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Epsilon Coronae Australis, HD175813, HIP93174, HR7152

Epsilon Coronae Australis is a blue to white eclipsing binary system subgiant star that can be located in the constellation of Corona Australis. The description is based on the spectral class. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it. The star has an estimated age of 1.70 Billion of Years but could be as young as 1.60 to 1.80 according to Hipparcos.

Epsilon Coronae Australis's Alternative Names

Epsilon Coronae Australis (Eps Cra) is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR7152. HIP93174 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD175813.

Epsilon Coronae Australis has alternative name(s) :- , eps CrA.

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

Location of Epsilon Coronae Australis

The location of the 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 star is compared to the celestial equator and is expressed in degrees. For Epsilon Coronae Australis, the location is 18h 58m 43.47 and -37° 06` 25.5 .

Proper Motion of Epsilon Coronae Australis

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 -110.62 ± 0.18 miliarcseconds/year towards the north and -132.40 ± 0.33 miliarcseconds/year east if we saw them in the horizon. The Radial Velocity, that is the speed at which the star is moving away/towards us is 57.90000 km/s with an error of about 1.20 km/s .

Epsilon Coronae Australis 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 8.93 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature, Age) of Epsilon Coronae Australis

Epsilon Coronae Australis has a spectral type of F3IV/V. This means the star is a blue to white subgiant star. The star is 7,371.00 Parsecs from the Galactic Centre or terms of Light Years is 24,041.50 s. The star has a B-V Colour Index of 0.39 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,775 Kelvin.

Epsilon Coronae Australis Radius has been calculated as being 2.19 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,525,967.13.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 2.21. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's Iron Abundance is -0.02 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

The stars age according to Hipparcos data files put the star at an age of about 1.70 Billion years old but could be between 1.60 and 1.80 Billion years old. In comparison, the Sun's age is about 4.6 Billion Years Old.

Epsilon Coronae Australis Apparent and Absolute Magnitudes

Epsilon Coronae Australis has an apparent magnitude of 4.83 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 2.45 If you used the 2007 Parallax value, you would get an absolute magnitude of 2.43. 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 Epsilon Coronae Australis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 33.43 which gave the calculated distance to Epsilon Coronae Australis as 97.57 light years away from Earth or 29.91 parsecs. It would take a spaceship travelling at the speed of light, 97.57 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 33.13 which put Epsilon Coronae Australis at a distance of 98.45 light years or 30.18 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.

The star's Galacto-Centric Distance is 7,371.00 Parsecs or 24,041.50 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Variable Type of Epsilon Coronae Australis

The star is a eclipsing binary system W Ursae Majoris 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. Epsilon Coronae Australis brightness ranges from a magnitude of 5.107 to a magnitude of 4.844 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.6 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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Epsilon Coronae Australis Facts

Visual Facts

Primary / Proper / Traditional NameEpsilon Coronae Australis
Alternative NamesEps Cra, HD 175813, HIP 93174, HR 7152, eps CrA
Spectral TypeF3IV/V
Multiple Star SystemNo / Unknown
Star TypeSubgiant Star
Colour blue to white
GalaxyMilky Way
ConstellationCorona Australis
Age1.70 Billion Years Old
Age Range1.60 - 1.80 Billion Years Old
Absolute Magnitude2.45 / 2.43
Visual / Apparent Magnitude4.83
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)18h 58m 43.47
Declination (Dec.)-37° 06` 25.5
Galactic Latitude-17.32 degrees
Galactic Longitude359.54 degrees
1997 Distance from Earth33.43 Parallax (milliarcseconds)
 97.57 Light Years
 29.91 Parsecs
2007 Distance from Earth33.13 Parallax (milliarcseconds)
 98.45 Light Years
 30.18 Parsecs
Galacto-Centric Distance24,041.50 Light Years / 7,371.00 Parsecs
Proper Motion Dec.-110.62 ± 0.18 milliarcseconds/year
Proper Motion RA.-132.40 ± 0.33 milliarcseconds/year
B-V Index0.39
Radial Velocity57.90 ± 1.20 km/s
Iron Abundance-0.02 ± 9.99 Fe/H
Semi-Major Axis7297.00
Stellar Luminosity (Lsun)8.93

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassEclipsing binary system
Variable Star TypeW Ursae Majoris
Mean Variability Period in Days0.591
Variable Magnitude Range (Brighter - Dimmer)4.844 - 5.107

Estimated Facts

Calculated Effective Temperature6,775 Kelvin

Sources and Links

SIMBAD SourceLink

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