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30 years ago, nobody knew for sure whether there were ANY planets around other stars. Today the number of confirmed planets just passed 4,000--and the variety out there is staggering. [a short thread]
A sweeping new paper (341 pages!) analyzes 426 nearby red dwarf stars. They seem to average at least 3 planets each, which translates to more than a trillion planets in the Milky Way, over 100 billion of them potentially habitable. arxiv.org/abs/1906.04644 
The Gemini Planet Imager is surveying 531 bright, nearby stars. It takes direct images of their planets, showing that Jupiter-like planets are common around the types of stars that light up the night sky. news.berkeley.edu/2019/06/12/jup…
One striking result is that most solar systems do not look like ours. In particular, Jupiter-like planets are rare around Sun-like stars. For some reason, our solar system seems to resemble the ones typically found around bigger, brighter stars. gemini.edu/node/21206
Nobody knows what Earth would be like without Jupiter around. "A planetary system with only terrestrial planets and no giant planets will probably be very different to ours," says co-author Franck Marchis. seti.org/press-release/…
Bottom line: Our galaxy is probably full of warm, Earth-size planets, but most of them may be very un-Earthlike. They might include "eyeball planets" or stranger things we haven't even considered yet. sciencealert.com/there-could-be…
