Universe Guide

Delta Circini

Delta Circini Facts

  • Delta Circini is a eclipsing binary sys main sequence star that can be located in the constellation of Circinus. The description is based on the spectral class.
  • Delta Circini is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (O8.5V) of the star, the star's colour is blue - white.
  • 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 3664.76 light years away from us. Distance

Delta Circini's Alternative Names

Delta Circini (Del 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 HR5664. HIP74778 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD135240.

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

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

Location of Delta Circini

The location of the main sequence 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 Delta Circini, the location is 15h 16m 56.90 and -60° 57` 26.1 .

Radial Velocity and Proper Motion of Delta 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 -3.06 ± 0.21 milliarcseconds/year towards the north and -1.90 ± 0.30 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 -17.80000 km/s with an error of about 1.00 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 Delta Circini

Delta Circini Colour and Temperature

Based on the star's spectral type of O8.5V , Delta Circini's colour and type is blue - white main sequence star. The star has a B-V Colour Index of -0.07 which means the star's temperature is about 10,845 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

Delta Circini Radius

Delta Circini estimated radius has been calculated as being 50.88 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 35,399,061.33.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 29.140395542688831039329226360. 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.

Delta Circini Apparent and Absolute Magnitudes

Delta Circini has an apparent magnitude of 5.04 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 -6.42 If you used the 2007 Parallax value, you would get an absolute magnitude of -5.21. 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 Delta Circini

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 0.51000 which gave the calculated distance to Delta Circini as 6395.36 light years away from Earth or 1960.78 parsecs. If you want that in miles, it is about 37,595,925,566,643,532.05, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 0.89000 which put Delta Circini at a distance of 3664.76 light years or 1123.60 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 231,757,521.39 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.

Travel Time to Delta 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 A3807363,339,197,007.19
Speed of Sound (Mach 1)767.2693,203,112,594.53
Concorde (Mach 2)1,534.541,601,554,209.92
New Horizons Probe33,00074,474,212.04
Speed of Light670,616,629.003,664.76

Variable Type of Delta Circini

The star is a eclipsing binary sys 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. Delta Circini brightness ranges from a magnitude of 5.203 to a magnitude of 5.034 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 3.9 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 Delta Circini Facts and Figures

Visual Facts

Primary / Proper / Traditional NameDelta Circini
Alternative NamesDel Cir, HD 135240, HIP 74778, HR 5664, del Cir
Spectral TypeO8.5V
Constellation's Main StarNo
Multiple Star SystemYes
Star Type Main Sequence Dwarf Star
GalaxyMilky Way
Absolute Magnitude -6.42 / -5.21
Visual / Apparent Magnitude5.04
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)15h 16m 56.90
Declination (Dec.)-60° 57` 26.1
Galactic Latitude-2.91120669 degrees
Galactic Longitude319.68822665 degrees
1997 Distance from Earth0.51000 Parallax (milliarcseconds)
 6395.36 Light Years
 1960.78 Parsecs
2007 Distance from Earth0.89000 Parallax (milliarcseconds)
 3664.76 Light Years
 1123.60 Parsecs
 231,757,521.39 Astronomical Units
Proper Motion Dec.-3.06000 ± 0.21000 milliarcseconds/year
Proper Motion RA.-1.90000 ± 0.30000 milliarcseconds/year
B-V Index-0.07
Radial Velocity-17.80000 ± 1.00 km/s

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassEclipsing binary sys
Variable Star TypeBeta Persei (Algol)
Mean Variability Period in Days3.902
Variable Magnitude Range (Brighter - Dimmer)5.034 - 5.203

Estimated Calculated Facts

Radius (x the Sun)29.14
Effective Temperature10,845 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
135240-60 5701.4A5.20000-13.00000-11.00000O8Blue

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