So these are the processes, the general processes
we think that take us from a planet.
Or sorry, from, from dust grains to planets.
But there's more to it than that.
And so there are basically five stages
if we're thinking about terrestrial planets that we
need to think about.
The first is, this planetary differentiation.
And then as time goes on, the heat that came from the
planet forming was going to be dissipated and and that material will cool.
And then there, we expect that all the debris
that's left over in the solar system is going
to rain down on these planets because they're giant
vacuum cleaners in some sense because of their gravity.
So we're going to get impact creating.
And then we'll almost in almost all
cases, the center is, or, sorry, the inner parts
of the planet are hot enough that it's flowing.
It's molten rock.
So we expect sometimes magma to make to, make
it to the surface and to restructure the surface.
And if there's an atmosphere, we also expect weathering over time.
So that's for terrestrial planets.
And the process that we've described.
Really makes sense for understanding terrestrial planets.
But what about the gas giants right?
I mean you know this, this idea of dust grains forming boulders,
etc.
Or you know forming rocks going all the way up to boulders and planetesimals.
How does that explain gas giants?
Well gas giants are a different story because we think there we need
to start with a rocky core of some kind, and then once it gets
to a certain point if there is still a lot of gas left in
the disk by this time, then, the gas is going to start to accrete.
It's going to start gravitationally pulling in gas.
And the gas will pile onto the, the rocky core.
And eventually, you'll get it a gas or an ice giant.
Now, there's two ways to do this.
One is sort of what is called core accretion.
This idea I'm sort of thinking of is that, you know?
You start with a rocky core.
And then you get the gas falling onto it.
But one big problem with this is that it may take so long to get that rocky core.
Tens of millions, or even hundreds of millions of years.
That by that time the gas may have dissipated from the disk.
The gas eventually leaves the disk, or is blown away
from the disk by, via usually the winds from the young star.
So that may happen in only a few million years.
So if you wait too long to build your core there may be no gas around to accrete.
That's why there's a second model
that people like, called the gravitational instability.
Where basically the disk has enough mass in it that parts of the disk.
Just like the, the cloud it's that formed
the whole solar system collapsed under its weight.
Parts of the disk may collapse under their own weight.
To immediately form a
gas giant.
So you know, who you know, which, which of these
two models actually occurs depends on who you're talking to.
We don't really have enough evidence yet to know which of
the models, core accretion or hydrodynamics
instability, is really the appropriate one.