Tides Might Be Responsible for Rarity of 'Trojan' Exoplanets, Study Claims

In astronomy, 'trojans' are distant worlds that co-orbit each other. Despite studies suggesting the possibility of its existence, there is still no evidence that shows us this type of system.

Do Trojan Exoplanets Exist?

Trojans are bodies, mostly asteroids, and planets, that share the same orbit. In theory, a set of trojans consists of a smaller planet that orbits the larger orb. In a new study, experts suggest we look for clues to this setup in our solar system rather than finding ones beyond our planetary backyard.

Most astronomers consider asteroids that orbit the sun in the same path as Jupiter's as trojans. However, this phenomenon could also happen in larger bodies, particularly exoplanets.

Research led by Search for Extraterrestrial Intelligence (SETI Institute) implies that larger worlds involved in a trojan set up and outside our system are simply waiting to be discovered. These planets likely have short-period orbits constantly thrown out of path because of the intense gravitational force a nearby star applies.

Experts say that trojan planets in the said condition are ejected from their respective places and eventually collide with other massive materials such as stellar bodies or even larger planets.

The recent study relied on our data of over 5,000 confirmed exoplanets. Most of these worlds were discovered close to their parent stars. These stars were also detected easily by astronomers, given that the light from their respective suns allows our instruments to chart their physical presence.

The authors of the research explain that trojan planets may exist. However, the current technologies limit what regions we can reach and the cosmic bodies we can see.

In addition, we might not be able to catch some of the trojans, as the behavior of these planets pushes them to drift away or disappear quickly compared to members of a normal star system.

Tidal Friction Causes Trojan Exoplanets to Drift, Disappear

According to the SETI specialists, the same interactive force that allows such tidal friction between our planet and the moon is also behind the reason why the tides slow Earth's rotation and gradually move the moon farther from us, Space reports.

This friction, according to scientists, is also present in the exoplanets involved in a trojan system. This setup might also include other bodies, including gas giant planets and stars, provided that each of them rotates around an intersecting Lagrange point.

When two bodies join in a trojan system, their significant gap in mass could disturb their orbits and make them unstable. The oscillations in a small planet could transition from oval shape to banana shape, leading to breaking their shared orbit. After this phase, the collision will occur.

Although finding trojans is challenging, we still have little chance to discover them. Scientists believe these systems are much easier to chart in younger planetary clusters.

Last October, NASA launched the Lucy spacecraft to observe the trojan asteroids of our solar system closer.

The paper was published in the journal Icarus, titled "Do tides destabilize Trojan exoplanets?"

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