Universe Guide

Gamma Circini

Gamma Circini Facts

  • Gamma Circini is a eruptive giant star that can be located in the constellation of Circinus. The description is based on the spectral class.
  • Gamma Circini is a main star of the constellation outline.
  • Based on the spectral type (B5III + F8) of the star, the star's colour is blue .
  • 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 448.64 light years away from us. Distance

Gamma Circini's Alternative Names

Gamma Circini (Gam Cir) is the Bayer Classification for the star. The Bayer Classification was created by Johann Bayer in 1603. The brightest star in the constellation is normally given the Alpha designation, there are exceptions such as Pollux which is Beta Geminorum.

The Id of the star in the Yale Bright Star Catalogue is HR5704. HIP75323 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD136415.

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

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

Location of Gamma Circini

The location of the giant 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 Gamma Circini, the location is 15h 23m 22.66 and -59° 19` 14.5 .

Radial Velocity and Proper Motion of Gamma Circini

Proper Motion

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 -34.24 ± 0.48 milliarcseconds/year towards the north and -12.97 ± 0.81 milliarcseconds/year east if we saw them in the horizon.

Radial Velocity

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is -16.90 km/s with an error of about 1.78 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.

Physical Properties of Gamma Circini

Gamma Circini Temperature and Colour

Based on the star's spectral type of B5III + F8 , Gamma Circini's colour and type is blue giant star. The star has a B-V Colour Index of 0.16 which means the star's temperature is about 8,017 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

Gamma 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 247.56 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Gamma Circini Radius

Gamma Circini estimated radius has been calculated as being 9.61 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 6,689,269.47.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 8.45. 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.

Gamma Circini Apparent and Absolute Magnitudes

Gamma Circini has an apparent magnitude of 4.48 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 -1.21. 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 Gamma Circini

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 6.40 which gave the calculated distance to Gamma Circini as 509.63 light years away from Earth or 156.25 parsecs. If you want that in miles, it is about 2,995,923,848,935,563.16, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 7.27 which put Gamma Circini at a distance of 448.64 light years or 137.55 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 28,371,526.40 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 7,295.00 Parsecs or 23,793.62 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 Gamma 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)
Airbus A380736408,784,571.24
Speed of Sound (Mach 1)767.269392,125,114.44
Concorde (Mach 2)1,534.54196,062,301.69
New Horizons Probe33,0009,117,134.68
Speed of Light670,616,629.00448.64

Variable Type of Gamma Circini

The star is a eruptive Gamma Cassiopeiae 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. Gamma Circini brightness ranges from a magnitude of 4.560 to a magnitude of 4.500 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.1 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 Gamma Circini Facts and Figures

Visual Facts

Primary / Proper / Traditional NameGamma Circini
Alternative NamesGam Cir, HD 136415, HIP 75323, HR 5704, gam Cir
Spectral TypeB5III + F8
Constellation's Main StarYes
Multiple Star SystemYes
Star TypeGiant Star
GalaxyMilky Way
Absolute Magnitude -1.49 / -1.21
Visual / Apparent Magnitude4.48
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)15h 23m 22.66
Declination (Dec.)-59° 19` 14.5
Galactic Latitude-1.96 degrees
Galactic Longitude321.24 degrees
1997 Distance from Earth6.40 Parallax (milliarcseconds)
 509.63 Light Years
 156.25 Parsecs
2007 Distance from Earth7.27 Parallax (milliarcseconds)
 448.64 Light Years
 137.55 Parsecs
 28,371,526.40 Astronomical Units
Galacto-Centric Distance23,793.62 Light Years / 7,295.00 Parsecs
Proper Motion Dec.-34.24 ± 0.48 milliarcseconds/year
Proper Motion RA.-12.97 ± 0.81 milliarcseconds/year
B-V Index0.16
Radial Velocity-16.90 ± 1.78 km/s
Semi-Major Axis7991.00
Stellar Luminosity (Lsun)247.56

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassEruptive
Variable Star TypeGamma Cassiopeiae
Mean Variability Period in Days0.055
Variable Magnitude Range (Brighter - Dimmer)4.500 - 4.560

Estimated Calculated Facts

Radius (x the Sun)8.45
Effective Temperature8,017 Kelvin

Sources and Links

SIMBAD SourceLink

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
136415-58 5908.4A5.20000-11.00000-41.00000B5Blue/White

Location of Gamma Circini in Circinus

Gamma Circini Location in Circinus

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

Circinus Main Stars

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