ARE EXOPLANETS SHRINKING WITH AGE?
As we all know, planets come in many different sizes, and you only have to look at our Solar System to see how varied they can be. Just take Mercury as the smallest, for example, and Jupiter as the most humongous. If you had enough Mercurys at your disposal, you could take 24,462 of them and pack them tightly into Jupiter. For comparison, you could do the same with 1,300 Earths.
Interestingly, though, there is a size gap. Try as you may, you’re not going to find too many planets anywhere in the universe that are between 1.5 and two times the size of Earth. You certainly won’t find them in our Solar System and, so far at least, there are very few in planetary systems elsewhere, suggesting there’s no middle ground between so-called rocky superEarths and larger gas-shrouded mini-Neptunes. Quite why, however, has been a mystery.
Such a gap was not apparent at first, certainly not when scientists began discovering planets outside of our Solar System from 1992. Back then the first extrasolar planet, or exoplanet, was found when astronomers Aleksander Wolszczan and Dale Frail provided evidence of two
