How Far Is Alpha Centauri From Earth? Astronomers Hunting Habitable Worlds in Star System

A new space telescope will search for habitable worlds orbiting stars in the Alpha Centauri system, a cluster of three stars comprising the sun's closest stellar neighbors.

The mission named TOLIMAN announced on Tuesday, is a collaboration between NASA's Jet Propulsion Laboratory, the Breakthrough Initiative, and Saber Astronautics.

The space telescope, planned for 2023, will search for planets in the so-called habitable zone around stars next door to our solar system. This habitable area is also sometimes called the "Goldilocks zones" because it's not too hot and not too cold to host planets with liquid water.

"Our nearest stellar neighbors – the Alpha Centauri and Proxima Centauri systems – are turning out to be extraordinarily interesting," Pete Worden, executive director of the Breakthrough Initiatives, said. "The TOLIMAN mission will be a huge step toward finding out if planets capable of supporting life exist there."

Alpha Centauri is host to two sun-like stars, and a third star – the red dwarf Proxima Centauri, which is already believed to have one planet in a Goldilocks orbit, discovered in 2016.

The custom-designed telescope is ideal for such a mission because it takes extremely fine measurements of a star's position. This means it can spot the tiny wobble caused when an orbiting planet gravitationally "tugs" on its parent star.

This could uncover exoplanets orbiting the two sun-like stars, which could in turn be a crucial step on the road to discovering life elsewhere in the cosmos.

"Getting to know our planetary neighbors is hugely important," University of Sydney astronomy researcher Professor Tuthill said. "These next-door planets are the ones where we have the best prospects for finding and analyzing atmospheres, surface chemistry, and possibly even the fingerprints of a biosphere – the tentative signals of life."

Despite being our most immediate neighbor, a trip to the triple star system isn't currently feasible. Though close in cosmic terms, the sun and the stars of Alpha Centauri are still separated by a distance of around 4.4 light-years. Tiny in terms of the Milky Way, a galaxy that spans over 105,000 light-years, but insurmountable for humanity at present.

Seeking to Travel Faster

It takes light from the stars of Alpha Centauri almost four-and-a-half years to reach us. Currently, the fastest spacecraft created by humanity is NASA's Parker Solar Probe, which used the gravity of the sun to accelerate to 330,000 miles per hour.

Though the fastest object ever created by humanity, 150 times faster than a bullet fired from a rifle, it is just under 0.5 percent of the speed of light, 660 million miles per hour.

That means if we could create a manned spacecraft that travels at this speed, it would still take over 880 years to reach the temperate planets that could be hosted by Alpha Centauri's two sun-like stars.

Despite their distance, Pete Klupar, chief engineer of Breakthrough Watch, is positive about our prospects of sending a probe to reach exoplanets around the stars of Alpha Centauri. He said: "These nearby planets are where humanity will take our first steps into interstellar space using high-speed, futuristic, robotic probes.

"If we consider the nearest few dozen stars, we expect a handful of rocky planets like Earth orbiting at the right distance for liquid surface water to be possible."

Exoplanet around two stars
A file photo of an exoplanet in orbit around two stars. A new telescope will search the Alpha Centauri star system for potentially habitable worlds. dottedhippo/Getty