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› Full SizeThe Hustle and Bustle of Our Solar System
This diagram illustrates the differences between orbits of a typical
near-Earth asteroid (blue) and a potentially hazardous asteroid, or PHA
(orange). PHAs are a subset of the near-Earth asteroids (NEAs) and have
the closest orbits to Earth's orbit, coming within 5 million miles
(about 8 million kilometers). They also are large enough to survive
passage through Earth's atmosphere and cause damage on a regional, or
greater, scale.
Our yellow sun sits at the center of the crowd,
while the orbits of the planets Mercury, Venus and Mars are shown in
grey. Earth's orbit stands out in green between Venus and Mars. As the
diagram indicates, the PHAs tend to have more Earth-like orbits than the
rest of the NEAs. The asteroid orbits are simulations of what a typical
object's path around the sun might look like.
The dots in the
background are based on data from NASA's NEOWISE, the asteroid-hunting
portion of the Wide-field Infrared Survey Explorer (WISE) mission, which
scanned the whole sky twice in infrared light before entering
hibernation mode in 2011. The blue and orange dots represent a
simulation of the population of near-Earth asteroids and PHAs,
respectively, which are larger than 330 feet (100 meters).
NEOWISE has provided the best overall look at the PHA population yet,
refining estimates of their numbers, sizes, types of orbits and
potential hazards. The NEOWISE team estimates that about 20 to 30
percent of the PHAs thought to exist have actually been discovered as
may 2012, the date of this image.Image Credit: NASA/JPL-Caltech
Guillermo Gonzalo Sánchez Achutegui
ayabaca@gmail.com
ayabaca@hotmail.com
ayabaca@yahoo.com
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