ELI5, Why do some extrasolar planets revolve much faster than planets here in the Solar Sytem?

Question

For example:

55 Cancri b: 0.7 days
Kepler-1649c: 19.5 days
Gliese 581g: 32 days

Compare it to Earth, which is 365 days and Mercury which is 88 days. What are the factors that cause these exoplanets revolve much faster?

In: 5

Answer 1

Something important to keep in mind when thinking about exoplanets is that both the planets in our solar system and the exoplanets that people are detecting are probably very atypical in different ways.

Some exoplanets are much easier to detect than others using current technology, for example large planets orbiting small stars are generally easier than small planets orbiting large stars. So the known exoplanets are almost certainly not representative of planets in general.

This is more speculative, but it’s likely that some kinds of planets and stars are far more hospitable to life than others. There’s a lot of debate about what the important factors are exactly. But it’s reasonable to suspect that our own solar system might be “weird” in some way that makes it especially suited to the development of life. In particular, it has been suggested that planets that orbit very close to their star, which orbit very quickly, would probably be tidally locked – that is, one side always faces the star and is always very hot, while the other side always faces away and is always very cold. Some people think that may make it difficult for life to develop.