The Sun is not stationary by any measure. It spins on its own axis, orbits the center of the Milky Way at roughly 230 kilometers per second, bobs up and down through the galactic plane, and rides along with our entire galaxy as it hurtles through the cosmos at hundreds of kilometers per second relative to the cosmic microwave background. The idea that the Sun sits fixed in space while planets revolve around it was an understandable simplification in the centuries after Copernicus, but reality involves layered motions happening simultaneously at very different scales.
Orbiting the Center of the Milky Way
The most dramatic motion of the Sun is its orbit around the center of the Milky Way galaxy. Sitting roughly 26,000 light-years from the galactic center, the Sun and its entire system of planets, moons, asteroids, and comets travel at about 230 kilometers per second along a roughly circular path. At that speed, one complete orbit takes somewhere between 225 and 250 million years, a period sometimes called a “galactic year.” For perspective, the last time the Sun was at this approximate position in its orbit, dinosaurs had not yet appeared on Earth.
This orbit is not perfectly circular. The Sun’s path has a slight eccentricity, meaning it drifts a bit closer to and farther from the galactic center over time. The gravitational landscape of the Milky Way is lumpy and dynamic, shaped by the mass of hundreds of billions of other stars, vast clouds of gas and dust, and the unseen influence of dark matter distributed throughout the galactic halo. All of these contribute small perturbations to what would otherwise be a clean ellipse.
Spinning on Its Own Axis
Beyond its orbit through the galaxy, the Sun rotates. But it does not spin the way a solid ball would. Because the Sun is a massive sphere of plasma rather than a rigid body, different latitudes rotate at different speeds. The equatorial regions complete a full rotation in about 25 days, while areas near the poles take closer to 35 days. This phenomenon is called differential rotation, and it has been confirmed through decades of observation.
Helioseismology, the study of sound waves propagating through the Sun’s interior, has revealed that this differential rotation is not just a surface feature. Data from multiple research groups using various observational techniques have shown that the pattern of faster-equator, slower-poles persists through much of the Sun’s convection zone, the outer roughly 30 percent of the Sun by radius. Below that convection zone, there is a transition toward more uniform rotation, where the interior spins more or less as a single unit.1International Astronomical Union Colloquium. The Sun’s Internal Differential Rotation From Helioseismology This boundary region, sometimes called the tachocline, is thought to play a central role in generating the Sun’s magnetic field, which in turn drives sunspots, solar flares, and the roughly 11-year solar cycle.
Drifting Through the Local Interstellar Medium
Zoom in from the galactic scale and the Sun is also moving relative to the stars and gas in its immediate neighborhood. Astronomers describe this with a concept called the “local standard of rest,” which is basically the average motion of stars near the Sun. Relative to that local average, the Sun travels at about 20 kilometers per second, heading roughly in the direction of the constellation Hercules. This motion has a real, physical consequence you can see with the right instruments.
As the Sun plows through the tenuous gas of the local interstellar medium, the solar wind, a constant stream of charged particles flowing outward from the Sun, collides with that interstellar material. The result is a vast bubble called the heliosphere, a region of space dominated by solar plasma. The shape and size of this bubble depend on the balance between the outward push of the solar wind and the inward pressure of the surrounding interstellar gas and magnetic field.2The Astrophysical Journal. Three-dimensional Features of the Outer Heliosphere Due to Coupling between the Interstellar and Heliospheric Magnetic Field. V. The Bow Wave, Heliospheric Boundary Layer, Instabilities, and Magnetic Reconnection
Because the Sun is moving, the heliosphere is not a perfect sphere. It is compressed on the side facing the direction of travel and stretched out behind into a long heliotail. Recent modeling has shown that this tail is not simply elongated but develops a sheet-like shape, influenced by the orientation of the interstellar magnetic field.3The Astrophysical Journal. The Global Structure of the Heliosphere Think of it as a comet-like structure, but instead of a small icy body with a tail of gas, it is an entire star system with a tail of solar plasma stretching for billions of kilometers behind it. The boundary of the heliosphere, the heliopause, was famously crossed by the Voyager 1 spacecraft in 2012, providing the first direct measurements of where the Sun’s influence ends and interstellar space begins.
