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HD 20868

HD 20868 Facts

  • HD 20868 is a subgiant star that can be located in the constellation of Fornax. The description is based on the spectral class.
  • HD 20868 is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (K3/K4IV) of the star, the star's colour is orange to red .
  • The star can not be seen by the naked eye, you need a telescope to see it.
  • It is calculated at being 4.500 Billion Years old. This information comes from ExoPlanet.
  • HD 20868 has at least 1 Extrasolar Planets believed to be in orbit around the star.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 150.72 light years away from us. Distance

HD 20868's Alternative Names

HIP15578 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD20868.

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

Location of HD 20868

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 HD 20868, the location is 03h 20m 42.49 and -33° 43` 49.2 .

Radial Velocity and Proper Motion of HD 20868

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 94.07 ± 0.95 milliarcseconds/year towards the north and 293.32 ± 1.38 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 46.29000 km/s with an error of about 0.01 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 HD 20868

HD 20868 Temperature and Colour

Based on the star's spectral type of K3/K4IV , HD 20868's colour and type is orange to red subgiant star. The star has a B-V Colour Index of 1.03 which means the star's temperature is about 4,792 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

HD 20868 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 0.29 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

HD 20868 Radius

HD 20868 estimated radius has been calculated as being 0.62 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 434,799.09.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 0.6483432464646107807957594608. 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.

HD 20868 Mass

The HD 20868's solar mass is 0.78 times that of our star, the Sun. The Sun's Mass is 1,989,100,000,000,000,000,000 billion kg. which to calculate using this website is too large. To give idea of size, the Sun is 99.86% the mass of the solar system.

HD 20868 Metalicity

The star's metallicity is 0.040000, this value is the fractional amount of the star that is not Hydrogen (X) or Helium (Y). An older star would have a high metallicity whereas a new star would have a lower one.

HD 20868 Estimated Age

The star is believed to be about 4.50 Billion years old. To put in context, the Sun is believed to be about five billion years old and the Universe is about 13.8 billion years old.

HD 20868 Apparent and Absolute Magnitudes

HD 20868 has an apparent magnitude of 9.92 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 6.68 If you used the 2007 Parallax value, you would get an absolute magnitude of 6.60. 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 HD 20868

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 22.47000 which gave the calculated distance to HD 20868 as 145.16 light years away from Earth or 44.50 parsecs. If you want that in miles, it is about 853,341,259,171,332.83, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 21.64000 which put HD 20868 at a distance of 150.72 light years or 46.21 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 9,531,430.28 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 7,415.00 Parsecs or 24,185.01 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 HD 20868

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)
Walking425,268,834,580.72
Car120842,294,486.02
Airbus A380736137,330,622.72
Speed of Sound (Mach 1)767.269131,733,900.79
Concorde (Mach 2)1,534.5465,866,864.55
New Horizons Probe33,0003,062,889.04
Speed of Light670,616,629.00150.72

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 HD 20868 Facts and Figures

Visual Facts


Primary / Proper / Traditional NameHD 20868
Alternative NamesHD 20868, HIP 15578
Spectral TypeK3/K4IV
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeSubgiant Star
ColourOrange to Red
GalaxyMilky Way
ConstellationFornax
Age4.50 Billion Years Old
Metalicity0.0400
Absolute Magnitude 6.68 / 6.60
Visual / Apparent Magnitude9.92
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)03h 20m 42.49
Declination (Dec.)-33° 43` 49.2
Galactic Latitude-57.33569699 degrees
Galactic Longitude233.83963156 degrees
1997 Distance from Earth22.47000 Parallax (milliarcseconds)
 145.16 Light Years
 44.50 Parsecs
2007 Distance from Earth21.64000 Parallax (milliarcseconds)
 150.72 Light Years
 46.21 Parsecs
 9,531,430.28 Astronomical Units
Galacto-Centric Distance24,185.01 Light Years / 7,415.00 Parsecs
Proper Motion Dec.94.07000 ± 0.95000 milliarcseconds/year
Proper Motion RA.293.32000 ± 1.38000 milliarcseconds/year
B-V Index1.03
Radial Velocity46.29000 ± 0.01 km/s
Eccentricity0.36460
Semi-Major Axis5525.0000000
Stellar Luminosity (Lsun)0.2900000

Companions (Multi-Star and Exoplanets) Facts


Exoplanet Count1

Estimated Calculated Facts


Radius (x the Sun)0.65
Effective Temperature4,792 Kelvin
Mass Compared to the Sun0.78

Sources and Links


SIMBAD SourceLink

List of Extrasolar Planets orbiting HD 20868


NameStatusMass (Jupiters)Orbital Period (Days)EccentricityDiscoveredSemi-Major AxisPeriastron
HD 20868 bConfirmed0.05380.8500.7520080.947356.200

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