In space, astronomers find countless different objects. These are stars, exoplanets, nebulae, asteroids, quasars. Some of these objects are in certain orbits. Are any celestial bodies moving in orbits around the stars?
What is a celestial body in circumstellar orbit?
First you need to consider what the concept of "orbit" means. This is the trajectory along which the celestial body rotates. For example, the Earth revolves around our sun - the sun. Around the Earth, in turn, the Moon makes its way. A celestial body in a circumstellar orbit can be, firstly, a planet, and secondly, an asteroid, as well as a comet. Smaller celestial bodies are not considered by astronomers here, since they are included in the category of space debris. After all, their orbits due to the small mass of such celestial bodies will not have the main property - periodicity. Any body of greater mass will be able to influence the trajectory of their movement - up to a complete stop.
Also, the Earth's satellites created by man have constant orbits. In shape, they resemble elongated ellipses. The closest point in the orbit is perigee, and the farthest is the apogee. Each celestial body in the circumstellar orbit of the Sun moves in the same direction. This is an amazing fact about the solar system, which is a proof of one of the hypotheses of its origin. According to this theory, the solar system arose from a cloud of dust and gas. In addition to thousands of small planets, even asteroids are moving in the same direction.
Asteroids in the Solar System
Scientists call asteroids celestial bodies whose diameter exceeds 30 meters. They, in turn, may have their own companions. The word "asteroid" was proposed by composer Charles Burney and astronomer William Herschel, it means "like a star." When observing asteroids, their appearance practically did not differ from stars. Stars looked like shining disks, and asteroids appeared as luminous dots. Currently, the so-called asteroid belts are of serious scientific interest to astronomers . They are one of the largest space objects in the solar system. Inside the solar system is the main asteroid belt, located between the orbits of the planets Mars and Jupiter.
Comets - celestial bodies with a trajectory
What other celestial body can be found in circumstellar orbit? The answer may seem surprising, but it is a comet. These celestial bodies also rotate in orbits around the sun. Translated from Greek, "comet" means "shaggy star." As you approach the Sun, the comet becomes brighter, and its foggy part stretches. Bright comets can be seen in the sky with the naked eye. The periods of rotation of these celestial bodies around the Sun can range from several years to entire decades.
When a comet is far from the Sun, it is invisible from Earth. And approaching, it becomes available to the ordinary observer. For the first time, the frequency of rotation of comets around the Sun was discovered by the scientist Halley in the 17th century. Watching one of the comets, he found out that it moves according to the same principle as other planets of the solar system. Halley predicted the comet's return date for Earth observers. The scientist’s prediction brilliantly came true.
Scientists find: an asteroid in the orbit of a dying star
In October 2013, astronomers discovered a celestial body in the circumstellar orbit of one of the distant dying stars. The luminary under the name G61 already belongs to the group of white dwarfs and is removed from the solar system at a distance of about 150 million light years. The celestial body that revolved around this star turned out to be an asteroid, on which scientists discovered a huge amount of water reserves. This discovery allowed astronomers to suggest that once inhabited planets like ours could exist in this system.
This case is the first when two key conditions for the emergence of life were discovered outside the solar system - a rocky surface and water that a celestial body possessed in circumstellar orbit. This suggests that once there was life. What forms it could take in this system - scientists can only guess. Analysis of the dying asteroid showed that it consisted of 26% water. In this way, it resembles the dwarf planet of the solar system - Ceres. Both in the asteroid found and in Ceres, the relative mass of water on them is much larger than on Earth.
G61 and the celestial body in circumstellar orbit - the answer lies in the future of the Earth
Earth is essentially a dry planet. Only 0.02% of its total mass is water. Scientists are sure that the oceans appeared after the Earth was formed. According to researchers, a large number of water-rich asteroids could collide with Earth. Having first found such a celestial body in circumstellar orbit, scientists made conclusions about the possible future of mankind. They suggest that after 6 billion years, alien explorers will likewise study rocky fragments revolving around our dying Sun and come to the conclusion that life could once exist on Earth.