Planets without Stars Might Have Moons Suitable for Life

A new study by astronomers says some moons might be suitable for life if the water remains liquid on them. Credit: Interpott.nrw / Wikimedia Commons / CC BY-SA 4.0

New research suggests that there may be places in the universe that could sustain life for billions of years.

Astrophysicist Giulia Roccetti and her team reported at the PLANET-ESLAB 2023 Symposium that some moons orbiting rogue planets could remain warm for over a billion years if they have the right orbit and atmosphere. Their findings were also published in the International Journal of Astrobiology.

Roccetti, who works at the European Southern Observatory in Garching, Germany, says that habitable conditions can exist in many places in the universe. However, for life to thrive, those conditions must be stable for a long time. They are looking for places where these conditions can exist for hundreds of millions or billions of years.

Habitability and stability are not dependent on Sun

The habitability and stability of a planet do not necessarily depend on its proximity to the sun. Astronomers have discovered around 100 starless planets, some of which may have formed from gas and dust clouds in the same way that stars form, while others were likely ejected from their home solar systems.

Computer simulations indicate that there may be just as many free-floating planets as there are stars in the galaxy.

Orphaned planets like these might have moons as well, and recent research suggests that these moons could be warm and hospitable. In 2021, researchers calculated that these moons need not be cold and barren places.

Condition for water to stay liquid on moons

Moons orbiting planets can become deformed by the planet’s gravity, which generates heat due to friction inside the moon. This happens to some of the moons in our solar system, such as Enceladus (around Saturn) and Europa (around Jupiter).

If these moons have a thick enough atmosphere that traps heat, especially one with carbon dioxide, they can stay warm enough for water to stay liquid on their surface. This water may come from chemical reactions caused by high-speed charged particles from space.

However, these moons won’t stay warm forever. The same gravitational forces that cause them to heat up also work to make their orbits more circular. As this happens, the amount of deformation and friction inside the moon decreases, resulting in less heat being produced.

Recent study suggests the likelihood of habitability on moons

Scientists conducted a new study on how planets and moons move in space. They did this by using a computer to run 8,000 simulations of a star that is like our sun. They found that when planets get thrown out of their solar system, their moons often come with them.

The scientists then ran more simulations of these moons, assuming they were the same size as Earth, to see if they could become habitable. On Earth, it took a few hundred million years for life to form. They wanted to see if the moons could stay warm for long enough for life to potentially form there.

The scientists did their calculations in three different ways. They looked at moons with an atmosphere like Earth’s, moons with an atmosphere ten times greater than Earth’s, and moons with an atmosphere 100 times greater than Earth’s.

They found that a moon with an atmosphere like Earth’s would only be habitable for about 50 million years. However, a moon with an atmosphere ten times greater than Earth’s could be habitable for almost 300 million years.

If a moon had an atmosphere 100 times greater than Earth’s, it could be habitable for 1.6 billion years. Although this may seem like a lot of pressure, it’s similar to the conditions on Venus, a planet similar in size to Earth.