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Tania Borealis

Alkafzah Borealis, Lambda Ursae Majoris, 33 Ursae Majoris

Proper NamesTania Borealis, Alkafzah Borealis
Bayer DesignationLambda Ursae Majoris
Flamsteed Number33 Ursae Majoris
HR (BSC)4033
ConstellationUrsa Major
Right Ascension10h 17m 6s
Declination+42° 54' 52"
Distance226 light years
69 parsecs
MagnitudeApparent: +3.44
Absolute: -0.76
Spectral ClassA2IV white subgiant
Optimum VisibilityMarch

A star in the southern regions of Ursa Major, the Great Bear, Tania Borealis forms an apparent pair with nearby Tania Australis to represent the rear legs of the bear. These two stars lie somewhat to the south and west from the Plough or Big Dipper formation, approaching the border of the faint neighbouring constellation of Leo Minor. Though Tania Borealis and Tania Australis share a name and appear close to each other in the sky, they are not related, and red Tania Australis is actually rather more distant from the Sun than its namesake to the north.

Tania Borealis in Ursa Major, with its red companion star Tania Australis visible to the southeast. The two stars are actually distant from one another in space, but are separated by less than two degrees on the celestial sphere. Imagery provided by Aladin sky atlas

There is some question over the precise distance to this star from the Solar System. Most sources suggest a value approaching 140 light years, but the most recent data release from the Gaia survey suggests a rather smaller parallax value than most other analyses, and this in turn implies a rather greater distance. This new parallax data suggests a considerably greater distance of 226 light years or more which, if correct, would place the two stars named Tania rather closer together in space than previously thought.

Tania Borealis is a hot white subgiant, approaching twice the temperature of the Sun as it burns the last of its hydrogen fuel and begins to evolve towards a true giant state. It is presently some three times the diameter of the Sun, and approximately sixty times as luminous.

The name Tania comes from Arabic thānia, meaning 'second', a name with its origins in Arabic star-lore. The close pair Tania Borealis and Tania Australis are one of three such pairs running northwestwards through Ursa Major, and these three pairs of stars were seen as the marks of gazelle springing through the sky. The two stars named Tania marked the middle of this springing progress, hence 'second' (its full original name being Al Fiḳrah al Thānia, 'the second spring'). The gazelle's first spring was represented by the stars Alula Borealis and Alula Australis to the southeast, and the third spring by stars with the traditional names Talitha Borealis and Talitha Australis to the northwest (this final pair are now officially known as Talitha and Alkaphrah).


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