The largest comet ever is heading toward the solar system! Will it hit the Earth?

◎ Sun Yu, intern reporter of Science and Technology Daily

On April 12, NASA's Hubble telescope confirmed the discovery of the largest comet ever seen. This "giant" comet is numbered C/2014 UN271, and its nucleus (the solid part at the center of the comet) is about 80 miles (about 128.7 kilometers) in diameter, 50 times that of most known comets, and its overall mass is about 500 trillion tons, 100,000 times that of an average comet.

The comet is reportedly traveling toward the inner solar system at a speed of 22,000 miles per hour (35,405.6 kilometers per hour). NASA predicts that the comet will reach perihelion, its closest point to the sun, in 2031 - about 1 billion miles (1.6 billion kilometers) from the orbit of Saturn.

Breaking the records of "biggest" and "farthest"

"This comet has aroused great interest among scientists. It has broken two records in human's current understanding of comets." Zhao Yuhui, a researcher at the Planetary Science and Deep Space Exploration Laboratory of Purple Mountain Observatory, Chinese Academy of Sciences, told Science and Technology Daily that this comet is the largest comet discovered by humans so far and is also the farthest comet from us when it was first observed.

NASA's website shows that the comet was discovered in the Dark Energy Survey observation data when it was about 3 billion miles (about 4.8 billion kilometers) from the sun, close to the distance of Neptune from the sun.

When asked why C/2014 UN271 is so large, Zhao Yuhui explained: "On the one hand, it was already very large when it was formed in the early days of the solar system. On the other hand, it may have experienced very few external collisions during its evolution, resulting in less fragmentation, and thus maintained its initial size."

Zhao Yuhui introduced the full name of the comet to reporters: "C/2014 UN271 (Bernardinelli-Bernstein) Comet". It was numbered 2014 UN271 according to the naming rules for asteroids, and the prefix "C/" was added after confirmation to indicate a comet. Pedro Bernardinelli and Gary Bernstein, astronomers at the University of Pennsylvania, are its discoverers.

No threat to Earth, may be visible to the naked eye

This "largest comet" has also become a hot topic recently, and many people are worried about whether it will "hit the earth."

"Its closest point to the sun is near the orbit of Saturn and will not pose any threat or harm to the Earth," Zhao Yuhui emphasized.

In fact, there is no definite record of a comet hitting the Earth. The closest observational record of a comet hitting a planet dates back to the 1994 comet-Jupiter collision.

When talking about comets, it is hard not to think of Halley's, the only short-period comet visible to the naked eye.

Zhao Yuhui compared C/2014 UN271 with Halley's Comet. "Halley returns every 76 years, while C/2014 UN271 comes from the depths of the Oort Cloud and has a return period of about 3-5 million years. We can see Halley with the naked eye, but whether we can see C/2014 UN271 with the naked eye depends on its activity."

When in the outer solar system, a comet is like a "dirty snowball" of ice and dust. When it gets closer to the sun, volatile ices such as carbon monoxide, carbon dioxide and water will sublimate under the action of solar radiation, and drive the movement of dust, forming a coma and a long tail that wraps around the comet nucleus. The more active the comet is, the brighter it is.

"Considering the huge size of C/2014 UN271, if it is very active at perihelion, it is possible to see it with the 'naked eye'," said Zhao Yuhui.

Bringing ancient information across millions of years

C/2014 UN271 is currently less than 2 billion miles (3.2 billion kilometers) from the Sun. It has been on an interstellar journey for more than 1.5 million years.

"The original large comet that came from the outer solar system will bring us important information about the early history of the solar system and the formation and evolution of planetesimals." Zhao Yuhui told reporters that scientists at home and abroad will continue to pay attention to and study C/2014 UN271, hoping to learn more information from it.

"The last time C/2014 UN271 flew to the planetary system of the solar system, humans were still in the process of evolution; and we have no way of knowing what state humans will be in when it visits next time. Like many long-period comets that come from the Oort Cloud, this return of C/2014 UN271 may be humanity's only chance to catch a glimpse of it," Zhao Yuhui wrote in a popular science article last August.

Scientists also expect that man-made spacecraft will be able to conduct close-range, high-precision detection of C/2014 UN271 before or after it reaches perihelion. "In nearly 10 years, we may have the opportunity to have close contact with C/2014 UN271 through a probe," said Zhao Yuhui.

Source: Science and Technology Daily

Editor: Liu Yiyang

Review: Julie

Final judge: Wang Yu