Monday , November 29 2021

Bad astronomy 2020 SO may not be an asteroid, but a Centaur rocket created in 1966 from the Moon mission


Astronomers have found a small object in space that will pass through a small area that is only 50,000 km from Earth on December 1, 2020. Not only that, the gravity of our planet will change its course, it will become a temporary moon on Earth!

Here’s the real shooter: This object is almost certain no an asteroid. Instead, astronomers believe it is a worn-out rocket from the robot moon mission launched in 1966!

An object called the 2020 SO was discovered in September 2020 by the Pan-STARRS telescope. He examines the sky, partly looking for objects near the Earth. It didn’t take long to see that the orbit was weird … it was there known. Its size, shape and geometry are very close to Earth’s orbit.

It would be very unusual for an asteroid, but expect that for a reinforcing rocket or space probe. So the astronomers went back into orbit and found something amazing: in September 1966 it was very close to Earth! If it were an asteroid, then it would mean that it will overtake us, but if it were truly a space mission, that could be the launch date.

And, as it happens, there was a spacecraft was then launched: Surveyor 2, a mission to place a probe on the Moon.


In fact, it gets better. Surveyor 2 was launched on September 20, 1966, using the Atlas-Centaur rocket. The first phase of the Atlas went well, and the upper stage of the Centaur pushed the spacecraft toward the Moon. However, the midway correction made by Surveyor 2 was tilted, and the spacecraft went into a fall that could not be recovered. A few days later it hit the Moon at almost 10,000 km / h. Aupa.

But that second stage, the Centaur booster, continued. The moon passed and went to orbit the Sun.

2020 Could that Centaur rocket be?

It is very likely. The 2020 SO brightness indicates that it is something like 4-10 meters wide. The centaur is about 3×13 meters, so it fits.

And there are even more subtle reasons to think that they are the same. A very careful measurement of the orbit of the object shows that the pressure of sunlight has a very large effect. Photons taken from the sun hit and reflect against the object, changing momentum over time. This force (similar to the YORP effect) slowly changes the orbit of an object, but is more pronounced when there are fewer (so usually smaller) massive objects. A worn rocket damper is a large empty tube, so that effect should be strong … as astronomers have found.

Since the orbit of the 2020 SO is similar to that of Earth, it happens quite slowly when it overtakes each other (as two cars on a highway move fast, but one car seems to be passing at a slow pace). In November 2020 it shifted to what is called the Earth’s Hill sphere, the volume of space around the Earth where the gravity of our planet predominates over the Sun. This volume has a radius of about 1.5 million kilometers.

Normally, an interplanetary object would pass through it, but by 2020 SO the Earth is moving slowly enough to capture it … in no time. It will take about four months to make a single large loop around us, then the gravity of the Moon and Earth in the second passage will give it enough energy to escape again, turning it into a satellite of the Sun again.

As December approaches, astronomers hope to be able to obtain observations that will tell us its composition. This can cause the case.

I notice that it happened before, the old space hardware passing through Earth and initially mixed with an asteroid. We also had temporary moons! The 2020 asteroid CD3 orbited the Earth a few years earlier before launching again in 2020. Another asteroid, 2006RH120, orbited the Earth for several months in 2006/7. Yet another object (20 cm wide) was incinerated in our atmosphere as a meteorite after first putting the Earth into orbit.

These have nicknames minimums, although it is a technical term temporarily captured objects, or TCOs. It’s an oddity in orbital mechanics, but interesting. I wonder if we can send a space probe into the not-so-distant future, as their slow speed toward us becomes a juicy goal.

… but what a surprise it would be if, like the 2020 SO, it had passed the top stage of an old space mission instead of an asteroid! It would be cool. Scientists may be disappointed, but I bet there would be some very interesting engineering data (e.g., solar wind erosion or the effects of micrometeorites) that rocket scientists can get their hands on. And if it’s an asteroid, that wouldn’t be so bad either.

So stay tuned. We should know a lot more in a few weeks about this enigmatic visitor from space.

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