The Quest for New Worlds Mario Livio STScI

2 Why Do We Care About Extrasolar Planets? Arguably the most intriguing question in science today: Is there intelligent life elsewhere?

3 SETI Searches in the Solar System Three Paths Toward an Answer Find exoplanets Find terrestrial planets In habitable zone Composition of atmosphere Out of chemical equilibrium Biomarkers (O 2, O 3 ) “Red edge” due to vegetation Find exoplanets Find terrestrial planets In habitable zone Composition of atmosphere Out of chemical equilibrium Biomarkers (O 2, O 3 ) “Red edge” due to vegetation

4 p = (4.5 ± 0.8) × 10 [Fe/H] (1.8 ± 0.3) p  N Fe 2 Scientific Prediction: Terrestrial Planets May Be Found in Unexpected Places AROUND MASSIVE WHITE DWARFS!  Terrestrial planets expected to be much more abundant in metal-rich environments (Fischer & Valenti).

5 Merging White Dwarfs About 15% of white dwarfs are formed by mergers. During merger, the lighter WD is dissipated to form a metal- rich disk around the massive WD.  Earths (probably lifeless) may be very common around massive white dwarfs! Could be detected in the infrared. Merging White Dwarfs

6 Number of Planets Periastron A More Philosophical Point: How Special is the Solar System? Intelligent life is humanity’s last bastion of being special. The “Copernican Principle” on the other hand, has taught us time and again that there is scientific “beauty” in theories of the universe in which we are mediocre!