Trillion-dollar platinum asteroid passes Earth. See it here

Monday, July 20, 2015, 1:25 AM - 600-m-wide asteroid 2011 UW158 captured the attention of astronomers this week, not only for its apparent rarity, but also because it could be valued at up to five trillion dollars.

While Pluto was making headlines this past week, as NASA's New Horizons spacecraft returned amazing pictures during its Tuesday flyby, some astronomers were focused on something a bit closer to home. An intriguing object, named asteroid 2011 UW158, made its closest pass by Earth since its discovery nearly 4 years ago, coming to within about six times the distance to the Moon on Sunday, July 15. 

This asteroid, which makes a roughly two-year orbit around the Sun, comes very close to the orbit of Earth. It will make an even closer pass by us, at about four times the distance to the Moon, on July 2, 2108. However, despite these relatively close passes and its size, since the 2108 flyby is the closest it will come until at least the year 2200, 2011 UW158 is not considered to be a danger to us.

The asteroid did draw the focus of two different radio observatories, though, the Goldstone Observatory in California and the Arecibo Observatory in Puerto Rico. Based on previous observations, astronomers at Goldstone labelled 2011 UW158 as "one of the strongest radar targets of the year."

Beaming radio waves out into space, these observatories gathered the reflected waves to get an exceptional look at the asteroid.

Measuring about 300 metres wide by 600 metres long, 2011 UW158 looks something like an "unshelled walnut," and was found to be spinning at a very high rate - once every 37 minutes.

At that speed, if the asteroid was among the most common type - a "rubble pile" collection of smaller stones held together by their mutual gravity - it would fly apart. Therefore, this must be one large rock flying through space.

"Its size, shape, and rotation suggest there is something more than gravity holding this object together or else the asteroid would break up due to its fast spin," said astronomer Dr. Patrick Taylor, the Planetary Radar scientist who led the observations.

"We expect that something this big should have been shattered into smaller pieces by collisions with other asteroids over the age of the Solar System," Dr. Taylor added. "It is interesting that something this large and apparently solid is still around."

Radar imagery of asteroid 2011 UW158. Credit: Arecibo Observatory

Another remarkable characteristic of this large rock is that it may contain up to $5 trillion worth of platinum locked up inside it. This is based on observations of the spectrum of light being reflected off the asteroid. Examining this to see what elements it holds revealed its platinum signature, and made it one of the primary targets of the asteroid mining company, Planetary Resources.

Although the asteroid was far too dim to be seen with the naked eye, it could be found with telescopes, and the Slooh Community Observatory was tracking it on Sunday afternoon from the Canary Islands, off the coast of northwestern Africa.

WATCH BELOW: Slooh Host Eric Edelman, astronomer Bob Berman and Planetary Resources President and Chief Engineer Chris Lewicki discuss asteroid UW158 and its potential worth.

Sources: Arecibo Planetary Radar (Facebook) | Slooh | NASA/JPL/Goldstone