mardi 19 février 2013

Russia asteroid impact: ESA update and assessment‏











Asteroid Watch.

19 February 2013

The first firm details of the 15 February asteroid impact in Russia, the largest in more than a century, are becoming clear. ESA is carefully assessing the information as crucial input for developing the Agency’s asteroid-hunting effort.

At 03:20 GMT on 15 February, a natural object entered the atmosphere and disintegrated in the skies over Chelyabinsk, Russia.

Asteroid trace over Chelyabinsk, Russia, on 15 February 2013

Extensive video records indicate a northeast to southwest path at a shallow angle of 20° above the horizontal. The entry speed is estimated at around 18 km/s – more than 64 000 km/h.

According to calculations by Peter Brown at the University of Western Ontario, Canada, drawing on extremely low-frequency sound waves detected by a global network, the object is estimated to have been about 17 m across with a mass of 7000–10 000 tonnes when it hit atmosphere.

It exploded with a force of nearly 500 kilotons of TNT – some 30 times the energy released by the Hiroshima atomic bomb – around 15–20 km above the ground.

With our current understanding of near-Earth objects, events of this magnitude are expected once every several of tens to 100 years.

Questions and answers with ESA's near-Earth object team

Nicolas Bobrinsky, Head of ESA’s Space Situational Awareness (SSA) programme, and Detlef Koschny, responsible for the programme’s Near-Earth Object activity, responded to questions about the event.

Orbit around Sun

- Was this event related to the predicted flyby of asteroid 2012 DA14, which passed Earth at 19:27 GMT that same day at just 28 000 km?

DVK: The trajectory, the location of entry into the atmosphere and the large time separation between the two events indicate that the Russian object was unrelated to 2012 DA14.

- What caused the damage on the ground? Did pieces hit people or buildings?

DVK: Many media reported that an airburst caused window breakage and some structural damage in downtown Chelaybinsk. Normally, some damage begins to occur at around five times normal air pressure at sea level. Widespread window damage is expected around 10–20 times this value.

As the explosion and fireball progressed along a shallow trajectory, the cylindrical blast wave would have propagated directly to the ground and would have been intense.

The terminal part of the explosion probably likely occurred almost directly over Chelyabinsk. This was perhaps the single greatest contributor to the blast damage.

video
Scientists have found fragments of the meteorite Chelyabinsk (in Russian)

We are waiting for confirmation from the Russian authorities that pieces of the object – bits of meteorite – have been found in the region. We’re unaware of any media reports of anyone or any structure being hit by any debris from the object itself.

Related links:

Space Situational Awareness: http://www.esa.int/Our_Activities/Operations/Space_Situational_Awareness2

Russian asteroid strike: http://orbiterchspacenews.blogspot.ch/2013/02/russian-asteroid-strike.html

Stranger in the night: space rock to make close Earth flyby: http://www.esa.int/Our_Activities/Operations/Stranger_in_the_night_space_rock_to_make_close_Earth_flyby

Asteroid 2012 DA14 - Near-Earth Asteroid Makes View Appearance: http://orbiterchspacenews.blogspot.ch/2013/02/asteroid-2012-da14-near-earth-asteroid.html

Spotting an ancient asteroid: http://www.esa.int/Our_Activities/Operations/Spotting_an_ancient_asteroid

SSA NEO Data Centre: http://neo.ssa.esa.int/

More information:

Centre for Planetary Science and Exploration: http://planetsci.uwo.ca/

Infrasound monitoring: http://www.ctbto.org/verification-regime/monitoring-technologies-how-they-work/infrasound-monitoring/

UNCOPUOS: http://www.oosa.unvienna.org/oosa/COPUOS/copuos.html

UNCOPUOS - 2013 session - presentations: http://www.unoosa.org/oosa/en/COPUOS/stsc/2013/presentations.html

Images, Video, Text, Credits: ESA / Alex Alishevskikh CC BY-SA 2.0 via http://www.flickr.com/photos/alexeya/ NASA / ROSCOSMOS TV / Russia 24.

Greetings, Orbiter.ch

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