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Psi Pegasi, 84 Pegasi, HD224427, HIP118131

Psi Pegasi is a red eruptive giant star that can be located in the constellation of Pegasus. Psi Pegasi is the brightest star in Pegasus 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.

Psi Pegasi is the Bayer Classification for the star. HIP118131 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD224427.

Psi Pegasi has alternative name(s), NSV 14777.

Location of Psi Pegasi

The location of the star in the galaxy 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 Psi Pegasi, the location is 23h 57m 45.55 and +25d08`29.3 .

Proper Motion of Psi 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 -31.60 ± 0.14 miliarcseconds/year towards the north and -35.24 ± 0.24 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Psi Pegasi

Psi Pegasi has a spectral type of M3III. This means the star is a red giant star. The star is 7437.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24256.7678932800000000s. The star has a B-V Colour Index of 1.58 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,827 Kelvin.

Psi Pegasi Radius has been calculated as being 33.36 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 23,210,287.87.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 36.74. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Psi Pegasi Apparent and Absolute Magnitudes

Psi Pegasi has an apparent magnitude of 4.63 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 -0.98 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.19. 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 Psi Pegasi

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 7.54 which gave the calculated distance to Psi Pegasi as 432.58 light years away from Earth or 132.63 parsecs. It would take a spaceship travelling at the speed of light, 432.58 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 6.85 which put Psi Pegasi at a distance of 476.15 light years or 145.99 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 7,437.00 Parsecs or 24,256.77 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Variable Type of Psi Pegasi

The star is a eruptive Irregular variable type which means that its size changes over time. The Variable Type is usually named after the first star of that type to be spotted. Psi Pegasi brightness ranges from a magnitude of 4.727 to a magnitude of 4.650 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.1 days (variability).

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.

Psi Pegasi Facts

Alternative Names

Flamsteed Name84 Pegasi
Flamsteed Short Name84 Peg
Short NameNSV 14777
Bayer DesignationPsi Pegasi
Hipparcos Library I.D.118131
Bonner DurchmusterungBD+24 4865
Henry Draper Designation224427

Visual Facts

Star Typegiant star
Absolute Magnitude-0.98 / -1.19
Visual / Apparent Magnitude4.63
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)23h 57m 45.55
Declination (Dec.)+25d08`29.3
Galactic Latitude-36.15 degrees
Galactic Longitude107.85 degrees
1997 Distance from Earth7.54 Parallax (milliarcseconds)
 432.58 Light Years
 132.63 Parsecs
2007 Revised Distance from Earth6.85 Parallax (milliarcseconds)
 476.15 Light Years
 145.99 Parsecs
Galacto-Centric Distance24,256.77 Light Years / 7,437.00 Parsecs
Proper Motion Dec.-31.60 ± 0.14 milliarcseconds/year
Proper Motion RA.-35.24 ± 0.24 milliarcseconds/year
B-V Index1.58
Radial Velocity-6.59 ± 0.23 km/s
Spectral TypeM3III
Colour(M) Red

Variable Star Details

Variable Star ClassEruptive
Variable Star TypeIrregular
Mean Variability Period in Days0.064
Variable Magnitude Range (Brighter - Dimmer)4.650 - 4.727

Estimated Facts

Calculated Effective Temperature3,827 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Multi-Star System

The star has been identified as being a multi-star system, one in which there is at least one star in close orbit to another star or two or more stars orbiting a central point. The stars may be of equal mass, unequal mass where one star is stronger than the other or be in groups orbiting a central point which doesn't necessarily have to be a star. More information can be found on my dedicated multiple star systems page. The source of the info is Simbad. The file is dated 2000 so any differences between this and any other source will be down to the actual source from where the information came from.


Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
224427+24 4865.0A4.70000-34.00000-33.00000M3Red
B1988

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