According to various scientific investigations that point to where comets originate , they are primarily from two zones: the Oort cloud, located between 50,000 and 100,000 AU from the Sun, and the Kuiper belt, located a little further from the orbit of Neptune.
In this sense, it is understood that long-lived comets originate in the Oort cloud, named after the astronomer Jan Hendrik Oort. This cloud consists of remnants from the concentrated solar nebula. This means that many comets that approach the Sun follow elliptical orbits so long that they only return after thousands of years. Furthermore, studying them helps us understand more about the origin of water and its relationship to comet formation.
When a star transits too close together in the solar system, the Oort cloud areas of comets are disrupted: some are thrown out of the solar system, but others decrease their orbits. To expose where short-cycle comets, such as Halley, originate, Gerard Kuiper proposed the existence of a belt of comets installed beyond Neptune, and this was named the Kuiper belt.
where do comets originate
The orbits of comets are tenaciously varied: their origins lie in the outer solar system, and they are prone to being profoundly disturbed (or disrupted) by close approaches from the major planets. Some are tucked into orbits very close to the Sun and are destroyed upon approach, while others are ejected from the solar system for good. You can read more about the composition of comets and their formation in this context, which helps us to better understand them.
Likewise, if their space is elliptical and of long or too long phase, they come from the hypothetical Oort cloud, but if their orbit is of short or medium-short cycle, they descend from the Edgeworth-Kuiper belt, although there are irregularities such as that of Halley, with a course of 76 years (short), which comes from the Oort cloud.
As comets grow larger, approaching the Sun and completing their orbits, they accumulate material and consequently shed it, diminishing in size. After a certain number of orbits , the comet will have "extinguished," and when the last volatile raw materials are depleted, it will transform into a standard, ordinary asteroid, as it will not be able to return to regain its mass. Examples of comets lacking these volatile raw materials include 7968 Elst-Pizarro and 3553 Don Quixote.
composition of comets
Comets can reach diameters of several tens of kilometers and are composed of water, methane, iron, magnesium, dry ice, ammonia, sodium, and silicates. Thanks to the low temperatures of the regions where they are found, these components are frozen . Research into the composition of comets has revealed much about their nature and how they might have influenced our planet.
Some studies suggest that the elements found in comets are organic matter and have crucial implications for life, implying that in the early stages of the creation of worlds, they impacted Earth and provided the origin for living beings. This is related to the mystery of space.
When a comet is revealed, it appears as a bright spot, with a visible stream of light against a background of stars known as 'fixed' stars. The first thing visible is the comet's axis, or coma; later, as the comet approaches the Sun , it begins to display what we commonly call the comet's tail, which gives it a magnificent appearance.
As the comet approaches the Sun, its nucleus becomes extremely hot, causing the ice to melt and vaporize. This vapor then flows backward, forming a tail that points away from the Sun and extends for millions of kilometers.
Similarly, comets exhibit different types of tails. The most common are the dust tail and the gas tail . The gas tail always extends in the opposite direction to sunlight, while the dust tail originates from the comet's orbit, positioned between the main tail and its trajectory. To better understand this phenomenon, you can review our article on why comets glow and how this relates to their evolution.
The encounter of photons that this object receives from space, like a shower of heat, contributes a sufficient amount of light, perceptible when observing the comet's display, thus irradiating every dust atom with sunlight. Furthermore, it is important to note that a third type of tail, composed of sodium ions, was observed in Comet Hale-Bopp .
Furthermore, these tails can extend enormously, reaching millions of kilometers in length. For example, when we mention Comet 1P/Halley, in its 1910 appearance, the tail was estimated to be around 30 million kilometers long, a fifth of the distance from the Earth to the Sun.
Similarly, each time a comet passes by the Sun it is damaged, because the material it sheds is never replenished. It is expected that, on average, a comet will pass close to the Sun about two thousand times before becoming completely decayed. Along a comet 's path , it sheds large amounts of small pieces of material; when almost all of its material has been shed and it no longer has enough to maintain its atmosphere, it is said to be a dead comet.
Other data where do comets originate
According to other similar studies, there is one more issue to explain. Given the low mass of the Oort Cloud , comets did not form there. The established standards explain this phenomenon by assuming that during the formation of the Solar System, when the celestial bodies formed, their immense masses disrupted the orbits of the previously formed comets, pushing them to the outer reaches of the Solar System. You can investigate further the role of cosmic dust in this phenomenon, which is essential for understanding it.
In this regard, recent research has focused on the theory that some of the comets appearing in the Oort Cloud actually originated in other celestial systems. When stars are born, they typically do so in large , closely spaced clusters of stars.
Subsequently, these stars move apart, each beginning its own progressive journey. Throughout its orbit around the Milky Way , the Oort Cloud of our Solar System may have interacted with the cloud of other stars, resulting in a reciprocal flow of comets. For more information, you can consult our article on comets that approach Earth.
To explain where short-lived comets like Halley's Comet originate, Gerard Kuiper proposed the existence of a belt of comets located beyond Neptune, the Kuiper Belt. Kuiper conjectured that the mass of Pluto (at that time overestimated) would disrupt the orbits of these small bodies, exciting them toward the inner Solar System.
Furthermore, the now-accepted theory was proposed in the 80s by Julio Fernández, based on the idea that if a region between 35 and 50 AU from the Sun had a mass roughly ten times that of Earth, organisms with masses similar to those of asteroids could have been created. These asteroids could then be disrupted by Neptune, causing them to explore the inner Solar System and better understand its environment. To learn more about trans-Neptunian objects , you can read our dedicated article.
However, the story doesn't end there. There are still more areas that can reveal where comets originate. Specifically, in the late 1990s, the first agglomerated asteroid (as they are called) was revealed, visibly displaying a dust tail . This asteroid, which aspired to be a comet, was nicknamed 133P/Elst-Pizarro, and since then, nine other objects of this type have been observed.