Our solar system will not collide with another star system in any meaningful timeframe, but the galaxy it lives in is on a collision course with the Andromeda galaxy. That merger begins in about 4 billion years. Before that, a single star called Gliese 710 will pass through the outer fringes of our solar system in roughly 1.35 million years, making it the closest known stellar encounter on the horizon. Neither event is likely to destroy planets or disrupt orbits in the way most people picture a “collision.”
The Andromeda Merger: What’s Actually Coming
The Andromeda galaxy is heading toward the Milky Way at about 250,000 mph. Gaia satellite measurements confirm the approach is nearly head-on, with a sideways velocity of only about 82 kilometers per second. The first close pass will happen roughly 2 billion years from now, with subsequent clashes over the following billions of years gradually reshaping both galaxies. By about 7 billion years from now, the two spirals will have merged into a single, football-shaped elliptical galaxy sometimes nicknamed “Milkomeda.”
The word “collision” is misleading here. Galaxies are mostly empty space. The distance between individual stars is so vast that during the merger, actual star-on-star collisions are essentially impossible. What changes are orbits. The gravitational chaos of two galaxies passing through each other reshuffles where stars end up. Simulations by astrophysicists T.J. Cox and Abraham Loeb estimate a 50 percent chance that our solar system gets pushed to three times its current distance from the galactic center (currently about 26,660 light-years). There’s also a 12 percent chance the solar system gets ejected from the merged galaxy entirely, flung into intergalactic space.
Will Anyone Be Around to See It?
Here’s the detail that changes the whole picture: the Sun has its own expiration date, and it arrives on roughly the same schedule. By the time Andromeda makes its first close pass in about 2 billion years, the Sun will still be burning hydrogen, but it will have brightened enough to boil Earth’s oceans. Life as we know it will already be gone. By 5 billion years from now, when the galaxies fully combine, the Sun will be nearing its red giant phase and the end of its life. So while the merger is real, it’s not a threat to life on Earth, because Earth won’t be habitable long before the merger finishes.
Gliese 710: A Closer, Sooner Encounter
A more immediate event involves Gliese 710, an orange dwarf star currently about 64 light-years away. Based on precise tracking data from the Gaia space observatory, this star will pass within roughly 13,365 astronomical units of the Sun in about 1.35 million years. For context, one astronomical unit is the distance from Earth to the Sun, and the outer boundary of the Oort Cloud (the shell of icy objects surrounding our solar system) extends to around 100,000 AU. So Gliese 710 will pass well inside the Oort Cloud, but still far from any planet. Neptune, the most distant major planet, orbits at only 30 AU.
The uncertainty in this prediction is significant. Ninety percent of simulated trajectories place Gliese 710 within 6,250 AU of the Sun, meaning a closer approach than the best estimate is plausible. At a distance of 4,000 AU, simulations show a significantly higher number of comets getting scattered from the Oort Cloud into the inner solar system. These perturbed comets wouldn’t arrive immediately; the increased impact risk for Earth would build over millions of years after the flyby.
Even in the closer-approach scenarios, this is not a collision. No star comes anywhere near the planets. The concern is limited to whether the gravitational nudge dislodges enough distant comets to slightly raise the odds of a comet impact on Earth millions of years later.
How Rare Are Close Stellar Passes?
Stars pass near the Sun with some regularity on astronomical timescales. The Gaia mission has cataloged dozens of stars that will come within a few light-years over the next several million years. Gliese 710 stands out because it comes so much closer than the rest, actually penetrating the Oort Cloud. But penetrating the Oort Cloud is not the same as threatening the planets. The inner solar system, where Earth and the other rocky planets orbit, occupies a tiny fraction of the space that a passing star traverses.
The broader pattern is reassuring. In the 4.6 billion years since the solar system formed, it has survived countless stellar flybys without losing a planet. Stars in our region of the galaxy are spaced far enough apart that direct gravitational disruption of planetary orbits requires an approach within a few hundred AU, and encounters that close are extraordinarily rare.
What About Radiation Risks?
During a galactic merger, stars can be pushed closer to the galactic center, where supernovae and gamma-ray bursts are more common. Some researchers have examined whether this could threaten planetary habitability through increased radiation exposure or more frequent comet showers. The current consensus is that these hazards are more limited than originally feared. The galactic center is dangerous, but “closer to the center” after a merger doesn’t necessarily mean close enough to matter, especially given the enormous scales involved.
For Gliese 710 specifically, the star itself poses no radiation threat. It’s a quiet, low-mass star roughly 60 percent the mass of the Sun. The only mechanism for harm is the indirect one: gravitational perturbation of comets that might eventually reach Earth’s neighborhood.
The Short Answer
No star is going to slam into our solar system. The closest known future encounter, Gliese 710, will pass through the outermost fringe of the solar system in 1.35 million years without approaching any planet. The Milky Way will merge with Andromeda starting in a few billion years, but galactic mergers don’t involve stars hitting each other. They involve orbits being rearranged across a vast, mostly empty space. By the time any of this becomes dramatic, Earth will have long since become uninhabitable due to the Sun’s natural aging.