The Breakthrough Listen Initiative, the largest ever scientific research program aimed at finding evidence of alien civilizations, has released data from the most comprehensive survey yet of radio emissions from the region around Sagittarius A*, a supermassive black hole that is four million times the mass of the Sun, and the so-called Earth Transit Zone, the plane of Earth’s orbit.
CSIRO’s Parkes radio telescope in New South Wales, Australia. Image credit: Shaun Amy.
The raw data — yet to be fully analyzed by astronomers — comes from a survey of the radio spectrum between 1 and 12 GHz.
About half was captured via the Parkes Radio Telescope in New South Wales, Australia, which, because of its location in the Southern Hemisphere, is perfectly situated and outfitted to scan the entire Galactic disk and center.
“The Galactic center, the most extraordinarily energetic area of our Galaxy, is an integral focus of our data gathering with all of our facilities,” said Breakthrough Listen principal investigator Dr. Andrew Siemion.
“It is there that an advanced civilization might somehow harness the energy of the supermassive black hole at the center of the Milky Way Galaxy to signal its existence.”
The remainder of the dataset was recorded by the Green Bank Observatory in West Virginia and the Automated Planet Finder.
NASA’s Spitzer Space Telescope, Chandra X-ray Observatory, and the NASA/ESA Hubble Space Telescope produced this composite image of the central region of our Milky Way Galaxy. Note that the center of the Galaxy is located within the bright white region to the right of and just below the middle of the image. Image credit: NASA / JPL-Caltech / ESA / CXC / STScI.
Galactic Center Survey
The so-far unanalyzed observations from the Galactic disk and center survey were a priority for Breakthrough Listen because of the higher likelihood of observing an artificial signal from that region of dense stars.
“If artificial transmitters are not common in our Galaxy, then searching for a strong transmitter among the billions of stars in the Galactic disk is the best strategy,” Dr. Simeon said.
On the other hand, putting a powerful, intergalactic transmitter in the core of our Galaxy, perhaps powered by Sagittarius A*, might not be beyond the capabilities of a very advanced civilization.
Galactic centers may be so-called Schelling points: likely places for civilizations to meet up or place beacons, given that they cannot communicate among themselves to agree on a location.
“The Galactic center is the subject of a very specific and concerted campaign with all of our facilities because we are in unanimous agreement that that region is the most interesting part of the Milky Way galaxy,” Dr. Siemion said.
“If an advanced civilization anywhere in the Milky Way wanted to put a beacon somewhere, getting back to the Schelling point idea, the Galactic center would be a good place to do it. It is extraordinarily energetic, so one could imagine that if an advanced civilization wanted to harness a lot of energy, they might somehow use the supermassive black hole that is at the center of the Milky Way Galaxy.”
An artist’s rendering of potentially habitable exoplanets, plus Earth (top right) and Mars (top center). Image credit: PHL@UPR Arecibo, phl.upr.edu / NASA / ESA / Hubble.
Earth Transit Zone Survey
In releasing the new data, Dr. Siemion highlighted a new analysis of radio emissions from 20 nearby stars that are aligned with the plane of Earth’s orbit such that an advanced civilization around those stars could see Earth pass in front of the Sun.
Conducted by the Green Bank Telescope, the survey observed in the radio frequency range between 4 and 8 GHz, the so-called C-band.
The data were then analyzed by Pennsylvania State University graduate student Sofia Sheikh, who looked for bright emissions at a single radio wavelength or a narrow band around a single wavelength.
“This is a unique geometry. It is how we discovered other exoplanets, so it kind of makes sense to extrapolate and say that that might be how other intelligent species find planets, as well. This region has been talked about before, but there has never been a targeted search of that region of the sky,” Sheikh said.
While the astronomers found no technosignatures, the analysis is gradually putting limits on the location and capabilities of advanced civilizations that may exist in our Galaxy.
“We didn’t find any aliens, but we are setting very rigorous limits on the presence of a technologically capable species, with data for the first time in the part of the radio spectrum between 4 and 8 GHz,” Dr. Siemion said.
“These results put another rung on the ladder for the next person who comes along and wants to improve on the experiment.”
