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HD 209961

HD 209961 Facts

  • HD 209961 is a rotating main sequence star that can be located in the constellation of Lacerta. The description is based on the spectral class.
  • HD 209961 is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (B2V SB) of the star, the star's colour is blue .
  • 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 4941.87 light years away from us. Distance

HD 209961's Alternative Names

HIP109082 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD209961.

HD 209961 has alternative name(s) :- V365 Lac, V365 Lac.

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+47 3692.

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

Location of HD 209961

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 HD 209961, the location is 22h 05m 51.22 and +48° 13` 53.4 .

Radial Velocity and Proper Motion of HD 209961

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 -4.95 ± 0.22 milliarcseconds/year towards the north and -0.73 ± 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 -12.90000 km/s with an error of about 4.30 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 209961

HD 209961 Temperature and Colour

Based on the star's spectral type of B2V SB , HD 209961's colour and type is blue main sequence star. The star has a B-V Colour Index of -0.08 which means the star's temperature is about 11,099 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

HD 209961 Radius

HD 209961 estimated radius has been calculated as being 8.52 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 5,927,151.74.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 21.398397775352382881917005048. 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 209961 Apparent and Absolute Magnitudes

HD 209961 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 -2.64 If you used the 2007 Parallax value, you would get an absolute magnitude of -4.64. 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 209961

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 1.66000 which gave the calculated distance to HD 209961 as 1964.84 light years away from Earth or 602.41 parsecs. If you want that in miles, it is about 11,550,558,278,246,084.27, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 0.66000 which put HD 209961 at a distance of 4941.87 light years or 1515.15 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 312,519,943.52 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 HD 209961

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)
Walking4828,525,050,089.06
Car12027,617,501,669.64
Airbus A3807364,502,853,533.09
Speed of Sound (Mach 1)767.2694,319,345,888.28
Concorde (Mach 2)1,534.542,159,670,129.39
New Horizons Probe33,000100,427,278.80
Speed of Light670,616,629.004,941.87

Variable Type of HD 209961

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. HD 209961 brightness ranges from a magnitude of 6.277 to a magnitude of 6.212 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 1.1 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 HD 209961 Facts and Figures

Visual Facts


Primary / Proper / Traditional NameHD 209961
Alternative NamesV365 Lac, HD 209961, HIP 109082, BD+47 3692, V365 Lac
Spectral TypeB2V SB
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star Type Main Sequence Dwarf Star
ColourBlue
GalaxyMilky Way
ConstellationLacerta
Absolute Magnitude -2.64 / -4.64
Visual / Apparent Magnitude6.26
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)22h 05m 51.22
Declination (Dec.)+48° 13` 53.4
Galactic Latitude-6.00593882 degrees
Galactic Longitude96.64212681 degrees
1997 Distance from Earth1.66000 Parallax (milliarcseconds)
 1964.84 Light Years
 602.41 Parsecs
2007 Distance from Earth0.66000 Parallax (milliarcseconds)
 4941.87 Light Years
 1515.15 Parsecs
 312,519,943.52 Astronomical Units
Proper Motion Dec.-4.95000 ± 0.22000 milliarcseconds/year
Proper Motion RA.-0.73000 ± 0.30000 milliarcseconds/year
B-V Index-0.08
Radial Velocity-12.90000 ± 4.30 km/s

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassRotating
Variable Star TypeAlpha2 Canum Venatic
Mean Variability Period in Days1.086
Variable Magnitude Range (Brighter - Dimmer)6.212 - 6.277

Estimated Calculated Facts


Radius (x the Sun)21.40
Effective Temperature11,099 Kelvin

Sources and Links


SIMBAD SourceLink

Related Stars


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