Merak (Beta Ursae Majoris)
Merak (Beta Ursae Majoris) is a star in the constellation Ursa Major, magnitude 2.4.
One of the Big Dipper’s Pointers — a white star from a family that still travels together.
Merak is one half of the most famous signpost in the northern sky, the Pointers of the Big Dipper, or Plough. Its name comes from the Arabic al-marāqq, “the loins” of the bear. Hindu astronomers knew it as Pulaha, one of the Seven Rishis, the sages of these seven stars.
It is a white star about 2.7 times the Sun’s mass and 68 times as luminous, some three-quarters of the way through its hydrogen-burning life. Around it orbits a disc of cold dust at about 120 kelvin, like the discs found around Vega and Fomalhaut.
Merak is also part of a real family. With four other Dipper stars it belongs to the Ursa Major moving group, stars born together about 500 million years ago and still travelling through space side by side. Much of the Dipper is not a chance line-up at all.
Merak (Beta Ursae Majoris) is 80 light-years away: the light we see from it set off in 1946, 11 years before Sputnik became the first artificial satellite.
Did you know?
- A yardstick for white stars. In 1943 Merak was listed as a spectral standard for white A1 stars, a reference against which the light of other stars was measured.
- Celestial Rotating Jade. In China it is Tiān Xuán, the Star of Celestial Rotating Jade, and the second star of the Northern Dipper.
A white 2nd-magnitude star at the outer edge of the Big Dipper’s bowl, the Pointer farther from Polaris. Draw a line from Merak through Dubhe and extend it about five times their separation to reach Polaris.
When and where to see it
It is best placed in the evening sky around April, when it crosses the meridian at about 10 pm local time (around midnight in March). It can be seen from everywhere north of 34°S and never sets north of 34°N.
At its highest it stands 84° up from 50°N, 69° up from 35°N, 34° up from the equator, below the horizon from 35°S.
Facts
- Type
- Star
- Constellation
- Ursa Major
- Designations
- Beta Ursae Majoris, β UMa, 48 UMa, HR 4295, HD 95418, HIP 53910
- Magnitude
- 2.4
- Position
- RA 11h 1.8m, Dec +56° 23′ (J2000)
- Spectral type
- A1IVps
- Colour
- white (B−V -0.02)
- Distance
- 80 light-years
- Discovered
- Known since antiquity
Open AstroPilot to see when Merak (Beta Ursae Majoris) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.