Universe Guide

20 Capricorni

20 Capricorni Facts

  • 20 Capricorni is a rotating variable star that can be located in the constellation of Capricornus. The description is based on the spectral class.
  • 20 Capricorni is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (Ap Si) 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 535.57 light years away from us. Distance

20 Capricorni's Alternative Names

The Id of the star in the Yale Bright Star Catalogue is HR8033. HIP103616 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD199728.

20 Capricorni has alternative name(s) :- AO Capricorni, AO Cap, AO Cap.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John named the stars in the constellation with a number and its latin name, this star's Flamsteed designation is 20 Capricorni. The Flamsteed name can be shortened to 20 Cap.

BD number is the number that the star was filed under in the Durchmusterung or Bonner Durchmusterung, a star catalogue that was put together by the Bonn Observatory between 1859 to 1903. The star's BD Number is BD-19 5982.

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

Location of 20 Capricorni

The location of the variable 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 20 Capricorni, the location is 20h 59m 36.13 and -19° 02` 06.8 .

Radial Velocity and Proper Motion of 20 Capricorni

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 -20.09 ± 0.31 milliarcseconds/year towards the north and 10.07 ± 0.42 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 -10.10000 km/s with an error of about 0.70 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 20 Capricorni

20 Capricorni Temperature and Colour

Based on the star's spectral type of Ap Si , 20 Capricorni's colour and type is blue - white variable star. The star has a B-V Colour Index of -0.11 which means the star's temperature is about 14,384 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

20 Capricorni 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 134.10 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

20 Capricorni Radius

20 Capricorni estimated radius has been calculated as being 1.11 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 772,008.36.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 1.384019757377084655396873688. 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.

20 Capricorni Apparent and Absolute Magnitudes

20 Capricorni has an apparent magnitude of 6.26 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 0.66 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.18. 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 20 Capricorni

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 7.58000 which gave the calculated distance to 20 Capricorni as 430.29 light years away from Earth or 131.93 parsecs. If you want that in miles, it is about 2,529,513,711,827,175.55, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 6.09000 which put 20 Capricorni at a distance of 535.57 light years or 164.20 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 33,868,445.19 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 7,286.00 Parsecs or 23,764.26 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 20 Capricorni

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 A380736487,992,048.90
Speed of Sound (Mach 1)767.269468,104,599.55
Concorde (Mach 2)1,534.54234,051,994.73
New Horizons Probe33,00010,883,701.45
Speed of Light670,616,629.00535.57

Variable Type of 20 Capricorni

The star is a rotating Alpha2 Canum Venatic 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. 20 Capricorni brightness ranges from a magnitude of 6.262 to a magnitude of 6.214 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 2.2 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 20 Capricorni Facts and Figures

Visual Facts

Primary / Proper / Traditional Name20 Capricorni
Alternative NamesAO Capricorni, AO Cap, HD 199728, HIP 103616, HR 8033, 20 Cap, BD-19 5982, AO Cap
Spectral TypeAp Si
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeVariable Star
GalaxyMilky Way
Absolute Magnitude 0.66 / 0.18
Visual / Apparent Magnitude6.26
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)20h 59m 36.13
Declination (Dec.)-19° 02` 06.8
Galactic Latitude-36.51711860 degrees
Galactic Longitude28.53705768 degrees
1997 Distance from Earth7.58000 Parallax (milliarcseconds)
 430.29 Light Years
 131.93 Parsecs
2007 Distance from Earth6.09000 Parallax (milliarcseconds)
 535.57 Light Years
 164.20 Parsecs
 33,868,445.19 Astronomical Units
Galacto-Centric Distance23,764.26 Light Years / 7,286.00 Parsecs
Proper Motion Dec.-20.09000 ± 0.31000 milliarcseconds/year
Proper Motion RA.10.07000 ± 0.42000 milliarcseconds/year
B-V Index-0.11
Radial Velocity-10.10000 ± 0.70 km/s
Semi-Major Axis6954.0000000
Stellar Luminosity (Lsun)134.1000000

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassRotating
Variable Star TypeAlpha2 Canum Venatic
Mean Variability Period in Days2.241
Variable Magnitude Range (Brighter - Dimmer)6.214 - 6.262

Estimated Calculated Facts

Radius (x the Sun)1.38
Effective Temperature14,384 Kelvin

Sources and Links

SIMBAD SourceLink

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