IN THE NEWS: Last week, NASA went public with their discovery of seven habitable planets orbiting the star TRAPPIST-1. What does this exciting news mean to our former knowledge of exoplanets? Professor Joshua Winn dives into the topic. (via CNN)
Professor Joshua Winn
The announcement of all the new planets around TRAPPIST-1 is incredibly good news. This system has something for everyone. This nearby small star has not just one, but seven terrestrial-sized planets, in the size range between Mars and Earth. We know they exist because when they circle around the star, they cause miniature eclipses, blocking a little bit of the starlight from reaching our telescopes. And because the star itself is to tiny (only 10% the size of the Sun), those eclipse signals are big and relatively easy to study.
For this reason planetary scientists will be able to study the atmospheres of these planets with the upcoming James Webb Space Telescope, to be launched in 2018. They’ll search for molecules that might betray the presence of life, or at least give clues about the geological and atmospheric processes on those planets. Nobody knew we’d have this opportunity so quickly! I had been worried it would take 5-10 more years to find such a favorable system.
Physicists are delighted that the planets are in an intriguing arrangement around the star, much closer together than the planets in the solar system. The planets’ orbital periods — the time needed to go all the way around the star — seem to have special mathematical relationships. The ratios are simple fractions, in just the same way that consonant musical notes have audio frequencies with simple ratios. A perfect fifth has notes with frequencies in the ratio 3:2, and so do some the planets’ orbital periods! It will be fun to try to figure out what causes this planetary harmony. It may be that the planets used to be more widely spread apart, but gravitational interactions early in the system’s history brought them together nearly as close as they could possibly be.
Engineers who are dreaming up new ways to propel spacecraft to the stars will be glad that TRAPPIST-1 is relatively nearby: “only” 40 light-years from our solar system. There are a few known planets that are even closer, but TRAPPIST-1 is the most attractive destination because there will be seven potentially Earth-like worlds to explore.
And of course artists and science fiction writers now have 7 new nearby worlds to stimulate their imaginations!