Cosmic Scale
Arcturus
Red giant · 37 light-years
How big is Arcturus?
Arcturus is about 3.5 × 10⁷ km across.
See Arcturus in 3D, at true scale
Arcturus is an ageing orange giant and the brightest star in the northern half of the sky. It belongs to an older population of stars that orbits the galaxy at a steep angle to the disk, so it is only passing through our neighbourhood.
At a glance
| Diameter | 3.5 × 10⁷ km |
|---|---|
| Mass | 2.15 × 10³⁰ kg |
| Diameter compared with Earth | 2,770 × Earth |
| Distance | 37 light-years |
| Surface | 4,286 K |
| Brightness | 170 Suns |
| Age | About 7 billion years |
Good to know
- Its light was used to open the 1933 Chicago World's Fair, focused onto a photocell to throw a switch.
- It is moving so fast relative to us that it will drift noticeably within half a million years.
- It shows what the Sun will look like in about five billion years.
- Next smaller: Sagittarius A* · 2.5 × 10⁷ km
- Next larger: Polaris · 5.2 × 10⁷ km