Bobbing Above and Below the Galactic Plane
The Sun’s orbit around the Milky Way is not confined to a single flat plane. It oscillates vertically, moving above and below the midplane of the galaxy in a slow, wave-like motion. The period of this oscillation is estimated at roughly 60 to 70 million years for a full cycle, meaning the Sun crosses the galactic midplane about once every 30 to 35 million years.
This vertical bobbing happens because the gravitational pull of the matter concentrated in the galactic disk acts like a restoring force. When the Sun drifts above the plane, the combined mass below it pulls it back down; it overshoots, passes through the midplane, and drifts below before being pulled back up again. The amplitude of this oscillation is modest in galactic terms, maybe a few hundred light-years above and below the midplane, but it may have subtle consequences. Some researchers have speculated that the Sun’s position relative to the denser midplane could influence how much cosmic radiation or interstellar debris reaches the inner solar system, though these hypotheses remain debated.
Studies of young stars in the Milky Way have shown that vertical motions are a general feature of stellar orbits, not something unique to the Sun. Research using data from the Gaia space telescope found that young stars systematically increase their vertical orbital energy over time, consistent with gravitational interactions gradually pumping up their oscillations.4IOP Publishing (The Astrophysical Journal). The Age-dependent Vertical Actions of Young Stars in the Galaxy In other words, the Sun’s bobbing is something that has likely gotten slightly more pronounced over its 4.6-billion-year lifetime.
The Sun and the Milky Way’s Spiral Arms
One question that naturally follows from the Sun’s galactic orbit is how it relates to the Milky Way’s spiral arms, those bright bands of gas, dust, and young stars that give spiral galaxies their distinctive shape. The spiral arms are not fixed structures that rotate with the stars. Instead, they behave more like density waves, regions of higher density that move through the disk at their own angular speed, called the pattern speed. Stars pass into and out of these denser regions as they orbit.
There is a special distance from the galactic center called the corotation radius, where a star’s orbital speed matches the spiral pattern speed exactly. A star at the corotation radius would stay in the same position relative to a spiral arm indefinitely. Observations of masers and star-forming regions near the Perseus arm suggest that the corotation radius lies beyond about 10,800 light-years from the galactic center, which places it well outside the Sun’s orbital radius.5The Astrophysical Journal. Offsets of Masers with Respect to the Middle of the Perseus Arm and the Corotation Radius in the Milky Way The Sun, sitting closer to the galactic center at about 26,000 light-years out, orbits faster than the spiral pattern rotates. This means the Sun periodically overtakes and passes through spiral arms rather than being permanently parked in one. Over its lifetime, the Sun has likely passed through several spiral arms, spending tens of millions of years in each one before moving on.
Passing through a spiral arm is not just a geometric curiosity. Spiral arms are regions of active star formation, denser interstellar gas, and higher rates of supernova explosions. The Sun’s passages through these regions may have exposed the solar system to elevated levels of cosmic rays and gravitational disturbances, though pinning specific events in Earth’s geological record to specific arm crossings remains speculative.
Large-Scale Motion Through the Universe
Step back even further and the Sun’s motion takes on yet another dimension. The entire Milky Way galaxy, along with its neighbors in the Local Group, is moving through space at substantial speed. Relative to the cosmic microwave background, the faint afterglow of the Big Bang that serves as the closest thing to a universal rest frame, our Local Group of galaxies is traveling at about 600 kilometers per second.
A significant portion of this motion appears to be gravitationally driven by an enormous concentration of mass called the Great Attractor, located roughly 150 to 250 million light-years away in the direction of the constellations Centaurus and Norma. Observations using surface brightness fluctuation measurements have confirmed a strong flow of galaxies converging toward a region about 70 megaparsecs (roughly 230 million light-years) from our Local Group, with peculiar velocities peaking at around 1,000 kilometers per second for galaxies in the thick of it and declining to essentially zero beyond that distance.6The Astrophysical Journal. Return to the Great Attractor: Strong Evidence for a Steradian-sized Flow Converging at ∼70 Mpc within the GA Supercluster and Aligned with the CMB Dipole Our own Local Group, sitting partway along this flow, participates in the infall with its measured peculiar velocity of about 600 kilometers per second relative to the CMB frame.
The Great Attractor is not the only structure pulling on us. Even larger concentrations of mass, including the Shapley Supercluster farther beyond, contribute to the overall motion. The point is that the Sun’s motion is not just local. It is embedded in a hierarchy of gravitational flows that extend across hundreds of millions of light-years.
