Researchers at Pennsylvania State University (Penn State) in the US have devised a new method to search our own Solar System for signals sent by an intelligent civilization.
According to his proposal, the extraterrestrials could be using the stars, among them perhaps also our Sun, to focus and amplify your communication signals. The paper describing the technique, explored as part of a Penn State graduate course on Searching for Extraterrestrial Intelligence (SETI), has been accepted for publication in Astronomical Journal and is now available on the arXiv preprint server.
Massive objects like stars and black holes cause light to bend as it passes through due to the object’s gravitational pull, according to Einstein’s Theory of General Relativity. The warped space around the object acts like the lens of a telescope, focusing and magnifying light, a well-known effect called gravitational lens.
“Astronomers have considered taking advantage of gravitational lensing as a way to build a giant telescope to look at planets around other stars,” explains Jason Wright, professor of astronomy and astrophysics and director of the Center for Extraterrestrial Intelligence at Penn State. “It has also been considered as a way that we humans could communicate with our own probes if we ever send them to another star. If an alien technological species were to use our Sun as a lens for interstellar communication efforts, we should be able to detect those communications if we look in the right place.”
Because communications across interstellar distances would face a variety of challenges related to transmission power and fidelity across such vast expanses, the researchers believe that any communication effort would likely involve a network of probes or relays, such as towers. cell phone in space. In this study, they looked at one of our closest stars, which should be the closest node in a communication network.
“Humans use networks to communicate around the world all the time,” says Nick Tusay, a graduate student who is part of the project. “When you use a cell phone, electromagnetic waves are transmitted to the nearest cell tower, which connects to the next tower and so on. Television, radio, and internet signals also take advantage of network communication systems, which have many advantages over point-to-point communications. On an interstellar scale, it makes sense to use stars as lenses, and we can infer where the probes should be located in order to use them.”
From Alpha Centauri
In this study, researchers looked at more than 550 times the distance between the Earth and the Sun across the sky from Alpha Centauri, the closest stars to our own system that could be the closest node in a communications network, which is where a probe would be placed in our Solar System to use the Sun as a lens. This allowed the researchers to potentially detect radio transmissions that could be signals sent directly to Earth to communicate with us, signals being sent to other probes exploring the solar system, or perhaps even signals being sent through gravitational lensing. back to Alpha Centauri.
“There have been some previous searches using optical wavelengths, but we chose to use radio wavelengths, because radio is a great way to communicate information across space,” says study co-author Macy Houston. “We included what are known as ‘waterhole’ wavelengths, which are often the focus of SETI searches because they would be an ideal part of the radio spectrum to communicate with and could act as a waterhole in the Earth. Earth, where many species gather. These wavelengths are generally free from other radio waves coming from cosmic objects, so it’s a clean part of the spectrum to communicate with.”
Studying these particular wavelengths also allowed the researchers to maximize the amount of data they could collect from the sky in a short period of time. They did it overnight using the Green Bank Telescope in West Virginia. Data collection and analysis were done in collaboration with Breakthrough Listen, a program dedicated to finding evidence of intelligent life beyond Earth.
The students did not detect any signals at the wavelengths they investigated that might be of extraterrestrial origin in the area they observed, suggesting that signals at these wavelengths were not sent toward Earth during the brief window they were in. looking at.
“Our search was limited to one night, so anything that wasn’t transmitted while we were looking wouldn’t be detected,” says Tusay. “Although our limited search could miss existing probes if they weren’t constantly transmitting on these frequencies, this was a good test to see if this type of search is possible.”
The researchers suggest that broadening their search to include additional observations, or observations directed at other nearby stars or other frequencies, could still prove fruitful. One of the students is exploring archival data to see if previous Breakthrough Listen observations have pointed to additional areas that might be optimal for probes using gravitational lensing.
“Lensing is not the most robust at these frequencies, although there are still good reasons why these frequencies could be used,” says Houston. “But we think the technique is sound, and we hope that students of the course in the years to come will be able to broaden our search.”