These exoplanets might have habitable exomoons

(NASA, JPL-Caltech and Wikimedia)

Life could not only exist on planets, but also in moons; and now astronomers have compiled a list of 234 known exoplanets that could potentially have a habitable exomoon.

In the list, at least 17 objects have a probability of above 50 percent of finding a habitable exomoon.

Since the end of the last century, space and ground-based telescopes have discovered more than 5.000 exoplanets.

However, so far there has not been a single reliable case of the discovery of an exomoon, just a few candidates.

The search for such bodies is extremely difficult, especially because they are very small.

At the same time, scientists already know extensive systems of satellites around the giant planets of the Solar System.

Also, there is no reason to assume that the formation of exomoons is not the same as it happened in the solar system.

That’s why researchers assume that very massive exogiants, with masses from 10 Jupiter masses, may have massive satellites.

Some of them might be the size of the Earth and a mass of at least 0.3 Earth masses, which can be detected using the transit method and the gravitational microlensing.

However, the radial velocity method is not suitable due to too little gravitational influence of the exomoon on the parent star.

Now astronomers from the Kapteyn Astronomical Institute have published a study on the habitability of potential exomoons orbiting known exoplanets.

First, the scientists compiled a list of exoplanet targets that might potentially have a habitable satellite.

They took the data catalog of the Encyclopedia of Extrasolar Planets and excluded objects with these characteristics:

• objects with masses greater than 13 Jupiter masses
• objects with a parent star mass less than 0.08 solar masses
• exoplanets with an orbital period or unknown semi-major axis
• objects with unknown mass, minimum mass and radius.

The final result was a set of 4140 known exoplanets.

Then, the team calculated the possible ranges of physical and orbital parameters for the satellite in each exoplanet using the Monte Carlo method.

The results were the probability of habitability for each simulated exomoon, defined as the ratio of habitable test satellites to 100,000 simulated satellites.

The habitability estimation was based on 2 factors:

• the radiation flux from the star reaching the exoplanet
• the heat generated on the exomoon due to the tidal forces from the exoplanet.

The final list contains 234 exoplanets that could have exomoons with a probability of habitability greater than 1%.

Also, 17 planets on the list have exomoons with a probability of being habitable above 50%.

In first and second place are the sub-Jupiters: Kepler-459b and Kepler-456b, which orbit sun-like stars.

The probability of finding a habitable exomoon in both planets is estimated at 69%-70%.

In third place is the gas exogiant HD 7199b, which has a 64% chance of having a habitable exomoon.

Finally, are the super-Earth Kepler-458b (probability about 60%) and the super-Earth Kepler-62f.

Source:

• Monthly Notices of the Royal Astronomical Society: https://academic.oup.com/mnras/article-abstract/513/4/5290/6581344?
• Universe Today: https://www.universetoday.com/155837/these-are-the-best-places-to-search-for-habitable-exomoons/

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