Astronomers have used JWST to image a bizarre ultra-hot Neptune exoplanet, revealing a dramatic difference in its hemispheres. The planet orbits so close to its star that it is "tidally locked," always showing the same side to the star. Temperatures reach 2000°C on the dayside but are cooler and darker on the other side. According to their observations, astronomers say the dayside has bright reflective clouds on its cooler western hemisphere but not on its eastern side.

Today's forecast: partially cloudy skies on an "ultra-hot Neptune"

Using the James Webb Space Telescope, astronomers led by doctoral student Louis-Philippe Coulombe investigate the extreme weather patterns and atmospheric properties of LTT 9779 b.

(nouvelles.umontreal.ca)

@fraser What does "Neptune" mean in this context?

@mike @fraser It means it’s about the size of Neptune (20-40 times the mass of Earth).

It completes an orbit around its star in less than a day. Neptune-sized planets that close to their stars normally have very little atmosphere left, so it’s interesting this one has managed to retain its atmosphere.

@bob_zim @fraser Ah, thank you — a Neptune-*sized* planet, then. Appreciated!

@mike @fraser Neptune-like in mass and in that it has a lot of atmosphere in addition to the small, rocky core.