An article published in the “Planetary Science Journal” reports a study on the seven planets of the ultra-cool dwarf star TRAPPIST-1’s system. A team of researchers led by astrophysicist Eric Agol of the University of Washington used data collected by the Spitzer Space Telescope over four years, by the Hubble and Kepler space telescopes, and by ground-based telescopes to obtain precise measurements of the planets’ masses and densities. The new calculations indicate that the seven planets have a very similar density, a new clue in the study of their composition with the possible similarities and differences compared to the rocky planets in the solar system.