Yes, asteroids and comets do hit the Sun, but the objects that actually strike the Sun are rare, and the vast majority of them are comets. An asteroid is a rocky body, primarily found in the main belt between Mars and Jupiter, while a comet is a mixture of ice, dust, and rock originating from the colder outer reaches of the solar system. While both types of objects orbit the Sun, they follow very different paths, and it is the comet’s highly elongated trajectory that makes it far more likely to plunge toward our star. The physics governing all solar system bodies dictates that direct impact is an unlikely outcome, requiring a significant shift from a stable orbit.
Solar System Stability and Orbital Mechanics
The reason most objects, including planets and the vast majority of asteroids, do not simply fall into the Sun is due to a delicate balance between two forces. The Sun’s immense gravitational pull constantly accelerates everything toward its center, which is the force that defines an orbit. However, every object also possesses a “sideways” speed, or tangential velocity, a relic of the solar system’s formation.
This sideways motion is the physical expression of angular momentum, a conserved quantity in physics that resists changes to an object’s rotation or orbit. An object in a stable orbit is constantly falling toward the Sun, but its velocity is so great that it continually misses, resulting in an elliptical path. To hit the Sun directly, an object must lose almost all its angular momentum, effectively removing its sideways speed.
The solar system’s major bodies, like planets, are in nearly circular orbits, meaning their angular momentum is extremely high and well-conserved. Therefore, a massive, long-term disruption is necessary to knock a stable planet or a main-belt asteroid onto a collision course. This explains why the inner solar system, with its established, low-eccentricity orbits, is generally safe from impacts. The fact that the Sun’s gravity is the only significant force on these bodies means their orbits will remain predictable for billions of years unless a major planetary encounter occurs.
Asteroids Versus Comets: Defining Sun-Grazers
Comets dominate the conversation about objects striking the Sun due to their distinct composition and orbital paths. Asteroids are primarily composed of rock and metal, formed in the warmer inner solar system, and tend to maintain relatively stable, low-inclination orbits within the Asteroid Belt. Comets, conversely, are icy “dirty snowballs” originating from the frigid Oort Cloud or the Kuiper Belt, regions far beyond the planets.
These distant origins mean that comets are often perturbed into highly eccentric, elongated orbits that can loop far into the outer solar system before swinging dramatically close to the Sun. It is these comets that are classified as “Sun-grazers,” defined as small bodies that pass within approximately 850,000 miles of the solar surface. While a tiny fraction of rocky objects may also follow such a path, Sun-grazers are almost exclusively cometary in nature, making them particularly susceptible to the Sun’s heat.
A specific family of these objects, the Kreutz group of Sun-grazing comets, accounts for about 85% of all comets observed near the Sun. These fragments are believed to have originated from a single, giant comet that broke apart centuries or millennia ago. Their existence confirms that comets are inherently more fragile and prone to orbital paths that bring them into the Sun’s immediate vicinity than their rocky counterparts.
The Mechanisms That Send Objects Sunward
The journey toward a solar collision requires a mechanism to strip an object of its stabilizing angular momentum. The most common trigger for this is gravitational perturbation, often involving a close encounter with a massive planet like Jupiter. The immense gravity of the gas giant can act as a sling-shot, dramatically altering a comet’s path and sending it on a plunging trajectory toward the inner solar system.
For smaller, rocky bodies like asteroids, a subtle yet continuous force known as the Yarkovsky effect can be the culprit. This effect is a non-gravitational force caused by the asymmetrical re-emission of heat from an asteroid’s surface as it rotates. If an asteroid is a retrograde rotator, spinning opposite to its orbital direction, the thermal thrust acts as a miniature brake, causing it to very slowly spiral inward toward the Sun over millions of years.
The fragmentation of a larger body also provides a steady source of sunward material. As comets enter the inner solar system, the heat and tidal forces cause them to break apart into smaller pieces, such as the fragments of the Kreutz group. These smaller bodies, having less mass, are then more easily influenced by gravitational and non-gravitational forces, accelerating their eventual demise toward the Sun.
The Final Moments: Vaporization and Disintegration
For the rare object that does get sent sunward, a direct impact with the Sun’s photosphere is often avoided because the object is destroyed before contact. As a comet approaches the Sun, the intense solar radiation causes the frozen ices to rapidly sublimate, turning directly into gas. This process creates the spectacular cometary tail and also causes the body to disintegrate, often miles above the solar surface.
The Sun’s powerful gravity exerts extreme tidal forces on any body that gets too close, stretching and tearing apart the nucleus in a process known as tidal disruption. This force can overwhelm the object’s own weak gravity that holds it together, shattering it into a stream of smaller fragments. Observatories like the Solar and Heliospheric Observatory (SOHO) frequently document these final moments, capturing images of comets disintegrating within the solar corona, the Sun’s outer atmosphere.
These observations confirm that the fate of most Sun-grazers is not a solid impact, but a fiery vaporization and dispersal into the solar wind. For instance, Comet C/2011 N3 was tracked by SOHO as it plunged to within 62,000 miles of the Sun’s surface before its signal disappeared entirely. While the material from the object ultimately joins the Sun’s plasma, the original body ceases to exist long before it can make physical contact with the star itself.