Comets are usually the smallest space objects in our system. Their diameter is only a few kilometers away. Since comets are composed of a mixture of ice and solid components, it is closer to the sun, they lose weight rapidly, leaving a trail of gas-dust - to whom.
The main asteroid belt is called the region located between the orbits of Mars and Jupiter, and are repositories for a set of objects of various sizes. They are mostly irregular in shape and most often identified as asteroids or minor planets. First the main asteroid belt has been described in the middle of the XIX century in the book Alexander von Humboldt Kosmos. The plan describes the physical world.
The total mass of the objects of the main belt is about four percent of the mass of the Moon, and more than half of its accounts for the four largest objects in this cluster: Ceres, Pallas, Vesta and Gigeyu. The average diameter of the asteroid more than 400 kilometers, the diameter of the largest of them, Ceres, which is the only dwarf planet in the zone, is more than 950 kilometers. At the same time other dimensions of bodies whose asteroid belt several million, significantly less of the smallest diameter of which is several tens of meters.
The belt is that the objects are not dumped in a heap, and highly dispersed throughout a given region of space. The reason for such low density that the gravitational field of Jupiter at the time made adjustments to the orbit of planetesimals. As a result, most of them broke up into fragments and was either thrown out of the solar system, or passed on elongated orbits.
Until recently, scientists believed that in the main asteroid belt comets are missing. However, according to the model developed by Colombian researchers who studied a group of newly discovered belt objects, there may be a large number of cometary bodies in a state of hibernation, and once the belt and all was full of active comets.
Most comets have orbits vysokoelliptichnymi, so they appear near the sun rarely and for short periods. Other bodies are required for this, even in terms of thousands of years, although there are about 500 korotkoperiodichnyh comets. They became such, flying too close to Jupiter, the gravity of which changed their trajectory.
Over the last decade has been opened another kind of main-belt comets - they have orbits, like asteroids, but still have the cometary nature. Scientists have long been able to explain their existence. We found that some of these objects is not dead, like comets, but only sleeping and could return to life if the energy they receive from the Sun will gradually grow - says Ignacio Ferrin. - And that is what we are witnessing today in the main asteroid belt.
It should be noted that the main-belt comets do not have tails, because due to their proximity to the Sun, the upper layers have lost their icy component.
If the flux of solar radiation increases, the deeper layers of the comet can warm up so that the gases began to retreat. As a result, the body is not only regain the status of a comet, but even leave the main belt. According to the authors, in addition to the already known dozens of resurrected comets in the zone there are others that are dormant. But assessing their number only after careful observation.
Moreover, according to the astronomers, millions of years ago, thousands remained in the zone of active cometary bodies, the aging often hibernate. We are still able to capture only the twelve, who, under the influence of Jupiter#39;s gravity began to actively move closer to the Sun at perihelion and as a result were able to restore your heating comet status. Meanwhile, the number of comets, which are still asleep, but in the long term and may rise again, it may be quite impressive.
