On Tuesday a group of Long Road Physicists attended a lecture by Dr Matt Bothwell of the Institute of Astronomy, University of Cambridge, on Exoplanets, Eddington and Gravitational Lensing. Dr Bothwell introduced the talk by reminding students that the 2019 Physics Nobel prize was awarded for Exoplanet research. He then explained that we have always known that there are fixed stars and wandering stars in the night sky and that we know now that the wandering stars are planets. We have only the data from our solar system so essentially all we know is based on one data point. Hence the search for other solar systems.
There are two techniques for this:
- Wobbles (Red Shift) which uses the fact that the orbiting planet has a gravitational attraction force on the sun, so the sun moves about the centre of mass of the orbiting planet and the sun, it wobbles. This can be measured using the redshift in the radiation.
- Shadows (Transit) which is where the shadow of the planet is observed moving across the face of the sun. This causes a reduction in the level of radiation from the star which can be measured. The Kepler satellite was launched in 2009 to take these measurements, and now there are over 4000 known exoplanets.
The main problem with both these is the observational bias that the data shows large planets very close to their sun as these are easily detected. This is completely different to our solar system. There are now 12 planets which have more than a 75% similarity to our Earth and these are all within 100 light-years from us (i.e. very close)
Dr Bothwell then opened up the scope of his talk to the question of the development of life on a planet, the time scale of this on earth and the “Filters” that would prevent this occurring. Currently, the key marker for life on a planet is the presence of Methane as this decays naturally due to sunlight and life forms create this as a by-product. He left us with the Fermi paradox, if the universe is so large with so many stars, “ Where is everyone else?”