It's on: the search for habitable planets around Alpha Centauri

A mission to discover new planets potentially capable of sustaining life around Earth’s nearest neighbouring star system, Alpha Centauri, has been announced.

Located just 4.37 light-years from Earth’s Sun, Alpha Centauri is a system with two sun-like stars. Either or both may host temperate planets, while a third star — the red dwarf Proxima Centauri — is already believed to have one planet in a ‘Goldilocks orbit’, discovered in 2016.

The new project will look for more planets in the Goldilocks zone, where temperatures could allow for liquid surface water on rocky planets. Scientists from The University of Sydney, in partnership with the Breakthrough Initiatives in California, Saber Astronautics in Australia and NASA’s Jet Propulsion Laboratory, have named the project TOLIMAN, which stands for ‘Telescope for Orbit Locus Interferometric Monitoring of our Astronomical Neighbourhood’.

“Our nearest stellar neighbours — the Alpha Centauri and Proxima Centauri systems — are turning out to be extraordinarily interesting,” said Dr Pete Worden, Executive Director of the Breakthrough Initiatives. “The TOLIMAN mission will be a huge step towards finding out if planets capable of supporting life exist there.”

Project leader Professor Peter Tuthill, from the Sydney Institute for Astronomy at The University of Sydney, is enthusiastic about this new window on the universe. He noted, “Astronomers have access to amazing technologies that allow us to find thousands of planets circling stars across vast reaches of the galaxy, yet we hardly know anything about our own celestial backyard.”

According to Prof Tuthill, getting to know our planetary neighbours is hugely important. He explained, “These next-door planets are the ones where we have the best prospects for finding and analysing atmospheres, surface chemistry and possibly even the fingerprints of a biosphere — the tentative signals of life.”

Most of the thousands of known planets outside the solar system, called exoplanets, have been discovered using space telescopes such as NASA’s Kepler and TESS missions. Finding exoplanets close to home will take more finely tuned instruments, which is where the TOLIMAN mission comes in.

Central to the mission is the deployment of a new type of telescope that uses a diffractive pupil lens. This mirror spreads starlight captured from nearby stars into a complex flower-like pattern that, paradoxically, makes it easier to detect perturbances of star movements that are the tell-tale signs of orbiting planets.

“Our TOLIMAN mission will launch a custom-designed space telescope that makes extremely fine measurements of the position of the star in the sky,” said Dr Eduardo Bendek, from NASA’s Jet Propulsion Laboratory. “If there is a planet orbiting the star, it will tug on the star betraying a tiny, but measurable, wobble.”

The project has received support from the Breakthrough Initiatives, a suite of scientific and technological programs engaged in the search for extra-terrestrial life. Pete Klupar, Chief Engineer of Breakthrough Watch, 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.”

Saber Astronautics has meanwhile received $788,000 from the Australian Government’s International Space Investment: Expand Capability grant, which will support the TOLIMAN mission. The company will provide spaceflight mission operations support, including satellite communications and command, space traffic management and a range of other flight services to download data from the satellite.

“TOLIMAN is a mission that Australia should be very proud of — it is an exciting, bleeding-edge space telescope supplied by an exceptional international collaboration,” said Saber Astronautics CEO Dr Jason Held. “It will be a joy to fly this bird.”

Image caption: A simulated view of the Alpha Centauri binary through the diffractive pupil proposed for the TOLIMAN telescope. Source: Peter Tuthill.

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