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Decrux, Delta Crucis, HD106490, HIP59747, HR4656

Decrux Location in Crux

Primary Facts on Decrux

  • Decrux's star type is subgiant star that can be located in the constellation of Crux. The description is based on the spectral class.
  • Decrux is a main star of the constellation outline.
  • Based on the spectral type (B2IV) of the star, the star's colour is blue .
  • Delta Crucis is the Bayer name for the star. It was assigned this name by Johann Bayer in 1603. The closer to the start of the Greek Alphabet the name, the brighter the star is. Alpha stars tend to be the brightest in the constellation. A notable exception is Pollux (Beta Geminorum) which is the brighest star in the Gemini constellation.
  • 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 345.15 light years away from us.

Decrux's Alternative Names

Delta Crucis (Del Cru) is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR4656. HIP59747 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD106490.

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

Location of Decrux

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 Decrux, the location is 12h 15m 08.76 and -58° 44` 56.0 .

Radial Velocity and Proper Motion of Decrux

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 -10.36 ± 0.10 miliarcseconds/year towards the north and -35.81 ± 0.15 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 22.20 km/s with an error of about 2.60 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.

Decrux 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 2,984.52 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 Decrux

Decrux has a spectral type of B2IV. This means the star is a blue subgiant star. The star is 7,351.00 Parsecs from the Galactic Centre or in terms of Light Years is 23,976.27 s. The star has a B-V Colour Index of -0.19 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 16,152 Kelvin.

Decrux Radius has been calculated as being 3.69 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,564,243.55.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 3.49. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Decrux Apparent and Absolute Magnitudes

Decrux has an apparent magnitude of 2.79 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 -2.45 If you used the 2007 Parallax value, you would get an absolute magnitude of -2.33. 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 Decrux

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 8.96 which gave the calculated distance to Decrux as 364.02 light years away from Earth or 111.61 parsecs. It would take a spaceship travelling at the speed of light, 364.02 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 9.45 which put Decrux at a distance of 345.15 light years or 105.82 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 21,826,789.71 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 7,351.00 Parsecs or 23,976.27 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

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 Decrux Facts and Figures

Visual Facts


Primary / Proper / Traditional NameDecrux
Alternative NamesDelta Crucis, Del Cru, HD 106490, HIP 59747, HR 4656
Spectral TypeB2IV
Constellation's Main StarYes
Multiple Star SystemNo / Unknown
Star TypeSubgiant Star
Colour blue
GalaxyMilky Way
ConstellationCrux
Absolute Magnitude -2.45 / -2.33
Visual / Apparent Magnitude2.79
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)12h 15m 08.76
Declination (Dec.)-58° 44` 56.0
Galactic Latitude3.79 degrees
Galactic Longitude298.23 degrees
1997 Distance from Earth8.96 Parallax (milliarcseconds)
 364.02 Light Years
 111.61 Parsecs
2007 Distance from Earth9.45 Parallax (milliarcseconds)
 345.15 Light Years
 105.82 Parsecs
 21,826,789.71 Astronomical Units
Galacto-Centric Distance23,976.27 Light Years / 7,351.00 Parsecs
Proper Motion Dec.-10.36 ± 0.10 milliarcseconds/year
Proper Motion RA.-35.81 ± 0.15 milliarcseconds/year
B-V Index-0.19
Radial Velocity22.20 ± 2.60 km/s
Eccentricity0.14
Semi-Major Axis6455.00
Stellar Luminosity (Lsun)2,984.52

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Estimated Facts


Calculated Effective Temperature16,152 Kelvin

Sources and Links


SIMBAD SourceLink

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