Michael Sterzik then has to make one thing clear: “It’s not like in science fiction films, in which the technology makes it possible at some point to fly off in spaceships and search for life. The search for life is carried out from Earth using scientific methods,” says the researcher who is doing exactly that: with the proof of life on other planets.
Sterzik works at the European Southern Observatory (Eso) in Garching, an international research center for astronomers. In cooperation with other European countries, several observatories are operated in the southern hemisphere, for example in Chile and Bolivia. The scientists commission the observation from the observatories. The collected data is then sent to Garching and processed there. The city in the northern district also coordinates the construction of research instruments and the development of new technologies. A total of around 700 people are employed at the observatory.
Sterzik occasionally gives lectures and tries to make his astronomical research area understandable to laypeople. As part of the “Wissenschaft zu Gast” series of the Werner-Heisenberg-Gymnasium, he gave his favorite lecture there on Thursday evening: The search for extraterrestrial life – and what we can learn from the earth in the process.
“There are innumerable suns in the universe and we know that on average one planet moves around each sun,” explains Sterzik. However, most of these planets are not in what is known as the habitable zone, i.e. at the correct distance from their sun. The habitable zone is based on the occurrence of liquid water, without which no life is possible. Most of the time it is either “hot Jupiter”, on which water evaporates immediately, or ice-cold planets, on which water freezes. There are only a few exceptions, the closest planet in a habitable zone is Proxima Centauri, which is over 4200 light years away from Earth.
The Garching researcher Michael Sterzik.
(Photo: ESO / OH)
“Golden Age of Astronomy”
The next step in the search for life is to find biosignatures such as oxygen. In order to clarify whether life actually exists on planets in habitable zones, the astronomers are trying to detect these biosignatures. “Oxygen freezes very quickly,” says Sterzik, “so that oxygen is available in gaseous form, it has to be continuously replenished”. This happens, for example, through photosynthesis of plants. Evidence of these biosignatures would therefore be a strong indicator of life. Sterzik is also researching in this area: “The only atmosphere known to us that contains biosignatures is the earth. But even the signals on earth are not easy to see. We just know that there is life here. But we do not know which signatures are visible from the outside. “
Sterzik’s research therefore uses the earth’s surface. “The light from the earth that is reflected on the dark side of the moon and thrown back onto the earth is the earth’s glow,” explains Sterzik. The earth shine shows what the earth would look like to an external observer. On the basis of these observations, the scientist develops methods of how best to determine the biosignatures on earth. The earth is used as a model planet on which the methodology is trained until these biosignatures can be accurately and precisely detected. “Those who can prove biosignatures will receive a Nobel Prize,” says Sterzik with conviction.
The researcher speaks of a “golden age of astronomy”. The methods of finding life have advanced rapidly over the past few decades. But even if traces of life were found on other planets at some point, science fiction stories are still a long way off. “There doesn’t just have to be life, this life also has to be intelligent and able to communicate,” says the astronomer. In addition, each life form only has a limited lifespan before it becomes extinct. This must overlap with ours. Sterzik is of the opinion: “The probability of the existence of such a life form is not very great.” That’s why he has no interest in science fiction: “I’ve always wanted to know and not speculate.”