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HD 22781, HIP17187

HD 22781 is a orange to red star that can be located in the constellation of Perseus. The description is based on the spectral class. The star can not be seen by the naked eye, you need a telescope to see it. It is calculated at being 4.750 Billion Years old. This information comes from ExoPlanet. HD 22781 has at least 1 Extrasolar Planets believed to be in orbit around the star.

HD 22781's Alternative Names

HIP17187 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD22781.

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+31 630.

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

Location of HD 22781

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 HD 22781, the location is 03h 40m 49.50 and +31° 49` 35.5 .

Proper Motion of HD 22781

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 -91.99 ± 0.66 miliarcseconds/year towards the north and 41.46 ± 1.11 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 22.10000 km/s with an error of about 4.80 km/s .

HD 22781 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 0.35 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, Mass) of HD 22781

HD 22781 has a spectral type of K0. This means the star is a orange to red star. The star is 7,429.00 Parsecs from the Galactic Centre or terms of Light Years is 24,230.67 s. The star has a B-V Colour Index of 0.84 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,331 Kelvin.

HD 22781 Radius has been calculated as being 0.61 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 424,335.05.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 0.63. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's solar mass is 0.75 times that of the Sun's. 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.

The star's metallicity is -0.370000, 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.

The star is believed to be about 4.75 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 22781 Apparent and Absolute Magnitudes

HD 22781 has an apparent magnitude of 8.78 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 6.27 If you used the 2007 Parallax value, you would get an absolute magnitude of 6.20. 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 22781

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 31.46 which gave the calculated distance to HD 22781 as 103.68 light years away from Earth or 31.79 parsecs. It would take a spaceship travelling at the speed of light, 103.68 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 30.51 which put HD 22781 at a distance of 106.90 light years or 32.78 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 7,429.00 Parsecs or 24,230.67 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

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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HD 22781 Facts

Visual Facts

Primary / Proper / Traditional NameHD 22781
Alternative NamesHD 22781, HIP 17187, BD+31 630
Spectral TypeK0
Multiple Star SystemNo / Unknown
Star TypeStar
Colour orange to red
GalaxyMilky Way
Age4.75 Billion Years Old
Absolute Magnitude6.27 / 6.20
Visual / Apparent Magnitude8.78
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)03h 40m 49.50
Declination (Dec.)+31° 49` 35.5
Galactic Latitude-18.57 degrees
Galactic Longitude160.07 degrees
1997 Distance from Earth31.46 Parallax (milliarcseconds)
 103.68 Light Years
 31.79 Parsecs
2007 Distance from Earth30.51 Parallax (milliarcseconds)
 106.90 Light Years
 32.78 Parsecs
Galacto-Centric Distance24,230.67 Light Years / 7,429.00 Parsecs
Proper Motion Dec.-91.99 ± 0.66 milliarcseconds/year
Proper Motion RA.41.46 ± 1.11 milliarcseconds/year
B-V Index0.84
Radial Velocity22.10 ± 4.80 km/s
Semi-Major Axis8051.00
Stellar Luminosity (Lsun)0.35

Companions (Multi-Star and Exoplanets) Facts

Exoplanet Count1

Estimated Facts

Calculated Effective Temperature5,331 Kelvin
Mass Compared to the Sun0.75

Sources and Links

SIMBAD SourceLink

List of Extrasolar Planets orbiting HD 22781

NameStatusMass (Jupiters)Orbital Period (Days)EccentricityDiscoveredSemi-Major AxisPeriastronInclination
HD 22781 bConfirmed0.97528.0700.819120111.167315.9202011.000

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