Caroline V. Morley

The three planets in the Kepler-51 system have long intrigued astronomers: they are Saturn-sized but less dense than water. These 'super-puff' worlds, with masses no more than ten Earths, are like cosmic dandelions — massive yet almost weightless. Their orbits are arranged like musicians in an orchestra, each playing its part, beating the rhythm with transits.

Around the star Epsilon Indi, visible to the naked eye from the Southern Hemisphere, orbits a planet the size of Jupiter. The temperature there is like a good freezer: minus 200 degrees Celsius. The James Webb Space Telescope has for the first time directly imaged it and measured the light the planet emits in the thermal range.

Steam over a boiling pot slightly tints the light of a flashlight: it blocks some colors and lets others through. That's roughly how we study the air of distant planets.

2,41 hours. That's exactly how long a day lasts on SIMP 0136 — a lonely planet-like object 6,1 parsecs away. That's twice as far as Proxima Centauri. Its mass ranges from 12,7 to 17,8 Jupiter masses, placing it on the boundary between planet and star.