Hello everyone and welcome to the Minescape Podcast.

I'm your host, Sean Carroll.

Some of you may remember back in October 2017, astronomers announced they discovered an

interstellar interloper in our solar system.

There was an object which they dubbed a mu-a-mu-a, which was flying through our solar system.

It was much like a comet, but comets come from the outer solar system.

They're in orbit around the sun very gently and then something knocks them out of their

orbit so they dive in closer to the sun and we can see them.

A mu-a-mu-a by contrast was moving so fast that it was clearly not bound to the sun gravitationally.

It came from way beyond this solar system and after it zoomed by the sun, it's going to

return back to interstellar space.

So of course, astronomers are very excited by this.

This is the first ever interstellar object in our neighborhood that we could see up close

and personally and many of them analyzed it.

They wrote papers, one such paper came out a year later by Havi Loeb, who was a professor

at the Harvard Smithsonian Center for Astrophysics, and Schmuel Bialli, who was a postdoc at Harvard

also, and it had the dry title of, Could Solar Radiation Pressure Explain a Mu-a-mu-a's

peculiar acceleration.

They go through and they do calculations and all these things.

Near the end of that paper, there's one little paragraph which, offhandedly, they say,

You know, it's possible Mu-a-mu-a is not a rock.

It's possible that it's not just a naturally occurring object at all, but is in fact constructed

...