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Yahoo
a day ago
- Science
- Yahoo
Could the Solar System Lose a Planet to a Passing Star?
There's a bit of a paradox about our galaxy: it's both jam-packed with stars and cavernously empty. The Milky Way is crowded in the sense that it holds hundreds of billions of stars, as well as sprawling clouds of gas and dust. But even so, there is a lot of elbow room: the nearest star to the sun is more than four light-years distant, separated from us by tens of trillions of kilometers. That's an immense distance and difficult to even analogize. Saying our fastest space probes would take tens of thousands of years to reach the nearest star is still such a ponderous concept that it's hard to grasp. Of course, there are more crowded spots, too. Some stellar clusters pack thousands of stars into a small volume of space, and the bustling galactic center swarms with stars. But out here in the galactic suburbs, stars are more spread out, providing one another plenty of room as they orbit through the Milky Way. [Sign up for Today in Science, a free daily newsletter] Still, given enough time, some stars will encroach on our personal space. About 80,000 years ago a small red dwarf called Scholz's star passed the sun at a distance of just 0.85 light-year. Looking ahead, about 1.3 million years hence, the star Gliese 710 will give us a close shave by 0.17 light-year. That may seem like a long time on a human scale, but that's barely a tick of the galactic clock. The sun and its retinue of planets, asteroids and comets have been around for more than 4.5 billion years. Across that yawning stretch of time, it's a near certainty the sun has had some close encounters of the stellar kind. What sort of effect does that have on the solar system? We know that the sun is surrounded by a vast halo of trillions of icy bodies collectively called the Oort Cloud; although each individual object is far too faint to see with modern equipment, every now and again, one will drop down into the inner solar system and grace our skies as a long-period comet. Estimates of the cloud's size vary, but it could stretch more than a light-year from the sun. A star passing through that region could gravitationally poke at those ice balls, nudging hundreds or even thousands of them toward the sun, and some of them could hit an inner planet. Some researchers have even speculated that such a close pass could provoke a mass extinction event. Research published in the Astrophysical Journal Letters showed that the passage of Scholz's star was unlikely to trigger such an event; the star is too much of a lightweight and was moving too quickly to significantly jostle the Oort Cloud and rain death upon our world. Given enough time, however, other stars could indeed stir up trouble in the distant reaches of the outer solar system. Happily, we probably have thousands of millennia to prepare. But such a celestial drive-by can have other unsettling consequences as well. Many astronomers have wondered about the long-term stability of the solar system's planets, given that they interact with each other gravitationally over the eons. The early solar system was wracked with profound instabilities, but more recently such effects have been far more subtle. Oddly enough, Mercury, the innermost planet, is particularly susceptible to these. The physics behind this is complex, but in a nutshell, small changes in the orbit of Neptune—the major planet most affected by a star passing by—propagate inward. It tugs on Uranus, which tugs on Saturn, which tugs on Jupiter, and the solar system's most massive planet affects everything else. Its orbit and that of Mercury can fall into a resonance in which the orbital periods (the 'years' of both planets) are simple ratios of each other. When this happens, Mercury gets an added kick (literally, like when a child on a playground swing kicks at the right moment, pumping up their oscillations). It's been known for decades that these effects can change the ellipticity of Mercury's orbit, sometimes stretching it out into a long oval. If the orbit were to get too elongated, Mercury could fall into the sun or get close enough to Venus to get flung out of the solar system. Mars, too, could fall prey to this; like Mercury, it has a more oval-shaped orbit than that of Earth or Venus and can find its orbit changing shape radically over a sufficiently long time frame. In the past, most of those simulations assumed the solar system to be in isolation, with no other stars nearby sticking their noses in our business. But we know that's not the case, and such stellar interference must be accounted for to understand the solar system's evolution. Many simulations that do include passing stars don't usually take all the effects into complete consideration; for example, they run their models for a few tens of millions of years even though it can take billions for gradually growing instabilities to have an impact. Others have used limited modeling of stellar