Star Wars fans will certainly enjoy the binary star systems, nicknamed the “Tatooine” systems, a reference to the planet on which Luke Skywalker stood to gaze at the twin suns in Star Wars: A New Hope. It turns out that some planets in real-life versions of these systems may also be receiving a much more realistic influence from them.
New research suggests that “rogue planets” wandering the Milky Way (i.e., planets isolated from host stars and living as cosmic orphans) may be ejected from double or binary star systems. But there is a change (literally)!
The team found that rogue planets were particularly likely to be ejected from “twisted Tatooine” systems. These are systems in which the stars and planets orbiting them are misaligned, thus existing at oblique angles to each other.
As telescopes have improved, detection of these roving planets has improved to the point where astronomers think the number of planetary bodies floating freely in relaxed arrangements, such as the solar system in the Milky Way, far outnumber stars. Recent projects have put the number of rogue planets ejected from their host systems in our galaxy as high as a quadrillion (10 followed by 14 zeros). This new twisted Tatooine may help explain findings From where rogue planets are very common.
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“A normal planetary system, such as our solar system, consists of multiple planets orbiting a single star. Binary stars, on the other hand, are also common and account for more than 50% of star systems,” said team leader Cheng Chen. the astrophysicist from the University of Leeds told Space.com. “If there are planets orbiting a binary, we call it a ‘peripheral planetary system’.”
Although we know that planet formation is a byproduct of star formation, we still do not know the production rates of planets. That’s because we can’t be sure how many of them have escaped from their systems and wander around the galaxy as hard-to-detect, icy bodies. These would be objects that are not illuminated or heated by a host star.
“More precise rogue planet demographic determinations could help us complete the final piece of the planet formation puzzle,” Chen said.
He went on to explain that the orbital planes of some of these planets may not align with the orbital planes of their host binary stars. Astronomers call these “tilted binary planets,” and their study may reveal the dominant mechanism for the formation of free-floating planets.
They were expelled from their cosmic home
Scientists believe that orphan planets form around baby stars, just like planets that remain “attached” to their stellar parents. Stars are essentially born from a collapsing cloud of gas and dust, but this process does not consume all the material in that cloud, leaving stars surrounded by “protoplanetary disks.” Extremely dense regions of these disks collapse, resulting in the formation of planets. This is what gave rise to the Solar System and its planets, including Earth, about 4.6 billion years ago.
The period following planet formation is believed to be particularly chaotic for these nascent systems, leading to “messy” gravitational interactions. take out planets.
In fact, researchers suggest that our solar system may have once had a fifth giant planet alongside Jupiter, Saturn, Uranus and Neptune during a chaotic period called “late instability.” The idea is that this “extra” planet is displaced from its orbit, then gravitational interactions with other giant planets will cause the unfortunate planet to be driven out of the solar system entirely.
But Chen and his team did not focus on a relatively simple, single-star system like the solar system to investigate the origins of rogue planets. Instead, they focused on more complex binary star systems, like the one seen in the iconic sunset over Tatooine.
“The three-or-more-body problem is much more complex than the two-body problem. The inner star pair can disturb the planet due to dynamic effects,” Chen said. “On the other hand, planet-planet interactions can also disrupt planetary orbits.”
The team simulated planetary systems in which two planets were separated from their stars by a certain distance and traced orbits inclined relative to the orbit of the central binary stars.
Chen and his colleagues experimented with a variety of systems containing different orbital inclinations and various planetary separations. They were also interested in the masses of the planets involved, while keeping one planet larger than the other.
“We found that a massive planet like Jupiter can disturb other smaller planets around the binary system and knock them out of the system. This can occur when two planets are close to each other or are located around orbital resonance zones,” Chen said.
The University of Leeds researcher also explained that the team’s previous work found that two Jupiter-sized planets around a single star can become unstable when the distance between them is very small, less than twice the distance between the Earth and the sun. But in this study, they found that a large planet tilted around a binary system can cause minor planet ejections even if the distance between them is wider.
This surprised Chen and his colleagues because it revealed that a wider variety of planets could be extracted from the twisted Tatooine systems than previously thought.
“Initially, we thought that only two large planets around the binary system could be expelled due to the strong dynamical effects and planet-binary interactions between the two planets,” Chen said. “We did not expect that small planets could be ejected so efficiently. As a result, circular systems can produce small to large stray planets.”
“Small planets are more common than high-mass planets,” he continued. “As a result, these systems may contribute to the population of rogue planets in the universe.”
This means that the systems the team investigated could explain the estimated wealth of Earth-sized rogue planets.
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Chen explained that the team is currently looking for other mechanisms that could produce rogue planets. This includes the possibility of other stars flying past planetary systems, causing a gravitational disturbance that would drive a planet into exile. This can be a highly effective way to produce rogue planets, whether around a single star or from a binary system.
Chen is unlikely to give up his research on rogue planets. This means that the Taiwanese astronomer’s efforts may help bring these cosmic orphans, independent of their stars, “from the cold” – at least figuratively.
“I love planets! I decided to become an astronomer when I was 8 years old and studied the nine planets in our solar system before Mike Brown changed that by reclassifying Pluto,” Chen joked. “But today, more than 10,000 exoplanets have been found that exhibit unexpected properties for us to study. Irregular planets are not alone; we should not let them remain orphans, but view them as members of our planetary family.”
The team’s research was published in The Astrophysical Journal Letters.