The large Apophis asteroid passed by Earth a few days ago, some 9,000,000 miles from our fair planet. The asteroid, which is named after an Egyptian demon, was said to measure 270 to 275 meters wide. The European Space Astronomy Center's Herschel Space Observatory observed as it neared, however, that it is much larger than that.
Herschel came to this conclusion by observing the asteroid using thermal infrared in different wavelengths, which you can see in the image above. Combining the infrared observations with optical measurements, Apophis's size estimates were refined, with the asteroid turning out to be about 20-percent larger in diameter than previously believed at 325 meters wide.
The European Space Astronomy Center's Goran Pilbratt offered this statement. "Although Apophis initially caught public interest as a possible Earth impactor, which is now considered highly improbable for the foreseeable future, it is of considerable interest in its own right, and as an example of the class of near Earth objects. Our unique Herschel measurements play a key role for the physical characterization of Apophis, and will improve the long-term prediction of its orbit."
Many call Apophis the doomsday asteroid because it was initially believed there was a small 2.9-percent chance of it hitting Earth in the year 2029. That information was later refined, with the asteroid actually passing by at a distance of about 22,000 miles. Apophis will near Earth again in the year 2036, but no one knows how close it will come to our planet.