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15 Arietis, HD13325, HIP10155, HR631

15 Arietis is a red pulsating giant star that can be located in the constellation of Aries. 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.

15 Arietis's Alternative Names

The Id of the star in the Yale Bright Star Catalogue is HR631. HIP10155 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD13325.

15 Arietis has alternative name(s) :- , NSV 00738.

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 Arietis with it shortened to 15 Ari.

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+18 277.

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

Location of 15 Arietis

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 Arietis, the location is 02h 10m 37.54 and +19° 30` 01.5 .

Proper Motion of 15 Arietis

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 -27.82 ± 0.30 miliarcseconds/year towards the north and 87.88 ± 0.49 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 62.04000 km/s with an error of about 0.22 km/s .

Physical Properties (Colour, Temperature) of 15 Arietis

15 Arietis has a spectral type of M3III. This means the star is a red giant star. The star is 7,511.00 Parsecs from the Galactic Centre or terms of Light Years is 24,498.13 s. The star has a B-V Colour Index of 1.64 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,671 Kelvin.

15 Arietis Radius has been calculated as being 34.46 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 23,978,808.67.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 28.93. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

15 Arietis Apparent and Absolute Magnitudes

15 Arietis has an apparent magnitude of 5.68 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 -0.87 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.49. 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 Arietis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 4.90 which gave the calculated distance to 15 Arietis as 665.64 light years away from Earth or 204.08 parsecs. It would take a spaceship travelling at the speed of light, 665.64 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 5.84 which put 15 Arietis at a distance of 558.50 light years or 171.23 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 7,511.00 Parsecs or 24,498.13 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 15 Arietis

The star is a pulsating Semi-Regular Star which are giants or supergiants of intermediate and late spectral 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. 15 Arietis brightness ranges from a magnitude of 5.761 to a magnitude of 5.685 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 5.0 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.

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15 Arietis Facts

Visual Facts


Primary / Proper / Traditional Name15 Arietis
Alternative NamesHD 13325, HIP 10155, HR 631, 15 Ari, BD+18 277, NSV 00738
Spectral TypeM3III
Multiple Star SystemNo / Unknown
Star TypeGiant Star
Colour red
GalaxyMilky Way
ConstellationAries
Absolute Magnitude-0.87 / -0.49
Visual / Apparent Magnitude5.68
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)02h 10m 37.54
Declination (Dec.)+19° 30` 01.5
Galactic Latitude-39.58 degrees
Galactic Longitude147.40 degrees
1997 Distance from Earth4.90 Parallax (milliarcseconds)
 665.64 Light Years
 204.08 Parsecs
2007 Distance from Earth5.84 Parallax (milliarcseconds)
 558.50 Light Years
 171.23 Parsecs
Galacto-Centric Distance24,498.13 Light Years / 7,511.00 Parsecs
Proper Motion Dec.-27.82 ± 0.30 milliarcseconds/year
Proper Motion RA.87.88 ± 0.49 milliarcseconds/year
B-V Index1.64
Radial Velocity62.04 ± 0.22 km/s
Eccentricity0.36
Semi-Major Axis6765.00

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassPulsating
Variable Star TypeSemi-Regular Star which are giants or supergiants of intermediate and late spectral
Mean Variability Period in Days5.032
Variable Magnitude Range (Brighter - Dimmer)5.685 - 5.761

Estimated Facts


Calculated Effective Temperature3,671 Kelvin

Sources and Links


SIMBAD SourceLink

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