One question, two correct answers

"What’s the nearest star to Earth?" is a classic trick question, and the trap is the word star. The Sun qualifies — it’s a perfectly ordinary G-class star that happens to sit 149.6 million kilometres away rather than trillions. If a teacher asks, that’s the expected answer.

What most people mean is the nearest other star, and that’s Proxima Centauri: a red dwarf discovered in 1915 by Robert Innes, observing from Johannesburg. The gap between the two answers is the whole point of the page — the second-nearest star is about 268,000 times further away than the first. Space is mostly the gap.

The nearest star is invisible

Here’s the joke the universe plays: our closest stellar neighbour cannot be seen. Proxima is a red dwarf with about an eighth of the Sun’s mass, glowing 18,000 times too faintly for the naked eye — you need a decent telescope to find it at all. The same is true of roughly three-quarters of all stars in the galaxy; the local neighbourhood is a fair sample.

Its two companions make up for it. Alpha Centauri A and B — a Sun-like pair orbiting each other every 80 years, 4.37 light-years away — blend into the third-brightest star in Earth’s night sky. From Australia it’s unmissable: the brighter of the two "Pointers" that aim at the Southern Cross. Proxima drifts around that pair on an orbit so wide it takes over half a million years to complete — close enough to belong to the system, far enough that astronomers argued about it for a century.

And Proxima has planets. Proxima b, announced in 2016, is roughly Earth-sized and orbits inside the habitable zone — on paper, liquid water is possible. In practice, Proxima is a flare star that periodically blasts its planets with radiation, so whether "habitable zone" means "habitable" is one of the livelier arguments in astronomy.

How far is 4.246 light-years, really?

Shrink the Sun to a one-metre beach ball sitting in Sydney. On that scale, Earth is a peppercorn about 107 metres down the street, and Pluto is a grain of sand six kilometres away — the whole Solar System fits in one suburb. Proxima Centauri? Another beach ball roughly 29,000 kilometres away — most of the way around the planet. Between the two balls: nothing.

That’s why the calculator above produces such absurd numbers. The fastest object humans have ever built, the Parker Solar Probe, would still need over six thousand years. Voyager 1, our fastest outbound craft, needs about 74 millennia. Light — the fastest anything can ever move — takes four and a quarter years, which is why the light you’d see from Proxima tonight left it before the last two Olympics.

Will anything we build ever get there?

One serious proposal exists. Breakthrough Starshot, announced in 2016 with backing from Yuri Milner and Stephen Hawking, would skip the rocket entirely: gram-scale chips attached to metre-scale light sails, pushed by a 100-gigawatt ground-based laser array to around 20% of light speed. Travel time to Alpha Centauri: about 20 years, plus 4.25 more for the photos to come home. The physics checks out; the engineering — a sail that survives the laser, a camera that weighs a gram, an aim that hits a star — is decades of unsolved problems stacked up.

Until then, the honest status is this: humanity’s farthest object, Voyager 1, has been flying for nearly fifty years and has covered about one six-hundredth of the distance to the nearest star. The number on this page isn’t just trivia — it’s the wall around the neighbourhood.

Frequently asked questions

Eight questions, one trick

Sources

• NASA — Proxima Centauri at 4.246 light-years; the Sun as Earth’s nearest star at 8.3 light-minutes.
• ESO — discovery of Proxima b (2016) and the Proxima planetary system.
• RECONS (Research Consortium on Nearby Stars) — the census of the nearest star systems.
• NASA/JPL Voyager mission — Voyager 1 speed (~61,000 km/h) and trajectory.
• NASA — Parker Solar Probe record speed (~690,000 km/h at closest approach).
• Breakthrough Initiatives — the Starshot light-sail concept (2016).
• Robert Innes, Union Observatory Johannesburg — discovery of Proxima Centauri (1915).

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