PCS 581 Lecture Notes - Lecture 10: Jupiter Icy Moons Explorer, Methane, Blasted
Lecture 10:
Finding Exoplanets
Which determines mass of the planet? Doppler Technique
If Transit is possible, then doing the other one is possible too
Tools of Discovery
Direct Imaging: finds young planets that are big, far from their star, their light tells us a
lot
Doppler Technique: finds big planets that are close to their star, can get orbit and mass
Transit Method: big, close planets, can get orbit and size, temperature and composition
Hard to find: Earth!!
The Facts we can Gather
Orbital period (all but direct imaging determines this), which gives orbital distance &
surface temperature
oOrbital shape (eccentricity) mostly from Doppler
Planet mass: Doppler only gives a lower limit
Planet size/radius: from transits (amount of light the planet blocks out)
Planet density: combine Doppler & transit info
Planet/atmosphere composition: direct imaging, transits
The Basic Discoveries
There ARE many other planets
oMaybe almost all stars have them
What are the planets like? In our system they are terrestrial or Jovian...
We have found other systems too, how do they compare to the Solar System?
The Planet Yield
3,735 confirmed exoplanets
2,723 candidates (not quite confirmed) from Kepler
= 6,458 exoplanets (or so)
Discoveries by Method
find more resources at oneclass.com
find more resources at oneclass.com
Hot Jupiters
At first, the most commonly found objects
Orbits as short as 1.2 days, cloud top temperatures up to 1300K
Hugely puffed up and low density
Hot Jupiters are commonly found because they are the easiest to find
Habitable Zones: Liquid Water
If a planet is in the habitable zone, does that prove that it has liquid surface water? No
If there is liquid surface water, is life guaranteed? No
Could life exist outside the habitable zone? Yes
Exoplanet Periodic Table
Kepler has a bias for Hot Jupiers
And still Super Earth’s are the most common
Therefore, super earths are the most common types of planets
Our Nearest Neighbour
find more resources at oneclass.com
find more resources at oneclass.com
Important because this is very close to us
Could be habitable
One problem: small stars are very unstable and give out flares which can endanger life
Multiple Star Systems
Majority (60%) of all Sun-like (G) stars are actually in binary star systems, or triples (like
Alpha Centauri), or more
Need to worry about habitable zone… and if the planets there can have stable orbits
The first two are possible because we have found planets that orbit systems like them
NASA’s Kepler Mission
Determining the frequency of Earth-size and larger planets in the habitable zone of Sun-
like stars
Launched with a small budget to detect planets – and has done an amazing job so far
Kepler’s View
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
If transit is possible, then doing the other one is possible too. Direct imaging: finds young planets that are big, far from their star, their light tells us a lot. Doppler technique: finds big planets that are close to their star, can get orbit and mass. Transit method: big, close planets, can get orbit and size, temperature and composition. Orbital period (all but direct imaging determines this), which gives orbital distance & surface temperature: orbital shape (eccentricity) mostly from doppler. Planet mass: doppler only gives a lower limit. Planet size/radius: from transits (amount of light the planet blocks out) There are many other planets: maybe almost all stars have them. In our system they are terrestrial or jovian At first, the most commonly found objects. Orbits as short as 1. 2 days, cloud top temperatures up to 1300k. Hot jupiters are commonly found because they are the easiest to find. And still super earth"s are the most common.
