Over the past few billion years, the solar system has evolved into a stable and resilient state. The Sun is located in the solar system, and the eight planets orbit it day and night, year after year. But occasionally, events can undermine such stable relationships.
Imagine a star that is very close to a supermassive black hole and is ejected from its original system by the black hole's gravitational pull. The "expelled" star wanders the universe as a rogue star. Let's further hypothesize: what would happen if a wandering star entered the solar system?(albeit a small probability event).
Seamount (one of the brightest stars in the universe) at the base of the ship is a wandering star Image Credit: NASA ESA
A recent study published in the Monthly Notices of the Royal Astronomical Society** simulated the entry of wandering stars within 100 AU of the Sun, conducted by the Bordeaux Astrophysical Laboratory in France in collaboration with the French National Centre for Scientific Research.
Most of the wandering stars (also known as interstellar stars or hypervelocity stars) are far from the solar system. For example, the famous wandering star Kappa Cassiopeae is 4,000 light-years away from the solar system, meaning that we will never cross paths with each other.
Bow shock caused by Wang Liangji running at high speedImage credit: NASA JPL-Caltech
Other reports, such as the discovery in 2012 by astronomers at Vanderbilt University, of 675 wandering stars, all of which were ejected after being entangled with the Milky Way's supermassive black hole. Fortunately, these wandering stars orbit far from the solar system.
The researchers explained that statistically speaking, it is extremely rare for a wandering star to affect other star systems in an empty universe. In the case of the Milky Way and its vicinity, for example, it occurs once in about 100 billion years (a wandering star within 100 AU of the galaxy), and although the probability is very low, it is still possible.
The research team conducted about 12,000 simulations to analyze the potential outcomes of wandering stars invading the solar system. The simulation is considered from multiple perspectives, with the main variables being the mass, velocity, and trajectory of the wandering star.
Scientists speculate that the wandering star HE0437-5439 was ejected by the black hole at the center of the Milky WayImage Credit: NASA
The result may be surprising, if a star passes within 100 AU of the Sun, then all 8 planets in the solar system have a high probability of surviving (95% probability). At the same time, the study also carefully analyzes the potential destruction of the planet, which is listed below:
Mercury collides with the Sun (probability 2.).54%)。
Mars collides with the Sun (probability 1..)21%)。
Venus strikes another planet (probability 1.).17%)。
Uranus is thrown (probability 1..)06%)。
Neptune is thrown (probability 0..)81%)。
Mercury strikes another planet (probability 0.).80%)。
Earth strikes another planet (probability 0.).48%)。
Saturn is thrown (probability 0.).32%)。
Mars strikes another planet (probability 0.).27%)。
The Earth collides with the Sun (probability 0.).24%)。
The image shows the simulation results of the study. Each dot represents a simulation run, and the color of the dots represents the carding of the surviving planets. The size of the dot is directly proportional to the mass of the wandering star. image credit：raymond et al. 2023
Mercury is the most "vulnerable" and has the highest probability of colliding with the Sun. Other results include Earth-Venus collisions, ejections of ice giants Uranus and Neptune, with only Earth and Jupiter surviving or only Jupiter surviving, and even a simulation in which eight planets were thrown out of the solar system, in what researchers call an "apocalyptic scenario."
Although the probability of survival is more than 95%, this does not mean that the habitat of individual planets is not affected by wandering stars, and their orbits are often disrupted by gravitational disturbances of wandering stars. In some severe cases, planets can even be gravitationally pulled to the Oort Cloud, a barren area about 50,000 100,000 AU from the Sun. The outer edge of the Oort cloud marks the edge of the structure of the solar system, that is, the edge of the gravitational influence of the Sun.
Star Comet C 2022E3 (ZTF) in 2022 from Oort Cloud Image credit:Rolando Ligustri
Finally, let's talk about the planet we live on. The researchers have proposed a range of potential outcomes: including the Moon hitting Earth, Earth colliding with another planet, Earth being banished to the Oort Cloud, Earth being captured by wandering stars, and more.
Researchers believe that except for the safe outcome of undisturbed or slightly disturbed, there is still a glimmer of life for the Earth to be captured by wandering stars, and the long-term survival of other scenarios is not optimistic. Of course, the probability of all of the above scenarios is extremely low.
Author: He Boxiang.
Editor in charge: Wang Qiru.
*The content represents the author's views only.
It does not represent the position of the Institute of Physics of the Chinese Academy of Sciences.
If you need it, please contact the original***
*: Shepherd Astronomy.
Edit: serendipity