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Vela X-1, HD77581, HIP44368

Vela X-1 is a blue eclipsing binary sys supergiant star that can be located in the constellation of Vela. The description is based on the spectral class. Vela X-1 is not part of the constellation but is within the borders of the constellation.

The star can not be seen by the naked eye, you need a telescope to see it.

Vela X-1's Alternative Names

HIP44368 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD77581.

Vela X-1 has alternative name(s) :- , GP Vel.

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

Location of Vela X-1

The location of the 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 star is compared to the celestial equator and is expressed in degrees. For Vela X-1, the location is 09h 02m 06.86 and -40° 33` 17.0 .

Radial Velocity and Proper Motion of Vela X-1

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 8.79 ± 0.34 miliarcseconds/year towards the north and -5.48 ± 0.43 miliarcseconds/year east if we saw them in the horizon.

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is -3.20 km/s with an error of about 0.90 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 Vela X-1

Vela X-1 has a spectral type of B0.5Ib. This means the star is a blue supergiant star. The star has a B-V Colour Index of 0.41 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,366 Kelvin.

Vela X-1 Apparent and Absolute Magnitudes

Vela X-1 has an apparent magnitude of 6.91 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 If you used the 2007 Parallax value, you would get an absolute magnitude of -3.22. 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 Vela X-1

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as -0.38 which gave the calculated distance to Vela X-1 as -8583.25 light years away from Earth or -2631.58 parsecs. It would take a spaceship travelling at the speed of light, -8583.25 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 0.94 which put Vela X-1 at a distance of 3469.82 light years or 1063.83 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 219,429,159.83 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 Vela X-1

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. Vela X-1 brightness ranges from a magnitude of 7.090 to a magnitude of 6.930 over its variable period. The smaller the magnitude, the brighter the star.

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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Vela X-1 Facts

Visual Facts


Primary / Proper / Traditional NameVela X-1
Alternative NamesHD 77581, HIP 44368, GP Vel
Spectral TypeB0.5Ib
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star Type very luminous Supergiant Star
Colour blue
GalaxyMilky Way
ConstellationVela
Absolute Magnitude / -3.22
Visual / Apparent Magnitude6.91
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)09h 02m 06.86
Declination (Dec.)-40° 33` 17.0
Galactic Latitude3.93 degrees
Galactic Longitude263.06 degrees
1997 Distance from Earth-0.38 Parallax (milliarcseconds)
 -8583.25 Light Years
 -2631.58 Parsecs
2007 Distance from Earth0.94 Parallax (milliarcseconds)
 3469.82 Light Years
 1063.83 Parsecs
 219,429,159.83 Astronomical Units
Proper Motion Dec.8.79 ± 0.34 milliarcseconds/year
Proper Motion RA.-5.48 ± 0.43 milliarcseconds/year
B-V Index0.41
Radial Velocity-3.20 ± 0.90 km/s

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassEclipsing binary sys
Variable Star TypeEclipsing
Variable Magnitude Range (Brighter - Dimmer)6.930 - 7.090

Estimated Facts


Calculated Effective Temperature6,366 Kelvin

Sources and Links


SIMBAD SourceLink

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