Are we alone in the universe? Breakthrough Listen, a scientific initiative looking for the presence and evidence of extraterrestrial civilisations beyond our world, was launched five years ago to answer this question that has fascinated the astronomy community for centuries. Now, a new catalogue compiled by the Breakthrough Listen team provides a conceptual answer to yet another probing question: are we looking for intelligent life beyond Earth in all the right places?
This comprehensive new ‘Exotica’ catalogue, released on 22 June, is the first in recent times to span the entire breadth of astrophysical phenomena: everything from distant galaxies, to objects in our own solar system. It contains a diverse list of objects of potential interest to astronomers who are searching for ‘technosignatures’—indicators of technology developed by extraterrestrial intelligence. The Breakthrough Listen team developed the catalogue conceptually, compiled it, and has shared it with the astronomical community, hoping that it can guide future surveys to study life beyond Earth.
An official release on the catalogue explains that ‘Exotica’ contains four categories of objects and, in total, a collection of over 700 distinct targets. “Sometimes a major new discovery was missed when nobody was looking in the right place, because they believed nothing could be found there. This happened with exoplanets, which might have been detected before the 1990s if astronomers looked for solar systems very different than ours. Are we looking in the wrong places for technosignatures? The Exotica catalogue will help us answer that question," says Dr. Brian Lacki, Breakthrough Listen theorist and lead author of the new catalogue, in the official release.
The four categories include ‘Prototypes’, a list containing at least one example of every known type of celestial object, such as planets and moons, stars at every point of their life cycle, small and big galaxies, star clusters and so on; ‘Superlatives’, objects with the most extreme properties. “These include examples like the hottest planet, stars with unusually high or low metal content, the most distant quasar and fastest-spinning pulsar, and the densest galaxy," the press release adds. The third category looks at ‘Anomalies’, targets or objects whose behavior is currently not explained properly. A popular example of such ‘anomalies’ is 'Oumuamua’ – the interstellar object that passed near Earth in 2017 and garnered global attention. The last category looks at a ‘control sample of sources’ that are not expected to produce any positive results.
The ‘Exotica’ catalogue is the latest of many techniques to understand and identify if intelligent life exists beyond our world. In August 2017, for instance, the team at Breakthrough Listen had detected 15 FRBs, or fast radio bursts, that originated from the location FRB 121102, a source in a galaxy about three billion light years away from Earth. FRBs are brief, bright pulses of radio emission from distant galaxies. In this particular instance, the FRBs were discovered with the help of a backend instrument—a set of parallel processing computers that analyse signals collected from a telescope—at the Green Bank Telescope in West Virginia.