"Planets are the rule rather than the exception, " said lead astronomer Arnaud Cassan at the Institute of Astrophysics in Paris.
WSJ: Galaxy Hosts 100 Billion Planets, in New Estimate
2.
Confirmation requires different methods than those used in Dr. Cassan's estimates.
WSJ: Galaxy Hosts 100 Billion Planets, in New Estimate
3.
To estimate the number of alien worlds, Dr. Cassan and his colleagues studied 100 million stars between 3, 000 and 25, 000 light-years from Earth with gravitational microlensing.
WSJ: Galaxy Hosts 100 Billion Planets, in New Estimate