Polaris+1B

=**POLARIS STAR**= Polaris, or the North Star, is the brightest star in the constellation Ursa Minor. It is very close to the north celestial pole (42′ away as of 2006), making it the current northern pole star."Polaris" comes from //Stella polaris//, the Latin form of its common name "Polar Star".Other names are the, North Star or Northern Star, the Lode Star or Load Star, or Polaris Borealis.

__PHYSICAL PROPERTIES__ Polaris has the common reputation of being the brightest star in the sky, whereas near dead-on second magnitude (2.02) it comes in at number 48. Its lower rank, however, is largely determined by its great distance of 430 light years. The star is actually an evolved class F (F7) yellow supergiant 2500 times more luminous than our Sun with a temperature of about 6000 Kelvin, which leads to a radius 45 times that of the Sun and a mass of six times solar.

Polaris is a trinary system, consisting of a large yellow Cepheid variable (α UMi A), orbited by a bright yellow dwarf (α UMi B) at a distance of about 2400 AU (360 billion kilometers, or 224 billion miles). Polaris B can be seen with even a modest telescope and was first noticed by William Herschel in 1780. Polaris is 431 light years (132 pc) from Earth, according to astrometric measurements of the Hipparcos satellite.

Dec.: -11.74 mas/yr || (132 ± 8 pc) || Physically, Polaris is very massive star of the 'F' bright yellow classification. It is particularly notable as being one of the nearest Cepheid variables to Earth; it is less then half the distance of Delta Cephei itself. This is important because Polaris' four-day cycle of swelling and contraction is directly related to its mass, which is in turn related to its luminosity. This means that we can calculate the star's absolute magnitude with some certainty, and comparing this with its observed apparent magnitude, we can compute its distance. Polaris' mean absolute magnitude is -3.50, and its mean apparent magnitude is +2.11, which gives us a distance of just over 431 light years.
 * ~ Characteristics ||
 * **Spectral type** || F7 Ib-II SB ||
 * **U-B color index** || 0.38 ||
 * **B-V color index** || 0.60 ||
 * **Variable type** || Cepheid variable ||
 * ~ Astrometry ||
 * **Radial velocity (Rv)** || -17 km/s ||
 * **Proper motion (μ)** || RA: 44.22 mas/yr
 * **Parallax (π)** || 7.56 ± 0.48 mas ||
 * **Distance** || 430 ± 30 ly
 * **Absolute magnitude (MV)** || -3.64 ||
 * ~ Details ||
 * **Mass** || 5.0 or 6.0 //M//☉ ||
 * **Radius** || 30 //R//☉ ||
 * **Luminosity** || 2200 //L//☉ ||
 * **Temperature** || 7200 K ||
 * **Metallicity** || ? ||
 * **Rotation** || ~17 km/s ||
 * **Age** || ? years ||