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Record-setting Asteroid Flyby - presented by Science@NASA
Talk about a close shave.
On Feb. 15th an asteroid about half the size of a football field
will fly past Earth only 17,200 miles above our planet's surface.
There's no danger of a collision,
but the space rock, designated 2012 DA14,
has NASA's attention.
'This is a record-setting close approach,'
says Don Yeomans of NASA's Near Earth Object Observation Program at JPL.
'Since regular sky surveys began in the 1990s,
we've never seen an object this big get so close to Earth.'
Earth's neighborhood is littered with asteroids
of all shapes and sizes,
ranging from fragments the size of beach balls
to mountainous rocks many kilometers wide.
Many of these objects hail from the asteroid belt,
while others may be corpses of long-dead, burnt out comets.
NASA's Near-Earth Object Observation Program
helps find and keep track of them,
especially the ones that come close to our planet.
2012 DA14 is a fairly typical near-Earth asteroid.
It measures some 50 meters wide,
neither very large nor very small,
and is probably made of stone,
as opposed to ice or metal.
Yeomans estimates that an asteroid like 2012 DA14 flies past Earth,
on average, every 40 years,
yet actually strikes our planet only every 1200 years or so.
The impact of a 50-meter asteroid is not cataclysmic--
unless you happen to be near it.
Yeomans points out that a similar-sized object
formed the mile wide Meteor Crater in Arizona
when it struck about 50,000 years ago.
'That asteroid was made of iron,' he says,
'which made it an especially potent impactor.'
The area was devastated for over 50 miles around.
Also, in 1908, something about the size of 2012 DA14
exploded in the atmosphere above Siberia,
leveling hundreds of square miles of forest.
Researchers are still studying the 'Tunguska Event'
for clues to the impacting object.
'2012 DA14 will definitely not hit Earth,' emphasizes Yeomans.
'The orbit of the asteroid is known well enough to rule out an impact.'
Even so, it will come interestingly close.
NASA radar will be monitoring the space rock
as it approaches Earth closer than many man-made satellites.
Yeomans says the asteroid will thread the gap between low-Earth orbit,
where the ISS and many Earth observation satellites are located,
and the higher belt of geosynchronous satellites,
which provide weather data and telecommunications.
'The odds of an impact with a satellite are extremely remote,' he says.
Almost nothing orbits where DA14 will pass the Earth.
NASA's Goldstone radar in the Mojave Desert
is scheduled to ping 2012 DA14 almost every day
from Feb. 16th through 20th.
The echoes will not only pinpoint the orbit of the asteroid,
allowing researchers to better predict future encounters,
but also reveal physical characteristics such as size, spin, and reflectivity.
A key outcome of the observing campaign
will be a 3D radar map showing the space rock from all sides.
During the hours around closest approach,
the asteroid will brighten until it resembles a star of 8th magnitude.
Theoretically, that's an easy target for backyard telescopes.
The problem, points out Yeomans, is speed.
'The asteroid will be racing across the sky,
moving almost a full degree
(or twice the width of a full Moon)
every minute.
That's going to be hard to track.'
Only the most experienced amateur astronomers are likely to succeed.
Those who do might experience a tiny chill when they look at their images.
That really was a close shave.
For more news about near-Earth asteroids and other perils,
visit science.nasa.gov.