HIP50750 is the reference name for the star in the Hipparcos Star Catalogue.
ER Leonis has alternative name(s) :- ER Leo, ER Leo.
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+16 2114.
More details on objects' alternative names can be found at Star Names .
The location of the variable 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 ER Leonis, the location is 10h 21m 47.08 and +15° 32` 03.6 .
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 3.45 ± 0.71 milliarcseconds/year towards the north and -15.53 ± 1.18 milliarcseconds/year east if we saw them in the horizon. . 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.
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.
|Primary / Proper / Traditional Name||ER Leonis|
|Alternative Names||ER Leo, HIP 50750, BD+16 2114, ER Leo|
|Constellation's Main Star||No|
|Multiple Star System||No / Unknown|
|Star Type||Variable Star|
|Absolute Magnitude||0.48 / -6.13|
|Visual / Apparent Magnitude||9.98|
|Naked Eye Visible||Requires a 7x50 Binoculars - Magnitudes|
|Right Ascension (R.A.)||10h 21m 47.08|
|Declination (Dec.)||+15° 32` 03.6|
|Galactic Latitude||53.44 degrees|
|Galactic Longitude||223.63 degrees|
|1997 Distance from Earth||1.26 Parallax (milliarcseconds)|
|2588.60 Light Years|
|2007 Distance from Earth||0.06 Parallax (milliarcseconds)|
|54360.56 Light Years|
|3,437,723,503.94 Astronomical Units|
|Proper Motion Dec.||3.45 ± 0.71 milliarcseconds/year|
|Proper Motion RA.||-15.53 ± 1.18 milliarcseconds/year|
|Mean Variability Period in Days||0.105|
|Variable Magnitude Range (Brighter - Dimmer)||9.893 - 9.946|
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