>>According to simulations and models, exoplanet sizes should be spread out relatively evenly. But with the exoplanet tally approaching 4,000, that hasn’t really been the case. A type of world dubbed a “hot Neptune” has been conspicuously few and far between, but a new observation may explain why. Hubble has now spotted a hot Neptune named GJ 3470b that’s vanishing at a record rate.<<

https://newatlas.com/fastest-shrinking-exoplanet-hot-neptune/57671/

PermeateFree said:

>>According to simulations and models, exoplanet sizes should be spread out relatively evenly. But with the exoplanet tally approaching 4,000, that hasn’t really been the case. A type of world dubbed a “hot Neptune” has been conspicuously few and far between, but a new observation may explain why. Hubble has now spotted a hot Neptune named GJ 3470b that’s vanishing at a record rate.<<

https://newatlas.com/fastest-shrinking-exoplanet-hot-neptune/57671/

I wouldn’t say that hot Neptunes are rare. All planets found by methods of occultation and Doppler shift are “hot”, 95% within the orbit of Mercury. So almost all Neptune-sized planets are hot Neptunes.

That said, there are more binary stars in extremely close orbits than hot Brown Dwarfs, and more hot Brown Dwarfs than hot Jupiters. So this could be the reason.

mollwollfumble said:

I wouldn’t say that hot Neptunes are rare. All planets found by methods of occultation and Doppler shift are “hot”, 95% within the orbit of Mercury. So almost all Neptune-sized planets are hot Neptunes.

That surprises me greatly – Firstly I would have thought that primarily gas/ice planets would not be able to form close to a star because the gasses would blow away due to the solar wind & photonic pressure. Secondly how could they be stable (for the same reasons) for any great length of time?

Spiny Norman said:

mollwollfumble said:

I wouldn’t say that hot Neptunes are rare. All planets found by methods of occultation and Doppler shift are “hot”, 95% within the orbit of Mercury. So almost all Neptune-sized planets are hot Neptunes.

That surprises me greatly – Firstly I would have thought that primarily gas/ice planets would not be able to form close to a star because the gasses would blow away due to the solar wind & photonic pressure. Secondly how could they be stable (for the same reasons) for any great length of time?

Perhaps they migrate inwards and are unstable and we happened to catch them at the right time

Spiny Norman said:

mollwollfumble said:

I wouldn’t say that hot Neptunes are rare. All planets found by methods of occultation and Doppler shift are “hot”, 95% within the orbit of Mercury. So almost all Neptune-sized planets are hot Neptunes.

That surprises me greatly – Firstly I would have thought that primarily gas/ice planets would not be able to form close to a star because the gasses would blow away due to the solar wind & photonic pressure. Secondly how could they be stable (for the same reasons) for any great length of time?

Stars and brown dwarfs are gas/ice giants. And they form even closer to their parent stars, and survive there in a stable orbit.

Although it is claimed that planets migrated inwards, this is possible only in the first million years after formation, or less, before the solar wind and UV light switches on. So would be extremely rare.