An article to be pulished in “The Astrophysical Journal” describes a research on the age of the TRAPPIST-1 system. This ultra-cool dwarf star has become increasingly popular thanks to the results of research on its planets. One of the problems was to establish its age and astronomer Adam Burgasser of the University of California, San Diego, and Eric Mamajek of NASA’s JPL provided an estimate between 5.4 and 9.8 billion years.