More commonly referred to as simply SDSS 1557, this is a double star combination which has a white dwarf star in the middle with an orbiting brown dwarf star. What makes this interesting is that there is a strong possibility that there is a rocky planet in orbit.
If you recall from the Star Wars films, Tatooine is a desert rocky planet famed for having two stars. Previous discoveries where planets have been discovered in double stars such as Algieba, the planets have been identified as a gas giant, like Jupiter. It was reported in Feb 2017, that this star could indeed have a rocky planet in orbit.
The problem having two stars is that both stars will exert a certain amount of pull on the asteroids and therefore preventing them from merging. It is thought that the asteroid belt situated between Mars and Jupiter was a failed planet. The gravity of Jupiter prevented the rocks from merging and creating a planet. UCL
The location of the dwarf 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 SDSS J155720.77+091624.6, the location is 15h 57m 20.776 and +09° 16` 24.69 .
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 -24.00 miliarcseconds/year towards the north and -8.00 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 the Sun is 0.00 km/s . 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.
SDSS J155720.77+091624.6 has a spectral type of DAZ D. This means the star is a white dwarf star.
|Primary / Proper / Traditional Name||SDSS J155720.77+091624.6|
|Spectral Type||DAZ D|
|Constellation's Main Star||No|
|Multiple Star System||No / Unknown|
|Star Type||Dwarf Star|
|Right Ascension (R.A.)||15h 57m 20.776|
|Declination (Dec.)||+09° 16` 24.69|
|Proper Motion Dec.||-24.00 milliarcseconds/year|
|Proper Motion RA.||-8.00 milliarcseconds/year|
|Radial Velocity||0.00 km/s|
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