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What you will learn in Exoplanets and the Search for Life

1. Finding the first ones
51 Pegasi b was a Jupiter in a four-day orbit, which no formation theory allowed. It was found first because it was the easiest thing to find, and that is the whole shape of the field in one sentence.
2. The transit method
A planet crossing its star blocks a fraction of the light equal to the ratio of their areas. For Jupiter across the Sun that is one per cent. For Earth it is 84 parts per million.
3. The wobble method
Radial velocity does not measure a planet's mass. It measures the mass times the sine of an angle nobody has measured, and the difference is a factor that can be anything.
4. Three more ways
Transits and radial velocities found almost everything we know. Direct imaging, microlensing and astrometry each see a different slice of the same galaxy, and none of them sees the slice the first two miss.
5. What is out there
Point a Kepler-class survey at our own Sun from ten parsecs and the expected number of planets it finds is 0.011. The catalogue is a picture of our instruments.
6. The habitable zone
Mars is inside the Sun's conservative habitable zone. It has been for the Sun's whole main-sequence life, and it is a frozen desert with six millibars of atmosphere.
7. Looking for life
A transit spectrum is a few hundred parts per million on top of a dip that is already 84. Every claimed biosignature so far has had a geological explanation, and that is what a robust one has to beat.

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1. Finding the first ones
51 Pegasi b was a Jupiter in a four-day orbit, which no formation theory allowed. It was found first because it was the easiest thing to find, and that is the whole shape of the field in one sentence.
2. The transit method
A planet crossing its star blocks a fraction of the light equal to the ratio of their areas. For Jupiter across the Sun that is one per cent. For Earth it is 84 parts per million.
3. The wobble method
Radial velocity does not measure a planet's mass. It measures the mass times the sine of an angle nobody has measured, and the difference is a factor that can be anything.
4. Three more ways
Transits and radial velocities found almost everything we know. Direct imaging, microlensing and astrometry each see a different slice of the same galaxy, and none of them sees the slice the first two miss.
5. What is out there
Point a Kepler-class survey at our own Sun from ten parsecs and the expected number of planets it finds is 0.011. The catalogue is a picture of our instruments.
6. The habitable zone
Mars is inside the Sun's conservative habitable zone. It has been for the Sun's whole main-sequence life, and it is a frozen desert with six millibars of atmosphere.
7. Looking for life
A transit spectrum is a few hundred parts per million on top of a dip that is already 84. Every claimed biosignature so far has had a geological explanation, and that is what a robust one has to beat.