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BL Orionis (Carbon Star) Facts

BL Orionis Facts

  • BL Orionis is a pulsating Carbon star that can be located in the constellation of Orion. The description is based on the spectral class.
  • BL Orionis is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (C5II) of the star, the star's colour is carbon red .
  • The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 65232.67 light years away from us. Distance

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 11.90000 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 of BL Orionis

BL Orionis Colour and Temperature

Based on the star's spectral type of C5II , BL Orionis's colour and type is carbon red Carbon star. The star has a B-V Colour Index of 2.34 which means the star's temperature is about 176 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

BL Orionis Radius

BL Orionis estimated 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 1106568.510001937349741096848. 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.

BL Orionis Iron Abundance

BL Orionis 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. The value comes from the Hipparcos Extended Catalog.

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 2.51000 which gave the calculated distance to BL Orionis as 1299.46 light years away from Earth or 398.41 parsecs. If you want that in miles, it is about 7,639,038,527,437,173.85, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 0.05000 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.

Travel Time to BL Orionis

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)
Walking410,936,528,314,017.36
Car120364,550,943,800.58
Airbus A38073659,437,653,880.53
Speed of Sound (Mach 1)767.26957,015,353,488.89
Concorde (Mach 2)1,534.5428,507,639,589.76
New Horizons Probe33,0001,325,639,795.64
Speed of Light670,616,629.0065,232.67

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 Latitude1.06319263 degrees
Galactic Longitude196.90533810 degrees
1997 Distance from Earth2.51000 Parallax (milliarcseconds)
 1299.46 Light Years
 398.41 Parsecs
2007 Distance from Earth0.05000 Parallax (milliarcseconds)
 65232.67 Light Years
 20000 Parsecs
 4,125,267,379.68 Astronomical Units
Proper Motion Dec.-5.65000 ± 0.36000 milliarcseconds/year
Proper Motion RA.-3.55000 ± 0.47000 milliarcseconds/year
B-V Index2.34
Radial Velocity11.90000 ± 1.80 km/s
Iron Abundance-0.1000 ± 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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