Asteroid Hunter Bags Its First Rock

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Jan. 9 2014 11:00 AM

NEOWISE Bags Its First Asteroid!

By Phil Plait

The near-Earth asteroid 2013 YP139 can be seen gliding through this composite NEOWISE image (red circles), with one shot highlighted at the bottom. Click to armageddonate.

Photo by NASA/JPL-Caltech

NEOWISE, NASA’s reanimated infrared space mission, has found its first asteroid!

Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death from the Skies!

Well, that didn’t take long. Not that I expected it would.

Called 2013 YP139, the rock is about 650 meters (0.4 miles) across. It’s on a highly elliptical orbit that takes it out from the Sun past Mars, and back in to just inside the Earth’s orbit. It’s actually a near-Earth asteroid; it can potentially swing by as close as 500,000 kilometers (300,000 miles) from our planet, a bit farther out than the Moon. The orbit is still uncertain right now, but rest easy: It seems likely it won’t get anywhere near the Earth for quite some time, probably a century or so.

The orbit of 2013 YP139 takes it just inside Earth's own orbit; it's currently about 40 million kilometers away.

Graphic by Photo by NASA/JPL-Caltech

NEOWISE stands for the Near-Earth Object Wide-field Infrared Survey Explorer. It used to be just WISE when it first launched; it operated for about a year, surveying the sky in infrared. It took amazing images of gas clouds, galaxies, and asteroids. Especially asteroids; they glow in the infrared and are actually easier to see in IR than visible light.

WISE ran out of coolant after a year in orbit. However, NASA decided to resurrect the mission, repurposing it to look for potentially hazardous asteroids (and no doubt wanting to tie it in with their plans to capture an asteroid as well). In September 2013 it was switched back on, its name was changed, and the hunt began anew.

NEOWISE started seeing asteroids right away, but it wasn’t until Dec. 29 that it found YP139, its first new one (that is, one never observed before). An added benefit to using NEOWISE for this search is that asteroid sizes are easier to determine when they’re observed in the IR. In visible light, a big dark rock can masquerade as a smaller, shinier one, but in the infrared they can’t hide their size. The more we know about each individual asteroid, obviously, the better.

NEOWISE is also paving the way for a next generation asteroid hunter called NEOCam, the Near-Earth Object Camera. This is already being tested at NASA’s JPL and will scan the skies looking for potential Earth impactors. Together with the B612 Foundation’s Sentinel mission, in the next few years we may finally start getting serious about looking for rocks with our name on them. Oddly enough, I’m all for this.

YP139 may be the first, but astronomers expect to find hundreds more over the next few years. My congratulations to my pal Amy Mainzer, the NEOWISE principal investigator, and the team that made this mission possible!