The Sun does not orbit a black hole in the way the Earth orbits the Sun, but it does orbit the center of the Milky Way galaxy, a region that contains the supermassive black hole known as Sagittarius A\ (Sgr A\). This orbit is governed by the combined, distributed gravity of the entire galaxy’s mass, not solely the black hole. Our solar system’s path is determined by billions of stars, vast clouds of gas and dust, and Dark Matter.
The Supermassive Black Hole at the Center of the Milky Way
The object at the very heart of the Milky Way is Sagittarius A\ (Sgr A\), a supermassive black hole located approximately 26,000 light-years from Earth. Its mass is roughly 4 million times that of our Sun. Although it does not emit light, it is observable because of the intense radio waves and X-rays emitted by hot gas spiraling toward it.
The presence of this object was confirmed when astronomers tracked the orbits of stars extremely close to the Galactic Center. Stars like S2 follow highly elliptical paths, whipping around Sgr A\ at speeds up to 17 million miles per hour. Analyzing these tight, fast orbits allowed researchers to calculate the mass and size of the unseen object. This evidence solidified the conclusion that Sgr A\ is a supermassive black hole, confined to a space smaller than the orbit of Mercury.
The Sun’s Actual Orbit Through the Galaxy
The Sun is currently situated in one of the Milky Way’s minor arms, the Orion Arm. Our solar system is in constant motion, revolving around the Galactic Center in a vast, nearly circular path. The Sun travels at approximately 140 miles per second (220 kilometers per second).
Despite this incredible velocity, the sheer size of the galaxy means one full circuit takes an enormous amount of time. The time required for the Sun to complete a single orbit is known as a Galactic Year, estimated to be about 225 to 250 million Earth years. Since its formation 4.6 billion years ago, the Sun has completed only about 20 such orbits.
The Sun’s orbital path is far more complex than a simple flat circle, as it also moves vertically relative to the galactic plane. As the solar system travels, it oscillates up and down, crossing the plane of the Milky Way’s disk like a horse on a carousel. This wave-like motion, or “bobbing,” has a period of approximately 60 million years.
Understanding Galactic Gravity and Mass Distribution
The Sun’s orbit is controlled by the gravitational pull of all the material within its orbital path, not primarily by the central black hole. Galactic motion dictates that a star orbits the total mass enclosed inside its trajectory. This enclosed mass includes billions of stars, interstellar gas and dust, and the dominant presence of Dark Matter.
The collective mass of this distributed material within the Sun’s 26,000 light-year radius orbit is immense, totaling hundreds of billions of solar masses. In contrast, the 4 million solar masses of Sgr A\ represent only a tiny fraction of the galaxy’s total gravitational influence at our distance. If the central black hole were to suddenly vanish, the Sun’s orbit would remain virtually unchanged.
Our stable orbital path is a direct result of this widely distributed mass, not a single, concentrated object. The gravitational force from any object diminishes rapidly with distance, following an inverse square law. Therefore, at 26,000 light-years away, the gravitational pull of the entire galaxy is the determining factor.