Universe Guide


Mu2 Scorpii, HD151985, HIP82545

Mu2 Scorpii is a blue subgiant star that can be located in the constellation of Scorpius. Mu2 Scorpii is the brightest star in Scorpius 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.

Mu2 Scorpii is the Bayer Classification for the star. HIP82545 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD151985.

Location of Mu2 Scorpii

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 Mu2 Scorpii, the location is 16h 52m 20.15 and -38d01`02.9 .

Proper Motion of Mu2 Scorpii

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 -23.32 ± 0.09 miliarcseconds/year towards the north and -11.09 ± 0.12 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Mu2 Scorpii

Mu2 Scorpii has a spectral type of B2IV. This means the star is a blue subgiant star. The star is 7259.00000000 Parsecs from the Galactic Centre or terms of Light Years is 23676.1971409600000000s. The star has a B-V Colour Index of -0.21 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 17,850 Kelvin.

Mu2 Scorpii Radius has been calculated as being 3.00 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,089,947.34.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 2.75. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Mu2 Scorpii Apparent and Absolute Magnitudes

Mu2 Scorpii has an apparent magnitude of 3.56 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 -2.44 If you used the 2007 Parallax value, you would get an absolute magnitude of -2.25. 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 Mu2 Scorpii

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 6.31 which gave the calculated distance to Mu2 Scorpii as 516.90 light years away from Earth or 158.48 parsecs. It would take a spaceship travelling at the speed of light, 516.90 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 6.88 which put Mu2 Scorpii at a distance of 474.07 light years or 145.35 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 7,259.00 Parsecs or 23,676.20 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.

Mu2 Scorpii Facts

Alternative Names

Bayer DesignationMu2 Scorpii
Hipparcos Library I.D.82545
Henry Draper Designation151985

Visual Facts

Star Typesubgiant star
Absolute Magnitude-2.44 / -2.25
Visual / Apparent Magnitude3.56
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)16h 52m 20.15
Declination (Dec.)-38d01`02.9
Galactic Latitude3.86 degrees
Galactic Longitude346.20 degrees
1997 Distance from Earth6.31 Parallax (milliarcseconds)
 516.90 Light Years
 158.48 Parsecs
2007 Revised Distance from Earth6.88 Parallax (milliarcseconds)
 474.07 Light Years
 145.35 Parsecs
Galacto-Centric Distance23,676.20 Light Years / 7,259.00 Parsecs
Proper Motion Dec.-23.32 ± 0.09 milliarcseconds/year
Proper Motion RA.-11.09 ± 0.12 milliarcseconds/year
B-V Index-0.21
Radial Velocity1.30 ± 0.80 km/s
Spectral TypeB2IV
Colour(B) blue

Estimated Facts

Calculated Effective Temperature17,850 Kelvin

Sources and Links

SIMBAD SourceLink

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