Polis / Mu Sagittarii Star Facts (Type, Distance, Magnitude, Age, Colour, Location and more)

Polis, also known as Mu Sagittarii (Bayer) is a giant star located in the constellation of Sagittarius, Half-Man/Half-Horse Archer. It is not part of the Sagittarius constellation outline but is within the borders of the constellation.

Based on the spectral type (B2III:), Polis colour is blue, which means that the star is one of the hottest stars in the Universe, hotter than our star.

Polis temperature is in the range of 10,000 to 30,000 Kelvin. Polis effective temperature is 6,750 Kelvin which is hotter than the Sun's effective temperature, which is 5,777 Kelvin. Based on a parallax of 0.09, Polis distance from Earth can be calculated at being 36,240.37 light years away or 9090.91 parsecs.

Polis is a naked-eye star, so you don't need a telescope or binoculars when you look up on a clear night. The lower the magnitude, the easier it will be to see it.

Polis is a beta persei (algol) variable star. Variable stars are stars whose size and/or brightness changes over time. Polis brightness ranges from 3.961 (dimmest) to 3.836 over a period of 0.113 days.

Location

The location of the Polis in the night sky is determined by the right ascension (R.A.) and declination (Dec.). These are equivalent to the Longitude and Latitude on Earth. The Right Ascension (Longitude) is expressed in time (hh:mm:ss) and is how far the star is along Earth's celestial equator. If the R.A. is positive, then it's eastwards and vice versa.

The Declination (Latitude) is how far north or south the object is compared to the celestial equator and is expressed in degrees. If the value is positive, it is north of the celestial equator. For Polis, the location is 18h 13m 45.81 and -21° 03` 31.8 .

Based on the location of Sagittarius, Polis can be located in the southern hemisphere of the celestial sky. The celestial hemisphere is equivalent to the hemispheres on Earth. Polis is on the Ecliptic. The Ecliptic is the path that the Earth takes as it orbits the Sun. As the Earth is titled, we therefore have Celestial and Ecliptic hemispheres and they can be different for a star.

Physical Properties

Spectral Type

Polis spectral type of B2III: which means its colour and type is blue giant star. There is no relationship between colour and size. For example, a red star can be large or small. Small stars are more energy efficient than larger stars and live longer.

Magnitude (Apparent / Absolute / Visible)

A number represents a star’s magnitude, whether apparent/visual or absolute. The smaller the number, the brighter the star is. The Sun is the brightest star and therefore has the lowest of all magnitudes, -26.74. A faint star will have a high number.

Polis apparent magnitude is 3.84, which is a measure of the star's brightness as seen from Earth. Apparent Magnitude is also known as Visual Magnitude.

If you use the 1997 parallax value, Polis' absolute magnitude is -10.95. If you use the 2007 parallax value, Polis' absolute magnitude is -11.39. Absolute Magnitude is the star's apparent magnitude from 10 parsecs or 32.6 light years. The magnitude assumes nothing is between the object and the viewer, such as dust clouds. To compare different stars' actual brightness, you would best use Absolute rather than Apparent Magnitude.

Polis is visible from Earth without needing binoculars or a telescope. The lower the Apparent Magnitude of a star or other object is, the easier it is to see in the night sky. An object with a magnitude greater than 6.5 cannot be seen without a telescope or other device.