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Rho1 Arae, HD152478, HIP82868

Primary Facts on Rho1 Arae

  • Rho1 Arae's star type is eruptive main sequence dwarf star that can be located in the constellation of Ara. The description is based on the spectral class.
  • Rho1 Arae is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (B3Vnpe) of the star, the star's colour is blue .
  • 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 644.59 light years away from us.

Rho1 Arae's Alternative Names

(Rho1 Arae) is the Bayer Classification for the star. HIP82868 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD152478.

Rho1 Arae has alternative name(s) :- , V846 Ara.

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

Location of Rho1 Arae

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 Rho1 Arae, the location is 16h 56m 08.85 and -50° 40` 29.2 .

Radial Velocity and Proper Motion of Rho1 Arae

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 -9.79 ± 0.29 miliarcseconds/year towards the north and -7.66 ± 0.39 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 19.00 km/s with an error of about 4.30 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.

Rho1 Arae Luminosity

Luminosity is the amount of energy that a star pumps out and its relative to the amount that our star, the Sun gives out. The figure of 121.32 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature) of Rho1 Arae

Rho1 Arae has a spectral type of B3Vnpe. This means the star is a blue main sequence dwarf star. The star is 7,221.00 Parsecs from the Galactic Centre or in terms of Light Years is 23,552.26 s. The star has a B-V Colour Index of -0.01 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 9,679 Kelvin.

Rho1 Arae Radius has been calculated as being 4.20 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,922,347.50.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 3.61. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Rho1 Arae Apparent and Absolute Magnitudes

Rho1 Arae 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 -0.51 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.18. 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 Rho1 Arae

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 4.34 which gave the calculated distance to Rho1 Arae as 751.53 light years away from Earth or 230.41 parsecs. It would take a spaceship travelling at the speed of light, 751.53 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 5.06 which put Rho1 Arae at a distance of 644.59 light years or 197.63 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 40,763,829.61 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.

The star's Galacto-Centric Distance is 7,221.00 Parsecs or 23,552.26 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 Rho1 Arae

The star is a eruptive 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. Rho1 Arae brightness ranges from a magnitude of 6.367 to a magnitude of 6.268 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.1 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 Rho1 Arae Facts and Figures

Visual Facts


Primary / Proper / Traditional NameRho1 Arae
Alternative NamesHD 152478, HIP 82868, V846 Ara
Spectral TypeB3Vnpe
Constellation's Main StarNo
Multiple Star SystemYes
Star Type main sequence Dwarf Star
Colour blue
GalaxyMilky Way
ConstellationAra
Absolute Magnitude -0.51 / -0.18
Visual / Apparent Magnitude6.30
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)16h 56m 08.85
Declination (Dec.)-50° 40` 29.2
Galactic Latitude-4.64 degrees
Galactic Longitude336.78 degrees
1997 Distance from Earth4.34 Parallax (milliarcseconds)
 751.53 Light Years
 230.41 Parsecs
2007 Distance from Earth5.06 Parallax (milliarcseconds)
 644.59 Light Years
 197.63 Parsecs
 40,763,829.61 Astronomical Units
Galacto-Centric Distance23,552.26 Light Years / 7,221.00 Parsecs
Proper Motion Dec.-9.79 ± 0.29 milliarcseconds/year
Proper Motion RA.-7.66 ± 0.39 milliarcseconds/year
B-V Index-0.01
Radial Velocity19.00 ± 4.30 km/s
Eccentricity0.14
Semi-Major Axis6857.00
Stellar Luminosity (Lsun)121.32
Associated / Clustered StarsRho2 Arae

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassEruptive
Variable Star TypeIrregular
Mean Variability Period in Days0.077
Variable Magnitude Range (Brighter - Dimmer)6.268 - 6.367

Estimated Facts


Calculated Effective Temperature9,679 Kelvin

Sources and Links


SIMBAD SourceLink

Related Stars


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