Looking for aliens who might be looking for us

Breakthrough Listen is the largest ever scientific research program aimed at finding evidence of civilizations beyond Earth. The scope and power of the search are on an unprecedented scale.

Recent data from a massive search for cosmic radio emission has allowed astronomers to look for technological signatures of extraterrestrial civilizations that might be looking for us. The initiative announced the public release of the data as well as research investigating these “technosignatures” at a media briefing Feb. 14 in Seattle, Washington, as part of the annual meeting of the American Association for the Advancement of Science.

The new research drove by Penn State graduate student Sofia Sheik, is enlivened by a technique Earth-bound astronomers use to identify and study planets outside of our solar system – exoplanets- called transit photometry. The method depends on sensitive equipment like NASA’s Kepler space telescope to distinguish the infinitesimal sip in a star’s light as orbiting planets go before the star from our view.

Right now for radio outflows, the astronomers searched for radio emanations from 20 nearby stars that are lined up with the plane of Earth‘s orbit to such an extent that an alien species around those stars could see Earth go before the Sun with such a telescope of their own.

Scientists used Green Bank Telescope in West Virginia to search for radio signals from potential exoplanets in the so-called C-band, radio waves with a frequency between 4 and 8 gigahertz.

Sheikh said, “This region has been talked about before, but there has never been a targeted search of this region of the sky. If other civilizations have telescopes like ours, they would know that the Solar System has planets from their transits, and even know that Earth has life. That is how we have discovered thousands of other exoplanets, so it kind of makes sense to extrapolate and say that that might be how other intelligent species find planets as well. And if they know we’re here, they might be signaling us.”

However, scientists did not found any technosignatures of civilization. The analysis and other detailed studies the Breakthrough Listen group has conducted are gradually putting limits on the location and capabilities of advanced civilizations that may exist in our galaxy.

Breakthrough Listen principal investigator Andrew Siemion said, “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 gigahertz. These results put another rung on the ladder for the next person who comes along and wants to improve on the experiment.”

“In this and other SETI searches, Breakthrough Listen looks for electromagnetic radiation that is consistent with a signal that we know technology produces or some anticipated signal that technology could produce, and that is inconsistent with the background noise from natural astrophysical events. This also requires eliminating signals from cellphones, satellites, GPS, internet, Wi-Fi, and myriad other human sources.”

Sheikh pointed the green Bank Telescope at each star for five minutes, pointed away for another five minutes, and repeated the process two more times. She then threw out any signal that didn’t disappear when the telescope pointed away from the star. Ultimately, she whittled an initial million radio spikes down to a couple hundred, most of which she was able to eliminate as Earth-based human interference. The last four unexplained signals turned out to be from passing satellites.

Sheikh said, “My search was sensitive enough to see a transmitter basically the same as the strongest transmitters we have on Earth, because the targets were nearby. So we know that there isn’t anything as strong as our strongest radars beaming something at us. Even though this is a very small project, we are starting to get at new frequencies and new areas of the sky.”

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