By Stef Verhagen
Researchers are looking for exoplanets orbiting nearby cool dwarf stars as they make up excellent candidates for executing a brilliant new way to search for extraterrestrial life. It has been discovered that ultraviolet radiation produced by these, usually volatile, stars can potentially envelop habitable exoplanets with a beautiful biofluorescence light. The team published their findings in Monthly Notices of the Royal Astronomical Society.
An artist’s impression of an alien world covered in a super ocean - Image and banner image credits: NASA exoplanet exploration
M stars
Cool dwarf stars (or M stars) have a life expectancy of trillions of years and are by far the most common stars around us. It is estimated that between 15 and 66% of all cool dwarf stars have planets orbiting them in the 'surface liquid water zone' (also called HZ zone). This is good news for astronomers and astrobiologists because many of them are close enough for future space or even ground-based characterization. The recently launched Transiting Exoplanet Survey Satelite (TESS) is expected to help a great deal with finding suitable exoplanet candidates.
TESS is a space telescope designed to detect exoplanets, and it is providing us with a remarkable treasure trove of potential exoplanet candidates. Currently, it has contributed to the discovery of 29 confirmed exoplanets in addition to 1043 candidate exoplanets. TESS is also expected to find a handful of nearby Earth like exoplanets in the HZ zone of their host stars.
Inspiration from Earth
M stars produce a lot of radiation, which can be damaging to life. The researchers looked at how organisms deal with damaging radiation here on Earth. One of the ways life on Earth deals with this radiation is called photoprotective biofluorescence. To prevent damage, proteins absorb harmful ultraviolet wavelengths and re-emit them as longer, safer wavelengths.
Panellus Stipticus another example of an organism that is capable of displaying bioluminescence - Image Credit: Ylem via Wikimedia Commons
Coral is an example of an organism that uses protective biofluorescence and was used in the study to create model spectra and colors for Earth-like planets. If this mechanism is beneficial to life on Earth, it might also be helpful to living things elsewhere in the universe that have to deal with damaging solar radiation. One can imagine that nearby exoplanets with oceans on them might have lifeforms similar to Earth's corals. Especially if you take in consideration that M stars produce even more radiation than our sun. If the surface of such a planet is covered with a highly effective fluorescent biosphere, it might cause its brightness to flare up in two orders of magnitude compared to analog worlds without such a biosphere.
All in all, we have yet another way to look for life beyond our home planet, thanks to this study. We are very excited about the future of habitable exoplanet-hunting!
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