Outside of the solar system, co-orbiting worlds, sometimes known as Trojans, have yet to be discovered. That's odd, according to a new study, because we see them all the time closer to home.
Trojans abound in our solar system; asteroids orbit the sun along the same path as a larger planet (such as Jupiter), around 60 degrees ahead of and behind it. It's possible, though, that tidal forces change the orbits of larger worlds, such as exoplanets.
While Trojan orbiting exoplanets may arise, the SETI (Search for Extraterrestrial Intelligence) Institute's research reveals that larger worlds with short-period orbits are driven out of their path by gravitational forces from a nearby star. The Trojan collides with the star or a larger planet after being ejected.
The findings have ramifications for our current collection of 5,000 exoplanets, which primarily includes worlds orbiting their parent stars since they are simpler to discover (either because they are easier to view as they move across a star from our perspective, or because their gravitational tug is a bit stronger on the star.)
In other words, Trojans may exist, but they are currently undetectable using existing methods. Alternatively, Trojans may be purged from host systems quite fast compared to the universe's history, making them more difficult to detect.
The connection between the Earth and the moon causes tidal friction on Earth, according to a press release from SETI. The Earth's rotation is slowed by the tides, which causes the moon to drift away from the Earth.
The current research extends this friction to planetary systems with more than two bodies, assuming a star, a gas giant planet, and a rocky planet all moving around Lagrange points, or gravitationally stable zones between numerous worlds.
The analysis implies that the Earth-sized planet's orbit would become unstable if the star's tides and the gigantic planet's tides worked together. The small planet's orbit will "transform from oval-shaped to banana-shaped and eventually break out of the shared orbit, crashing with either the star or the massive planet," according to the press release.
While the tidal forces may eject Trojans before they can be observed, there may still be some in younger systems that can be observed. A NASA mission in flight may also provide new information on how Trojans act. Lucy was launched in October to take a close look at Trojan asteroids, which is a first.
On Icarus May 21, a study based on the findings was accessible in pre-proof. Anthony Dobrovolskis, a research scientist at the SETI Institute, is in charge of the project.
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