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Radboud University > Faculty of Science > Department of Astrophysics

SETI – Search for Extraterrestrial Intelligence

Kepler-11 planets - NASA/Tim PyleAre we alone in the universe, or are there other civilizations? What once used to be part of science fiction has now become a serious science question. The new LOFAR telescope may be an unexpected but perhaps powerful tool to help search for signatures of intelligent life on planets around distant stars.

In the recent decade astronomers have discovered hundreds of planets in orbit around other stars in our Milky Way, so-called extrasolar planets. In fact, more detailed space-based studies suggest that there may actually be tens of billions of planets hiding in our galaxy, some which have properties roughly similar to Earth and thus might be able to host life (see e.g., the Keppler mission.

Hence, since a long time people have wondered whether life and perhaps intelligent life might exist elsewhere in the universe. Since, scientists have not yet really understood how life began on Earth, the answer how frequent extraterrestrial life is, remains very uncertain: Life may be ubiquitous throughout the universe or humans are absolutely unique. How to decide between those two extreme positions?

One way is to search for life forms, like bacteria, on other planets in our own solar system, e.g., on Mars. These planets we can reach directly, however, most other planets in our galaxy will remain out of our reach for a very long time to come - perhaps forever. Another method would be to search the light passing though the atmosphere of extrasolar planets for specific spectral fingerprints left behind by gas typically produced by life forms. This is, however, very indirect and subject to interpretation. Finally, one can search for evidence for the presence of intelligent life, through man-made radio or laser transmitters, which can be transmitted and received over long distances. If life is indeed ubiquitous and planets are numerous, than one could indeed imagine that in an optimistic scenario thousands of civilization like ours could exist. But, how to find them?

Already 50 years ago astronomers (Project Ozma) started to look for radio signals from other worlds and the term SETI (Search for ExtraTerrestrial Intelligence) was coined. Early searches focused on individual stars, since they had only a narrow field of view they could observe at once. With the LOFAR radio telescope we now have a new tool at our disposal. For example, in certain modes and for a very limited time (seconds using the Transient Buffer Boards (TBBS)) the telescope could look at the entire sky and at all octaves between 10-90 MHz at once. In this mode LOFAR could detect certain types of (reasonable) radar transmitters pointed towards us from the edge of the galaxy within a second. So, if anyone wants to tell us something, LOFAR could be listening.

As part, of our transient detection (FRATS) efforts, we will – as a side-project – be looking for such signals as well and at least exclude that anyone is `talking´ to us. After all, as LOFAR demonstrates, low-frequency telescopes present the first technology that can search all-sky, all frequencies at once. So, ETI should have better chosen that frequency range. In addition there is also a small program, spearheaded by Alan Penny, that targets individual stars directly.

High-Resolution spectrum from LOFAR TBBs Direction towards narrow-band transmission seen in LOFAR TBB data

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