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AU Microscopii

AU Microscopii Facts

  • AU Microscopii is a rotating/eruptive main sequence star that can be located in the constellation of Microscopium. The description is based on the spectral class.
  • AU Microscopii is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (M1Ve) of the star, the star's colour is red .
  • The star can not be seen by the naked eye, you need a telescope to see it.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 32.32 light years away from us. Distance

AU Microscopii's Alternative Names

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 GL 803. The star was part of the original catalogue devised by German Astronomer Wilheim Gliese of stars located within 20 parsecs of Earth. Star Names

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

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

Location of AU Microscopii

The location of the main sequence 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 object is compared to the celestial equator and is expressed in degrees. For AU Microscopii, the location is 20h 45m 09.34 and -31° 20` 24.1 .

Radial Velocity and Proper Motion of AU Microscopii

Proper Motion

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 milliarcseconds/year towards the north and 279.96 ± 1.06 milliarcseconds/year east if we saw them in the horizon.

Radial Velocity

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is -4.50000 km/s with an error of about 0.25 km/s . When the value is negative then the star and the Sun are getting closer to one another, likewise, a positive number means that two stars are moving away. Its nothing to fear as the stars are so far apart, they won't collide in our life-time, if ever.

Physical Properties of AU Microscopii

AU Microscopii Colour and Temperature

Based on the star's spectral type of M1Ve , AU Microscopii's colour and type is red main sequence star. The star has a B-V Colour Index of 1.47 which means the star's temperature is about 4,042 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

AU Microscopii 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 0.07 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

AU Microscopii Radius

AU Microscopii estimated 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. 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 0.3263052780472684597844571263. The figure is derived at by using the formula from SDSS rather than peer reviewed papers. It 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 100.59000 which gave the calculated distance to AU Microscopii as 32.43 light years away from Earth or 9.94 parsecs. If you want that in miles, it is about 190,643,820,852,344.47, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 100.91000 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.

Using the 2007 distance, the star is roughly 2,044,069.99 Astronomical Units from the Earth/Sun give or take a few. An Astronomical Unit is the distance between Earth and the Sun. The number of A.U. is the number of times that the star is from the Earth compared to the Sun. 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*.

Travel Time to AU Microscopii

The time it will take to travel to this star is dependent on how fast you are going. U.G. has done some calculations as to how long it will take going at differing speeds. A note about the calculations, when I'm talking about years, I'm talking non-leap years only (365 days).

The New Horizons space probe is the fastest probe that we've sent into space at the time of writing. Its primary mission was to visit Pluto which at the time of launch (2006), Pluto was still a planet.

DescriptionSpeed (m.p.h.)Time (years)
Walking45,418,582,362.32
Car120180,619,412.08
Airbus A38073629,448,817.19
Speed of Sound (Mach 1)767.26928,248,670.87
Concorde (Mach 2)1,534.5414,124,317.03
New Horizons Probe33,000656,797.86
Speed of Light670,616,629.0032.32

Variable Type of AU Microscopii

The star is a rotating/eruptive BY Draconis and Erup 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.

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Additional AU Microscopii Facts and Figures

Visual Facts


Primary / Proper / Traditional NameAU Microscopii
Alternative NamesAU Mic, HD 197481, HIP 102409, Gliese 803, AU Mic
Spectral TypeM1Ve
Constellation's Main StarNo
Multiple Star SystemYes
Star Type Main Sequence Dwarf Star
ColourRed
GalaxyMilky Way
ConstellationMicroscopium
Absolute Magnitude 8.82 / 8.83
Visual / Apparent Magnitude8.81
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)20h 45m 09.34
Declination (Dec.)-31° 20` 24.1
Galactic Latitude-36.80163918 degrees
Galactic Longitude12.65549504 degrees
1997 Distance from Earth100.59000 Parallax (milliarcseconds)
 32.43 Light Years
 9.94 Parsecs
2007 Distance from Earth100.91000 Parallax (milliarcseconds)
 32.32 Light Years
 9.91 Parsecs
 2,044,069.99 Astronomical Units
Galacto-Centric Distance24,109.99 Light Years / 7,392.00 Parsecs
Proper Motion Dec.-360.61000 ± 0.58000 milliarcseconds/year
Proper Motion RA.279.96000 ± 1.06000 milliarcseconds/year
B-V Index1.47
Radial Velocity-4.50000 ± 0.25 km/s
Eccentricity0.02500
Semi-Major Axis7264.0000000
Stellar Luminosity (Lsun)0.0700000

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


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

Estimated Calculated Facts


Radius (x the Sun)0.33
Effective Temperature4,042 Kelvin

Sources and Links


SIMBAD SourceLink

Related Stars


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