Yapeng Zhang

Using the Keck telescope and spectroscopy (light analysis that reveals rotation speed), astronomers measured 32 objects: from giant planets to brown dwarfs — bodies heavier than planets but lighter than stars that never ignited.

130 light-years away, four giant planets orbit the young star HR 8799—each 5 to 10 times more massive than Jupiter. They lie far from the star, at distances from 15 to 70 astronomical units (one astronomical unit is the distance from Earth to the Sun).

Three and a half parsecs from the Sun, among the dim stars of the southern sky, hides a world that astronomers have been trying to see for thirty years. Epsilon Indi Ab is a gas giant, cold as a winter night: its temperature is about 275 kelvins, just above the freezing point of water.

A baker adds more sugar to the dough, and the pie turns out different. So it is with a star: the composition of its "dough"—the cloud of gas and dust from which planets are born — determines what worlds will form around it.

In the attic, you find an old, worn suitcase. From the stickers and scratches, you can guess where it's been. Astronomers have long searched for a similar 'sticker' for planets, and thought they found it in carbon monoxide molecules. Ordinary carbon monoxide consists of a carbon-12 atom and an oxygen atom.

A world where a year lasts just one and a half Earth days, and the star in its sky is hundreds of times larger than our Sun. This is KELT-9 b — a gas giant heated to temperatures at which iron vaporizes. Its atmosphere is not just hot; it is literally boiling away into space, like steam rising from a giant cauldron.