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AT Circini

AT Circini Facts

  • AT Circini is a eclipsing subgiant star that can be located in the constellation of Circinus. The description is based on the spectral class.
  • AT Circini is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (A5IV/Vs) of the star, the star's colour is blue - white .
  • The star can not be seen by the naked eye, you need a telescope to see it.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 489.00 light years away from us. Distance

AT Circini's Alternative Names

HIP68692 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD122314.

AT Circini has alternative name(s) :- AT Cir, AT Cir.

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

Location of AT Circini

The location of the subgiant 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 object is compared to the celestial equator and is expressed in degrees. For AT Circini, the location is 14h 03m 38.30 and -66° 44` 07.2 .

Proper Motion of AT 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 -26.65 ± 0.46 milliarcseconds/year towards the north and -39.42 ± 0.72 milliarcseconds/year east if we saw them in the horizon. . 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.

Physical Properties of AT Circini

AT Circini Temperature and Colour

Based on the star's spectral type of A5IV/Vs , AT Circini's colour and type is blue - white subgiant star. The star has a B-V Colour Index of 0.34 which means the star's temperature is about 7,016 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

AT Circini 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 16.27 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

AT Circini Radius

AT Circini estimated radius has been calculated as being 3.18 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 2,214,083.73.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 2.84. The figure is derived at by using the formula from SDSS rather than peer reviewed papers. It has been known to produce widely incorrect figures.

AT Circini Apparent and Absolute Magnitudes

AT Circini has an apparent magnitude of 7.62 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 1.49 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.74. 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 Circini

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 5.95 which gave the calculated distance to AT Circini as 548.17 light years away from Earth or 168.07 parsecs. If you want that in miles, it is about 3,222,486,070,818,059.49, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 6.67 which put AT Circini at a distance of 489.00 light years or 149.93 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 30,925,066.91 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 7,306.00 Parsecs or 23,829.49 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Travel Time to AT Circini

The time it will take to travel to this star is dependent on how fast you are going. U.G. has done some calculations as to how long it will take going at differing speeds. A note about the calculations, when I'm talking about years, I'm talking non-leap years only (365 days).

The New Horizons space probe is the fastest probe that we've sent into space at the time of writing. Its primary mission was to visit Pluto which at the time of launch (2006), Pluto was still a planet.

DescriptionSpeed (m.p.h.)Time (years)
Walking481,982,882,895.25
Car1202,732,762,763.18
Airbus A380736445,559,146.17
Speed of Sound (Mach 1)767.269427,400,991.80
Concorde (Mach 2)1,534.54213,700,217.38
New Horizons Probe33,0009,937,319.14
Speed of Light670,616,629.00489.00

Variable Type of AT Circini

The star is a eclipsing Beta Persei (Algol)/ 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. AT Circini brightness ranges from a magnitude of 8.200 to a magnitude of 7.699 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 3.3 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.

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Additional AT Circini Facts and Figures

Visual Facts


Primary / Proper / Traditional NameAT Circini
Alternative NamesAT Cir, HD 122314, HIP 68692, AT Cir
Spectral TypeA5IV/Vs
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeSubgiant Star
ColourBlue
GalaxyMilky Way
ConstellationCircinus
Absolute Magnitude 1.49 / 1.74
Visual / Apparent Magnitude7.62
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)14h 03m 38.30
Declination (Dec.)-66° 44` 07.2
Galactic Latitude-4.86 degrees
Galactic Longitude309.99 degrees
1997 Distance from Earth5.95 Parallax (milliarcseconds)
 548.17 Light Years
 168.07 Parsecs
2007 Distance from Earth6.67 Parallax (milliarcseconds)
 489.00 Light Years
 149.93 Parsecs
 30,925,066.91 Astronomical Units
Galacto-Centric Distance23,829.49 Light Years / 7,306.00 Parsecs
Proper Motion Dec.-26.65 ± 0.46 milliarcseconds/year
Proper Motion RA.-39.42 ± 0.72 milliarcseconds/year
B-V Index0.34
Stellar Luminosity (Lsun)16.27

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassEclipsing
Variable Star TypeBeta Persei (Algol)/
Mean Variability Period in Days3.257
Variable Magnitude Range (Brighter - Dimmer)7.699 - 8.200

Estimated Calculated Facts


Radius (x the Sun)2.84
Effective Temperature7,016 Kelvin

Sources and Links


SIMBAD SourceLink

Related Stars


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