Recently, a large comet has been fired out of the circle, it is the largest comet ever discovered by humans, and its name is C/2014 UN271.
The prefix "C/" indicates comet (Comet), and 2014 is the year to which it is named.
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On April 12, NASA's Hubble telescope confirmed that it was flying into the interior of the solar system.
So this big comet is far away, what's so special about it, where is it now, will it crash into the earth? Can we see it? Please come with me and see —
Why the attention?
What makes this comet special is that it is big, old, and far away.
★ Great
Comets are composed of three parts: a cometary nucleus, a coma, and a comet tail, and we use the nucleus to see the size.
Most of the comets that have been observed are only a few kilometers in diameter. But the nucleus of the oversized comet is 136.8 kilometers (85 miles) in diameter — 50 times larger than most comets; estimated at 500 trillion tons — 100,000 times more massive than a typical comet.
It is the largest comet object ever discovered by the Hubble Space Telescope. The previous record holder for the largest comet nucleus was Comet C/2002 VQ94, discovered in 2002, which is about 96 km (60 mi) in diameter.
https://www.nasa.gov/feature/goddard/2022/hubble-confirms-largest-comet-nucleus-ever-seen
★ Old
Comets are remnants of the early solar system, ice-cold debris left over from the formation of planets. The great comet has experienced more than 1.5 million years of interstellar travel, which means that it has existed since the early days of human evolution.
As the comet approaches the Sun's window, Earthlings have more opportunities to observe it and further obtain information about the early solar system through its data.
★ Far
When the comet was first discovered in October 2014, it was 29 astronomical units (4.3 billion kilometers) from the Sun, close to the distance between Sun and Neptune, the farthest comet ever discovered.
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★ Heavy and light
Astronomers estimate that the comet has a mass of about 500 trillion tons. What is this concept? Some people have calculated the mass of Taishan, not counting the zero, about 300 billion tons. As the saying goes, it is heavier than Tarzan, so this comet is 1700 times more massive than Tarzan, which is really heavy enough.
Compared with the 160 km diameter queen asteroid (20 Massalia), the mass of the queen star is about 520 trillion tons, and in the case of close size, the mass of this super large comet is about one ten-thousandth of that of the queen star asteroid. Although the comet is large, it is not very dense, so it is very light.
Where is it now?
According to a 2021 observation, it is close to the sun again, about 19 astronomical units (about 2.8 billion kilometers), and at that distance, the temperature is only about minus 211°C (minus 348 degrees Fahrenheit). Today the comet is falling almost perpendicular to the plane of our solar system.
It is currently moving at the edge of the solar system at 35,405 kilometers per hour (22,000 mph), which is about 35 times the speed of sound propagating through the air (340 m/s). It will continue to approach the orbital plane of the Sun for years to come, and then move away again.
Its closest distance to the Sun is also more than 1.6 billion kilometers — a little further than the average distance between the Sun and Saturn.
When will I get to Earth?
According to astronomers, in April 2031, about 10.11 astronomical units, the comet will be closest to the sun and earth.
Can it hit the Earth?
According to astronomical calculations, the great comet that arrived nine years later was not malicious — it was no closer to the Sun than saturn's orbit when it was closest, 10 times the distance between the Sun and the Earth. So unless it happens unexpectedly, it doesn't pose a threat to the planet.
In fact, although there is no exact record of "comet hitting the earth" in history, there are observational records of comet impacts on planets, that is, "comet collisions" in 1994.
In the late 1980s and early 1990s, Comet Shoemaker-Levy 9 broke into the solar system, and its original fate was to fall into the sun, but it was captured by Jupiter's gravity halfway through.
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In 1992 it had flown just 110,000 kilometers above Jupiter, a half-diameter distance for Jupiter with a diameter of 70,000 kilometers. As the largest planet in the solar system, Jupiter's gravity "tore" Comet Sumek-Levy 9 into 21 fragments, which orbited Jupiter for another two years.
The debris then crashed into Jupiter's surface for five days, causing a violent explosion. The total energy released by the impact is equivalent to a 40 trillion-ton TNT equivalent explosion. This is also the first time that humans have witnessed the rare astronomical phenomenon of celestial collisions.
Can we see it?
The only thing that can be seen with the naked eye is Halley's Comet. Humans can see Halley naked, but whether they can see C/2014 UN271 with naked eyes also depends on its activity. The more active the comet, the brighter it is.
In general, the closer to the sun, the brighter and larger the coma, reaching hundreds of thousands of kilometers in diameter, and sometimes comparable to the sun, or even exceeding the diameter of the sun.
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"Considering the size of C/2014 UN271, if it is highly active at perihelion, it is possible to see it 'naked-eye'." Zhao Yuhui, a researcher at the Purple Mountain Observatory of the Chinese Academy of Sciences, said.
With 9 years to go until 2031, our understanding of it will reach new heights as humans track it. Continental space science has developed by leaps and bounds in recent years, and I believe there will be more opportunities to study comets, asteroids and other celestial bodies, reach more distant deep space, and explore the mysteries of the infinite universe!
Expert: Yan Liu, Center for Space Application Engineering and Technology, Chinese Academy of Sciences