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Alpha Pyxidis, HD74575, HIP42828, HR3468

Alpha Pyxidis is a blue giant star that can be located in the constellation of Pyxis. The description is based on the spectral class. Alpha Pyxidis is the 1st brightest star in Pyxis 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.

Alpha Pyxidis's Alternative Names

Alpha Pyxidis (Alf Pyx) is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR3468. HIP42828 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD74575.

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

Location of Alpha Pyxidis

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 Alpha Pyxidis, the location is 08h 43m 35.55 and -33° 11` 11.1 .

Proper Motion of Alpha Pyxidis

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 10.43 ± 0.09 miliarcseconds/year towards the north and -14.27 ± 0.14 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 us is 15.30000 km/s with an error of about 2.70 km/s .

Alpha Pyxidis 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 6,959.36 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 Alpha Pyxidis

Alpha Pyxidis has a spectral type of B1.5III. This means the star is a blue giant star. The star is 7,474.00 Parsecs from the Galactic Centre or terms of Light Years is 24,377.45 s. The star has a B-V Colour Index of -0.18 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 15,433 Kelvin.

Alpha Pyxidis Radius has been calculated as being 6.22 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 4,330,324.07.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 6.46. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's Iron Abundance is -0.13 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

Alpha Pyxidis Apparent and Absolute Magnitudes

Alpha Pyxidis has an apparent magnitude of 3.68 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 -3.39 If you used the 2007 Parallax value, you would get an absolute magnitude of -3.47. 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 Alpha Pyxidis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 3.86 which gave the calculated distance to Alpha Pyxidis as 844.98 light years away from Earth or 259.07 parsecs. It would take a spaceship travelling at the speed of light, 844.98 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 3.71 which put Alpha Pyxidis at a distance of 879.15 light years or 269.54 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 7,474.00 Parsecs or 24,377.45 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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Alpha Pyxidis Facts

Visual Facts


 Alpha Pyxidis
Alternative NamesAlf Pyx, HD 74575, HIP 42828, HR 3468
Spectral TypeB1.5III
Multiple Star SystemNo / Unknown
Star TypeGiant Star
Colour blue
GalaxyMilky Way
ConstellationPyxis
Absolute Magnitude-3.39 / -3.47
Visual / Apparent Magnitude3.68
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)08h 43m 35.55
Declination (Dec.)-33° 11` 11.1
Galactic Latitude5.77 degrees
Galactic Longitude254.99 degrees
1997 Distance from Earth3.86 Parallax (milliarcseconds)
 844.98 Light Years
 259.07 Parsecs
2007 Distance from Earth3.71 Parallax (milliarcseconds)
 879.15 Light Years
 269.54 Parsecs
Galacto-Centric Distance24,377.45 Light Years / 7,474.00 Parsecs
Proper Motion Dec.10.43 ± 0.09 milliarcseconds/year
Proper Motion RA.-14.27 ± 0.14 milliarcseconds/year
B-V Index-0.18
Radial Velocity15.30 ± 2.70 km/s
Iron Abundance-0.13 ± 9.99 Fe/H
Eccentricity0.06
Semi-Major Axis7939.00
Stellar Luminosity (Lsun)6,959.36

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Estimated Facts


Calculated Effective Temperature15,433 Kelvin

Sources and Links


SIMBAD SourceLink

Location of Alpha Pyxidis in Pyxis


Alpha Pyxidis (Alpha Pyxidis) Location in Pyxis

The map was generated using Night Vision, an awesome free application by Brian Simpson.

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