encounters, meaning that they haven't included the entire possible range of masses, velocities and passage distances expected from stars in the galaxy. Research published online in the planetary science journal Icarus last month attempts to address all these factors in more robust simulations of the solar system's dynamic evolution. What the authors find is that some celestial bodies are a little less stable than previously thought, given how often stars pass by the sun. Not surprisingly, Pluto is the hardest hit. (The researchers only modeled the eight major planets plus Pluto.) Previously, Pluto was thought to have a pretty stable orbit, but the new simulations show that over the course of about five billion years, there's a 4 percent chance for Pluto to be ejected from the solar system entirely. These passes also increase Mercury's odds of an unhappy end. Previous studies showed a roughly 1 percent chance of it dropping into the sun or being ejected from the solar system because of planetary dynamics in the next five billion years or so, but according to the new study, there's an additional 0.56 percent chance that these events could occur via stellar interactions. Mars, too, has a 0.3 percent chance of the fate of getting an extreme sunburn or starlessly wandering the galaxy. Earth isn't immune, either. The new research finds that our own fair world has a 0.2 percent chance of being involved in a planetary collision or ejected into interstellar space. The odds are low, certainly, but higher than I'd care for given the world-shattering stakes. At this point I think I should remind you of the timescale involved: we're talking five billion years into the future, which is roughly the same amount of time that's elapsed since the solar system was born in the first place. That's a long time, so this is not something you or I should personally worry about. Plus, we don't know of any stars that will pass terribly close to us for several million years anyway. In the shorter term, I'm more concerned about—in chronologically ascending order—global warming (at the timescale of decades), medium-sized asteroids (centuries), supervolcanoes (hundreds of millennia) and giant-sized asteroids (tens of millions of years). Remember, too, that the solar system has been around a long time and, crucially, Earth is still here. It's been batted around a bit, but life persists. Over the very long term, the universe is a dangerous place, but for now, for us—cosmically speaking, at least—we can breathe easy.
Scientific American
4 days ago
- Science
- Scientific American
How a Passing Star Could Oust Planets from the Solar System
There's a bit of a paradox about our galaxy: it's both jam-packed with stars and cavernously empty. The Milky Way is crowded in the sense that it holds hundreds of billions of stars, as well as sprawling clouds of gas and dust. But even so, there is a lot of elbow room: the nearest star to the sun is more than four light-years distant, separated from us by tens of trillions of kilometers. That's an immense distance and difficult to even analogize. Saying our fastest space probes would take tens of thousands of years to reach the nearest star is still such a ponderous concept that it's hard to grasp. Of course, there are more crowded spots, too. Some stellar clusters pack thousands of stars into a small volume of space, and the bustling galactic center swarms with stars. But out here in the galactic suburbs, stars are more spread out, providing one another plenty of room as they orbit through the Milky Way. On supporting science journalism If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today. Still, given enough time, some stars will encroach on our personal space. About 80,000 years ago a small red dwarf called Scholz's star passed the sun at a distance of just 0.85 light-year. Looking ahead, about 1.3 million years hence, the star Gliese 710 will give us a close shave by 0.17 light-year. That may seem like a long time on a human scale, but that's barely a tick of the galactic clock. The sun and its retinue of planets, asteroids and comets have been around for more than 4.5 billion years. Across that yawning stretch of time, it's a near certainty the sun has had some close encounters of the stellar kind. What sort of effect does that have on the solar system? We know that the sun is surrounded by a vast halo of trillions of icy bodies collectively called the Oort Cloud; although each individual object is far too faint to see with modern equipment, every now and again, one will drop down into the inner solar system and grace our skies as a long-period comet. Estimates of the cloud's size vary, but it could stretch more than a light-year from the sun. A star passing through that region could gravitationally poke at those ice balls, nudging hundreds or even thousands of them toward the sun, and some of them could hit an inner planet. Some researchers have even speculated that such a close pass could provoke a mass extinction event. Research published in the Astrophysical