Small and Rocky or Big and Gassy: The Two Main Kinds of Planets

Exoplanets come in two main flavors — and that tells us something about the universe.

By Natalie Hinkel, The Conversation
Jan 21, 2020 6:00 AMFeb 14, 2020 4:12 PM
DustRing-browse
A planet-forming disk made from rock and gas surrounds a young star. (Credit: NASA/JPL-Caltech)

Newsletter

Sign up for our email newsletter for the latest science news
 

Scientists have discovered over 4,000 exoplanets outside of our Solar System, according to NASA’s Exoplanet Archive.

Some of these planets orbit multiple stars at the same time. Certain planets are so close to their star that it takes only a handful of days to make one revolution, compared to the Earth which takes 365.25 days. Others slingshot around their star with extremely oblong orbits, unlike the Earth’s circular one. When it comes to how exoplanets behave and where they exist, there are many possibilities.

And yet, when it comes to sizes of planets, specifically their mass and radius, there are some limitations. And for that, we have physics to blame.

0 free articles left
Want More? Get unlimited access for as low as $1.99/month

Already a subscriber?

Register or Log In

0 free articlesSubscribe
Discover Magazine Logo
Want more?

Keep reading for as low as $1.99!

Subscribe

Already a subscriber?

Register or Log In

Stay Curious

Sign up for our weekly newsletter and unlock one more article for free.

 

View our Privacy Policy


Want more?
Keep reading for as low as $1.99!


Log In or Register

Already a subscriber?
Find my Subscription

More From Discover
Stay Curious
Join
Our List

Sign up for our weekly science updates.

 
Subscribe
To The Magazine

Save up to 40% off the cover price when you subscribe to Discover magazine.

Copyright © 2025 LabX Media Group