An artist's impression shows a planet, right, orbiting the star Alpha Centauri B, center, a member of the triple star system that is the closest to Earth.
An artist's impression shows a planet, right, orbiting the star Alpha Centauri B, center, a member of the triple star system that is the closest to Earth. ESO/L. Calcada/AP
Scientists say they have detected the nearest planet outside of our solar system, an alien world about the size of Earth that's orbiting a star called Alpha Centauri B.
Imaginary planets in the Alpha Centauri star system have been a staple of science fiction for decades. That's because the three stars in this system—Alpha Centauri A, B, and C—are only about four light years from our Sun. That's far away, but it's still closer than everything else beyond our solar system, so Alpha Centauri has long been a tempting destination for storytellers who dream of interstellar travel.
Now, in the journal Nature, scientists say they've detected the first real planet in this star system.
For more than four years, a team of European astronomers used a telescope in Chile to make observations of Alpha Centauri B. They saw the star make a tell-tale wobble that meant a planet's gravity was tugging on the star.
The newly detected planet has a mass that's similar to that of Earth, but it zips around its star once every 3.2 days. It's so close to its star that its surface might be made of super hot molten rock, more than 2000 degrees Fahrenheit.
It's not the kind of place that looks likely to support life as we know it, researchers say, but systems with a planet like this one often have more planets orbiting farther away from the star.
"I think that the prospects are excellent for finding further planets in this system," says Greg Laughlin, an astrophysicist at the University of California, Santa Cruz who spoke during a press conference on the new discovery.
He notes that Alpha Centauri is a nearby, well-known star system that's practically a household name. "To find out that planet formation did occur there is just extraordinarily exciting," says Laughlin.
Scientists have made confirmed discoveries of more than 800 planets orbiting distant stars in recent years, but this is the closest neighbor ever detected outside of our solar system.
The find has thrilled planetary science experts like Marc Kuchner, an astrophysicist at NASA's Goddard Space Flight Center. He is most excited about the possibility of someday sending a probe to visit planets found in Alpha Centauri.
"Inside every astronomer is a space cadet, and this is the place to go," says Kuchner. "This is the destination that everyone talks about in the interstellar travel discussions."
With today's technology, going to this 'nearby' neighbor would take thousands of years.
But Laughlin says that if a planet was discovered in the so-called habitable zone of an Alpha Centauri star, where conditions might be right for liquid water or maybe even life, there might be a groundswell of popular support for the development of new, exotic forms of propulsion that might get a spacecraft there much faster.