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Tau1 Lupi, HD126341, HIP70574

Tau1 Lupi is a blue pulsating subgiant star that can be located in the constellation of Lupus. Tau1 Lupi is the brightest star in Lupus based on the Hipparcos 2007 apparent magnitude. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

Tau1 Lupi is the Bayer Classification for the star. HIP70574 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD126341.

Tau1 Lupi has alternative name(s), tau01 Lup.

Location of Tau1 Lupi

The location of the star in the galaxy 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 Tau1 Lupi, the location is 14h 26m 08.24 and -45d13`17.0 .

Proper Motion of Tau1 Lupi

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 -14.67 ± 0.11 miliarcseconds/year towards the north and -13.09 ± 0.21 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Tau1 Lupi

Tau1 Lupi has a spectral type of B2IV. This means the star is a blue subgiant star. The star is 7157.00000000 Parsecs from the Galactic Centre or terms of Light Years is 23343.5105300800000000s. The star has a B-V Colour Index of -0.14 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 13,196 Kelvin.

Tau1 Lupi Radius has been calculated as being 6.95 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 4,836,510.98.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 7.31. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Tau1 Lupi Apparent and Absolute Magnitudes

Tau1 Lupi has an apparent magnitude of 4.56 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 -2.95 If you used the 2007 Parallax value, you would get an absolute magnitude of -3.06. 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 Tau1 Lupi

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 3.15 which gave the calculated distance to Tau1 Lupi as 1035.44 light years away from Earth or 317.46 parsecs. It would take a spaceship travelling at the speed of light, 1035.44 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 2.99 which put Tau1 Lupi at a distance of 1090.85 light years or 334.45 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.

The star's Galacto-Centric Distance is 7,157.00 Parsecs or 23,343.51 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 Tau1 Lupi

The star is a pulsating Beta Cephei 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. Tau1 Lupi brightness ranges from a magnitude of 4.524 to a magnitude of 4.494 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.

Tau1 Lupi Facts

Alternative Names

Short Nametau01 Lup
Bayer DesignationTau1 Lupi
Hipparcos Library I.D.70574
Henry Draper Designation126341

Visual Facts

Star Typesubgiant star
Absolute Magnitude-2.95 / -3.06
Visual / Apparent Magnitude4.56
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)14h 26m 08.24
Declination (Dec.)-45d13`17.0
Galactic Latitude14.50 degrees
Galactic Longitude319.92 degrees
1997 Distance from Earth3.15 Parallax (milliarcseconds)
 1035.44 Light Years
 317.46 Parsecs
2007 Revised Distance from Earth2.99 Parallax (milliarcseconds)
 1090.85 Light Years
 334.45 Parsecs
Galacto-Centric Distance23,343.51 Light Years / 7,157.00 Parsecs
Proper Motion Dec.-14.67 ± 0.11 milliarcseconds/year
Proper Motion RA.-13.09 ± 0.21 milliarcseconds/year
B-V Index-0.14
Radial Velocity-21.50 ± 2.80 km/s
Spectral TypeB2IV
Colour(B) blue

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeBeta Cephei
Mean Variability Period in Days0.177
Variable Magnitude Range (Brighter - Dimmer)4.494 - 4.524

Estimated Facts

Calculated Effective Temperature13,196 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Multi-Star System

The star has been identified as being a multi-star system, one in which there is at least one star in close orbit to another star or two or more stars orbiting a central point. The stars may be of equal mass, unequal mass where one star is stronger than the other or be in groups orbiting a central point which doesn't necessarily have to be a star. More information can be found on my dedicated multiple star systems page. The source of the info is Simbad. The file is dated 2000 so any differences between this and any other source will be down to the actual source from where the information came from.


Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
126341-44 9322.2A4.60000-13.00000-15.00000B3Blue/White
-44 9321.2B9.30000-37.00000-7.00000M0Red1913

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