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SYFY WIRE Bad Astronomy

NASA’s WISE Asteroid Hunter Is Back in Business

By Phil Plait

Iâm very pleased to see that NASAâs Wide-field Infrared Survey Explorer, or WISE, is back in business! Itâs been resurrected as NEOWISE, for Near-Earth Object Wide-field Infrared Survey Explorer.

WISE launched in 2009 and spent over a year mapping the sky in infrared light. This is where cooler galactic dust glows, making WISE images some of the prettiest Iâve ever seen (see related posts below). But asteroids in our own solar system are peppy little emitters of infrared, too, so WISE was an excellent tool to hunt them down. The satellite ran out of coolant in 2011 and was put into hibernation. However, in September 2013 it was switched back on to continue the hunt, part of NASAâs new push to look for near-Earth asteroids.

Astronomers have released the first few images from the now-revived NEOWISE, and itâs already turning up space rocks. The picture above shows a star field with the asteroid 872 Holda, seen as the series of red dots moving across the sky as NEOWISE took a set of exposures. Holda is big, about 42 kilometers (26 miles) across, and orbits the Sun between Mars and Jupiter, safely away from Earth.

Asteroids like Holda are not the main targets of NEOWISE, however. As its name suggests, it will be looking for smaller rocks that get near our own lovely blue-green world, posing a threat if they should impact us. My friend Amy Mainzer, the NEOWISE principal investigator, has said everything looks good on board, and they expect to start finding previously undetected asteroids over the next few months.

Not surprisingly, Iâm all for this. I take the threat of asteroid impacts very seriously, and itâs good to see NASA looking in this direction as well. As NEOWISE shakes out, itâll also help Mainzer and her colleagues better understand how to use NEOCAM, the Near-Earth Object Camera, which theyâre building. Itâs a next generation version of NEOWISE, specifically designed to hunt for potentially threatening rocks.

The advantages of NEOWISE (and NEOCAM) over ground-based telescopes are substantial. The biggest is that it can detect fainter asteroids, but also important is that by looking in the thermal infrared, where warm objects glow, a better size can be determined for an asteroid. When we look in visible light, we have to estimate the asteroidâs size based on how bright and how far away it is. But thatâs a problem; a shiny small asteroid will look just as bright as a big dark one. By looking in the infrared, NEOWISE cuts through that; the infrared light emitted is a more direct measure of the asteroidâs size, independent of how bright or dark it is to the eye.

Itâs not often a space mission gets a second chance to do good, important work, and itâs really nice to see this fantastic mission get another shot. My congratulations to the team, and may they find as many space rocks as they can handle. Itâs the first, necessary step in preventing the end of our world.

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