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HM Librae - HD137613 - HIP75694

HM Librae is a pulsating star that can be located in the constellation of Libra. The star can not be seen by the naked eye, you need a telescope to see it.

HIP75694 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD137613.

HM Librae has alternative name(s), HM_Lib.

Location of HM Librae

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 HM Librae, the location is 15h 27m 48.32 and -25d10`10.1 .

Proper Motion of HM Librae

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 -10.28 ± 0.40 miliarcseconds/year towards the north and 0.40 ± 1.01 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Temperature, Radius) of HM Librae

HM Librae has a spectral type of C. This means the star is a star. The star has a B-V Colour Index of 1.19 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,586 Kelvin. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

HM Librae Apparent and Absolute Magnitudes

HM Librae has an apparent magnitude of 7.49 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 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.38. 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 HM Librae

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as -1.36 which gave the calculated distance to HM Librae as -2398.26 light years away from Earth or -735.29 parsecs. It would take a spaceship travelling at the speed of light, -2398.26 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 1.68 which put HM Librae at a distance of 1941.45 light years or 595.24 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.

Variable Type of HM Librae

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. HM Librae brightness ranges from a magnitude of 8.000 to a magnitude of 8.000 over its variable period. The smaller the magnitude, the brighter the star.

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.

HM Librae Facts

Alternative Names

Traditional/Proper NameHM Librae
Short NameHM Lib
Hipparcos Library I.D.75694
Henry Draper Designation137613

Visual Facts

Star Type star
Visual / Apparent Magnitude7.49
Naked Eye VisibleRequires a 7x50 Binoculars - Ref: Wiki
Right Ascension (R.A.)15h 27m 48.32
Declination (Dec.)-25d10`10.1
Galactic Latitude25.55 degrees
Galactic Longitude342.17 degrees
1997 Distance from Earth-1.36 Parallax (milliarcseconds)
 -2398.26 Light Years
 -735.29 Parsecs
2007 Revised Distance from Earth1.68 Parallax (milliarcseconds)
 1941.45 Light Years
 595.24 Parsecs
Proper Motion Dec.-10.28 ± 0.40 milliarcseconds/year
Proper Motion RA.0.40 ± 1.01 milliarcseconds/year
B-V Index1.19
Radial Velocity54.80 ± 2.60 km/s
Spectral TypeC

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeSemi-Regular Star which are giants or supergiants of intermediate and late spectral

Estimated Facts

Calculated Effective Temperature4,586 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars


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