[btilly]

See https://www.space.com/43015-interstellar-visitor-oumuamua-no... for the math.

But you're still focusing on the wrong thing. The idea of "a complicated gravity assist" getting something going this fast in the Solar System is laughable. The only thing in the Solar System heavy enough to do a gravity assist on the necessary scale is the Sun itself, and it started nowhere near the Sun.

[aaron695]

That link is great thanks.

For it to be real I'd expect billions of things passing through yearly, maybe daily. For something as large as Oumuamua I'd intuitively expect millions or billions of small rocks coming through.

"We find that such objects collide with the Sun once every 30 years, while about 2 pass within the orbit of Mercury each year."

But I worry about anything like this talking in human years, like "30 years". I'd expect every million years or millions a year when talking about the universe.

I understand as our technology grows, first we find yearly events and then improve. But the theoretical must make sense to me in non human timelines.

[btilly]

There could well be millions or billions of sand particle sized objects coming through constantly.

The Solar System is big. Almost all of them will pass through and miss everything. We literally have no way to notice them.

Incidentally we have spotted a second interstellar object. https://en.wikipedia.org/wiki/2I/Borisov is more what we were expecting them to look like.