As for the latter, Newton offered a way of calculating gravity and predicting the orbits of the planets. Since then, astronomers have discovered that Solar system is just a small point of light orbiting the center of the Milky Way galaxy. Sometimes other stars will pass close to the solar system, which can cause a dramatic shake that can kick objects out of their orbits.
These “star bypasses” are common and play an important role in the long-term development of planetary systems. As a result, the long-term stability of the solar system has been the subject of scientific study for centuries. According to a new study by a team of Canadian astrophysicists, the inhabitants of the solar system can rest easy. After conducting a series of simulations, they decided that a star will not pass and disrupt our solar system for another 100 billion years. Beyond that, the possibilities are a bit scary!
The research was led by Garett Browna doctoral student in computational physics from the Department of Physical and Environmental Sciences (PES) at University of Toronto and Scarborough. He was joined by Hanno Bridle, an associate professor of astrophysics (and Brown’s mentor) also from PES at UT Scarborough. The magazine describing their results was recently published in Monthly announcements from the Royal Astronomical Journal. As they suggested in their essay, the study of passing stars could reveal much about the history and evolution of planetary systems.
As Brown explained The universe today via e-mail, this is especially true of stars such as the solar system during its early history:
“The full extent to which stellar flight passes in the evolution of planetary systems is still an active area of research. For planetary systems formed in a star cluster, the consensus is that stellar flight plays an important role while the planetary system remains within the star cluster. This is usually the first 100 million years of planetary risk “After the disappearance of star clusters, the occurrence of star flights decreases dramatically, reducing their role in the evolution of planetary systems.”
The most accepted theory for the formation of the solar system is known as Nebulosity hypotheseswhich says that the sun was formed by a massive cloud of dust and gas (known as a nebula) which underwent gravity collapse in its center.
The remaining dust and gas then form a disk around the sun, which slowly collects to form a system of planets. In one version of the hypothesis, the sun was formed due to disturbances in the nebula, possibly from a close flight of another star (or a supernova). But as Brown explained, passing stars will probably also have played a role in planet formation.
“During planetary evolution, when there is a disk of dust and gas around a star, passing stars are expected to be responsible for disk truncation, which would prevent the formation of planets on wider, more distant orbits,” he said. “For planets that have already been formed on wide orbits, passing stars are believed to be responsible for removing or destabilizing the outermost planets.”
Another generally accepted theory is that our sun was formed about 4.5 billion years ago as part of a star cluster that it left a long time ago. With these theories in mind, Brown and Rein investigated how being part of a cluster (and therefore subject to stellar flight) could have changed the solar system once its planets were formed and were part of an established system. They found that the role that star flying plays depends on how strongly the passing star can disrupt the system. They further determined that the passing of stars can dynamically destabilize a system, causing planets to crash into each other or be ejected.
This posed a significant challenge due to a problem that has plagued astronomers ever since Newton proposed his theory of universal gravity. To put it briefly, it’s all about the N-body problem, which describes the difficulty of predicting the individual movements of a group of celestial objects that interact with each other in terms of gravity. Solving this exactly is still a mathematical impossibility, so astronomers are forced to make numerical estimates. But as Brown said, there are still two major problems with these calculations:
“First, the motion of the planets is chaotic, which means that small differences in the initial conditions of the system will result in dramatically different outcomes (even differences as small as part of a trillion). And two, the time scales are dramatically different. We can get a “For the long-term stability of the solar system, this can give us a ratio of simulations that stop destabilizing compared to the number of simulations that remain stable until the end of the integration period.”
“But solving the time scale issue is much more difficult. Sophisticated numerical methods have been developed over the last 50 years, making this more manageable, but we basically need to simulate the motion of the planets one day at a time for billions of years. This requires an incredible amount of computational resources. We usually want to know if the solar system will remain stable for the rest of the sun’s life (about 5 billion years) Even with modern computers (as fast as they are) it can easily take 3-4 weeks to run just a 5 billion year simulation of the solar system. “
To even begin to get reasonable statistics, Brown added, researchers must perform thousands of different simulations. There are two ways to do this: run the simulations on a single computer for up to 70 years or more or use thousands of different computers simultaneously for a month. This not only makes statistical analysis very complicated but also very expensive. For their analysis, Brown and Rein used Niagara supercomputer at the University of Toronto’s SciNet Center, which is part of the Digital Research Alliance of Canada network.
