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Tau4 Serpentis, 17 Serpentis, HD139216, HIP76423

Tau4 Serpentis is a red pulsating giant star that can be located in the constellation of Serpens. The star can not be seen by the naked eye, you need a telescope to see it.

Tau4 Serpentis's Alternative Names

Tau4 Serpentis is the Bayer Classification for the star. HIP76423 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD139216.

Tau4 Serpentis has alternative name(s) :- , tau04 Ser.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John numbered the stars in the constellation with a number and the latin name, this star's Flamsteed designation is 17 Serpentis with it shortened to 17 Ser.

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+15 2890.

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

Location of Tau4 Serpentis

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 Tau4 Serpentis, the location is 15h 36m 28.19 and +15° 06` 05.0 .

Proper Motion of Tau4 Serpentis

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 8.89 ± 0.33 miliarcseconds/year towards the north and -3.66 ± 0.46 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 -27.11000 km/s with an error of about 0.72 km/s .

Tau4 Serpentis 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 155.2500000 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) of Tau4 Serpentis

Tau4 Serpentis has a spectral type of M5II-III. This means the star is a red giant star. The star is 7282.00000000 Parsecs from the Galactic Centre or terms of Light Years is 23751.2147100800000000s. The star has a B-V Colour Index of 1.2 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,489 Kelvin.

Tau4 Serpentis Radius has been calculated as being 12.26 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 8,532,645.66.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 15.87. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Tau4 Serpentis Apparent and Absolute Magnitudes

Tau4 Serpentis has an apparent magnitude of 6.51 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 0.50 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.06. 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 Tau4 Serpentis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 6.27 which gave the calculated distance to Tau4 Serpentis as 520.20 light years away from Earth or 159.49 parsecs. It would take a spaceship travelling at the speed of light, 520.20 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 4.86 which put Tau4 Serpentis at a distance of 671.12 light years or 205.76 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 7,282.00 Parsecs or 23,751.21 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Variable Type of Tau4 Serpentis

The star is a pulsating Semiregular late- (M, C, S or Me, Ce, Se) giants with poorly defined periodicity 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. Tau4 Serpentis brightness ranges from a magnitude of 6.397 to a magnitude of 6.052 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.4 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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Tau4 Serpentis Facts

Visual Facts

Alternative NamesHD 139216, HIP 76423, 17 Serpentis, 17 Ser, BD+15 2890, tau04 Ser
Star TypeGiant Star
GalaxyMilky Way
Absolute Magnitude0.50 / -0.06
Visual / Apparent Magnitude6.51
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)15h 36m 28.19
Declination (Dec.)+15° 06` 05.0
Galactic Latitude49.88 degrees
Galactic Longitude24.09 degrees
1997 Distance from Earth6.27 Parallax (milliarcseconds)
 520.20 Light Years
 159.49 Parsecs
2007 Revised Distance from Earth4.86 Parallax (milliarcseconds)
 671.12 Light Years
 205.76 Parsecs
Galacto-Centric Distance23,751.21 Light Years / 7,282.00 Parsecs
Proper Motion Dec.8.89 ± 0.33 milliarcseconds/year
Proper Motion RA.-3.66 ± 0.46 milliarcseconds/year
B-V Index1.20
Radial Velocity-27.11 ± 0.72 km/s
Semi-Major Axis7988.00
Stellar Luminosity (Lsun)155.25
Spectral TypeM5II-III
Associated / Clustered StarsTau1 Serpentis
Tau2 Serpentis
Tau3 Serpentis
Tau5 Serpentis
Tau6 Serpentis
Tau8 Serpentis
Colour(M) Red

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeSemiregular late- (M, C, S or Me, Ce, Se) giants with poorly defined periodicity
Mean Variability Period in Days0.353
Variable Magnitude Range (Brighter - Dimmer)6.052 - 6.397

Estimated Facts

Calculated Effective Temperature4,489 Kelvin

Sources and Links

SIMBAD SourceLink

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