Minggu, 17 Februari 2013


What is a meteorite? And what is an asteroid?

 Picture from Video - Courtesy of Youtube
An asteroid, like the one due to pass harmlessly – if closely – by earth this evening, is a small rock in orbit around a star – a bit like a tiny planet.
Small pieces of space debris such as parts of asteroids or parts of comets on a collision course with earth are called meteoroids.
When meteoroids enter the earth’s atmosphere they are called meteors.
Most meteors burn up in the atmosphere, but if they survive and strike the surface of the earth – as the object or objects in Russia may have – they are called meteorites.
A comet, by the way, is an object consisting of a central mass surrounded by dust and gas that may form a tail, orbiting a star, usually in an eccentric orbit.

Good morning. A meteor streaked across the sky above the Ural Mountains in Russia this morning, injuring more than 400 people, in the last report injuring around 1,200 people many hurt by broken glass, and causing explosions.
Fragments of the meteor fell in a thinly populated area of the Chelyabinsk region, the Russian Emergency Ministry said in a statement.
Reports conflicted on what exactly happened in the clear skies. A spokeswoman for the Emergency Ministry, Irina Rossius, told the Associated Press that there was a meteor shower, but another ministry spokeswoman, Elena Smirnikh, was quoted by the Interfax news agency as saying it was a single meteor.
We’ll have ongoing coverage here as we get more information. In the meantime, here's the best footage of the meteor strike so far (here, here and here).

Meteorite explodes over Russia: key questions answered

Hundreds of people in Chelyabinsk have been injured after a huge meteorite flared in the sky above the city, but what is it?


What hit Russia on Friday morning?

A space rock, which the Russian Academy of Sciences estimates weighed about 10 tonnes. Videos show a bright trail streaking through the sky, which is the object burning up as it entered the Earth's atmosphere. The rock hit the atmosphere at a speed of at least 54,000km/h (33,000mph), compressing the air in its path and heating it to thousands of degrees, which gives off light. The sharp compression of the air creates a shock wave, which is heard as a sonic boom in many of the videos.


Was it one meteor or a shower?

Footage clearly shows a single object streaking across the sky, but it is believed the rock shattered some 18-32 miles (30-50km) above ground. Some videos show a sudden brightening as the body fragmented during its fiery passage through the atmosphere.


How rare is this sort of event?

Around 40,000 tonnes of space rocks fall to Earth every year, mostly in the form of dust and relatively small meteorites. The last time something major struck the Earth was in 1908, when an asteroid about 50 metres across exploded in the air above the Tunguska region of Siberia. It flattened forests over an area of hundreds of square miles. Friday morning's event was a tiny fraction of this magnitude. Something like this probably happens every decade but usually takes place over an unpopulated area.


Has anyone ever been killed by a meteorite?

No one is previously recorded to have been killed by a meteorite falling from the sky. There are stories of a dog being killed in Egypt in 1911 and a boy being hit but not seriously injured in Uganda in 1992. Most of the Earth's surface is uninhabited by humans, so meteorites usually fall over desolate areas or the oceans.


What's the difference between an asteroid, a meteor, a meteorite and a meteoroid?

Astronomers love their definitions. A meteoroid is anything in orbit around the sun that is smaller than 10 metres. It becomes known as an asteroid above this size and up to about 1,000 kilometres. A meteor is a speck of dust that burns up in the atmosphere creating a shooting star. A meteorite is a larger fragment, from pebble to boulder-sized, that survives to strike the surface of the Earth.
These definitions are blurring, however. Almost everyone it seems is using the word meteor to describe the object that hit Russia. Blame Sean Connery. Back in 1979, he starred in a disaster movie about an asteroid that was to strike Earth. They called the movie Meteor.


Why did we not see this coming?

The Russian meteorite hit during the daytime. The glare of the sun masked its approach, like a fighter pilot using the sun to blind an enemy to the attack. There could be thousands of asteroids that orbit closer to the sun than the Earth, approaching our planet only occasionally and always from "out of the sun". They are virtually impossible to spot from Earth because they are always masked by daylight. Only a space telescope could see these effectively. The European Space Agency's Gaia mission will help discover more of these asteroids.


Is it connected with the asteroid close pass on Friday night?

No, the Royal Astronomical Society in London and the European Space Agency in Darmstadt, Germany, both say that the approach of Friday morning's strike is unrelated to the approach of space rock 2012 DA14, which will draw extremely close to Earth on Friday night. According to Nasa's Near-Earth Object Observation Programme, an asteroid like 2012 DA14 flies this close on average only once every 40 years – although it will still be some 17,100 miles above our heads. Nevertheless, this is closer to the Earth than many artificial satellites.


What do we do if we spot something big heading for Earth?

