Universe Guide


Pennae Caudalis (Pi2 Cygni) - HD207330 - HIP107533

Pennae Caudalis (Pi2 Cygni) is a blue giant star that can be located in the constellation of Cygnus. Pi2 Cygni is the Bayer Classification for the star. HIP107533 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD207330. Pennae Caudalis has alternative name(s), 81 Cygni , 81 Cyg. Pennae Caudalis is a multiple star system with 2 stars orbiting in its solar system.

Location of Pennae Caudalis

The location of the star in the galaxy 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 Pennae Caudalis, the location is 21h 46m 47.61 and +49d18`34.5 .

Proper Motion of Pennae Caudalis

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 -002.00 ± 000.27 towards the north and 002.77 ± 000.34 east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Pennae Caudalis

Pennae Caudalis has a spectral type of B3III. This means the star is a blue giant star. The star has a B-V Colour Index of -0.12 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 12,367 Kelvin.

Pennae Caudalis has been calculated as 10.29 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 7,159,680.90.km.

Pennae Caudalis Apparent and Absolute Magnitudes

Pennae Caudalis has an apparent magnitude of 4.23 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 -3.52 If you used the 2007 Parallax value, you would get an absolute magnitude of -3.42. 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 Pennae Caudalis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 2.82 which gave the calculated distance to Pennae Caudalis as 1156.61 light years away from Earth or 354.61 parsecs. It would take a spaceship travelling at the speed of light, 1156.61 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 2.95 which put Pennae Caudalis at a distance of 1105.64 light years or 338.98 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.

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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

Pennae Caudalis Facts

Alternative Names

Traditional NamePennae Caudalis
Short Name81 Cyg
Bayer DesignationPi2 Cygni
Alternative Name(s)81 Cygni
Hipparcos Library I.D.107533
Bonner DurchmusterungBD+48 3504
Henry Draper Designation207330

Visual Facts

Star Typegiant star
Absolute Magnitude-3.52 / -3.42
Apparent Magnitude4.23
Right Ascension (R.A.)21h 46m 47.61
Declination (Dec.)+49d18`34.5
1997 Distance from Earth2.82 Parallax (milliarcseconds)
 1156.61 Light Years
 354.61 Parsecs
2007 Revised Distance from Earth2.95 Parallax (milliarcseconds)
 1105.64 Light Years
 338.98 Parsecs
Proper Motion Dec.-2.00 ± 0.27 milliarcseconds/year
Proper Motion RA.2.77 ± 0.34 milliarcseconds/year
B-V Index-0.12
Spectral TypeB3III
Colour(B) blue
Stars in Solar System2

Estimated Facts

Radius (x the Sun)10.29
Calculated Effective Temperature12,367 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Multi-Star System

The star has been identified as being a multi-star system, one in which there is at least one star in close orbit to another star or two or more stars orbiting a central point. The stars may be of equal mass, unequal mass where one star is stronger than the other or be in groups orbiting a central point which doesn't necessarily have to be a star. More information can be found on my dedicated multiple star systems page. The source of the info is Simbad. The file is dated 2000 so any differences between this and any other source will be down to the actual source from where the information came from.

Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
207330+48 3504.0A4.400004.00000-2.00000B3Blue/White

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