Wikipedia walk: Asteroids

https://en.wikipedia.org/wiki/Asteroid
Asteroids, big rocks floating around our solar system. Sometimes they hit Earth and kill the dinosaurs. The name derived from 'aster' (star) 'oid' (like), because they were star-like in being points of light in the sky that didn't resolve into circles with the telescopes of the era in which they were identified, while those telescopes did show noticably circular planets and the rings of Saturn. But they're not stars, because stars don't move (on human time scales).

With varying quality we have data on 504,000 to 780,000 asteroids. We're discovering and tracking an additional 2000 near-Earth objects every year.

Telescopes and Surveys. We have a couple telescopes doing non-stop survey work of the sky in Arizona and Hawaii, there are and have been others, and the LSST in Chile, coming online around 2021, looks awesome. These surveys image the whole sky every few days and software can automatically check, "hey, did that speck of light move?". If yes, it might be an asteroid. These projects are already moving "big data" with substantial storage and computation needs, and the LSST is going to take that up a big notch.

I think it's cool that we have telescopes devoted full time to scanning the sky, and big data backing them up doing analysis. This kind of research makes a bunch of our sci-fi future possible. They have short lists of a few dozen asteroids a relatively short hop from Earth that we could mine. They have lists of asteroids that might impact Earth that we can keep an extra close watch on them so that we don't go the way of the dinosaurs. From the apparent distribution of objects in our solar system, we probably know about over 90% of the 1km+ objects that might hit earth, and better technology and techniques are pushing that coverage higher and object size threshold lower (future goals of a couple projects are all the objects over 140m or over 30m). All this for a global budget of just a few tens of millions of dollars. We can do this. When we have it together, humanity is awesome.