How large planets form

It was early noted that a lot of the larger exoplanets, which were detected first, have eccentric orbits. This week come two articles about them: when they form, and how they end up.

Can I just say that Ji Wang looks like Oriental Elon Musk or am I going to get this blog demonetised for that... oh yeah! This is a hobby. MUAHAHAH

Anyway 王吉 is talking ⪆10 AU which is further-out than Jupiter, even than Saturn. Those are the ones we can see separate from the star specifically: 51 Eri b, β Pic b, HIP 65426 b, HR 8799c and e, AF Lep b, and YSES 1 c. These formed over an early stage (⪅2 Myr) when large amounts of solids are available in young massive protoplanetary disks. UPDATE 3/17 51 Eri b and HR 8799 can be seen.

Ji Wang is aware of the "Grand Tack" theory of our ice and gas giants. He agrees: these four all formed further out, to migrate to where they run now. This suggests that other large exoplanets, which we perceive mainly from radial-velocity measurements, might also have formed early before their own inward migrations. Which brings us to Gregory Gilbert, Erik Petigura, and (undergrad) Paige Entrican; Entrican apparently writing the code. It seems that after "runaway" accretion from superearth to Neptunian, the planets get large enough to mess around with each other. Then they get eccentric where the usual superearth simply doesn't have the power to nudge, say, a nearby Venerian.

Over billions of years, though, I suspect that inner planets of these superplanets get pulled into eccentricity anyway. We really do need to train 'scope on 82 Eridani.