To Proxima Centauri
The nearest star to the Sun is a dim red dwarf whose light left it a little over four years ago.
Proxima Centauri is about 4.24 light years away, roughly 40 trillion kilometres. It belongs to the Alpha Centauri system, circling the brighter pair Alpha Centauri A and B at a distance of about 13,000 AU and taking more than half a million years to complete one orbit.
It is a red dwarf, about 15% of the Sun's width and less than 1% as luminous. Despite being the nearest star, it is far too faint to see without a telescope. It was discovered in 1915 by Robert Innes, working at the Union Observatory in Johannesburg.
In 2016 astronomers announced Proxima b, a planet of at least about 1.1 Earth masses, orbiting every 11.2 days in the zone where liquid water could in principle exist. Whether it could support life is uncertain, because Proxima is prone to violent flares that would bathe the planet in radiation.
Distances like this resist intuition. Voyager 1, the fastest spacecraft heading out of the solar system at about 17 km/s, would need some 75,000 years to get there. Shrink the Sun to a grain of sand one millimetre across and Proxima would be another grain about 29 kilometres away.
- Size
- 4.02 × 10¹⁶ m
- Distance
- about 4.24 light years
- Type
- Red dwarf (M5.5)
- Radius
- about 0.15 Sun