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BY Microscopii

BY Microscopii Facts

BY Microscopii's Alternative Names

HIP103168 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD198853.

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

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

Location of BY Microscopii

The location of the giant 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 BY Microscopii, the location is 20h 54m 06.58 and -27° 55` 30.7 .

Radial Velocity and Proper Motion of BY 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 -17.36 ± 0.30 milliarcseconds/year towards the north and -11.13 ± 0.52 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 25.20 km/s with an error of about 0.60 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 (Colour, Temperature) of BY Microscopii

BY Microscopii Colour and Temperature

BY Microscopii has a spectral type of M1III. This means the star is a red giant star. The star has a B-V Colour Index of 1.63 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,700 Kelvin.

BY Microscopii Radius

Radius has been calculated as being 34.87 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 24,265,738.46.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 37.37. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

BY Microscopii Apparent and Absolute Magnitudes

BY Microscopii has an apparent magnitude of 6.41 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 -0.93 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.08. 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 BY Microscopii

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 3.41 which gave the calculated distance to BY Microscopii as 956.49 light years away from Earth or 293.26 parsecs. It would take a spaceship travelling at the speed of light, 956.49 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 3.18 which put BY Microscopii at a distance of 1025.67 light years or 314.47 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 64,863,641.64 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 7,173.00 Parsecs or 23,395.70 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 BY Microscopii

The star is a unknown Small-Amplitude Red 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. BY Microscopii brightness ranges from a magnitude of 6.522 to a magnitude of 6.491 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 7.3 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 BY Microscopii Facts and Figures

Visual Facts


Primary / Proper / Traditional NameBY Microscopii
Alternative NamesBY Mic, HD 198853, HIP 103168, BY Mic
Spectral TypeM1III
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeGiant Star
ColourRed
GalaxyMilky Way
ConstellationMicroscopium
Absolute Magnitude -0.93 / -1.08
Visual / Apparent Magnitude6.41
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)20h 54m 06.58
Declination (Dec.)-27° 55` 30.7
Galactic Latitude-37.93 degrees
Galactic Longitude17.39 degrees
1997 Distance from Earth3.41 Parallax (milliarcseconds)
 956.49 Light Years
 293.26 Parsecs
2007 Distance from Earth3.18 Parallax (milliarcseconds)
 1025.67 Light Years
 314.47 Parsecs
 64,863,641.64 Astronomical Units
Galacto-Centric Distance23,395.70 Light Years / 7,173.00 Parsecs
Proper Motion Dec.-17.36 ± 0.30 milliarcseconds/year
Proper Motion RA.-11.13 ± 0.52 milliarcseconds/year
B-V Index1.63
Radial Velocity25.20 ± 0.60 km/s
Eccentricity0.21
Semi-Major Axis6845.00

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassUnknown
Variable Star TypeSmall-Amplitude Red
Mean Variability Period in Days7.323
Variable Magnitude Range (Brighter - Dimmer)6.491 - 6.522

Estimated Calculated Facts


Radius (x the Sun)37.37
Effective Temperature3,700 Kelvin

Sources and Links


SIMBAD SourceLink

Related Stars


Comments and Questions

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