Merak / Beta Ursae Majoris Star Facts (Type, Distance, Magnitude, Age, Colour, Location and more)

Merak, also known as Beta Ursae Majoris (Bayer) is a main sequence star located in the constellation of Ursa Major, The Big Bear. Merak is a major star and forms part of the constellation.

Based on the spectral type (A1V), Merak colour is blue - white, although not the hottest stars, they are considerably hotter than our own star which is white.

Merak temperature is in the range of between 7,500 and 10,000 Kelvin. Merak effective temperature is 4,732 Kelvin which is cooler than the Sun's effective temperature which is 5,777 Kelvin. Merak is the 80th brightest star in the night sky and the 5th brightest star in Ursa Major based on the Hipparcos 2007 apparent magnitude. Based on a parallax of 40.9, Merak distance from Earth can be calculated at being 79.75 light years away or 24.35 parsecs.

Merak 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.

Location

The location of the Merak 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 Merak, the location is 11h 01m 50.39 and +56° 22` 56.4 .

Based on the location of Ursa Major, Merak can be located in the northern hemisphere of the celestial sky. The celestial hemisphere is equivalent to the hemispheres on Earth. Merak is north of 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

Merak spectral type of A1V which means its colour and type is blue - white main sequence 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.

Merak 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. Merak Luminosity figure of 63.99 comes from the Vizier online catalogue. The star generates more energy than our star.

Iron Abundance

Merak Iron Abundance is -0.03 with an error value of 9.99 Fe/H, with the Sun having a value of 1 to put it into context. The value comes from the Hipparcos Extended Catalog.

Merak Surface Gravity

The Surface Gravity of Merak as measured in CGS (Centimeter-Gram-Second) is 3.830. The gravity has a relationship to its mass and radius. The larger the mass, the larger the gravity. Merak surface gravity has an uncertainty range of between - and +.

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.

Merak apparent magnitude is 2.34, 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, Merak' absolute magnitude is 0.41. If you use the 2007 parallax value, Merak' absolute magnitude is 0.40. 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.

Merak 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.