Journal Letters showed that the passage of Scholz's star was unlikely to trigger such an event; the star is too much of a lightweight and was moving too quickly to significantly jostle the Oort Cloud and rain death upon our world. Given enough time, however, other stars could indeed stir up trouble in the distant reaches of the outer solar system. Happily, we probably have thousands of millennia to prepare. But such a celestial drive-by can have other unsettling consequences as well. Many astronomers have wondered about the long-term stability of the solar system's planets, given that they interact with each other gravitationally over the eons. The early solar system was wracked with profound instabilities, but more recently such effects have been far more subtle. Oddly enough, Mercury, the innermost planet, is particularly susceptible to these. The physics behind this is complex, but in a nutshell, small changes in the orbit of Neptune—the major planet most affected by a star passing by—propagate inward. It tugs on Uranus, which tugs on Saturn, which tugs on Jupiter, and the solar system's most massive planet affects everything else. Its orbit and that of Mercury can fall into a resonance in which the orbital periods (the 'years' of both planets) are simple ratios of each other. When this happens, Mercury gets an added kick (literally, like when a child on a playground swing kicks at the right moment, pumping up their oscillations). It's been known for decades that these effects can change the ellipticity of Mercury's orbit, sometimes stretching it out into a long oval. If the orbit were to get too elongated, Mercury could fall into the sun or get close enough to Venus to get flung out of the solar system. Mars, too, could fall prey to this; like Mercury, it has a more oval-shaped orbit than that of Earth or Venus and can find its orbit changing shape radically over a sufficiently long time frame. In the past, most of those simulations assumed the solar system to be in isolation, with no other stars nearby sticking their noses in our business. But we know that's not the case, and such stellar interference must be accounted for to understand the solar system's evolution. Many simulations that do include passing stars don't usually take all the effects into complete consideration; for example, they run their models for a few tens of millions of years even though it can take billions for gradually growing instabilities to have an impact. Others have used limited modeling of stellar encounters, meaning that they haven't included the entire possible range of masses, velocities and passage distances expected from stars in the galaxy. Research published online in the planetary science journal Icarus last month attempts to address all these factors in more robust simulations of the solar system's dynamic evolution. What the authors find is that some celestial bodies are a little less stable than previously thought, given how often stars pass by the sun. Not surprisingly, Pluto is the hardest hit. (The researchers only modeled the eight major planets plus Pluto.) Previously, Pluto was thought to have a pretty stable orbit, but the new simulations show that over the course of about five billion years, there's a 4 percent chance for Pluto to be ejected from the solar system entirely. These passes also increase Mercury's odds of an unhappy end. Previous studies showed a roughly 1 percent chance of it dropping into the sun or being ejected from the solar system because of planetary dynamics in the next five billion years or so, but according to the new study, there's an additional 0.56 percent chance that these events could occur via stellar interactions. Mars, too, has a 0.3 percent chance of the fate of getting an extreme sunburn or starlessly wandering the galaxy. Earth isn't immune, either. The new research finds that our own fair world has a 0.2 percent chance of being involved in a planetary collision or ejected into interstellar space. The odds are low, certainly, but higher than I'd care for given the world-shattering stakes. At this point I think I should remind you of the timescale involved: we're talking five billion years into the future, which is roughly the same amount of time that's elapsed since the solar system was born in the first place. That's a long time, so this is not something you or I should personally worry about. Plus, we don't know of any stars that will pass terribly close to us for several million years anyway. In the shorter term, I'm more concerned about—in chronologically ascending order— global warming (at the timescale of decades), medium-sized asteroids (centuries), supervolcanoes (hundreds of millennia) and giant-sized asteroids (tens of millions of years). Remember, too, that the solar system has been around a long time and, crucially, Earth is still here. It's been batted around a bit, but life persists. Over the very long term, the universe is a dangerous place, but for now, for us—cosmically speaking, at least—we can breathe easy.
