Many Exoplanets Are 'Water-Worlds,' a Fresh Study Suggests

A new paper by astronomer Li Zeng suggests that among the thousands of discovered exoplanets in the Milky Way, there are way more ‘water worlds’ than we thought before.

Sub-Neptune exoplanets

Mr. Zeng, who is a Postdoc Fellow at Harvard, focuses on studying planets bigger than Earth but smaller than Neptune. The paper reveals that it is highly probable that those planets contain approximately 25% or more ice or fluids.

‘"Perhaps every typical sun-like star has one or more water-worlds […] perhaps our Solar system is less typical," concludes the scientist. This is not the scenario we have long imagined. 

The novelty of this research is that scientists thought that the exoplanets, scrutinized by Dr. Zeng, are ‘gas dwarfs.’ Gas dwarfs are gas planets with a rocky core enveloped by volatiles. Backed-up by his study which relies on the known exoplanets found by the Kepler Space Telescope, Dr. Zeng says that

"The current estimate is that every star in our galaxy has its own planetary system […] planet formation is a universal physical process accompanying star formation."

The way astronomers study our universe is that they take our solar system as a core example and comparing it to others, but thanks to massive advancements in technical apparatus they now tend to realize that our solar system is an extraordinary assembly, not an average.

Gaia helped

It is extremely difficult to provide reliable data on exoplanets for numerous reasons. First of all, they are very far from us, but more importantly, they are orbiting around host stars. A star is massive and incredibly bright compared to a planet; thus, most of our knowledge of the worlds are inferred. Even to measure the exact distance and size of stars around our solar system is a hard task.

Thanks to fellow astronomers and technical innovation, Dr. Zeng could work with the most precise set of data: "Many uncertainties in the measurements of planet radii previously resulted from our unknown of precise stellar radii, which in turns is a result of inaccurate distance estimates of those host stars, […] Gaia solved it."

Our solar system is special…

As we concluded earlier, our habitat is being far from typical in the galactic highways. This is the reason why there are no water-worlds speeding around the Sun.  Dr. Zeng explains that it's either water-worlds or gas giants in a solar system: "Our solar system had formed the gas giant Jupiter early on, which probably had prevented or interfered with the formation and growth of super-Earths and sub-Neptunes."

When are we going to know MORE?

There’s good news for those exoplanet-lovers out there! A project by NASA is a two year long exoplanet-hunt, using all the high-end tech gadgets, imaginable. The program is called TESS (Transiting Exoplanet Survey Satellite), and its mission is to ‘discover thousands of exoplanets in orbit around the brightest dwarf stars in the sky […] is expected to find planets ranging from small, rocky worlds to giant planets, showcasing the diversity of planets in the galaxy.’



We are staying tuned, TESS!