Brachium — Star in Libra
HIP 73714; Sigma Librae; 20 Librae
About Brachium
Description
Brachium is a red giant of spectral type M3III at magnitude 3.29, one of the reddest naked-eye stars in the zodiac. Located about 292 light-years from Earth, it has a cool surface temperature of about 3,600 K. Despite being in Libra, it was historically designated Gamma Scorpii, reflecting its former association with the Scorpion's claws.
Observing Tips
Brachium lies at the southeastern edge of Libra, near the border with Scorpius. Its deep red color is apparent in binoculars. Best observed May through July when Libra is well-placed.
History
The name Brachium is Latin for 'arm,' though historically this star was called Gamma Scorpii before being reassigned to Libra. Its position on the old Scorpion's claw reflects the time when Libra's stars were considered part of Scorpius.
Fun Facts
Brachium's former designation as Gamma Scorpii is a reminder that the Romans created Libra by 'borrowing' the Scorpion's claws — the names Zuben Elgenubi and Zuben Elschemali (meaning 'southern claw' and 'northern claw') preserve this history.
Observe
1Physical Properties
2Position & Identifiers
3How easy to spot?
| Equipment | Bortle 3 | Bortle 4 | Bortle 5 |
|---|---|---|---|
| Naked eye Naked eye | Easy | Easy | Medium+ |
| 50 mm finder 50mm finder | Easy | Easy | Easy |
| 150 mm telescope 150mm scope | Easy | Easy | Easy |
Bortle 3 = rural · 4 = outer suburbs · 5 = suburbs
4Visibility
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5Survey Image
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Explore
7
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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