Other Worlds

Key facts

PSR B1257+12 planets

The first planets ever confirmed outside our Solar System were found in a very strange place: orbiting a pulsar, the spinning leftover core of an exploded star. Nobody expected planets there!

51 Pegasi b

51 Pegasi b was the first planet found orbiting a star like our Sun. It shocked astronomers: a giant planet like Jupiter, but so close to its star that it races around it in just over four days.

HD 209458 b (Osiris)

HD 209458 b was the first exoplanet caught passing in front of its star, and the first whose atmosphere was detected. The star’s heat is so intense that the planet’s gas is boiling away into space, forming a comet-like tail.

TRAPPIST-1

TRAPPIST-1 is a small, cool star with seven rocky planets, all roughly the size of Earth, packed closer to their star than Mercury is to the Sun. Three of them are in the zone where liquid water might be possible.

Kepler-186f

Kepler-186f was the first Earth-sized planet discovered in the habitable zone of another star. It gets about a third of the energy Earth gets from the Sun, so if it has water, it may be cold – but not necessarily frozen.

K2-18 b

K2-18 b is a planet bigger than Earth but smaller than Neptune, in its star’s habitable zone. The James Webb Space Telescope found methane and carbon dioxide in its atmosphere, and some scientists think it could be covered by a deep ocean.

Quiz

1. Roughly how many exoplanets have been confirmed?

   • ☐ About 60
   • ☐ About 600
   • ☐ More than 6,000
   • ☐ Over a million

2. The “transit method” finds planets by…

   • ☐ Photographing them directly
   • ☐ Spotting tiny dips in a star’s light
   • ☐ Listening for radio messages
   • ☐ Measuring the star’s temperature

3. What is a star’s “habitable zone”?

   • ☐ Where aliens live
   • ☐ The distance where liquid water could exist on a planet
   • ☐ The area around a black hole
   • ☐ The centre of a planet

Find it in the sky

Use the Sky Finder at seethestar.com. Tick what you find and write when you saw it.