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Phekda, Phad, Gamma Ursae Majoris, 64 Ursae Majoris

Proper NamesPhecda, Phekda, Phad
Bayer DesignationGamma Ursae Majoris
Flamsteed Number64 Ursae Majoris
HR (BSC)4554
ConstellationUrsa Major
Right Ascension11h 53m 50s
Declination+53° 41' 41"
Distance83 light years
26 parsecs
MagnitudeApparent: +2.4
Absolute: +0.4
Spectral ClassA0V White Main Sequence Star
Optimum VisibilityMarch / April (Usually visible from northern latitudes)
NotesA luminous white star emitting some sixty times the light energy of the Sun, Phecda rotates extremely rapidly on its axis within a surrounding cloud of material. From Earth, it lies on a close line of sight to the distinctive barred spiral galaxy M109.

This white star forms a part of the prominent asterism of the Plough or Big Dipper within Ursa Major, the Great Bear. It lies at the southeastern corner of the ploughshare (or the dipper's bowl), but within Ursa Major it also forms the point where the bear's rear legs meet its body (hence its name, which comes from the Arabic for 'thigh' of the bear).

Pheca shines against the backdrop of the M109 Group, a populous cloud of galaxies running through central Ursa Major. The galaxy that gives this group its name, the barred spiral M109, lies less than a degree from Phecda in the sky, and is visible in this image to the southeast (lower left) of the star. Imagery provided by Aladin sky atlas

Along with four of the other six stars in the Plough (and numerous other less prominent stars) Phecda forms part of the Ursa Major Moving Group, a group of several dozen stars though to have a shared origin some three hundred million years ago, following a mutual course through the Galaxy towards a point in the constellation Sagittarius.

Like most of the stars in this group, Phecda has a white spectral classification. A comparatively massive star in comparison to the Sun, it is notable for its high rotational velocity, and the enclosing envelope of gas detectable through its spectrum. Phecda lies about 83 light years from the Solar System.


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