The Star That Died Twice
In 2014, astronomers witnessed a star going supernova. This is already an unusual event, but what makes it truly special is the fact that the star already went supernova in 1954. So far, the best explanation for this event is that it's a pulsational-pair instability supernova, in which a truly massive star in effect blows off its outer layer, leaving its innards intact to start the process over. The only problem with this hypothesis is that, according to our theories, the stars that explode this way shouldn’t exist anymore. But apparently, the cosmos doesn’t care for our theories.
The Solar corona, the aura of plasma that surrounds the Sun, is too hot. It exceeds millions of degrees and we are not sure how it got that hot. It is about 1,000 times hotter than the Sun’s surface, which needless to say is a bit counterintuitive. After all, you wouldn't expect the air over a fire to be hotter than the fire itself. Unlike a fire though, the corona extends for thousands of kilometers and somehow is still much hotter than the surface below as well as the interplanetary space beyond.
Researchers are unclear what could cause the corona to be so hot. There might not even be a single process, with the high temperatures reached thanks to multiple factors. Several proposed mechanisms show promise (such as nanoflares), but there are still many questions left to answer.
Venus Winds Speed
Winds on Venus move too fast for our current climate models of how an atmosphere should behave. They move 60 times faster than the planet’s rotation on its axis and it's not easy to reconcile this with what we know. On Earth, winds are created by pressure differences in two nearby areas. These pressure differences are created by differences in temperature in the air. And yet Venus doesn't have any dramatic gradients to justify such powerful winds.
The clouds on Venus don't make sense, either. There is a huge stationary wave in the clouds of the upper atmosphere and irregular patterns on the planet’s night side, as well as a weird Y-shape visible on its day side. Observations of the changing weather are still being taken, so perhaps one day we will uncover the cause of such complexity.