Close Encounters With Passing Stars
Because all stars in the Milky Way are in motion, their paths occasionally bring them close to one another. The Sun has had, and will continue to have, relatively close stellar encounters. The most notable upcoming flyby involves Gliese 710, a K-type star with about 60 percent of the Sun’s mass. Observations from the Gaia spacecraft have confirmed that Gliese 710 will pass within roughly 10,500 astronomical units of the Sun in about 1.29 million years.7Universe. Oort Cloud Comets: Perturbations Due to the Passage of Gliese 710
That distance, while enormous by everyday standards, places Gliese 710 well within the outer reaches of the Oort Cloud, the vast shell of icy bodies thought to surround the solar system at distances of thousands to tens of thousands of astronomical units. As Gliese 710 passes through, its gravity will perturb the orbits of long-period comets, potentially sending some of them on new trajectories toward the inner solar system.7Universe. Oort Cloud Comets: Perturbations Due to the Passage of Gliese 710 This is not science fiction speculation; it is a straightforward consequence of the Sun and nearby stars all moving through the galaxy on their own paths, occasionally crossing close enough to feel each other’s gravitational pull.
Such encounters happen because stellar orbits are not neatly separated lanes. Stars move at different speeds, in slightly different directions, and occasionally their trajectories converge. Over the Sun’s 4.6-billion-year history, there have likely been many such close passages, some possibly closer than the upcoming Gliese 710 flyby, though reconstructing them precisely is difficult because small uncertainties in stellar velocities compound over millions of years.
The Andromeda Collision and the Sun’s Far Future
On the longest timescales, the Sun’s trajectory is shaped by an event that will transform the Milky Way itself. The Andromeda galaxy, the nearest large spiral galaxy to our own, is approaching the Milky Way at roughly 110 kilometers per second. Simulations indicate that the two galaxies will have their closest approach in about 4.3 billion years, then gradually merge over a span of roughly 10 billion years into a single, larger galaxy sometimes nicknamed “Milkomeda.”8Astronomy & Astrophysics. Future merger of the Milky Way with the Andromeda galaxy and the fate of their supermassive black holes
The merger timeline is somewhat longer than earlier estimates suggested, with the full coalescence now predicted to take about 10 billion years rather than the 5 or 6 billion years sometimes quoted in popular accounts.8Astronomy & Astrophysics. Future merger of the Milky Way with the Andromeda galaxy and the fate of their supermassive black holes For the Sun specifically, the merger’s early stages will unfold while our star is still on the main sequence, though it will be nearing the end of its hydrogen-burning life. Whether the Sun and its planets survive the gravitational reshuffling of a galactic merger is hard to predict precisely. Galaxy mergers are surprisingly gentle for individual star systems because the distances between stars are so vast relative to their sizes. The odds of direct stellar collisions during a merger are vanishingly small. But the Sun could easily be flung onto a very different orbit within the merged galaxy, potentially ending up much farther from the new galactic center or on a more eccentric path than the relatively circular orbit it follows today.
Why “Stationary” Has No Meaning in Space
One reason the question “is the Sun stationary?” persists is that everyday intuition about motion does not translate cleanly to astrophysics. On Earth, “stationary” means not moving relative to the ground. In space, there is no ground. Every measurement of motion requires choosing a reference frame, and the answer changes depending on what you measure against. Relative to Earth, the Sun appears to move across the sky. Relative to the galactic center, the Sun races at 230 kilometers per second. Relative to the cosmic microwave background, the Sun, the Milky Way, and the entire Local Group are collectively moving at 600 kilometers per second. Relative to a photon of light, the Sun is practically standing still.
None of these descriptions is more “true” than the others in a fundamental sense. But all of them confirm that the Sun is in constant, complex motion at every scale. It rotates, it orbits, it oscillates, it drifts through the interstellar medium, it participates in large-scale cosmic flows, and it is heading toward an eventual galactic merger. The Sun has never been stationary and never will be. The layers of motion simply were not visible until we developed the instruments and theoretical frameworks to detect them, a process that began with Copernicus removing Earth from the center of the universe and has continued with spacecraft like Gaia mapping the positions and velocities of billions of stars across the Milky Way.