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Theta1 Microscopii

Theta1 Microscopii Facts

Theta1 Microscopii's Alternative Names

Theta1 Microscopii (The01 Mic) is the Bayer Classification for the star. The Bayer Classification was created by Johann Bayer in the early nineteenth century. The brightest star in the constellation is normally given the Alpha designation although there are exceptions such as Pollux which is Beta Geminorum.

The Id of the star in the Yale Bright Star Catalogue is HR8151. HIP105382 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD203006.

Theta1 Microscopii has alternative name(s) :- , the01 Mic.

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

Location of Theta1 Microscopii

The location of the variable 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 Theta1 Microscopii, the location is 21h 20m 45.58 and -40° 48` 34.2 .

Radial Velocity and Proper Motion of Theta1 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 20.38 ± 0.66 milliarcseconds/year towards the north and 71.92 ± 1.19 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 2.30 km/s with an error of about 2.80 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.

Theta1 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 36.64 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature) of Theta1 Microscopii

Theta1 Microscopii Colour and Temperature

Theta1 Microscopii has a spectral type of A2p. This means the star is a blue - white variable star. The star has a B-V Colour Index of 0.02 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 9,824 Kelvin.

Theta1 Microscopii Radius

Radius has been calculated as being 2.02 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,408,643.86.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 2.14. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Theta1 Microscopii Apparent and Absolute Magnitudes

Theta1 Microscopii has an apparent magnitude of 4.80 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 1.01 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.89. 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 Theta1 Microscopii

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 17.49 which gave the calculated distance to Theta1 Microscopii as 186.49 light years away from Earth or 57.18 parsecs. It would take a spaceship travelling at the speed of light, 186.49 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 16.54 which put Theta1 Microscopii at a distance of 197.20 light years or 60.46 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 12,470,683.29 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 7,360.00 Parsecs or 24,005.62 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 Theta1 Microscopii

The star is a eclipsing binary sys Eclipsing 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. This is a some uncertainty as to the type but the type mentioned is the current variable star classification for this star. Theta1 Microscopii brightness ranges from a magnitude of 4.842 to a magnitude of 4.817 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 2.1 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 Theta1 Microscopii Facts and Figures

Visual Facts


Primary / Proper / Traditional NameTheta1 Microscopii
Alternative NamesThe01 Mic, HD 203006, HIP 105382, HR 8151, the01 Mic
Spectral TypeA2p
Constellation's Main StarYes
Multiple Star SystemYes
Star TypeVariable Star
ColourBlue
GalaxyMilky Way
ConstellationMicroscopium
Absolute Magnitude 1.01 / 0.89
Visual / Apparent Magnitude4.80
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)21h 20m 45.58
Declination (Dec.)-40° 48` 34.2
Galactic Latitude-44.95 degrees
Galactic Longitude1.19 degrees
1997 Distance from Earth17.49 Parallax (milliarcseconds)
 186.49 Light Years
 57.18 Parsecs
2007 Distance from Earth16.54 Parallax (milliarcseconds)
 197.20 Light Years
 60.46 Parsecs
 12,470,683.29 Astronomical Units
Galacto-Centric Distance24,005.62 Light Years / 7,360.00 Parsecs
Proper Motion Dec.20.38 ± 0.66 milliarcseconds/year
Proper Motion RA.71.92 ± 1.19 milliarcseconds/year
B-V Index0.02
Radial Velocity2.30 ± 2.80 km/s
Eccentricity0.14
Semi-Major Axis8440.00
Stellar Luminosity (Lsun)36.64
Associated / Clustered StarsTheta2 Microscopii

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassEclipsing binary sys
Variable Star TypeEclipsing probably
Mean Variability Period in Days2.122
Variable Magnitude Range (Brighter - Dimmer)4.817 - 4.842

Estimated Calculated Facts


Radius (x the Sun)2.14
Effective Temperature9,824 Kelvin

Sources and Links


SIMBAD SourceLink

Multi-Star System

The star has been identified as being a multi-star system, one in which there is at least one star in close orbit to another star or two or more stars orbiting a central point. The stars may be of equal mass, unequal mass where one star is stronger than the other or be in groups orbiting a central point which doesn't necessarily have to be a star. More information can be found on my dedicated multiple star systems page. The source of the info is Simbad. The file is dated 2000 so any differences between this and any other source will be down to the actual source from where the information came from.


Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
203006-4114475.2A4.9000076.0000018.00000A2White
B7.4000076.0000018.000001991

Microscopium Main Stars


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