Exoplanets, or planets outside of our solar system, can provide scientists with a lot of information about how the universe works. Sometimes these distant planets can help scientists to better understand planets in our own neighborhood.
Most of those planets are discovered indirectly, by looking for a wobble in starlight, or blockage that indicates a planet is passing by the star and interrupting its light. Sometimes we manage to get actual images of a new planet—such as this recent discovery—51 Eridani B.
This planet, which was discovered with the Gemini Planet Imager in Chile, is about twice the size of Jupiter, and orbits its star at a little more than the distance that Saturn orbits the Sun. There are a lot of interesting things about 51 Eridani B, including its size. It’s the smallest planet that we’ve managed to get images of outside out own solar system. Most other planets we can “photograph” are between five and 13 times the size of Jupiter.
This planet is also young, basically a baby Jupiter, less than 20 million years old. That sounds like a lot, but remember that the dinosaurs became extinct 65 million years ago, and it gives you some perspective. Or, compare that age to our own Jupiter, which is around 4.5 billion years old.
51 Eridani B is dominated by methane, much like Jupiter, and further study will give us the opportunity to learn a lot about gas giants. It’s sort of like studying a baby planet, albeit one that is massive compared to Earth, and which we won’t be able to watch age, per se.
But getting an idea of what this planet is like now, and combining that with what we know about modern Jupiter and have figured out about that planet’s past, can tell us a lot about the formation and evolution of gas giants.