Sephdar / Eta Sagittarii Star Facts (Type, Distance, Magnitude, Age, Colour, Location and more)

Sephdar, also known as Eta 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 (M2III), Sephdar colour is red, which means that the star is one of the colder stars in the Universe, colder than our star.

Sephdar temperature is in the range of between 2,400 to 3,700 Kelvin. Based on the spectral type (M2III) as we don't have the exact temperature', we can deduce that the surface temperature of Sephdar is in the order of below 3,500K based on the notes from Harvard University. To put this in context, the temperature of our Sun is about 5,778 Kelvin as said by Google.

Based on a parallax of 22.35, Sephdar distance from Earth can be calculated at being 145.93 light years away or 45.72 parsecs.

Sephdar 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.

Sephdar is a long period variable star. Variable stars are stars whose size and/or brightness changes over time. Sephdar brightness ranges from 3.171 (dimmest) to 3.125 over a period of 0.031 days.

Location

The location of the Sephdar 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 Sephdar, the location is 18h 17m 37.73 and -36° 45` 40.6 .

Based on the location of Sagittarius, Sephdar can be located in the southern hemisphere of the celestial sky. The celestial hemisphere is equivalent to the hemispheres on Earth. Sephdar 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

Sephdar spectral type of M2III which means its colour and type is red 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.

Sephdar Luminosity

Luminosity is the amount of energy a star pumps out relative to the amount that our star, the Sun, gives out. Our star, the Sun's value is 1. Sephdar luminosity figure of 369.93 is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012. The star generates more energy than our star.

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.

Sephdar apparent magnitude is 3.1, 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, Sephdar' absolute magnitude is -0.20. If you use the 2007 parallax value, Sephdar' absolute magnitude is -0.15. 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.

Sephdar 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.