Space News & Blog Articles

The 500-Meter Aperture Spherical Telescope (FAST), (aka. Tianyan, “Eye of Heaven”), is the largest radio observatory in the world. Since the observatory became operational in January 2020, this facility has made significant contributions to radio astronomy and the Search for Extraterrestrial Intelligence (SETI). In particular, the observatory has been instrumental in detecting Fast Radio Burts (FRBs) and other cosmic phenomena that could be (but probably aren’t) possible indications of extraterrestrial communications.

Last week, while sifting through FAST data, the China Extraterrestrial Civilization Research Group (CECRG) from Beijing Normal University revealed that they discovered several signals that might be artificial in origin (a possible indication of an advanced civilization). These signals consisted of narrow-band electromagnetic radio transmission and were considered one of the best candidates for an extraterrestrial signal. Ah, but there’s a snag. According to subsequent news releases, those radio transmissions were apparently from Earth!

Since the first SETI experiments began in the early 1960s (with Project Ozma), radio transmissions have remained the primary signature for which researchers have been looking. As the world’s largest and most sensitive radio telescope (even larger than the venerable Arecibo Observatory), FAST is the world’s premier radio facility dedicated to SETI research. One of its six main objectives* is to search the cosmos for possible technosignatures – i.e., indications of technological activity.

To this end, Beijing Normal University, the National Astronomical Observatory of the Chinese Academy of Sciences (NAO/CAS), and the Berkeley SETI Research Center at UC Berkeley have partnered to create an international SETI research effort. In 2018, FAST took the first step by installing debugged back-end equipment to screen useful narrow-band candidate signals from background radio noise. By September 2020, the observatory officially began conducting science operations that included synchronous sky surveys and targetted exoplanet observations.

The team discovered two groups of “suspicious signals” that same year while processing data from the 2019 synchronic sky survey. This year, said CECRG team leader Professor Zhang Tongjie, the team found more possible radio signals while looking through data obtained during an exoplanet observation campaign. The Chinese state-affiliated news source Global Times shared the story on June 13th (since deleted), attesting to this discovery. As Prof. Zhang said in a statement to Chinese media:

A newly discovered supercluster of galaxies is so distant that astronomers say its light has been traveling for over twelve billion years to reach telescopes on Earth. But this cluster, named SPT2349 ?56 is gigantic, and so old that it is actually classified as a proto-cluster of galaxies, meaning it might be one of the earliest large clusters of galaxies in our Universe. It is also one of the most actively star-forming proto-clusters known.

Supercluster SPT2349 ?56 was discovered in the submillimeter band by the South Pole Telescope. Astronomer Matthew Ashby from the Harvard Smithsonian Center for Astrophysics (CfA) was one of the team members who conducted follow-up observations with the Gemini Observatory, the Hubble Space telescope and the Spitzer Space Telescope in order to conduct deep observations at optical and infrared wavelengths.  

The South Pole Telescope (SPT) is a 10-meter-diameter telescope located at the Amundsen-Scott South Pole Station, Antarctica. In addition to its primary mission of measuring the cosmic microwave background, the SPT is part of the Event Horizon Telescope project. Credit: Daniel Luong-Van

SPT2349 ?56 hosts hundreds of galaxies, including over thirty submillimeter-bright galaxies and dozens of other luminous and/or spectroscopically confirmed star-forming galaxies. Even though this is a cluster of galaxies from the early Universe, galaxy mergers and active star formation is taking place at an incredible rate, producing over ten thousand stars per year. The astronomers said one of its brightest sources appears to be the merger of over twenty galaxies.

One of the goals of the observations was to try to obtain the stellar mass of the system; however the team was unsuccessful. They said not knowing the stellar mass of the system made it impossible, for example, to know whether the huge burst of stars they observed was the result of an extraordinary efficiency or simply arose because the system was so extremely large.

A typical supercluster contains all the galaxy groups and galaxy clusters that seem to be associated with one another through mutual gravitational attraction, and contains about a quadrillion solar masses. Astronomers have estimated that there are 130 superclusters located within 1.3 billion light-years of the Milky Way. Another supercluster from the early Universe that was detected by the South Pole Telescope in 2010, weighs in at around 800 trillion Suns, and holds hundreds of galaxies.

In the decades-long search for extraterrestrial intelligence, there has never been confirmed evidence of an alien signal. There have, however, been a few tantalizing mysteries. Perhaps the greatest of these is known as the Wow Signal.

Observed on 15 August 1977 by the Big Ear radio telescope at Ohio University, the signal was a strong, continuous, narrow band radio signal lasting at least 72 seconds. Our knowledge of the signal is limited given the design of Big Ear. Rather than being able to track radio signals like most modern radio telescopes, Big Ear was set to a particular elevation and relied on Earth’s rotation to scan across the sky. The reason the Wow Signal lasts 72 seconds is because that’s how long it took the source to sweep across Big Ear’s observation range.

Big Ear was also a passive telescope. Astronomers simply set it up, and it would run on its own, recording the strength of signals as it goes. Because of this, the signal was only discovered days after the event when recorded observations were reviewed. By the time astronomers could go back to observe the source, the event was long over.

An aerial view of the Big Ear telescope. Credit: Bigear.org / NAAPO

But despite having just one observation, the Wow Signal is considered the strongest candidate for an extraterrestrial signal. Several natural origins have been proposed, but all of them are a bit lacking. The most basic idea is that the signal was of terrestrial origin, perhaps a plane passing overhead, or a radio signal scattered off space debris. But a plane wouldn’t be in range for more than 72 seconds, and there is no record of such a flight. A scattered signal is possible, but the strength of the signal would be unusual, and the frequency of the Wow Signal is within a range where transmissions are restricted.

Several years ago it was proposed that the signal might have been caused by comets that were near the observed area of the sky, but this has since been disproven. While two comets were close to the source location, they weren’t really within the observed range. And comets aren’t likely to emit such a strong narrowband signal.