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BL Orionis (Carbon Star) Facts

BL Orionis Facts

BL Orionis's Alternative Names

The Id of the star in the Yale Bright Star Catalogue is HR2308. HIP30564 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD44984.

BL Orionis has alternative name(s) :- , BL Ori.

BD number is the number that the star was filed under in the Durchmusterung or Bonner Durchmusterung, a star catalogue that was put together by the Bonn Observatory between 1859 to 1903. The star's BD Number is BD+14 1283.

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

Location of BL Orionis

The location of the carbon 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 BL Orionis, the location is 06h 25m 28.18 and +14° 43` 19.2 .

Radial Velocity and Proper Motion of BL Orionis

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 -5.65 ± 0.36 milliarcseconds/year towards the north and -3.55 ± 0.47 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 11.90 km/s with an error of about 1.80 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.

Physical Properties (Colour, Temperature) of BL Orionis

BL Orionis Colour and Temperature

BL Orionis has a spectral type of C5II. This means the star is a carbon red carbon star. The star has a B-V Colour Index of 2.34 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 176 Kelvin.

BL Orionis Radius

Radius has been calculated as being 21,973.27 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 15,289,003,652.03.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 1106568.51. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's Iron Abundance is -0.10 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

BL Orionis Apparent and Absolute Magnitudes

BL Orionis has an apparent magnitude of 6.30 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 -1.70 If you used the 2007 Parallax value, you would get an absolute magnitude of -10.21. 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 BL Orionis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 2.51 which gave the calculated distance to BL Orionis as 1299.46 light years away from Earth or 398.41 parsecs. It would take a spaceship travelling at the speed of light, 1299.46 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 0.05 which put BL Orionis at a distance of 65232.67 light years or 20000 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 4,125,267,379.68 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 BL Orionis

The star is a pulsating Slow Irregular 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. BL Orionis brightness ranges from a magnitude of 6.445 to a magnitude of 6.151 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 BL Orionis Facts and Figures

Visual Facts


Primary / Proper / Traditional NameBL Orionis
Alternative NamesBl Ori, HD 44984, HIP 30564, HR 2308, BD+14 1283, BL Ori
Spectral TypeC5II
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeCarbon Star
ColourRed
GalaxyMilky Way
ConstellationOrion
Absolute Magnitude -1.70 / -10.21
Visual / Apparent Magnitude6.30
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)06h 25m 28.18
Declination (Dec.)+14° 43` 19.2
Galactic Latitude1.06 degrees
Galactic Longitude196.91 degrees
1997 Distance from Earth 2.51 Parallax (milliarcseconds)
 1299.46 Light Years
 398.41 Parsecs
2007 Distance from Earth0.05 Parallax (milliarcseconds)
 65232.67 Light Years
 20000 Parsecs
 4,125,267,379.68 Astronomical Units
Proper Motion Dec.-5.65 ± 0.36 milliarcseconds/year
Proper Motion RA.-3.55 ± 0.47 milliarcseconds/year
B-V Index2.34
Radial Velocity11.90 ± 1.80 km/s
Iron Abundance-0.10 ± 9.99 Fe/H

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassPulsating
Variable Star TypeSlow Irregular
Mean Variability Period in Days0.242
Variable Magnitude Range (Brighter - Dimmer)6.151 - 6.445

Estimated Calculated Facts


Radius (x the Sun)1,106,568.51
Effective Temperature176 Kelvin

Sources and Links


SIMBAD SourceLink

Related Stars


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