This attempt is to prepare for preventing other near-Earth asteroids from hitting the earth. Dual planetary system, taken about 2 and a half minutes before the impact Source/NASA.

text/Christine

At 7:14 am on September 27, 2022, the Mission Control Center of the Applied Physics Laboratory of Johns Hopkins University announced that the mission of the DART spacecraft launched by NASA to impact an asteroid 11 million kilometers away from the ground has been successfully completed.

This attempt was made in preparation to prevent other near-Earth asteroids from hitting the earth. This is also the first time that humans have launched a planetary defense test.

The impact of the asteroid does not threaten the safety of the earth.

00 In the past decade, the asteroid monitoring plan launched by humans is to prevent the tragedy of the "Xicthulub asteroid impact" incident 65 million years ago. According to statistics, more than 25 million celestial bodies of size that are enough to threaten the earth have been found. Judging from statistics from 1980 to the present, the discovery speed of near-Earth asteroids is still increasing exponentially. They move very quickly, most of them reaching about 72,000 km/h.

Scientists have indeed monitored that many asteroids once threatened the earth, but in the end they all missed each other. But no one can tell whether the next near-Earth asteroid will suddenly hit the earth.

Many movies are imagining the occurrence of this event. For example, in the recent popular " Loneliness Moon ", it describes the situation where an asteroid almost caused the destruction of humans on Earth after hitting the earth.

It is this concern that prompted NASA to implement this asteroid defense plan. Compared with the rocket fairing that encapsulates it, the

However, the asteroid selected this time does not threaten the earth from the original observed orbit. It is an asteroid in a dual planetary system called Didymos, called Dimorphos, with a diameter of about 163 meters.

Another asteroid in the same system is larger, with a diameter of about 780 meters. Currently people call them "twin stars" and "twin stars". During the DART impact, the Didymos system was about 11 million kilometers away from the earth.

One of the reasons why they were chosen is that the size of this twin star is similar to that of many NEO bodies. Judging from the near-Earth celestial bodies that have been discovered so far, there are about 1.2 million like twin stars with diameters greater than 0.5 kilometers; while twin stars with diameters greater than 0.1 kilometers have been observed.

In addition, the location of this dual planetary system is not far or near to the Earth. They are located at a distance of about 28.6 earth and moons. Even if the orbits change after being impacted, they will not pose a real threat to the earth for a while.

But this distance is one fifth of the closest distance between Earth and Mars . Human current technology can be reached without too much effort.

, and this location is also convenient for shooting and observation on the Hubble Space Telescope, Weber Space Telescope on Earth, NASA's asteroid probe "Lucy" and most astronomical telescopes on the ground.

DART spacecraft is destined to "sacrifice"

. DART, a spacecraft that hits an asteroid, has a volume (length, width and height) of only 1.8 meters x 1.9 meters x 2.6 meters, and costs about US$325 million (approximately RMB 2.324 billion).

In order to fly independently, DART is equipped with two large solar panels , and the "armspan" can reach about 19 meters when it is fully expanded. It was launched at 1:21 a.m. on November 24 last year (East Time). The Falcon 9 rocket equipped with SpaceX was launched at Vandenberg Air Force Base, California.

Since DART is destined to "sacrifice" after this impact, it also carries a "little assistant" to record the moment and photos after it hit.

This "little assistant" is Cube Star LICIACube. It looks like a small box. It can detach the DART and adjust orbital flight with its own propulsion system.

DART had been traveling in space for 10 months before this impact. The only instrument it carries is the optical navigation camera DRACO. While it is constantly approaching the asteroid, it is also constantly capturing images of the two asteroids. It will also support the spacecraft's autonomous navigation system SMART Nav, guiding the DART to impact.

and cubic star LICIACube separated from DART on September 11, and finally approached the impact site again for on-site recording.

At present, all data is still being received because LICIACube does not carry large antennas and the images it takes will be transmitted back to Earth one by one in the next few weeks.

LICIACube's image will be with the images returned by DRACO to provide us with an intuitive view of the impact of collisions, helping researchers better describe the effectiveness of kinetic energy impacts when deflecting asteroids.

Of course, the purpose of DART's impact is to change the trajectory of this asteroid. When it hits the twin star at a speed of 6.6 km/s, the twin star's orbital speed is expected to change by 0.1%.

has been successfully completed. As for whether the orbital velocity of the twin stars has changed, it remains to be proved by the observation data obtained through the astronomical telescope in the next step.

This is not the first time that a spacecraft hits a celestial body

Although the planetary defense plan is launched for the first time, DART is not the first human spacecraft like DART that actively collided with outer space stars.

Before this, Deep Impact and Hayabusa 2 both hit the stars in outer space. But their purpose is different from DART.

For example, "Deep Impact" is a comet probe of NASA. It is designed to study the core components of the Temple 1 comet .

The detector was successfully launched on January 12, 2005. On July 3 of the same year, a 372-kg copper bomb was released, hitting the nuclear of comet . Observers on Earth received information about the impact event 8 minutes after the impact was completed.

That was the first human being to actively arouse the detection of the surface matter of Comet , costing about US$330 million.

and "Halababu 2" is an asteroid probe launched by Japan's aerospace research and development agency . It was launched from the H-2A launch vehicle at 12:22 Beijing time on December 3, 2014, and was launched from the Seed Island Cosmic Center. In mid-2018, he met and probed the asteroid 1999 JU3 (Dragon Palace).

In April 2019, "Falaenor 2" fired a metal bomb at the surface of "Ryugu", causing an impact crater about 10 meters wide. The detector then collected the material aroused by the metal bomb and carried the sample material back to Earth at the end of 2020.

June 6, 2022, according to Japanese media reports, "Halababu 2" discovered the "source of life" - amino acid from the sand sample brought back to the earth from the asteroid "Ryugu". This is the first time that the presence of amino acids is confirmed outside the Earth, and it is of great significance to understand how these crucial organic molecules arrive at the Earth.

On September 23 this year, the Japanese Aerospace Research and Development Agency announced that the rock samples of the asteroid "Ryugu" brought back to Earth by Hayabusa 2 also contain liquid water.

, and the DART spacecraft in this mission completed the world's first autonomous impact demonstration of planetary defense technology. It will provide scientists with key data on developing planetary defense plans.

The completion of this project is not only an exciting moment for NASA, but also for aerospace history and human history. This exercise is extremely important to the future of the earth.

researchers believe: "Planetary defense is a project that requires joint global efforts and affects everyone on Earth." About four years later, the "Hera" mission of the European Space Agency (ESA) will also conduct a detailed investigation of the two asteroids, especially the craters left after the DART impact. In addition, they will also conduct accurate measurements of the mass of Dimorphos. (For more news, please follow Yangchengpai pai.ycwb.com)

Source | Yangcheng Evening News·Yangchengpai

Editor | Yizhina

Proofreading | Xie Zhizhong