The Sun, a G-type main-sequence star, is the gravitational anchor and energy source for our entire solar system. Its diameter of approximately 1.4 million kilometers makes it seem like an object of unimaginable size, capable of containing over a million Earths. Despite its local dominance, the Sun is merely a medium-sized star in the broader context of the universe. When looking beyond our stellar neighborhood, the answer to whether anything is bigger than the Sun is a definitive yes. The cosmos is populated by objects and structures, from individual stars in later stages of life to massive collections of billions of stars, built on a scale far grander than our solar system suggests.
Stars That Dwarf Our Sun
The Sun’s modest size is a consequence of its classification as a main-sequence star, fusing hydrogen in its core for billions of years. Stars that begin with greater mass evolve quickly and expand dramatically into giants, supergiants, and hypergiants. This expansion occurs when the star exhausts its core hydrogen fuel and begins fusing hydrogen in a shell, causing the outer layers to swell outward.
The most physically enormous stars are typically red supergiants or hypergiants, which are among the largest objects by volume in the universe. A well-known example is Betelgeuse, a red supergiant in the constellation Orion, which has a radius roughly 764 times that of the Sun. If Betelgeuse were placed at the center of our solar system, its outer atmosphere would extend past the orbit of Mars and potentially reach the asteroid belt.
Even Betelgeuse is significantly smaller than the current record holders for stellar size. The red hypergiant UY Scuti, located thousands of light-years away in the constellation Scutum, holds an estimated radius up to 1,700 times that of the Sun. If the Sun were replaced by UY Scuti, the star’s surface would likely engulf the orbits of Jupiter and Saturn, completely swallowing the inner planets.
Another contender is Stephenson 2-18, a red supergiant whose size estimates are somewhat uncertain due to its distance and obscuring dust, but which may possess a radius up to 2,150 times greater than the Sun. If Stephenson 2-18 were centered in our solar system, its sheer volume is so immense that it could contain nearly 10 billion objects the size of our Sun.
Understanding the Scale of Black Holes
Black holes present a unique comparison because their size is defined by their mass, not their physical matter. Stellar-mass black holes, which form from the collapse of a single massive star, typically have an event horizon—the point of no return—that is only tens of kilometers in diameter, making them physically smaller than the Sun. Their influence and mass, however, define their immense scale.
The Supermassive Black Holes (SMBHs) found at the centers of nearly all large galaxies are where the size comparison truly surpasses the Sun. Our own Milky Way galaxy hosts Sagittarius A (Sgr A), an SMBH with a mass approximately 4.3 million times that of the Sun. Despite this enormous mass, the event horizon of Sgr A has a diameter of only about 44 million kilometers, which is roughly 30 times the diameter of the Sun.
This physical size remains relatively small; if Sgr A were placed at the center of our solar system, its event horizon would still be smaller than the orbit of Mercury. The true scale of an SMBH is measured by the gravitational influence it exerts over millions of stars and vast clouds of gas and dust.
The Immense Size of Galaxies
The next significant jump in scale involves moving from individual celestial objects to the vast collections of stars, gas, dust, and dark matter known as galaxies. Our Sun is merely one of the estimated 100 to 400 billion stars that make up the Milky Way galaxy. Measuring a galaxy’s size requires a different unit entirely: the light-year, the distance light travels in one year.
The Milky Way is a barred spiral galaxy with a diameter estimated to be around 100,000 light-years. This means light takes 100,000 years to travel from one edge of our galaxy to the other. Compared to the Sun’s diameter of 1.4 million kilometers, the galaxy’s size represents a scale increase of many orders of magnitude.
Even the Milky Way is not the largest galaxy in the universe. Some elliptical galaxies, which are thought to form through the merger of smaller galaxies, are dramatically larger. The galaxy IC 1101, located over a billion light-years away, is an example of a supergiant elliptical galaxy.
The size of IC 1101 is subject to varying measurements, but the most massive estimates place its diameter at up to 4 to 6 million light-years across. This single galaxy could contain more than 60 times the volume of the Milky Way, holding an estimated 100 trillion stars.
Structures That Define the Cosmos
The ultimate scale in the universe is defined not by single galaxies, but by the massive structures they form through gravitational clustering. Galaxies are not scattered randomly but are grouped into galaxy clusters, which contain hundreds or even thousands of individual galaxies. These clusters, in turn, are bound together into even larger groupings called superclusters.
Our home supercluster is named Laniakea, a Hawaiian word meaning “immense heaven.” This structure encompasses the Milky Way and approximately 100,000 other galaxies, stretching across an estimated 500 million light-years of space. Superclusters are themselves arranged along vast, thread-like formations called cosmic filaments, which are the largest observable structures in the cosmos.
These filaments and the immense, empty regions they surround, known as voids, form a foam-like pattern called the cosmic web. This web represents the large-scale structure of the universe, with filaments acting as boundaries between the largest voids. Defined by distances measured in hundreds of millions and even billions of light-years, these superstructures are the most expansive cosmic entities known to science.