Eyes on the skies in mid-February as an asteroid about half the size of a football field will make an extremely close approach to the Earth at a distance closer than many man-made satellites.
On February 15, asteroid 2012 DA14 will pass between the Earth and the Moon and be within 17,200 miles of Earth’s surface according to NASA (See video: http://www.youtube.com/watch?v=GwidzVHvbGI). Don Yeomans, Manager of NASA’s Near Earth Object Program at JPL, says “This is a record-setting close approach. Since regular sky surveys began in the 1990s, we’ve never seen an object this big get so close to Earth.”
Although the asteroid will come uncomfortably close, scientists say there is no chance of impact. “2012 DA14 will definitely not hit Earth,” says Yeomans. “The orbit of the asteroid is known well enough to rule out an impact.” Still, NASA will be monitoring the asteroid closely, as it will pass between what is known as the low-Earth orbit (where the International Space Station and many Earth-observation satellites are located) and the “higher belt of geosynchronous satellites, which provide weather data and telecommunications.”
NASA’s Goldstone radar in the Mojave Desert will be tracking 2012 DA14. The asteroid will travel south to north rapidly at a speed of 17,800 mph, and will provide a unique opportunity for scientists to study its size, shape, and orbit more closely as well as create a “3D radar map showing the space rock from all sides.”
According to NASA, “2012 DA 14 is a fairly typical near-Earth asteroid.” The space rock measures about 50 meters across, making it mid-sized. Yeomans says that he “estimates that an asteroid like 2012 DA14 flies past Earth, on average, every 40 years, yet actually strikes our planet only every 1,200 years or so.”
An object of similar size to 2012 DA14 impacted the Earth about 50,000 years ago according to Yeomans, forming the mile-wide Meteor Crater in Arizona. That asteroid differed from 2012 DA14 in that “it was made of iron, which made it an especially potent impacter.” 2012 DA14 is believed to be “probably made of stone, as opposed to metal or ice.”
More recently in 1908, “something about the size of 2012 DA14 exploded in the atmosphere above Siberia.” Known as the Tunguska Event, the explosion leveled approximately 830 square miles of forest and produced a shock wave estimated to have been a 5.0 on the Richter Scale.
As 2012 DA14 makes its closest approach, it will become as bright as a star of 7th or 8th magnitude. In comparison, the brightest star in our skies is Sirius with a magnitude of -1.44. When determining brightness of stars, the smaller the number, the brighter the star—a magnitude 1 star is brighter than a magnitude 2 star and so on. Because 2012 DA14 is expected to be about a magnitude 7 or 8, it will not be visible to the naked eye. Amateur astronomers with backyard telescopes should be able to pick it up, however.
2012 DA14 will undergo a change in its orbit due to its close encounter with Earth, reducing its orbital period from 377 days to 317 days. The rocky asteroid’s next approach with Earth will occur on February 16, 2046.
The close call with 2012 DA14 will be a good test for scientists to gather information in anticipation of another potentially hazardous asteroid that will be making very close approaches in 2029 and 2036. That asteroid, known as 99942 Apophis, is much larger than 2012 DA14.
Threats from asteroids are real, and astronomers are constantly seeking ways to locate and track them earlier. NASA’s Near-Earth Object Program looks for these types of objects and determines if their orbits can potentially be hazardous to our planet. With an estimated half million near-Earth objects yet to be discovered, odds are that someday, one will make its deep impact known here on Earth.
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