The Parkes Radio Telescope in southeastern Australia is trained on Proxima Centauri, the star closest to our sun, and the planet recently discovered there. After two weeks of commissioning work, the Parkes telescope aimed its giant radio dish toward the star Monday in the hopes — however scant — that the planet known as Proxima b hosts life, of the sort that can communicate using radio waves.
“Nearby stars are naturally very interesting to us, and of course nearby planets by extension,” Andrew Siemion, director of the Berkeley SETI Research Center and member of the Breakthrough Listen team, said in an interview. “That’s why knowing there’s a potentially habitable planet around our nearest neighbor is such an exciting thing.”
Monday’s observing run marks the newest entry in the 10-year, $100 million Breakthrough Listen project to look for signs of intelligent life beyond Earth. The Green Bank Telescope in West Virginia and the Automated Planet Finder at Lick Observatory are already monitoring the skies in a targeted search. And just last month, Breakthrough Listen signed an agreement with China’s brand-new FAST telescope.
But Parkes is crucial for one important reason: It can see the southern sky, which is home to Proxima Centauri but is inaccessible to Green Bank and other storied scopes.
Siemion says Proxima was an ideal first target for the famed radio telescope, which played a vital role in transmitting the first messages from another world: Photos and broadcasts from Apollo 11. Australians consider it a national monument, and are much more familiar with Parkes than Americans are with comparable radio observatories, like the Very Large Array or the Green Bank Telescope, he says.
While the moon landing transmissions were quite a feat, receiving messages from a civilization just one star over would of course change everything.
Breakthrough Listen started looking for extraterrestrial signals well before anyone knew Proxima Centauri b existed. The Green Bank Telescope’s dedicated Breakthrough Listen instrument has been looking to the skies for nine months, and engineers from Berkeley SETI installed a similar setup at Parkes. They spent two weeks testing and commissioning the hardware before flipping it on Nov. 7 to look at Proxima.
Parkes is a single-dish telescope, which offers some benefits over multiple-dish arrays like the VLA or the Atacama Large Millimeter/sub-millimeter Array in Chile. They offer the largest amount of area on the sky for a given collecting area, which makes them prime candidates for SETI searches or other interesting phenomena like fast radio bursts, Danny Price, project scientist for Breakthrough Listen at Parkes, said in an interview.
Commissioning radio receivers in varying frequencies can be difficult, because local transmitters — like cell phones, microwave ovens, radios and more — can interfere with distant signals from deep space. Engineers have to write software to make sure a would-be SETI signal isn’t actually someone’s cell phone call. To do this, the telescope looks at Proxima, then looks away, then looks at calibration sources like pulsars, which are rapidly spinning neutron stars.
Proxima itself poses some other astrophysical challenges. It’s a flare star, meaning it constantly spews X-rays and other radiation into space (and toward its planet). Price says the team is hoping to detect stellar flares using the Breakthrough setup.
Those observations, as well as data management and other software tricks of the trade, will benefit not only SETI but the broader radio astronomy community, including the forthcoming Square Kilometer Array, according to Price.
“From a technological point of view, we’re kind of blazing some trails,” he says. “Part of the problem that we will face, and SKA will face, is just the sheer volume of data. Storing that, moving it around, and processing it is challenging, so the kind of solutions we’re coming up with will be broadly applicable.”
By opening eyes on the southern hemisphere — where observers can peer into the heart of the Milky Way, not to mention other nearby galaxies — the Parkes telescope makes Breakthrough Listen the largest coordinated SETI project ever undertaken. The Parkes program will share data and search methods with the FAST telescope, which is the world’s largest filled-aperture radio receiver, to speed up the time it takes to make followup observations. Russian billionaire Yuri Milner, founder of Breakthrough Listen and the other Breakthrough Initiatives, says Parkes was an important milestone in his search.
“These major instruments are the ears of planet Earth, and now they are listening for signs of other civilizations,” he said in a statement.
Alien-hunting has long played an outsize role in popular culture and science fiction, especially with respect to its regard among scientists, and certainly with respect to its funding in astronomy and astrophysics. But the Breakthrough project is changing that. Now, with observatories on three continents sharing data and viewing techniques, SETI is no longer fringe — it’s on the cutting edge.
“It will take a while for that message to propagate through people’s consciousnesses,” says Price. “But we now know there are many more exoplanets than anyone imagined. It really is a different time, and a very exciting time, and a great time to be looking.”
Proxima Centauri itself has loomed large in pop culture since its discovery 101 years ago last month. The star closest to our own is smaller and redder than the sun and its two sunlike companions, Alpha Centauri A and B. But this has meant no diminution in its stature. And the star’s dim countenance is actually good news for the small, rocky world circling it in a breakneck 11-day orbit. Because the star is dimmer, Proxima b is in the habitable zone, where conditions could be just right for liquid water to exist on its surface. It’s roughly in the same position of Proxima’s habitable zone as Earth is in the sun’s habitable zone.
Of course, this doesn’t mean Proxima b can host life. If it did, there’s no telling whether Proximans would be intelligent. And even if they were intelligent, there’s no reason to assume they would be able to transmit radio signals directly toward the middle-aged, medium-sized yellow star closest to their own.
If they were, though, and they knew how to direct a beacon toward us, Parkes would be able to find them.
“Not just philosophically, but technically speaking, it really presents our best opportunity to detect a civilization that is only marginally more advanced than our own,” Siemion says.
In the next generation, more powerful optical telescopes will scrutinize the star and try to study the planet’s atmosphere. Ultimately, our first sign of life could come via another Breakthrough initiative, Breakthrough Starshot, in which Milner aims to send a fleet of thin space sails to the Alpha Centauri system.
In the meantime, the telescope at Parkes will be bending an ear.