As Brown explained, he and Rein used two main methods to calculate the potential disruptions caused by overflying.
“The first was an analytical estimate developed in 1975 by Douglas Heggie and refined over the years by his associates. It is an approximation that assumes that the relative velocity between the two stars is small compared to the orbits of the planets. This analytical estimate allows us to to very quickly calculate the magnitude of how a bypass will change a planet’s half-size axis. “
The second method used the numerical integrations with REBOUND, a multifunctional N-body code with open source code for collision dynamics developed by Hanno Rein and co-workers. Between these two methods, Brown and Rein were able to simulate a star flight numerically and then measure the state of the system before and after. In the end, their results indicated that disturbances of the solar system would require a very close bypass and that a star meeting of this kind is unlikely to happen for a very long ago. in Brown:
“We found that critical changes in Neptune’s orbit needed to be in the order of 0.03 AU or 4.5 billion meters to have any impact on the long-term stability of the solar system. These critical changes can increase the probability of instability during the life of the solar system by ten times. we that a critical star flight like this can occur once every 100 billion years in the region in which the solar system is currently located.
“[W]e estimated that we would have to wait about 100 billion years before a stellar flight past the solar system would simply increase the odds of dismantling its current architecture by ten times (and it is still not a guarantee of destruction).
Given the turbulent history of the solar system, it is understandable that the thought of stellar flight (and the resulting disruptions) would cause concern for some. After all, astronomers theorize that “planetary shakes” can be a common feature of the evolution of a system and that large objects are regularly ejected from the outer parts of a system due to bypasses. A good example is Neptune’s largest moon Triton, which is believed to have formed in the Kuiper Belt and was thrown towards the inner solar system, where Neptune captured it (which led to the destruction of Neptune’s original satellites).
In addition, gravitational interactions with other star systems are the reason why we have comets with long periods, where objects that are kicked out of the Oort cloud at regular intervals pass through the inner solar system. The idea that a near bypass could send many comets our way (or larger objects like a planetoid) sounds like a doomsday scenario! But as Douglas Adams famously said, “Do not panic!” Stellar bypasses not only occur regularly, they usually pass light years away and do not affect the solar system.
In many ways, this is similar to Near Earth Asteroids (NEA) and the possibility that one will collide with Earth one day. Although we know that effects have happened in the past that were devastating (like Chicxulub Impact Event who killed the dinosaurs approx. 65 million years ago) NEAs make frequent passes with the earth regularly that do not pose a threat. In addition, recent analyzes of two NEAs considered “potentially dangerous” (2022 AE1 and Apophis) found that neither would threaten the earth for a long time.
What’s more, recent observations from missions such as ESA’s Gaia Observatory has provided the most accurate information about the correct motions and velocities of stars in the Milky Way galaxy. As Brown noted, this included data on upcoming flights and how close they will pass our system:
“Two notable stars are HD 7977, which may have passed within 3,000 AU (0.0457 light-years) from the sun about 2.5 million years ago, and Gliese 710 (or HIP 89825), which is expected to pass within about 10,000 AU. (0.1696) light-years) of the sun in about 1.3 million years from now. If one makes rough calculations, both of these stars will have no significant effect on the evolution of the solar system. “
In addition, much will happen from time to time, and it is highly unlikely that humanity will be involved in witnessing such an event. If we assume that we have not driven ourselves to extinction or left Earth to explore other parts of the galaxy, the planet Earth will cease to be habitable long before that. “Given that the sun will expand and engulf the earth in about 5 billion years, physical distance from other stars is not a problem we need to worry about,” Brown said.
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