Time of India
23-06-2025
- Science
- Time of India
Earth might get kicked out of the solar system; scientists sound the alarm
Most of us go through life assuming Earth's place in the universe is secure. We picture our planet as a blue marble, peacefully orbiting the Sun in a cosmic dance that's guaranteed to go on for billions of years. Tired of too many ads? go ad free now But a new study is quietly challenging that idea, and it's doing so with science, not speculation. According to researchers writing in the journal , a rare but possible event could one day push Earth out of the solar system entirely. The culprit? A wandering star. No, this isn't science fiction. Scientists used thousands of orbital simulations to explore what would happen if a nearby star passed a little too close to our solar system. What they found was both fascinating and a little unnerving: even a modest gravitational nudge could create instability, ultimately disrupting planetary orbits, including Earth's. It's not likely to happen tomorrow, or even in a million years. But the possibility is real, and the consequences are enormous. How a star could upend the solar system In space terms, our solar system is like a calm pond, but even the smallest pebble can cause ripples. According to the study in Icarus, a passing star within 10,000 astronomical units (AU) could be that pebble. That's about 0.16 light-years away far enough to sound safe, but close enough to disturb the Oort Cloud, a massive halo of icy debris that surrounds our solar system. If a star's gravitational pull nudges this distant region, the disturbance could slowly travel inward. Over time, that gravitational imbalance could destabilise the orbit of Mercury, which has the most eccentric orbit of the inner planets. And that's where things get serious. Tired of too many ads? go ad free now Earth Why Mercury matters more than you'd think The simulations showed that Mercury is like a domino. If it starts to drift due to a star's influence, it could eventually set off a chain reaction that pulls Venus, Earth, or Mars into unstable paths. In the most extreme scenarios, Earth could either fall into the Sun or get flung out into deep space, becoming a 'rogue planet.' The good news? According to the study, Earth's odds of getting ejected or crashing into the Sun are only around 0.2% to 0.3% over the next five billion years. Small, yes, but not zero. Mercury, on the other hand, has up to an 80% chance of destabilisation in those same simulations. Is there any real-world precedent? Actually, yes. Astronomers already know of real stars on paths that could bring them dangerously close to our solar system. One of them, Gliese 710, is expected to pass through the outer edge of the Oort Cloud in about 1.3 million years. While it won't come close enough to harm Earth directly, its approach serves as a reminder that close stellar encounters are not rare in cosmic terms. This isn't just theoretical work. Observatories like Gaia, run by the European Space Agency, are already tracking thousands of stars and mapping their trajectories to predict future flybys. In fact, Gaia data was instrumental in identifying Gliese 710's path. The chain reaction: From calm to chaos Here's how such a scenario could play out: A nearby star drifts into the outskirts of our solar system. Its gravity disturbs the Oort Cloud and alters the orbits of far-out objects. Over millions of years, that gravitational tug moves inward, affecting Mercury. Mercury's orbit shifts enough to destabilise nearby planets. Earth, caught in the gravitational mess, could spiral into the Sun—or be cast out into the cold void. It's the cosmic version of a slow-motion car crash, with one unexpected swerve turning into a full-on pileup. So... should we be worried? Not immediately. Earth's orbit is still remarkably stable. In fact, NASA and other agencies confirm that our planet has maintained a steady path around the Sun for billions of years. The chance of a catastrophic event happening in our lifetimes or in the next few million years is extremely low. But the study is a humbling reminder that we're part of a much larger galactic ecosystem. We don't live in a perfectly sealed solar system. We're just one part of a dynamic, shifting universe, where stars drift and gravity acts like a quiet puppeteer. What it teaches us about Earth's fragile place in space This kind of research is less about fear and more about perspective. It's not that Earth is doomed; it's that stability is borrowed, not guaranteed. The idea that a distant, barely visible star could, over millions of years, change everything, adds another layer to our understanding of cosmic vulnerability. It also helps scientists improve future models. By understanding how small nudges affect planetary motion, astronomers can better predict everything from asteroid trajectories to long-term climate models influenced by orbital patterns.
