# Watch house-size asteroid 2023 MU2 fly by Earth at over 2,000 mph (video)

#### p3orion

"Racing past", "zoomed", "staggering 2000 mph", "incredible speed"

Am I missing something? While mach 2.5 is impressive (but not unheard of) for a tactical military jet, it seems a bit pedestrian for astronomical objects. Objects in low Earth orbit go nearly nine times as fast, and even the moon, more than twice as far from Earth as this asteroid's passage, lopes along in its orbit at about 1700 mph.

How fast do close-passing asteroids usually go?

#### Unclear Engineer

Yes, there is something wrong with this number. If that was actually the total differential speed at its "closest approach" distance, then it should not have been able to avoid going into orbit around the Earth.

I am wondering if that was some sort of apparent speed, given the angle of observation, and there was another component to the speed vector going radially away from the line of observation that made enough total velocity so that the path past the Earth is "open" instead of becoming a closed ellipse.

#### p3orion

Yes, there is something wrong with this number. If that was actually the total differential speed at its "closest approach" distance, then it should not have been able to avoid going into orbit around the Earth.

I am wondering if that was some sort of apparent speed, given the angle of observation, and there was another component to the speed vector going radially away from the line of observation that made enough total velocity so that the path past the Earth is "open" instead of becoming a closed ellipse.
I would have thought so too, but the writer seems pretty definite. It's not a typo either, as he expressed the speed as both 2000 mph and Mach 2.5 (not exact, but close enough.) And it can't be an unusual apparent speed; every object passes at a 90 degree angle at or close to its closest point of approach.

Maybe it was a slow news day, or the writer is just easily impressed.

By the way: "Unclear Engineer", nice!

#### Unclear Engineer

I did check other places on the Internet, and did not find any other speed or explanation.

And, I agree that the direction should be perpendicular to the line of sight at the "closest approach" point.

But, the physics/orbital mechanics are pretty clear that what was reported cannot be correct. So, the only issue is what the reporter(s) got wrong because they don't understand orbital mechanics. It is pretty clear that somebody who is impressed with "2,000 mph" has nil understanding of the speeds involved with aircraft, launch vehicles. or satellite orbits.

#### p3orion

Looks like the "fix" was to change the title to remove "zoomed," but near as I can tell, the text is the same as it was.

As for "nil understanding" note the author's credentials: BS in physics and astronomy from an online college.

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