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NW Serpentis, HD168797, HIP89977

NW Serpentis is a blue eruptive main sequence dwarf 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.

NW Serpentis's Alternative Names

HIP89977 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD168797.

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

The Gould star designation is one that was designed by American astronomer, Benjamin Apthorp Gould. Gould stars are predominantly in the Southern and Equatorial constellations but do appear in northern constellations such as Bootes and Orion. The star has the designation 35 Cau G. Serpentis. There are no stars with a Gould designation in Ursa Major for example.

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+05 3704.

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

Location of NW 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 NW Serpentis, the location is 18h 21m 28.40 and +05° 26` 08.7 .

Proper Motion of NW 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 -10.52 ± 0.42 miliarcseconds/year towards the north and -0.51 ± 0.62 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 -12.30000 km/s with an error of about 0.90 km/s .

Physical Properties (Colour, Temperature) of NW Serpentis

NW Serpentis has a spectral type of B3Ve. This means the star is a blue main sequence dwarf star. The star has a B-V Colour Index of -0.04 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 10,195 Kelvin.

NW Serpentis Radius has been calculated as being 18.29 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 12,724,828.94.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 5.76. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

NW Serpentis Apparent and Absolute Magnitudes

NW Serpentis has an apparent magnitude of 6.14 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 -3.93 If you used the 2007 Parallax value, you would get an absolute magnitude of -1.42. 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 NW Serpentis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 0.97 which gave the calculated distance to NW Serpentis as 3362.51 light years away from Earth or 1030.93 parsecs. It would take a spaceship travelling at the speed of light, 3362.51 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 3.08 which put NW Serpentis at a distance of 1058.97 light years or 324.68 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.

Variable Type of NW Serpentis

The star is a eruptive 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. NW Serpentis brightness ranges from a magnitude of 6.174 to a magnitude of 6.101 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.1 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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NW Serpentis Facts

Visual Facts


Primary / Proper / Traditional NameNW Serpentis
Alternative NamesHD 168797, HIP 89977, 35 Cau G. Serpentis, BD+05 3704, NW Ser
Spectral TypeB3Ve
Multiple Star SystemNo / Unknown
Star Type main sequence Dwarf Star
Colour blue
GalaxyMilky Way
ConstellationSerpens
Absolute Magnitude-3.93 / -1.42
Visual / Apparent Magnitude6.14
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)18h 21m 28.40
Declination (Dec.)+05° 26` 08.7
Galactic Latitude9.13 degrees
Galactic Longitude34.39 degrees
1997 Distance from Earth0.97 Parallax (milliarcseconds)
 3362.51 Light Years
 1030.93 Parsecs
2007 Distance from Earth3.08 Parallax (milliarcseconds)
 1058.97 Light Years
 324.68 Parsecs
Proper Motion Dec.-10.52 ± 0.42 milliarcseconds/year
Proper Motion RA.-0.51 ± 0.62 milliarcseconds/year
B-V Index-0.04
Radial Velocity-12.30 ± 0.90 km/s

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Variable Star Details


Variable Star ClassEruptive
Variable Star TypeIrregular
Mean Variability Period in Days0.062
Variable Magnitude Range (Brighter - Dimmer)6.101 - 6.174

Estimated Facts


Calculated Effective Temperature10,195 Kelvin

Sources and Links


SIMBAD SourceLink

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