Star
Arcturus
K1.5 III red giant
The brightest star in the northern celestial hemisphere. Arcturus is an aging giant that has exhausted hydrogen in its core. Follow the arc of the Big Dipper's handle to find it — 'arc to Arcturus'.
In your sky
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Key facts
Distance
36.7 light-years
Apparent mag.
−0.05
Radius
~25 × Sun
Luminosity
~170 × Sun
Temperature
~4,290 K
Spectral type
K1.5III
True colour from its B–V index (1.23): a surface around 4300 K.
Did you know
- Its light was used to open the 1933 Chicago World's Fair.
- It moves unusually fast across the sky relative to the Sun.
- It is probably 7–8 billion years old.
