Universe Guide


AT Capricorni, HD195040, HIP101098

AT Capricorni is a white to yellow subgiant star that can be located in the constellation of Capricornus. The star can not be seen by the naked eye, you need a telescope to see it.

HIP101098 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD195040.

Location of AT Capricorni

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 AT Capricorni, the location is 20h 29m 36.85 and -21d07`34.6 .

Proper Motion of AT Capricorni

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 -11.99 ± 0.66 miliarcseconds/year towards the north and 2.51 ± 1.37 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of AT Capricorni

AT Capricorni has a spectral type of G6III/IV. This means the star is a white to yellow subgiant star. The star has a B-V Colour Index of 1.16 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,558 Kelvin.

AT Capricorni Radius has been calculated as being 262.67 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 182,768,039.61.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 32.31. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

AT Capricorni Apparent and Absolute Magnitudes

AT Capricorni has an apparent magnitude of 9.01 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 -6.22 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.67. 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 AT Capricorni

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 0.09 which gave the calculated distance to AT Capricorni as 36240.37 light years away from Earth or 11111.11 parsecs. It would take a spaceship travelling at the speed of light, 36240.37 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 0.73 which put AT Capricorni at a distance of 4467.99 light years or 1369.86 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.

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.

AT Capricorni Facts

Alternative Names

Traditional/Proper NameAT Capricorni
Hipparcos Library I.D.101098
Bonner DurchmusterungBD-21 5735
Henry Draper Designation195040

Visual Facts

Star Typesubgiant star
Absolute Magnitude-6.22 / -1.67
Visual / Apparent Magnitude9.01
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)20h 29m 36.85
Declination (Dec.)-21d07`34.6
Galactic Latitude-30.61 degrees
Galactic Longitude23.29 degrees
1997 Distance from Earth0.09 Parallax (milliarcseconds)
 36240.37 Light Years
 11111.11 Parsecs
2007 Revised Distance from Earth0.73 Parallax (milliarcseconds)
 4467.99 Light Years
 1369.86 Parsecs
Proper Motion Dec.-11.99 ± 0.66 milliarcseconds/year
Proper Motion RA.2.51 ± 1.37 milliarcseconds/year
B-V Index1.16
Radial Velocity-21.90 ± 0.80 km/s
Spectral TypeG6III/IV
Colour(G) White to Yellow

Estimated Facts

Calculated Effective Temperature4,558 Kelvin

Sources and Links

SIMBAD SourceLink

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