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AU Microscopii, HD197481, HIP102409

AU Microscopii is a red rotating/eruptive main sequence dwarf star that can be located in the constellation of Microscopium. AU Microscopii is the brightest star in Microscopium based on the Hipparcos 2007 apparent magnitude. The star can not be seen by the naked eye, you need a telescope to see it.

HIP102409 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD197481. The Gliese ID of the star is Gliese GL803. The star was part of the original catalogue devised by German Astronomer Wilheim Gliese of stars located within 20 parsecs of Earth. Ref : Star Names.

AU Microscopii has alternative name(s), AU Mic.

Location of AU Microscopii

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 AU Microscopii, the location is 20h 45m 09.34 and -31d20`24.1 .

Proper Motion of AU Microscopii

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 -360.61 ± 0.58 miliarcseconds/year towards the north and 279.96 ± 1.06 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of AU Microscopii

AU Microscopii has a spectral type of M1Ve. This means the star is a red main sequence dwarf star. The star is 7392.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24109.9943884800000000s. The star has a B-V Colour Index of 1.47 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,042 Kelvin.

AU Microscopii Radius has been calculated as being 0.33 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 228,091.25.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 0.33. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

AU Microscopii Apparent and Absolute Magnitudes

AU Microscopii has an apparent magnitude of 8.81 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 8.82 If you used the 2007 Parallax value, you would get an absolute magnitude of 8.83. 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 AU Microscopii

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 100.59 which gave the calculated distance to AU Microscopii as 32.43 light years away from Earth or 9.94 parsecs. It would take a spaceship travelling at the speed of light, 32.43 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 100.91 which put AU Microscopii at a distance of 32.32 light years or 9.91 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 7,392.00 Parsecs or 24,109.99 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 AU Microscopii

The star is a rotating/eruptive BY Draconis and Eruptive UV Ceti 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. AU Microscopii brightness ranges from a magnitude of 8.806 to a magnitude of 8.727 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 4.9 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.

AU Microscopii Facts

Alternative Names

Traditional/Proper NameAU Microscopii
Short NameAU Mic
Hipparcos Library I.D.102409
Gliese ID803
Henry Draper Designation197481

Visual Facts

Star Typemain sequence dwarf star
Absolute Magnitude8.82 / 8.83
Visual / Apparent Magnitude8.81
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)20h 45m 09.34
Declination (Dec.)-31d20`24.1
Galactic Latitude-36.80 degrees
Galactic Longitude12.66 degrees
1997 Distance from Earth100.59 Parallax (milliarcseconds)
 32.43 Light Years
 9.94 Parsecs
2007 Revised Distance from Earth100.91 Parallax (milliarcseconds)
 32.32 Light Years
 9.91 Parsecs
Galacto-Centric Distance24,109.99 Light Years / 7,392.00 Parsecs
Proper Motion Dec.-360.61 ± 0.58 milliarcseconds/year
Proper Motion RA.279.96 ± 1.06 milliarcseconds/year
B-V Index1.47
Radial Velocity-4.50 ± 0.25 km/s
Spectral TypeM1Ve
Colour(M) Red

Variable Star Details

Variable Star ClassRotating/Eruptive
Variable Star TypeBY Draconis and Eruptive UV Ceti
Mean Variability Period in Days4.890
Variable Magnitude Range (Brighter - Dimmer)8.727 - 8.806

Estimated Facts

Calculated Effective Temperature4,042 Kelvin

Sources and Links

SIMBAD SourceLink

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