New Asteroid Discovered in Odd Earth Orbit –The Frequency of Major Impacts

Asteroids1 Apostolos Christou and David Asher from the Armagh Observatory in Northern Ireland announced the discovery of an asteroid near Earth called Asteroid 2010 SO16 that  orbits the sun in what is referred to as a "horseshoe orbit."

Although the accepted wisdom is that horseshoe orbits are not stable, Christou and Asher have run simulations that show that SO16 remains in this horseshoe orbit for anywhere from 120,000 to over a million years.

A horseshoe orbit gets its name because when viewed from Earth’s point of view, the asteroid appears to travel in a shape of a horseshoe. While, from the perspective of the asteroid, it is in a continual orbit around the sun. Objects closer to the sun will orbit at a faster rate than objects of a further distance.


Because the Earth is larger than the asteroid, its gravity will work to pull the asteroid away from the Sun, eventually pulling the asteroid into an orbit which is a greater distance from the sun than Earth. The asteroids new orbital track will then be slower than that of Earth, making it appear to fall behind and look as though it is going in the opposite direction.

As both the Earth and the asteroid continue to orbit, eventually the Earth will catch up to the asteroid and the process will reverse, with the Earth’s gravity pulling the asteroid back into the smaller orbit.

Currently SO16 is traveling at one of its closest approach points and will hold a place in the evening sky for several decades to come.

Stephen Hawking believes that one of the major factors in the possible scarcity of intelligent life in our galaxy is the high probability of an asteroid or comet colliding with inhabited planets.

Through Earth's history such collisions occur, on the average every one million years. If this figure is correct, it would mean that intelligent life on Earth has developed only because of the lucky chance that there have been no major collisions in the last 70 million years. Other planets in the galaxy, Hawking believes, on which life has developed, may not have had a long enough collision-free period to evolve intelligent beings.

“The threat of the Earth being hit by an asteroid is increasingly being accepted as the single greatest natural disaster hazard faced by humanity,” according to Nick Bailey of the University of Southampton's School of Engineering Sciences team, who has developed a threat-identifying program.[ Image: Comet Shoemaker-Levy 9 collision with Jupiter]

The team used raw data from multiple impact simulations to rank each country based on the number of times and how severely they would be affected by each impact. The software, called NEOimpactor (from NASA's "NEO" or Near Earth Object program), has been specifically developed for measuring the impact of 'small' asteroids under one kilometer in diameter.

Early results indicate that in terms of population lost, China, Indonesia, India, Japan and the United States face the greatest overall threat; while the United States, China, Sweden, Canada and Japan face the most severe economic effects due to the infrastructure destroyed.

The top ten countries most at risk are China, Indonesia, India, Japan, the United States, the Philippines, Italy, the United Kingdom, Brazil and Nigeria.

“The consequences for human populations and infrastructure as a result of an impact are enormous,” says Bailey. “Nearly one hundred years ago a remote region near the Tunguska River witnessed the largest asteroid impact event in living memory when a relatively small object (approximately 50 meters in diameter) exploded in mid-air. While it only flattened unpopulated forest, had it exploded over London it could have devastated everything within the M25. Our results highlight those countries that face the greatest risk from this most global of natural hazards and thus indicate which nations need to be involved in mitigating the threat.”

What would happen to the human species and life on Earth in general if an asteroid the size of the one that created the famous K/T Event of 65 million years ago at the end of the Mesozoic Era that resulted in the extinction of the dinosaurs impacted our planet.

As Stephen Hawking says, the general consensus is that any comet or asteroid greater than 20 kilometers in diameter that strikes the Earth will result in the complete annihilation of complex life — animals and higher plants. (The asteroid Vesta, for example, one of the destinations of the Dawn Mission, is the size of Arizona).

How many times in our galaxy alone has life finally evolved to the equivalent of our planets and animals on some far distant planet, only to be utterly destroyed by an impact? Galactic history suggests it might be a common occurrence.

Vredefort The asteroid that hit Vredefort located in the Free State Province of South Africa is one of the largest to ever impact Earth, estimated at over 10 km (6 miles) wide, although it is believed by many that the original size of the impact structure could have been 250 km in diameter, or possibly larger (though the Wilkes Land crater in Antarctica, if confirmed to have been the result of an impact event, is even larger at 500 kilometers across). The town of Vredefort is situated in the crater (image).

Dating back 2,023 million years, it is the oldest astrobleme found on earth so far, with a radius of 190km, it is also the most deeply eroded. Vredefort Dome Vredefort bears witness to the world’s greatest known single energy release event, which caused devastating global change, including, according to many scientists, major evolutionary changes.

What has kept the Earth "safe" at least the past 65 million years, other than blind luck is the massive gravitational field of Jupiter, our cosmic guardian, with its stable circular orbit far from the sun, which assures a low number of impacts resulting in mass extinctions by sweeping up and scatters away most of the dangerous Earth-orbit-crossing comets and asteroids.

More information: A long-lived horseshoe companion to the Earth, arXiv:1104.0036v1 [astro-ph.EP] http://arxiv.org/abs/1104.0036

The Daily Galaxy via

MIT Technology Review 

University of Southhampton (England)

rationalvedanta.net

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