A high school student has ruled out half the stars in a galaxy where the search for extraterrestrial life is futile. His catalog can already be applied to any set of stellar data.
Where to look for extraterrestrial life
Most SETI programs focus on the nearest and brightest stars. This makes sense from the perspective of signal strength, but it overlooks the key point that not all stars are equally suitable for the emergence of complex life.
Some have excessively high temperatures and short lifespans, others are too young, and still others have low metallicity. Observing them may turn out to be a waste of telescope time.
Filtering by seven criteria
Sahin Torlakcik, a high school student in Turkey, approached the problem differently. Instead of searching for the best candidates, he systematically eliminated the worst ones. His research has just been accepted for publication in the peer-reviewed journal Publications of the Astronomical Society of the Pacific.
The method is based on seven stellar parameters applied to nearly 1.75 million stars from the Gaia space telescope archive. Stars heavier than 1.5 solar masses are excluded because their lifespans are too short. Stars younger than 3 billion years are also unsuitable, since it took roughly that long for life on Earth to evolve beyond the single-celled organism stage. The criteria also include a lack of heavy metals, the instability of binary systems, photometric variability, and the radiation activity of red dwarfs.
Result and methodological detail
The model filtered out about 55% of the stars, leaving 777,835 priority candidates. The largest contributions came from the stars’ age and metallicity, with each parameter filtering out about 29% of the total.
The approach to stellar age is particularly interesting. The study’s author, Sahin Torlakcik, applied the threshold not to the minimum but to the maximum value of the age range. As a result, 355,086 stars that a stricter approach would have excluded remained on the list of candidates.
Comparison with another program
The catalog was compared with the list of targets for the Breakthrough Listen program, SETI’s most well-known radio project. It turned out that more than half of its target objects would fall under the exclusion criteria, primarily due to low metallicity.
This is not a criticism of the program, but rather a reflection of two different approaches. One is optimized for signal detection, while the other focuses on the likelihood of life existing. Together, they provide a list of stars that are the top candidates for observation.
The catalog and filtering tool are available online and can be applied to any stellar dataset.
According to phys.org
