'Ultrahot Neptune' discovered around sunlike star


Oct 22, 2019
The space.com report noted "Mysteriously, LTT 9779 b still appears to possess a thick atmosphere, one consisting of nearly 10% of its mass, or equal to about 2.6 times Earth's mass, Jenkins said. One would expect ultrahot Neptunes "to lose their atmospheres very early due to the high-energy radiation received from the star, so for this planet we must think about more exotic types of formation scenarios," Jenkins said.

One possible explanation for this ultrahot Neptune's thick atmosphere "is that the planet was originally much larger, maybe a gas giant like Jupiter, that migrated too close to the star," Jenkins said. In this scenario, the star's gravity would have stripped off much of the exoplanet's atmosphere. After it lost much of its mass, the world then might have moved a little further away from the star, and ended up with a Neptune-like mass, he said."

Various exoplanet finds show up that challenge conventional thinking about their origins, this is another example. We can postulate that the exoplanet formed much larger and migrated but observing this happen, seems difficult :)