Oct. 14 – 2B03 14/10/2011 9:34:00 AM
Arrived 5 mins late.
Velocity (Doppler) method – as a planet orbits around a star, it exerts a
gravitational force on that star.
Larger planet (or close) , larger change in V.
3rd method – directly observing them (above 2 we just see the influence).
Both transit and Doppler favour larger planets.
Vast majority found were massive, and close to parent stars.
Observational bias, doesn’t mean all planets are large and live close
to their stars.
In future, we want to concentrate on finding earth-sized planets.
o Hard to find as a result of its small size.
Planets don’t give off light, light comes from reflective light from parent star.
Signs of life – looking for signatures that we know are important for certain
Not at this stage yet – we are still finding them.
Closer to star, harder to find the planet. (Amidst the noise of the sun).
Farther orbits; easier to see.
o Planets become almost as bright as stars in the infrared.
Disk material is the material from which planets form.
There are others besides the 3 we discussed (we not going to discuss). How do Planetary Systems form?
When you take a big round object, with a bit of spin (angular
momentum), it forms a disc.
Close to the forming star, you can make dust grains (particles with
heavy elements [carbons, silicates], and come together to form
chunks of rocks.
if you join enough of this material, you can create terrestrial
o Close to the star, you get the rocky stuff.
Outer planets made out of ices. Other molecules form ices,
methane and ammonia. Close to the forming star, there is no
frozen shit, just heavy elements.
o Cores of ices that form at large radii
o Jupiter and Saturn have cores of ices, and have hydrogen and
helium gas around it.
Key points of slide: Key points - rocky, close to star. Ice and gas
form at larger distances
o Form far away, but move there over time -> planet formation
Ices cant exist at small radii.
o Rocky stuff out there at larger radii, but primarily ice.
o Ice planets large, and rocky not too large.
o Frost Line – beyond this radius, where ices can exit.
Zone around any given star that is a favourable place for life to
Life as we know it requires liquid water. We consider habitable zone
those places where liquid water can exist.
Flawed concept – so many other factors that influence life.
Atmosphere, migration are some of those factors.
Gliese 581 picture. 2 planets that s