Near-Earth Objects (NEOs)
are those asteroids or comets that can come closer than 1.3 A.U. from the Sun.
See Near-Earth Objects (NASA-JPL, Ron Baalke).
See Asteroids and Comets (The Planetary Society).
See also Closest Approaches to the Earth by Minor Planets (IAU: Minor Planet Center).
Potentially Hazardous Asteroids (PHAs)
are those that can come closer than 0.05 A.U. from the Earth and have more than 150 m in diameter.
Presently more than 300 Potentially Hazardous Asteroids (PHAs) are known. But all of them have been classified as "with virtually no chance of impact or damages"; 0 in "The Torino Scale" (NASA-JPL, Ron Baalke).
A Reduced Estimate of the Number of Kilometric Asteroids Near to the Earth
David Rabinowitz, Eleanor Helin, Kenneth Lawrence and Steven Pravdo
Near-Earth asteroids are small rocky objects (with diameter < 10 Km) whose orbits are close to that of the Earth. The majority have a probability of approximately 0.5% of colliding with the Earth for the next million years. The total number of such objects with diameters > 1 Km has been estimated in the range of 1,000 to 2,000, which would mean a probability close to 1% for a catastrophic collision with the Earth for the next millennium. However, these numbers are poorly bounded due to the limitations of previous searches, using photographic plates. (1 Km is the smaller size of a body whose impact on Earth would produce global effects). We report an analysis of our search for asteroids near Earth, which used improved detection technologies. We see that the total number of asteroids with diameter > 1 Km is about half of the previously estimated. With the current rate of detection of asteroids about... With the current rate of detection of near-Earth asteroids, some 90% will have probably been detected in the next 20 years.
This decrease by a factor of 2 does not substantially alter the significance of the danger of near-Earth asteroids. However, we have shown continuous automated searches to provide reliable means to characterize the size of the population of near-Earth asteroids. Now we can reliably predict the level of effort required to fully catalog those near-Earth asteroids capable of causing global devastation.
The research described in this work was carried out by the Jet Propulsion Laboratory (JPL), California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA).
From Nature 403, 165 - 166 (2000). © Macmillan Publishers Ltd.
Recieved on August 13; accepted on November 17, 1999.
See the known Near-Earth Objects (NEOs) that have visited and will visit us, at NEO Earth Close Approaches.
For information on "1950 DA", a near-Earth asteroid rediscovered on December 31 '00, and its encounter on 2880 with up to 0.33% of impact risk (100 times more than any other), see Threatening Asteroid Aids Planetary Prognosticators (Sky and Telescope, April 4, 2002).
For information on "2002 MN", a near-Earth asteroid discovered on June 17 '02, and its encounter on June 14 '02 at a distance of just 120,000 Km (0.3 of the distance to the Moon), see A Close Asteroid Fly-By (Sky and Telescope, June 19, 2002).
See also NEO Earth Close Approach Tables.
For information on "2002 NY40", a near-Earth asteroid with near 800 m in diameter and a period of 3.03 years discovered on July 14 '02, and its encounter on August 18 '02 at just 530,000 Km (0.0035 UA) de distancia (1.3 times the distance to the Moon), see How to Watch Saturday's Asteroid Flyby (Sky and Telescope, August 14, 2002).
Vea también NEO Earth Close Approach Tables y 2002NY40, en Near Earth Objects Dynamic Site (NEODyS-2).
"2004 FH", a near-Earth asteroid of some 30 m in diameter and a period of 270 days, discovered on March 16 '04, and its encounter on March 18 '04 (22:08 UT) at a distance of just 42,700 Km (0,000285 AU) (0.13 times the distance to the Moon).
"Asteroid 2003 SQ 222 had the Earth-approaching record by flying on September 27, 2003, just 84,000 km from our planet.
The crossing occurred over the South Atlantic Ocean and could be seen with binoculars only from areas of Asia, Europe and the southern hemisphere."
For information on 2004 FH, see Closest Asteroid Flyby Ever (Sky and Telescope, March 18, 2004) and Asteroid 2004 FH's Record Flyby (Sky and Telescope, March 24, 2004).
Asteroid Population Doubles:
Observations of 1996 and 97 of the Space Infrared Observatory of the European Space Agency show that the asteroid belt contains nearly twice the number of objects previously estimated.
The new census involved an account of asteroids observed in selected regions, and its extrapolation to the entire sky.
The result, says Edward Tedesco (TerraSystems), suggests that the main belt (between Mars and Jupiter) contains 1.1 to 1.9 million of Minor Planets, of more than 1 Km in diameter. Studies in 1998 and 2001 had estimated a count of more than 1 Km in 860,000 and 740,000 objects, respectively.
See Asteroid Population Doubles (Sky and Telescope, April 5, 2002).
The impacts of asteroids and comets have both destroyed as molded the life on Earth since its formation.
The Earth orbits the Sun inside a vast swarm of nearby asteroids (NEAs).
The probability of an unacceptable collision in this century is of ~2%.
We now have the ability to anticipate an impact and prevent it.
See Sentinel Mission [B612 Foundation]
(The first comprehensive dynamic map of the inner Solar System)
- B612 Mission: To significantly alter the orbit of an asteroid, in a controlled manner, by landing a nuclear powered plasma engine directly on it, to push the asteroid out of its current orbit, just enough to avoid an impact with Earth. (B612 is the asteroid home of The Little Prince in the tale of Antoine de Saint-Exupery)
A New Count of Potentially Hazardous Asteroids:
The asteroid-hunting portion of the WISE mission, called NEOWISE, sampled 107 PHAs to make predictions about the population as a whole. Findings indicate there are roughly 4,700 PHAs, plus or minus 1,500, with diameters larger than 330 feet (about 100 meters). So far, an estimated 20 to 30 percent of these objects have been found.
See A New Count of Potentially Hazardous Asteroids (NASA Science News. May 16, 2012)
This page was updated on: April 15 '06, May 31 '12, August 31 '14
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