I suspect that when most people think about asteroids approaching Earth, they picture them coming from deep space, out past Mars and Jupiter.
But there’s a substantial population of asteroids where the rocks spend most of their time inside Earth’s orbit, closer to the Sun. These little beasties are hard to find because they tend not to stray too far from the Sun in the sky, so they’re up mostly during the day or twilight hours.
For my biweekly column at Sen.com, I wrote about a newly discovered asteroid called 2015 QM3 that is on such an orbit, swinging it past not just Earth, but also Venus and Mercury! It’s a curious object, getting close enough to all three planets that over millions of years its orbit is certainly unstable. Not many such asteroids are known (just 17!) so any time we find a new one it helps us understand the complicated dynamics of near-Earth objects.
My articles for Sen.com are subscription only, but for $5 a month you get access to a lot of pretty cool astronomical info. I check it for news and interesting photos every day. You should too.
My thanks to my friend and esteemed astronomical colleague Amy Mainzer for her help with some info about QM3 … and also for announcing the asteroid in the first place