Universe Guide


AX Circini, HD130701, HIP72773

AX Circini is a blue to white pulsating luminous giant star that can be located in the constellation of Circinus. AX Circini is the brightest star in Circinus 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.

HIP72773 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD130701.

AX Circini has alternative name(s), AX Cir.

Location of AX Circini

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 AX Circini, the location is 14h 52m 35.27 and -63d48`35.3 .

Proper Motion of AX Circini

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 -5.37 ± 0.58 miliarcseconds/year towards the north and -10.42 ± 0.86 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of AX Circini

AX Circini has a spectral type of F8II + A/F. This means the star is a blue to white luminous giant star. The star has a B-V Colour Index of 0.66 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,739 Kelvin.

AX Circini Radius has been calculated as being 19.29 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 13,419,322.74.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 31.42. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

AX Circini Apparent and Absolute Magnitudes

AX Circini has an apparent magnitude of 5.91 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 -1.55 If you used the 2007 Parallax value, you would get an absolute magnitude of -2.61. 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 AX Circini

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 3.22 which gave the calculated distance to AX Circini as 1012.93 light years away from Earth or 310.56 parsecs. It would take a spaceship travelling at the speed of light, 1012.93 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 1.98 which put AX Circini at a distance of 1647.29 light years or 505.05 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.

Variable Type of AX Circini

The star is a pulsating Delta Cepheid 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. AX Circini brightness ranges from a magnitude of 6.228 to a magnitude of 5.782 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 5.3 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.

AX Circini Facts

Alternative Names

Traditional/Proper NameAX Circini
Short NameAX Cir
Hipparcos Library I.D.72773
Henry Draper Designation130701

Visual Facts

Star Typeluminous giant star
Absolute Magnitude-1.55 / -2.61
Visual / Apparent Magnitude5.91
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)14h 52m 35.27
Declination (Dec.)-63d48`35.3
Galactic Latitude-4.01 degrees
Galactic Longitude315.83 degrees
1997 Distance from Earth3.22 Parallax (milliarcseconds)
 1012.93 Light Years
 310.56 Parsecs
2007 Revised Distance from Earth1.98 Parallax (milliarcseconds)
 1647.29 Light Years
 505.05 Parsecs
Proper Motion Dec.-5.37 ± 0.58 milliarcseconds/year
Proper Motion RA.-10.42 ± 0.86 milliarcseconds/year
B-V Index0.66
Radial Velocity-20.90 ± 4.60 km/s
Spectral TypeF8II + A/F
Colour(F) blue to white

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeDelta Cepheid
Mean Variability Period in Days5.273
Variable Magnitude Range (Brighter - Dimmer)5.782 - 6.228

Estimated Facts

Calculated Effective Temperature5,739 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
130701-63 3436.4A6.20000-10.00000-4.00000F8Yellow/White

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