For the past seven years, the wreckage of the SpaceX Falcon 9 rocket has been silently orbiting the Earth in orbit, and its presence is almost "unattended." But its fate has recently changed, and it was predicted to hit the moon, attracting the attention of astronomers around the world. Astronomers say this will be the first known accidental collision of a rocket with the moon.
On January 21, astronomy research software developer Bill Gray posted on social platforms: "The wreckage of the 4-ton Falcon 9 rocket will hit the far side of the moon at 7:25 (Eastern Time) on March 4, leaving a 20-meter-sized crater." ”
On the 26th, this prediction was confirmed by McDowell, a professor at the Harvard-Smithsonian Center for Astrophysics, on Twitter: "There will indeed be an impact on March 4. ”
Gray said: "Although there is some uncertainty about the timing and location of the collision, it is inevitable that the rocket wrecks collide with the moon. The collision will occur within a time error of a few minutes and a distance of several kilometers. ”
It is reported that the Falcon 9 rocket was used by SpaceX, founded by Elon Musk, in 2015 to launch the Deep Space Climate Observatory (DSCOVR) satellite for the U.S. Oceanic And Atmospheric Agency (NOAA), which is responsible for monitoring the solar wind from the sun to better predict space weather.
Space X starship test-launched in Texas, USA, on November 12, 2021.
Why crash
After sending the satellites into orbit, the rocket wreckage is usually sent back to Earth's atmosphere by SpaceX, where it burns and disappears due to frictional heat with the atmosphere.
But after the Falcon 9 rocket sent the satellite into orbit about 1.5 million kilometers away from Earth, it did not have enough fuel to return to Earth and was "abandoned" in a high orbit in space. In this way, it looped through the Earth-Moon system in a long, circular orbit for nearly seven years.
Professor McDowell said: "Due to fuel depletion, the upper end of the rocket is dead, it is just following the laws of gravity" and "since 2015, the rocket has been pulled by the different gravitational pulls of the Earth, the Moon and the Sun, making its path chaotic".
The trajectory of the upper end of the Falcon 9 rocket, which approached the moon on January 5 this year, is expected to collide with the moon on March 4 after approaching Earth on the 21st.
A space object in low orbit around the Earth that collides with the International Space Station or satellite could pose a danger, but because the falcon 9 rocket is located very far from Earth, it is forgotten and no one is worried about it. Gray said: "I was the only one tracking the object. ”
After seven years, the aimless wandering life is finally coming to an end.
Gray said the upper part of the rocket passed less than 10,000 kilometers from the moon on the 5th. Gray believed that the upper end of the rocket would pass through an orbit close to Earth, so he commissioned astronomers to make observations. Gray predicted from the data collected that March 4, at 7:25 a.m. (Eastern Time), would be the end of its life, when it would collide with the moon and explode itself on contact.
The scene observed on the 20th of this month from the upper end of the Falcon 9 rocket. The dotted line from the bottom right to the top left of the frame is the upper part of the rocket.
What are the consequences
"It's fun, but it's not a big deal," Professor McDowell wrote on Twitter.
Many spacecraft have hit the moon so far, but this is the first accidental impact that is not planned. NASA has previously deliberately sent rocket parts and spacecraft to hit the moon.
In February 2009, a spacecraft sent by NASA hit the moon.
"Since the collision occurred on the far side of the moon, the impact was not visible from Earth. But determining its timing and location is still important, which could provide scientists with the opportunity to study below the lunar surface, with NASA's Lunar Reconnaissance Orbiter (LRO) and India's Chandrayaan 2 expected to observe craters created by collisions," Gray wrote. The collision is expected to leave a 10-20 meter crater on the moon.
Gray said that while there is nothing to worry about, the incident is a good reminder that we need better ways to deal with space junk.
Such objects are usually abandoned in extremely long orbits around the Earth, and if they come back and hit us, they will come in at a faster speed and at a more perpendicular angle to the atmosphere, and some debris is more likely to survive re-entry into the atmosphere.
Gray said: "If they do enter and hit Earth, there is a very small probability that there is a very small probability that a small percentage will survive and crash into the ground." ”
Of course, since such incidents are extremely rare, they do not pose any real threat to people at the moment.
"It's better for it to hit the moon than to let it hit Earth, either from a safety standpoint or because we can't learn much interesting things if it hits Earth," Gray said.
Lunar landscape in view of southern France on May 13, 2019.
Author | Tang Xing
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