"I have loved the stars too fondly to be fearful of the night."
--Galileo Galilei.

Wednesday 1 April 2009

Near-miss asteroid

Near-miss asteroid

Here's a snippet I picked up:

ANOTHER ASTEROID PASSES BY
Spaceweather.com

Newly-discovered asteroid 2009 FH passed by the Earth on March 17 at
a distance of only 85,000 km (0.00057 AU), only a little more than
twice the height of a geosynchronous communications satellite. This
is the second time in March that an asteroid has flown so close to
the Earth. As described in the last Bulletin, on March 2 one passed
only 72,000 km away. Measuring some tens of metres in diameter, the
two are approximately Tunguska-class objects, so they do not pose a
global threat but would cause local damage if they actually hit the
Earth. In the past, asteroids of that size often passed unnoticed,
but recent improvements in asteroid surveys have resulted in growing
numbers of space rocks caught in the act of near-Earth fly-bys.

------- ends --------

Yes, I'd say that was a bit close!

But only last November another asteroid missed us by only 45,000km - which is an 8th of the distance to the moon. What's more, it was only detected a few hours before, so if it had been inbound there wouldn't have been anything we could have done. Just the month before that, and with a whole day's warning, one did reach us; exploding in the skies over Sudan. All spooky stuff.

If an asteroid only 250 metres across were to hit our planet it would cause an explosion over 30,000 times the power of the Hiroshima bomb. The Krakatoa eruption of 1831 was half that power and killed over 36,000 people.

But the overall chance of 'death by asteroid' has been calculated as 1 in 10 million per year.

But it seems the powers that be in the world are finally taking note and doing something about the possibility of an asteroid actually being on collision course with Earth.

There are all kinds of scenarios for dealing with a potential 'hitter', one of them does not include blasting it with a nuclear bomb! Why not? Because of the risk of turning it into thousands of pieces which would scatter in every direction - including ours; so we'll leave that idea to the movies.

Early warning systems are the key, and in that respect there are plans to track every potential threat using automated surveys, such as that of the Catalina Sky Survey. This is a group of three telescopes - two in Arizona and one in Australia which will closely examine the sky. Software then takes the images and looks for movement. Anything found is then passed to real astronomers for further examination.

NASA is also involved. They are bringing on the huge 8 metre Large Synoptic Survey Telescope (LSST) in Chile for 2015. It is so big that they anticipate finding virtually all the remaining asteroids.

Once found the asteroids are assessed for risk using the Torino Scale. This works like the Richter scale for earthquakes and is simply a scale from 1 to 10 to classify the threat risk of an asteroid actually hitting our planet.

It is likely that for anything large enough to cause significant damage, that there will be plenty of warning so that plans can be put in place to deflect it. This deflection will need to take place far enough out so that not much is required. The closer to us, the more difficult the task - hence the early warning systems.

The most sensible options seem to be using gravity tractors, kinetic impact (different from nuclear bomb), rocket motors, space mirrors or even painting it!

As long as plans are in motion in time, then there's a chance of success. But it does need all the nations of the world to co-operate and agree - and here's where there may be stumbling blocks. But we live in hope.

(Issue 201 of the BBCs Focus magazine is my main source of information for this blogpost.)

-- Lynda