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BT Phoenicis

BT Phoenicis Facts

BT Phoenicis's Alternative Names

HIP3852 is the reference name for the star in the Hipparcos Star Catalogue.

BT Phoenicis has alternative name(s) :- , BT Phe.

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

Location of BT Phoenicis

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 BT Phoenicis, the location is 00h 49m 29.44 and -55° 45` 52.4 .

Proper Motion of BT Phoenicis

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 1.55 ± 0.81 milliarcseconds/year towards the north and 6.97 ± 1.12 milliarcseconds/year east if we saw them in the horizon. . 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 BT Phoenicis

BT Phoenicis Colour and Temperature

BT Phoenicis has a spectral type of M2. This means the star is a red variable star. The star has a B-V Colour Index of 1.6 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,775 Kelvin.

BT Phoenicis Radius

Radius has been calculated as being 13.84 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 9,628,179.96.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 14.62. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

BT Phoenicis Apparent and Absolute Magnitudes

BT Phoenicis has an apparent magnitude of 9.39 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 0.99 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.87. 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 BT Phoenicis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 2.09 which gave the calculated distance to BT Phoenicis as 1560.59 light years away from Earth or 478.47 parsecs. It would take a spaceship travelling at the speed of light, 1560.59 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 1.98 which put BT Phoenicis at a distance of 1647.29 light years or 505.05 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 104,173,314.51 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.

Variable Type of BT Phoenicis

The star is a pulsating Semi-Regular Star w 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. BT Phoenicis brightness ranges from a magnitude of 9.641 to a magnitude of 9.383 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.2 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 BT Phoenicis Facts and Figures

Visual Facts


Primary / Proper / Traditional NameBT Phoenicis
Alternative NamesHIP 3852, BT Phe
Spectral TypeM2
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeVariable Star
ColourRed
GalaxyMilky Way
ConstellationPhoenix
Absolute Magnitude 0.99 / 0.87
Visual / Apparent Magnitude9.39
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)00h 49m 29.44
Declination (Dec.)-55° 45` 52.4
Galactic Latitude-61.36 degrees
Galactic Longitude303.50 degrees
1997 Distance from Earth2.09 Parallax (milliarcseconds)
 1560.59 Light Years
 478.47 Parsecs
2007 Distance from Earth1.98 Parallax (milliarcseconds)
 1647.29 Light Years
 505.05 Parsecs
 104,173,314.51 Astronomical Units
Proper Motion Dec.1.55 ± 0.81 milliarcseconds/year
Proper Motion RA.6.97 ± 1.12 milliarcseconds/year
B-V Index1.60

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassPulsating
Variable Star TypeSemi-Regular Star w
Mean Variability Period in Days0.222
Variable Magnitude Range (Brighter - Dimmer)9.383 - 9.641

Estimated Calculated Facts


Radius (x the Sun)14.62
Effective Temperature3,775 Kelvin

Sources and Links


SIMBAD SourceLink

Related Stars


Comments and Questions

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