Alula Borealis — Double Star in Ursa Major
HIP 55219; Nu Ursae Majoris; 54 Ursae Majoris
About Alula Borealis
Description
Alula Borealis, Nu Ursae Majoris, is a K-type subgiant of spectral class K0 IV about 399 light-years away, marking the northern paw-print of the Third Leap of the Gazelle. It pairs with Alula Australis (Xi UMa) to form the southernmost of the three classic Arabic "leaps" asterisms in Ursa Major. Alula Borealis hosts a known exoplanet, Nu UMa b, a super-Jupiter in a 1600-day orbit.
Observing Tips
Alula Borealis and Alula Australis sit 1.5 degrees apart in the south of Ursa Major, and in binoculars they show a distinct orange-yellow hue from Alula Borealis versus Xi UMa's paler yellow. Alula Borealis is easier to identify first: it is the brighter of the two (magnitude 3.49 vs 3.79 for Xi). Best observed January through May.
History
The name "Alula" comes from the Arabic "al-qafzah al-ūlā," "the first leap," originally applied to the nearer-to-the-bear pair. Over time Western labeling reversed the numbering, so the star farthest from the Dipper became "First" and the nearest became "Third." The discovery of the Nu UMa b planet was announced in 2009.
Fun Facts
Nu UMa is part of a very old Arabic sky-tradition where the stars around Ursa Major represented the footsteps of a gazelle fleeing a pursuing bear — the bear's four paws were represented by Dubhe, Merak, Phecda, and Megrez, and the gazelle's three leaps by the paired stars of the Alula, Tania, and Talitha groupings. This predates both the Greek Great Bear story and the Big Dipper asterism.
Observe
1Physical Properties
2Position & Identifiers
3How easy to split?
| Telescope | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| 80 mm refractor 80mm refr. | V. hard+ | V. hard+ | V. hard+ |
| 150 mm Newton 150mm Newt. | Hard+ | Hard+ | Hard+ |
| Celestron C8 (203 mm SCT) C8 203mm | Medium | Medium | Medium |
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
4Visibility
Set a location in User Settings to see visibility data.
5Multiple Star System C,D: optical
Separation over time
Slow change over generations — observable in lifetime comparisons.
Measured from the WDS observational archive. No orbital solution has been derived — most likely the period is too long to fit an orbit to the available measurement arc.
Eyepiece View
A: 3.5 · B: 10.1 · Sep: 7.4″ · PA: 149° · N up, E right
Resolved · Rayleigh: 2.3″ · Dawes: 1.9″ · Eff: 2.3″
Explore
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Size Comparison
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Compare Stars
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Spectral Classification
10
Hertzsprung-Russell Diagram
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Stellar Lifecycle
12
Blackbody Spectrum
13
Stellar Absorption Spectrum
Simulated absorption spectrum based on spectral type. Hover over lines to identify elements.
14
Stellar Fusion
Discover
15Stellar Notes
16
Light Travel Time Machine
17
Relativistic Travel
Nearby in the Sky
Other targets within a few degrees — pan your scope a little and keep exploring.
Visibility scores assume a 150 mm Newton at Bortle 4.
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