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FL Serpentis, HD134943, HIP74386

FL Serpentis is a red pulsating giant star that can be located in the constellation of Serpens. The description is based on the spectral class. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

FL Serpentis's Alternative Names

HIP74386 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD134943.

FL Serpentis has alternative name(s) :- , FL 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+19 2935.

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

Location of FL Serpentis

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 FL Serpentis, the location is 15h 12m 04.27 and +18° 58` 33.6 .

Proper Motion of FL 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 10.07 ± 0.37 miliarcseconds/year towards the north and -15.13 ± 0.65 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 -35.84000 km/s with an error of about 0.21 km/s .

FL 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 414.82 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 FL Serpentis

FL Serpentis has a spectral type of M4III. This means the star is a red giant star. The star is 7,296.00 Parsecs from the Galactic Centre or terms of Light Years is 23,796.88 s. The star has a B-V Colour Index of 1.41 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,143 Kelvin.

FL Serpentis Radius has been calculated as being 30.50 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 21,221,156.95.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 26.56. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

FL Serpentis Apparent and Absolute Magnitudes

FL Serpentis has an apparent magnitude of 5.90 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 -1.13 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.83. 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 FL Serpentis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 3.93 which gave the calculated distance to FL Serpentis as 829.93 light years away from Earth or 254.45 parsecs. It would take a spaceship travelling at the speed of light, 829.93 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 4.51 which put FL Serpentis at a distance of 723.20 light years or 221.73 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 7,296.00 Parsecs or 23,796.88 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 FL Serpentis

The star is a pulsating Slow Irregular 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. FL Serpentis brightness ranges from a magnitude of 5.960 to a magnitude of 5.740 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.2 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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FL Serpentis Facts

Visual Facts


Primary / Proper / Traditional NameFL Serpentis
Alternative NamesHD 134943, HIP 74386, BD+19 2935, FL Ser
Spectral TypeM4III
Multiple Star SystemYes
Star TypeGiant Star
Colour red
GalaxyMilky Way
ConstellationSerpens
Absolute Magnitude-1.13 / -0.83
Visual / Apparent Magnitude5.90
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)15h 12m 04.27
Declination (Dec.)+18° 58` 33.6
Galactic Latitude56.76 degrees
Galactic Longitude26.32 degrees
1997 Distance from Earth3.93 Parallax (milliarcseconds)
 829.93 Light Years
 254.45 Parsecs
2007 Distance from Earth4.51 Parallax (milliarcseconds)
 723.20 Light Years
 221.73 Parsecs
Galacto-Centric Distance23,796.88 Light Years / 7,296.00 Parsecs
Proper Motion Dec.10.07 ± 0.37 milliarcseconds/year
Proper Motion RA.-15.13 ± 0.65 milliarcseconds/year
B-V Index1.41
Radial Velocity-35.84 ± 0.21 km/s
Eccentricity0.10
Semi-Major Axis7499.00
Stellar Luminosity (Lsun)414.82

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassPulsating
Variable Star TypeSlow Irregular
Mean Variability Period in Days0.185
Variable Magnitude Range (Brighter - Dimmer)5.740 - 5.960

Estimated Facts


Calculated Effective Temperature4,143 Kelvin

Sources and Links


SIMBAD SourceLink

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
B7.900001967
134943+19 2935.0A6.00000-14.000007.00000M4Red

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