The Oddly Lopsided Planet: WASP-107b's Mysterious Atmosphere

A planet where one side is always day, and the other is always night. That's what happens on WASP-107b, but there’s something strange about it. Its atmosphere is taller on one side than the other, making it look lopsided. This might not sound like a big deal, but for astronomers, it's a surprise. WASP-107b is what we call a gas giant, similar to Jupiter in our solar system. However, it’s much less dense and has a peculiar atmosphere. The side facing the star is bathed in constant daylight, while the other side stays in perpetual night. This difference makes the planet's atmosphere stretch out more on one side than the other. You might think this kind of asymmetry is normal for hot Jupiters – planets similar to WASP-107b that orbit close to their stars. But here’s the thing: WASP-107b is cooler than most of these planets, with an average temperature of around 890 degrees Fahrenheit. Scientists believe that at such temperatures, planets shouldn't have noticeably lopsided atmospheres. So, what's going on? It’s not just about the temperature difference between the day and night sides. The winds and how heat moves around the planet also matter. The team of astronomers who found this peculiarity thinks that the key factor is the temperature contrast between the two parts of the terminator – the line dividing day from night. On WASP-107b, the atmosphere on the night side flows towards the day side, making it shorter and more compact.