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This is Part 4 of a series on interstellar comets.
Read Parts1,2, and3. So that's all nice.
But why now? That's the question everyone asks.
We went decades — centuries, millennia really — without seeing a single rock that didn't have a "Made in the Solar System" sticker on it.
Then, in the span of less than ten years, we get the Big Three: 'Oumuamua, Borisov, and now 3I/ATLAS. Did the galaxy suddenly decide to start throwing its trash in our yard? Is there some kind of cosmic pile-up happening just outside the Oort Cloud? Nah.
The truth is a lot less conspiracy theory and a lot more "we finally turned on the porch lights." You're never going to notice the strangers zooming through town if you never bother to open the windows. For most of human history, we were looking at the sky through a straw.
We could see the big stuff — the planets, the bright stars, the occasional great comet that scared everyone into thinking the world was ending.
But everything else was invisible. Specifically, Pan-STARRS.
This is a telescope system in Hawaii that scans the entire sky, over and over again, looking for things that move.
It's a cosmic motion detector.
And wouldn't you know it, as soon as we started looking for things that move, we started finding them.
'Oumuamua was the first.
It was the proof of concept. But we're just getting started. If Pan-STARRS is a porch light, the upcoming Vera C.
Rubin Observatory is a stadium floodlight.
Currently being finished in the high Atacama desert of Chile, the Rubin Observatory is a beast.
It's got a mirror the size of a small apartment and a camera that's a three-gigapixel monster.
Every few nights, it will photograph the entire visible sky.
Let me say that again: the entire visible sky, every few nights.