Universe Guide


Sigma Persei, 35 Persei, HD21552, HIP16335

Sigma Persei is a orange to red giant star that can be located in the constellation of Perseus. Sigma Persei is the brightest star in Perseus 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.

Sigma Persei is the Bayer Classification for the star. HIP16335 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD21552.

Sigma Persei has alternative name(s), Sig Per. Sigma Persei has at least 1 Extrasolar Planets believed to be in orbit around the star.

Location of Sigma Persei

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 Sigma Persei, the location is 03h 30m 34.48 and +47d59`42.6 .

Proper Motion of Sigma Persei

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 18.48 ± 0.17 miliarcseconds/year towards the north and 3.56 ± 0.26 miliarcseconds/year east if we saw them in the horizon.

Sigma Persei 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 58.0000000 that I have given is based on the Spectral Types page that I have found on the Internet. You might find a different figure, one that may have been calculated rather than generalised that I have done. The figure is always the amount times the luminosity of the Sun. It is an imprecise figure because of a number of factors including but not limited to whether the star is a variable star and distance.

Physical Properties (Colour, Temperature, Radius) of Sigma Persei

Sigma Persei has a spectral type of K3III. This means the star is a orange to red giant star. The star is 7494.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24442.6809993600000000s. The star has a B-V Colour Index of 1.36 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,224 Kelvin.

Sigma Persei Radius has been calculated as being 25.32 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 17,617,649.41.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 25.79. 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 -0.15 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

Sigma Persei Apparent and Absolute Magnitudes

Sigma Persei has an apparent magnitude of 4.36 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 -0.81 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.85. 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 Sigma Persei

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 9.23 which gave the calculated distance to Sigma Persei as 353.37 light years away from Earth or 108.34 parsecs. It would take a spaceship travelling at the speed of light, 353.37 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 9.07 which put Sigma Persei at a distance of 359.61 light years or 110.25 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 7,494.00 Parsecs or 24,442.68 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.

Sigma Persei Facts

Alternative Names

Flamsteed Name35 Persei
Flamsteed Short Name35 Per
Short NameSig Per
Bayer DesignationSigma Persei
Hipparcos Library I.D.16335
Bonner DurchmusterungBD+47 843
Henry Draper Designation21552

Visual Facts

Star Typegiant star
Absolute Magnitude-0.81 / -0.85
Visual / Apparent Magnitude4.36
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)03h 30m 34.48
Declination (Dec.)+47d59`42.6
Galactic Latitude-6.83 degrees
Galactic Longitude148.48 degrees
1997 Distance from Earth9.23 Parallax (milliarcseconds)
 353.37 Light Years
 108.34 Parsecs
2007 Revised Distance from Earth9.07 Parallax (milliarcseconds)
 359.61 Light Years
 110.25 Parsecs
Galacto-Centric Distance24,442.68 Light Years / 7,494.00 Parsecs
Proper Motion Dec.18.48 ± 0.17 milliarcseconds/year
Proper Motion RA.3.56 ± 0.26 milliarcseconds/year
B-V Index1.36
Radial Velocity14.36 ± 0.19 km/s
Iron Abundance-0.15 ± 9.99 Fe/H
Spectral TypeK3III
Colour(K) Orange to Red

Companions (Multi-Star and Exoplanets) Facts

Exoplanet Count1

Estimated Facts

Luminosity (x the Sun)58.0000000
Calculated Effective Temperature4,224 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

List of Extrasolar Planets orbiting Sigma Persei

NameStatusMass (Jupiters)Orbital Period (Days)EccentricityDiscoveredSemi-Major AxisPeriastron
Sig Per BConfirmed6.5579.8000.320141.884.000

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