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15 Pegasi, HD207978, HIP107975, HR8354

15 Pegasi is a blue to white subgiant star that can be located in the constellation of Pegasus. The description is based on the spectral class. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it. The star has an estimated age of 3.30 Billion of Years but could be as young as 3.00 to 4.50 according to Hipparcos.

15 Pegasi's Alternative Names

The Id of the star in the Yale Bright Star Catalogue is HR8354. HIP107975 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD207978.

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 15 Pegasi with it shortened to 15 Peg.

BD number is the number that the star was filed under in the Durchmusterung or Bonner Durchmusterung, a star catalogue that was put together by the Bonn Observatory between 1859 to 1903. The star's BD Number is BD+28 4215.

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

Location of 15 Pegasi

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 15 Pegasi, the location is 21h 52m 29.96 and +28° 47` 37.3 .

Proper Motion of 15 Pegasi

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 -62.37 ± 0.26 miliarcseconds/year towards the north and -58.81 ± 0.32 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 us is 18.93000 km/s with an error of about 0.09 km/s .

15 Pegasi 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 3.94 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) of 15 Pegasi

15 Pegasi has a spectral type of F6IVwvar. This means the star is a blue to white subgiant star. The star is 7,396.00 Parsecs from the Galactic Centre or terms of Light Years is 24,123.04 s. The star has a B-V Colour Index of 0.42 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,635 Kelvin.

15 Pegasi Radius has been calculated as being 1.54 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,070,714.00.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 1.52. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's Iron Abundance is -0.53 with an error value of 0.01 Fe/H with the Sun has a value of 1 to put it into context.

The stars age according to Hipparcos data files put the star at an age of about 3.30 Billion years old but could be between 3.00 and 4.50 Billion years old. In comparison, the Sun's age is about 4.6 Billion Years Old.

15 Pegasi Apparent and Absolute Magnitudes

15 Pegasi has an apparent magnitude of 5.52 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 3.31 If you used the 2007 Parallax value, you would get an absolute magnitude of 3.33. 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 15 Pegasi

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 36.15 which gave the calculated distance to 15 Pegasi as 90.22 light years away from Earth or 27.66 parsecs. It would take a spaceship travelling at the speed of light, 90.22 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 36.43 which put 15 Pegasi at a distance of 89.53 light years or 27.45 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.

The star's Galacto-Centric Distance is 7,396.00 Parsecs or 24,123.04 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

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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15 Pegasi Facts

Visual Facts


Primary / Proper / Traditional Name15 Pegasi
Alternative NamesHD 207978, HIP 107975, HR 8354, 15 Peg, BD+28 4215
Spectral TypeF6IVwvar
Multiple Star SystemNo / Unknown
Star TypeSubgiant Star
Colour blue to white
GalaxyMilky Way
ConstellationPegasus
Age3.30 Billion Years Old
Age Range3.00 - 4.50 Billion Years Old
Absolute Magnitude3.31 / 3.33
Visual / Apparent Magnitude5.52
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)21h 52m 29.96
Declination (Dec.)+28° 47` 37.3
Galactic Latitude-19.54 degrees
Galactic Longitude82.05 degrees
1997 Distance from Earth36.15 Parallax (milliarcseconds)
 90.22 Light Years
 27.66 Parsecs
2007 Distance from Earth36.43 Parallax (milliarcseconds)
 89.53 Light Years
 27.45 Parsecs
Galacto-Centric Distance24,123.04 Light Years / 7,396.00 Parsecs
Proper Motion Dec.-62.37 ± 0.26 milliarcseconds/year
Proper Motion RA.-58.81 ± 0.32 milliarcseconds/year
B-V Index0.42
Radial Velocity18.93 ± 0.09 km/s
Iron Abundance-0.53 ± 0.01 Fe/H
Eccentricity0.34
Semi-Major Axis10318.00
Stellar Luminosity (Lsun)3.94

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Estimated Facts


Calculated Effective Temperature6,635 Kelvin

Sources and Links


SIMBAD SourceLink

Related Stars


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