Eyeball Exoplanets: These Strange Worlds May Be Staring At Us From Space

NASA has already discovered more than 4,000 exoplanets in different planetary systems and 4,900 more are waiting to be confirmed as extraterrestrial worlds. The list may soon include what astronomers describe as “eyeball planets.”

These potential exoplanets literally look like giant eyeballs, floating and staring at the vast universe. Experts explained that they got their weird appearance because of tidal locking, which also occurs on Earth, ScienceAlert reported

Tidal locking keeps one side of a planet facing a body it is orbiting, like a star, because of the speed of its orbit and rotation. For example, we never see the far side of the Moon because it is tidally locked to Earth. 

However, our planet is not locked to the Sun. That allows humans to experience day and night. Meanwhile, eyeball exoplanets are believed to be tidally locked to their stars, with only one side always exposed to heat and the other in the dark.  

Eyeball planets may have different surfaces. Some worlds may have one side that is dry since all water was burned away by stellar radiation, while the other side in darkness may be covered in ice because of the lack of heat. 

The exoplanets in such conditions may be able to support life on their “glacial ring,” where perpetual twilight occurs. With good amounts of heat from the star, the area may have melting glaciers that could support vegetation, according to a 2013 study in the journal Astrobiology

There are also icy eyeball planets. These worlds orbit farther from their stars, exposing them to lower levels of heat. 

However, extremely cold eyeballs may also support life. Astronomer Sean Raymond said despite being covered in ice, the planets’ day side have a liquid ocean. 

"Hot eyeball and icy eyeball planets are extreme cases, but any planet that is tidally locked to its star is likely to look very different on its day side and its night side," Raymond said in an article posted on Nautilus. "Differences could come from clouds clustered in certain areas, from preferential melting of ice on the day side or freezing of ice on the night side, or from any number of other possible sources. The galaxy may be littered with wild varieties of eyeball planets!"

Eyeball Exoplanet Artist's impression of the exoplanet TRAPPIST-1f, located in the Aquarius system of TRAPPIST-1. NASA/JPL-Caltech