The Earth revolves around the Sun and orbits in the same orbit each year (in a different position in the Milky Way), but in the Orbit of the Earth, it is not only the Earth that is running, and at the Lagrange L4 and L5 points of the Earth, there are also some asteroids that are basically in common orbit with the Earth, and these asteroids are called "Trojan asteroids".
Speaking of Trojan asteroids, many friends know that there are large groups of such small bodies running on both sides of Jupiter's orbit, they are basically in orbit with Jupiter, under the influence of the common gravity of Jupiter and the Sun, asteroids running near L4 and L5 points of Jupiter, in fact, not only Jupiter, but also in the Sun and Saturn, Uranus, Neptune and other respective orbits Lagrange L4 and L5 points are also found to exist, these asteroids also belong to the Trojan asteroid type.
Earth is the fifth largest planet in the solar system (mass and volume), the Earth around the Sun also has its own Lagrange L4 and L5 points, in these two points of gravity more stable there are asteroids, they are the Earth's Trojan asteroids.
Earth's first Trojan asteroid, discovered in 2011, numbered 2010 TK7 and about 400 meters in diameter, is located at Lagrange L4 of the Helios-Terrestrial System and has been with Earth for hundreds of years.
On February 1 of this year (2022), researchers in Spain and the United States published a paper in the journal Nature Communications that they found a new Trojan asteroid, named 2020 XL5, which is much larger than 2010 TK7, with a diameter of about 1200 meters, which is considered "big" among asteroids.
The researchers used observations from large astronomical telescopes located in Chile, the United States and Spain at the L4 and L5 points of the Sun-Earth Lagrange, and with the help of computer model analysis, discovered 2020 XL5 and its characteristics, believing that it is the most common C-type asteroid in the solar system, the main components are carbon and some minerals, the surface color is black, and the reflective ability is weak, which also makes it difficult to find.
The researchers believed through analysis that 2020 XL5 was originally just an asteroid "wandering" in the solar system, but about 500 to 1000 years ago, it was captured by the earth's gravity and began to orbit the sun in nearly the same orbit as the earth, with an average distance of 1.001 astronomical units from the sun, located in front of the earth's orbit, which can be called the earth's "pawn" or "pioneer", and calculations found that it will be in orbit with the earth for at least 4000 years. Counting the 2010 TK7 discovered a decade ago, there are currently two "pawns" on Earth.
Many friends may be worried that since this asteroid is in common orbit with the earth, will it hit the earth because of the difference in the speed of the earth? This possibility is basically non-existent, because it is located at the L4 point of the Solar Lagrangian, which has the stability of the common gravitational pull of the Sun and the Earth, and most of the time it is located 90 million to 270 million kilometers in front of the Earth's orbit, so there is basically no encounter with the Earth.
However, the gravitational situation in the solar system is very complicated, even at lagrange L4 point on the sun and earth, it will also interfere with the gravitational pull of Venus, Mars, and the moon, not to mention that this asteroid also has its own operating law, observations have found that it operates in a saddle-shaped orbit, the farthest distance from the sun is about 1.39 astronomical units (solar-Earth distance), the nearest time is about 0.61 astronomical units, and the current distance from the earth is 0.68 astronomical units, about 100 million kilometers away.
The researchers believe that the above gravitational interference and its operating characteristics will eventually escape the Lagrange L4 point in 2020 and leave the gravitational control of the Earth, but this time will be at least 4000 years later.
Although scientists have only seen two Earth Trojan asteroids, it is speculated that there should be more such asteroids at the L4 and L5 points of the Heliosian Lagrangge, but they are relatively far away from the Earth, small in size, and are not easy to observe, but with the advancement of human space observation technology and the attention to such asteroids, there should be more Earth Trojan asteroids found.
Astronomers believe that the asteroid 2020 XL5 may have great uses, such as the future for human deep space exploration or interstellar travel and migration, such as gravitational wave detection and deep space optical detection, it is necessary to be far away from the earth, in fact, the position is very suitable, can be built on it large astronomical telescope or gravitational wave detection equipment, making it a natural ideal observatory.
Because 2020 XL5 is large enough, the largest or up to 900 million cubic meters, the speed is also very high, nearly 30 kilometers per second, as long as its operating speed is slightly increased, it can be far away from the solar system, then in the future, human interstellar travel, you can enter the interior of this asteroid, build a small space city in it, create a sustainable living system, and use nuclear fusion to generate energy to push the asteroid out of the solar system, or you can make it a miniature version of the "wandering earth", It can accommodate more than a hundred people to live in its interior for thousands of years, enough for a small number of humans to complete the interstellar migration.
Resources:
Guangming Network February 3, 2022 article ""Together" 4000 years, researchers have found an asteroid with the orbit of the earth"
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