What we've seen is that two groups had gone through and made painstaking measurements
of, effectively, the spectra of stars over time. By making those measurements with exquisite accuracy of wavelength,
they were able to use the doppler shift to convert the shifts wavelength into velocities.
When they did this work, they discovered planets.
But these were weird planets. It's nothing like our own solar system.
In own solar system the big massive planets, like Jupiter and Saturn, are a long way out.
But here, we're talking things with a comparable masses of gas giants,
but these are practicably skimming the surface of the star or in highly eccentric orbits very close in, so it's very weird.
Well, you say it's weird, but whose to say our solar system should be typical?
I mean, why would we not expect to have these types of planes out there?
Well, the reason why people didn't expect these sort of planets is because of what's called the 'Snow Line Theory',
this is a theory of how gas giants form. If you remember, when we talked about solar system formation,
the idea was you started with tiny, little grains of stuff that stuck together
to make bigger and bigger lumps until, eventually, they end up with planets.
In the inner solar system, the only lumps we can have are lumps of rock,
but in the outer solar system, where it was colder, you have lumps of ice, and because ice is mostly hydrogen,
there's a lot more hydrogen out there, that's the most common element in the universe,
so there should be a lot more ice out there than there are rocks closer in. There's also rocks further out as well.
What this means is that the planets are further out, in our own solar system the snow line is probably somewhere in the asteroid belt,
things beyond there should be able to get much bigger because they can be made of ice as well as rock.
In the inner solar system, the ice will just all evaporate away.
So, what that means is that the planets further out will get bigger, not much bigger,
maybe three or four times bigger, but once they're three or four times bigger, their gravity is stronger
and they can then start sucking in all this hydrogen and helium gas that's around,
at which point they get very much bigger, like 300 times bigger like Jupiter is.
This is the standard theory, and this said that you should only be able to form really big planets out beyond the snow line.
Okay, so we have a mystery on our hands of why we have these objects,
these gas giants right next to their stars and so, once again, another mystery confronts us.
So, how are we going to solve this?
Well, clearly we're going to need more data and some good theoretical thinking
and that's what we'll cover in the next lesson.