Imagine looking up at the night sky and noticing a brilliant new star growing brighter every month. Unlike ordinary stars, it appears to be moving steadily across the heavens. Astronomers discover that it is not merely passing through the background: the star is heading toward our Solar System.
What would happen if a star passed close enough to disturb Earth’s orbit, send comets toward the inner planets or disrupt the distant boundaries of our Solar System?
The scenario sounds like a cosmic disaster movie, but stellar encounters are real astronomical events. Stars move through the Milky Way, and their gravitational influence can reshape planetary systems over millions of years. Astronomers have even identified a star predicted to make an unusually close approach to our Solar System in the distant future.
The important distinction is distance. A star passing through the distant outskirts of our Solar System could disturb icy objects without directly threatening Earth. A star passing close to the planets would be a much more extreme—and vastly less likely—event.
Stars Do Not Stay in One Place
The stars appear fixed in the night sky because they are so far away that their movement is difficult to notice over a human lifetime. In reality, every star travels through the galaxy under the influence of gravity.
Our Sun is moving around the centre of the Milky Way, accompanied by its planets and other Solar System objects. Other stars follow their own trajectories, and occasionally their paths bring them relatively close to the Sun.
Astronomers use measurements of stellar positions, distances and velocities to predict these encounters. The European Space Agency’s Gaia mission has greatly improved this work by mapping the positions and motions of enormous numbers of stars.
In a 2026 study, researchers from the Institute of Space Sciences in Spain examined thousands of stellar encounters and found that stars approach within roughly 3.3 light-years of the Sun about once every 95,000 years on average. Much closer encounters are considerably rarer.
These encounters do not generally involve stars colliding. Space is enormous, and even a close stellar passage usually means that the two stars remain separated by trillions of kilometres.
Read the 2026 research summary from the Institute of Space Sciences.
The Real Star Expected to Approach Our Solar System
One of the most closely studied future encounters involves Gliese 710, an orange dwarf star currently about 62 light-years from Earth.
Based on measurements from the Gaia mission and subsequent orbital calculations, Gliese 710 is expected to pass through the distant outskirts of our Solar System in approximately 1.3 million years. Current estimates place its closest approach at roughly 10,000–11,000 astronomical units from the Sun. One astronomical unit is the average distance between Earth and the Sun.
That may sound close in astronomical terms, but it is still thousands of times farther away than Neptune’s orbit.
Gliese 710 is expected to pass through the region associated with the Oort Cloud, a vast and largely unexplored reservoir of icy bodies surrounding the Solar System. Its gravity could disturb some of these objects, changing their trajectories and sending a fraction toward the inner Solar System.
The encounter is not predicted to occur during a human lifetime, and it is not expected to send the star plunging through the planetary region.
The European Space Agency’s explanation of close stellar encounters describes how passing stars can disturb distant comets even when they remain far beyond the planets.
What Would Happen If a Star Entered the Oort Cloud?
The Oort Cloud is believed to contain enormous numbers of icy bodies on distant, loosely bound orbits. Unlike the relatively flat planetary system, this reservoir is thought to extend in a roughly spherical distribution around the Sun.
Its existence is inferred from the orbits of long-period comets, rather than from direct observations of the entire cloud. Scientists estimate that its outer regions may extend tens of thousands of astronomical units from the Sun, potentially farther.
A passing star could gravitationally disturb objects in this region. Some might be pushed onto new orbits, while others could be ejected from the Solar System altogether.
A portion could travel inward, eventually becoming long-period comets that approach the Sun and potentially cross the orbital paths of the planets.
That does not mean Earth would automatically face a devastating bombardment. Most objects would not strike a planet, and the journey from the distant Oort Cloud to the inner Solar System can take a very long time. Many comets would never come close to Earth.
A 2026 numerical study of Gliese 710’s future encounter modelled the effects on a large population of hypothetical Oort Cloud comets. The simulations found that the encounter could redirect some objects toward the inner Solar System while scattering many others into interstellar space.
