and Links


SIMBAD SourceLink

List of Extrasolar Planets orbiting Fomalhaut


NameStatusMass (Jupiters)Orbital Period (Days)EccentricityDiscoveredSemi-Major AxisPeriastron
Fomalhaut bConfirmed3.0320000.0000.112008115

Related Stars

Fomalhaut Solar System


This is a N.A.S.A. impression of what the solar system might look like. If the star is not on display, its because its so small compared to the orbits of the outer planets. The green area denotes the habital zone which if the planet is within that area, life could exist. The habital zone might not appear on the picture because its outside the area for the picture. Our planets show the orbit of the planet if its was in our solar system. For more information about the planet and other exoplanetary stuff, visit N.A.S.A.

Fomalhaut Solar System

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