Universe Guide

Hamal (Alpha Arietis) - HD12929 - HIP9884 - HR617

Hamal (Alpha Arietis) is an orange to red giant star that can be located in the constellation of Aries. It is the 50th brightest star in the night sky. Alpha Arietis is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR617. HIP9884 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD12929. Hamal has alternative name(s), 13 Arietis , 13 Ari. Hamal has at least 1 Extrasolar Planets believed to be in orbit around the star.

Location of Hamal

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 Hamal, the location is 02h 07m 10.29 and +23d27`46.0 .

Proper Motion of Hamal

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 -148.08 ± 000.14 towards the north and 188.55 ± 000.25 east if we saw them in the horizon.

Hamal 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 70.0000000 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, Mass, Radius) of Hamal

Hamal has a spectral type of K2III. This means the star is an orange to red coloured giant star. The star has a B-V Colour Index of 1.15 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,576 Kelvin.

Hamal has been calculated as 12.54 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 8,723,954.32.km. The star's solar mass is 2.00 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 metallicity is 0.000000, this value is the fractional amount of the star that is not Hydrogen (X) or Helium (Y). An older star would have a high metallicity whereas a new star would have a lower one.

Hamal Apparent and Absolute Magnitudes

Hamal has an apparent magnitude of 2.01 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 0.48 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 Hamal

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 49.48 which gave the calculated distance to Hamal as 65.92 light years away from Earth or 20.21 parsecs. In 2007, Hipparcos data was revised with a new parallax of 49.56 which put Hamal at a distance of 65.81 light years or 20.18 parsecs.

It would take a spaceship travelling at the speed of light, 65.92 years using the 1997 distance to get there. We don't have the technology or spaceship that can carry people over that distance yet.

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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

Hamal Facts


Traditional NameHamal
Short Name13 Ari
English MeaningThe ram
Bayer DesignationAlpha Arietis
Alternative Name(s)13 Arietis
Hipparcos Library I.D.9884
Yale Bright Star Catalogue (HR) Id617
Bonner DurchmusterungBD+22 306
Henry Draper Designation12929
ConstellationAries
Celestial TypeStar
Absolute Magnitude0.48 / 0.49
Apparent Magnitude2.01
Right Ascension (R.A.)02h 07m 10.29
Declination (Dec.)+23d27`46.0
1997 Distance from Earth49.48 Parallax (milliarcseconds)
 65.92 Light Years
 20.21 Parsecs
2007 Distance from Earth49.56 Parallax (milliarcseconds)
 65.81 Light Years
 20.18 Parsecs
Proper Motion Dec.-148.08 ± 0.14 milliarcseconds/year
Proper Motion RA.188.55 ± 0.25 milliarcseconds/year
B-V Index1.15
Spectral TypeK2III
Brightest in Night Sky50th
Colour(K) Orange to Red
Star Typegiant star
Exoplanet Count1
Radius (x the Sun)12.54
Luminosity (x the Sun)70.0000000
Calculated Effective Temperature4,576 Kelvin
Mass Compared to the Sun2.00
Metallicity0.00000

Location of Hamal in Aries


Hamal (Alpha Arietis) Location in Aries

The map was generated using Night Vision, an awesome free application by Brian Simpson.


List of Extrasolar Planets orbiting Hamal


NameMass (Jupiters)Orbital Period (Days)EccentricityDiscoveredSemi-Major AxisPeriastronLongitudeInclination
alf Ari b1.8380.8000.2520111.289.000

Hamal 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.

Hamal Solar System


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