A university budget gives researchers just one chance to look at the planets of Alpha Centauri

Getting to know our nearest interstellar neighbour hasn’t been easy even though Alpha Centauri is fortuitously close. But the tightly packed triple system tends to dazzle attempts at finding potentially habitable planets.

“It makes things more difficult for everyone except me,” says  Professor Peter Tuthill from the University of Sydney’s Institute for Astronomy and School of Physics.

Alpha Centauri A (Rigil Kentaurus) and Alpa Centauri B (Toliman) are both sun-like yellow stars. Proxima Centauri is a smaller, cooler red dwarf.

“We’re kind of freaky lucky because, if you rewind history hundreds of 1000s of years, you don’t find sun-like stars anywhere near as close,” he told Cosmos Science. “It’s only four lightyears away at the moment. I mean, that’s still an awfully long way for our technology. But, having said that, at least it’s not the 12 or so we’d otherwise expect”.

Tuthill has backing from the “Breakthrough Initiative,” funded by billionaire Yuri Milner, to search for life beyond Earth. And while astronomers have found 55 planets in potentially life-supporting orbits , they haven’t yet managed a good look at our nearest neighbours.

“The whole point of my Toliman mission is that it wouldn’t work if it were a single star,” Tuthill says. “It needs a binary star. So it flips the script on the problems astronomy faces and turns a challenge into an opportunity.”

Now the University of Sydney has signed a deal with microsatellite provider EnduroSat to build and operate a small spacecraft to carry into orbit a new camera system built by Tuthill. It’s no ordinary camera.

“The telescope engraves a fingerprint on the incoming starlight. And when you get a fingerprint, you get a whole lot more information than you would from a much more expensive telescope that can capture a much cleaner image”.

Put simply; it pinpoints the precise position of each of the two yellow stars. And that means any “wobble” induced by the gravity of orbiting planets can be sifted out from “a whole lot of boring numbers”.

“If there’s an Earth-like planet in one of their Goldilocks Zones, it’ll tug its parent star around by a couple of hundred kilometres,” Tuthill says. “That may sound like a lot, but over four lightyears, that’s a vanishingly small signal to try and find amid a very noisy background”.

And it has to be done on a budget.

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“We’ve had to deliver large observatory class performances on a CubeSat,” he says. “We’re pushing the envelope well beyond where a small mission should be asked to go.”

The satellite has to be as stable as the Hubble Space Telescope to point and maintain the camera’s attitude. “Hubble’s the size of a bus,” he says.

It also must have the thermal and mechanical stability of the Gaia Astronomical Observatory.

“That’s the size of a small car”.

Even five years ago, the project wouldn’t have been possible, he adds. The computer processing power needed to sift through the mountains of data – while aboard a low-power satellite in low-earth orbit – simply didn’t exist.

“We don’t simply just look at the star and get an image. We do something much more complicated than that,” Tuthill says. “And that requires a lot of computer power to unravel this subtle signal engraved on our data stream.”

Then there’s the need to compensate for the thermal expansion and buffeting of the low-orbit cubesat as it passes over deserts and oceans – let alone move between night and day.

“We’re trying to make some of the most stable measurements ever made, but pushing it to a higher orbit where things are more serene would blow our budget,” he explains.

All this makes the launch of his Toliman Observatory a nail-biting experience.

“These small satellites are difficult because you can’t fly redundant systems,” he says. “You’ve got one radio, one attitude control system … and that makes and problem much harder to recover from.”