Tania Borealis (Lambda Ursae Majoris)

Tania Borealis, Lambda Ursae Majoris (λ UMa), is a blue-white subgiant star located 138 light-years away in the northern constellation Ursa Major. With an apparent magnitude of 3.45, it is easily visible to the unaided eye. The star is part of the Three Leaps of the Gazelle, a relatively bright star pattern formed by the six stars that mark the Great Bear’s paws.

Star type

Tania Borealis is a blue-white star subgiant of the spectral type A2 IV. It has almost exhausted its supply of hydrogen in its core and is currently evolving into a giant.

Lambda Ursae Majoris has a mass 2.11 times that of the Sun and a radius of 2.3 solar radii. With a surface temperature of 9,247 K, it is 37 times more luminous than the Sun. It spins at 50 km/s and has an estimated age of 380 million years.

Tania Borealis (Lambda Ursae Majoris), image credit: ESO/Digitized Sky Survey 2 (CC BY 4.0)

Facts

Tania Borealis is one of the six stars that form the Three Leaps of the Gazelle, along with Tania Australis (Mu Ursae Majoris), Alula Australis (Xi Ursae Majoris), Alula Borealis (Nu Ursae Majoris), Talitha (Iota Ursae Majoris) and Alkaphrah (Kappa Ursae Majoris). In depictions of the constellation Ursa Major, these stars mark the feet of the Great Bear.

The Three Leaps asterism consists of three pairs of stars. Alula Australis and Alula Borealis form the first leap, Tania Australis and Tania Borealis the second leap, and Talitha and Alkaphrah the third leap. In old Arabic lore, the star pattern was called Kafzah al Thiba’, “the springs of the gazelle.” It represents the leaps of a gazelle that fled across a large pond after being startled by a lion.

Three Leaps of the Gazelle, image: Stellarium

Name

The name Tania Borealis (pronunciation: /ˈteɪniə ˌbɒriˈælɪs/) comes from the Arabic Al Fiḳrah al Thānia, meaning “the second leap” or “the second spring.” The word borealis means “northern” or “the north side.”

The International Astronomical Union’s (IAU) Working Group on Star Names (WGSN) approved the name Tania Borealis for Lambda Ursae Majoris on July 20, 2016.

In traditional Chinese astronomy, Tania Borealis was known as 中台一 (Zhōng Tái yī), the Star of First Middle Step. It was part of an asterism called Three Steps, formed by the six stars of the Three Leaps of the Gazelle. The asterism was part of the Supreme Palace Enclosure, which represented the imperial court.

Location

Tania Borealis and its neighbour Tania Australis appear almost halfway from the Big Dipper in Ursa Major to the Sickle in Leo. The Sickle is an asterism that outlines the celestial Lion’s head. Tania Borealis is the northern of the two stars.

The stars of the Second Leap of the Gazelle stand out in the night sky near the constellation Leo Minor (the Smaller Lion). The faint constellation appears just south of the Great Bear’s feet.

The location of Tania Borealis (Lambda Ursae Majoris), image: Stellarium

Tania Borealis and Tania Australis can be used to find the Little Pinwheel Galaxy (NGC 3184), an unbarred spiral galaxy 39.8 million light years away, the barred spiral galaxy NGC 3198, which lies 47 million light years away. The Little Pinwheel has an apparent visual magnitude of 10.4 and NGC 3198 shines at magnitude 10.3.

Tania Australis, Tania Borealis, NGC 3184 and NGC 3198, image credit: ESO/Digitized Sky Survey 2 (CC BY 4.0)

The fainter galaxies NGC 3202, NGC 3205, NGC 3207, and IC 598 appear in the same field as Tania Borealis. The first three are members of a small galaxy group located 330 million light-years away.

Galaxies near Tania Borealis, image credit: ESO/Digitized Sky Survey 2 (CC BY 4.0)

Constellation

Tania Borealis is located in the constellation of Ursa Major. The Great Bear is one of the Greek constellations, listed by the Greco-Roman astronomer Claudius Ptolemy in his Almagest in the 2nd century CE. In Greek legend, it is associated with Callisto, a nymph turned into a bear by the goddess Hera.

Ursa Major is the third largest constellation in the sky, after Hydra and Virgo. It is the largest constellation in the northern celestial hemisphere, occupying an area of 1,280 square degrees.

The Great Bear is also one of the most familiar northern constellations. Its seven bright stars form the Big Dipper, the best-known asterism in the far northern sky. These are the hot B-type star Alkaid (Eta Ursae Majoris), the orange giant Dubhe (Alpha Ursae Majoris), and the A-type stars Mizar (Zeta Ursae Majoris), Alioth (Epsilon Ursae Majoris), Phecda (Gamma Ursae Majoris), Megrez (Delta Ursae Majoris), and Merak (Beta Ursae Majoris).

Ursa Major constellation map by IAU and Sky&Telescope magazine (Roger Sinnott & Rick Fienberg) (CC BY 3.0)

Other notable stars in the constellation include the M-type dwarf Lalande 21185, the fourth nearest system to the Sun (after Alpha Centauri, Barnard’s Star and Wolf 359), the variable contact binary star W Ursae Majoris, the yellow giant Muscida (Omicron Ursae Majoris), the Sun-like star Chalawan (47 Ursae Majoris) with three orbiting exoplanets, and the K-type dwarf HIP 57274, which also hosts a system of three planets.

Bright deep sky objects in Ursa Major include the galaxies Messier 81 and Messier 82 (Bode’s Galaxy and the Cigar Galaxy), Messier 101 (the Pinwheel Galaxy), Messier 108 and Messier 109, and the planetary nebula Messier 97 (the Owl Nebula).

The best time of the year to observe the stars and deep sky objects in Ursa Major is during the month of April, when the constellation is high above the horizon in the early evening. The entire constellation is visible from locations north of the latitude 30° S.

The 10 brightest stars in Ursa Major are Alioth (Epsilon UMa, mag. 1.77), Dubhe (Alpha UMa, mag. 1.79), Alkaid (Eta UMa, mag. 1.86), Mizar (Zeta UMa, mag. 2.04), Merak (Beta UMa, mag. 2.37), Phecda (Gamma UMa, 2.438), Psi Ursae Majoris (mag. 3.01), Tania Australis (Mu UMa, mag. 3.06), Talitha (Iota UMa, mag. 3.14), and Theta Ursae Majoris (mag. 3.166).

Tania Borealis – Lambda Ursae Majoris