The results illustrate a plausible gravitational effect, not a prediction that Earth will be hit by a comet shower.
Read the research in Universe: Oort Cloud Comets: Perturbations Due to the Passage of Gliese 710.
What If the Star Passed Much Closer to the Planets?
Now consider a far more extreme hypothetical: a star passing through the region occupied by the major planets.
The consequences would depend on the star’s mass, speed and closest distance from the Sun, as well as the geometry of the encounter. There is no single outcome for every possible flyby.
A sufficiently close passage could alter planetary orbits through gravitational interactions. Smaller bodies in the Solar System would be particularly vulnerable because their orbits can be changed more easily. Some comets and asteroids might be redirected, while certain distant objects could be ejected.
If a star passed extremely close to Earth, its gravity could potentially alter Earth’s orbit. A direct collision with the Sun or a planet would be catastrophic, but such a collision is not a realistic prediction for any known upcoming stellar encounter.
The star’s radiation would also matter if it approached close enough. A luminous star passing very near Earth could produce dangerous heating and radiation exposure. But at the distances associated with ordinary stellar flybys, gravitational effects on distant small bodies are a more plausible concern than direct damage to Earth.
Importantly, a star does not need to enter the inner Solar System to influence it. Gravity can act across enormous distances, although its effects weaken with distance.
Could a Passing Star Throw Earth Out of Its Orbit?
This is one of the most dramatic possibilities, but it requires a particularly close and dynamically disruptive encounter.
Earth remains in orbit because of the Sun’s gravitational attraction. A passing star would exert its own gravitational force, changing the motions of the Sun and planets to some degree.
For Earth to be ejected from the Solar System, the encounter would have to change its orbital energy sufficiently for it to escape the Sun’s gravitational binding. That outcome is physically possible in extreme gravitational encounters, but it is not an expected consequence of a star passing through the distant Oort Cloud.
The planets would not necessarily respond identically. Their orbital distances, velocities and positions during the encounter would affect how they were perturbed. Some orbits could change only slightly, while objects in vulnerable configurations could experience larger disturbances.
In the most extreme hypothetical scenario, a major orbital change could alter Earth’s climate over long timescales by changing its distance from the Sun or its orbital characteristics. But these outcomes should not be presented as inevitable effects of every stellar passage.
Would We See the Star Coming?
If a star were on a trajectory that brought it dangerously close to the Solar System, astronomers could potentially identify the risk well in advance.
A star’s future path can be calculated from its position, distance and velocity. Space missions such as Gaia provide increasingly precise measurements that help researchers predict stellar encounters and identify uncertainties in those predictions.
A newly recognised star would not suddenly appear next to Earth without any warning simply because it was moving through the galaxy. However, the reliability of a prediction depends on the quality of the measurements, the star’s properties and the accuracy of the dynamical model.
An object described as a rogue star is sometimes understood to mean a star travelling without a gravitationally bound stellar system. The term is also used more loosely in popular writing for stars moving through space on unusual paths. A star passing the Sun does not necessarily qualify as a rogue star in the strict astronomical sense.
Should We Be Worried?
There is no evidence that a star is on course to pass dangerously close to Earth during our lifetime. The best-known predicted encounter, Gliese 710, is expected in approximately 1.3 million years and will remain far beyond the planetary region.
Nevertheless, stellar encounters are scientifically important. They help astronomers understand how planetary systems evolve, how comets are redistributed and how the Solar System has changed throughout its history.
The real danger in the most extreme hypothetical scenario would come from a sufficiently close gravitational encounter—not simply from seeing a new star in the sky.
A star passing through the outer Solar System could reshape the distant comet population without destroying the planets. A much closer encounter could have more serious consequences, but it is an extraordinarily different scenario.
For now, the universe offers no indication that such a disaster is imminent. The more remarkable discovery is that astronomers can use precise measurements of distant stars to reconstruct encounters that will unfold millions of years from today.
