Missing planets have lost gas

All known planets that are up to about 1.5 times the size of the earth are rocky planets and all planets that are more than twice the size of the earth are gas planets.

In our solar system, the smallest gas planet is Neptune, which is about four times larger than Earth, but around other stars there are gas planets with a diameter of about 2.5 times Earth’s diameter.

The new theory says that gas planets smaller than this simply can not hold together on their own. The atmosphere seeps away over a period of billions of years and leaves a small, solid core.

In this way, the small gas planets jump over the size gap and are instead transformed into small rocky planets.

–