A recently formed working group of the United Nations Committee on the Peaceful Uses of Outer Space would be called into session. Known as the space mission planning advisory group, it is composed of scientists from Nasa, the European Space Agency and the world's other space agencies. The group would immediately meet to advise on the best strategy for dealing with the asteroid. It would also advise on who has the expertise to build the different parts of the necessary spacecraft, and who should pay for it. Then it would pass the decision into the hands of politicians.


Are any regions of Earth more at risk than others?

No. Incoming asteroids and meteoroids can come from any direction. Additionally, the Earth rotates once a day, presenting every hemisphere to the different directions of space.


Will Friday's impact have any after-effect?

Friday's impact was certainly not enough to knock the Earth off its axis, nor imperil telecommunications networks. The shockwave was compressed air rather than the electromagnetic pulse (EMP) created by nuclear weapons and solar flares. Neither is there a real risk of alien death viruses. Meteorites fall to Earth all the time – none has brought space bugs yet. Although there are theories that microbes could hitch rides on space rocks, there is no incontrovertible evidence that this is a widespread phenomenon.


Was it linked to the asteroid?

Australian website the Conversation has been asking experts whether the meteor strike is linked to asteroid 2012 DA14, which is expected to pass closely by the earth tonight.
Phil Bland, an asteroid expert at Curtin University, said:
Is it connected to the flyby? A lot of folks would say “no”. Personally, I’ve always kind of liked the idea that there are streams of asteroid debris – so you can have smaller stuff that precede and trail a bigger object. It seems like an awful big coincidence if it’s not connected.
But Simon O’Toole, an astronomer at the Australian Astronomical Observatory, said he was “not so sure”.
It has been suggested that this is linked to 2012 DA14. I’m not so sure about this. It might be, but the universe is filled with a lot of unusual coincidences. As pointed out elsewhere, DA14 is still half a million kilometres away, travelling at 8km per second, for a start! Could it be part of the asteroid that has broken away and reached earth already? This seems unlikely to me.
He added that there was no confirmation that the meteorites had exploded: “so far the confirmed damage was almost certainly caused by a shock wave as the object broke the sound barrier”, he said, adding:
If this was a meteor entering the atmosphere, it’s a stark reminder of how vulnerable we are and why we need to monitor the skies very closely for potentially larger objects.


Why are there so many videos from people's cars?

Anyone who has ever seen one of those YouTube video compilations of terrifyingly dangerous Russian drivers will know that every Russian driver seems to have a camera mounted on his or her dashboard. But why?
In Russia, everyone should have a camera on their dashboard. It’s better than keeping a lead pipe under your seat for protection (but you might still want that lead pipe) ...
Psychopaths are abundant on Russian roads. You best not cut anyone off or undertake some other type of maneuver that might inconvenience the 200-pound, six-foot-five brawling children you see on YouTube hopping out of their SUVs with their dukes up ... These fights happen all the time and you can’t really press charges. Point to your broken nose or smashed windows all you want. The Russian courts don’t like verbal claims. They do, however, like to send people to jail for battery and property destruction if there’s definite video proof ...
Dash-cam footage is the only real way to substantiate your claims in the court of law. Forget witnesses. Hit and runs are very common and insurance companies notoriously specialize in denying claims. Two-way insurance coverage is very expensive and almost completely unavailable for vehicles over ten years old–the drivers can only get basic liability.
She adds that there are moments of humanity among the crashes, but basically "aside from the kindness of strangers, it’s just you and that little gadget versus the hell that is the other people on the road".


What caused the explosion?

Authorities in Chelyabinsk said the blast (which you can hear clearly on this video) had been heard at an altitude of 10,000 metres (32,800ft), suggesting it occurred when the meteor or meteors entered the earth’s atmosphere.
As the meteorites shot across the sky, they sent fireballs crashing to earth. The shockwave from the explosion when the meteor entered the earth's atmosphere smashed windows, injuring 400 people, three of them seriously, buckled shop fronts, set off car alarms and affecting mobile phone signals. A wall was damaged at the Chelyabinsk Zinc Plant but there was no environmental threat, a plant spokeswoman said.
Reader Stuart Forbes sends this video, which shows the meteorites streaking across the sky at 4min 40sec and the sound of the explosion and shockwave at 7min.
Residents in Chelyabinsk heard the explosion at about 9.20am local time (5.20am GMT), saw a bright light and felt a shockwave, according to Reuters.
Viktor Prokofiev, 36, a resident of Yekaterinburg in the Urals Mountains, said:
I was driving to work, it was quite dark, but it suddenly became as bright as if it was day. I felt like I was blinded by headlights.
Andrei, a resident of Chelyabinsk, told Reuters:
I was standing at a bus stop, seeing off my girlfriend. Then there was a flash and I saw a trail of smoke across the sky and felt a shockwave that smashed windows.
This map shows the location of Chelyabinsk.

Source: guardian.co.uk 
any news agency around the world and newspapers online.
Video - Courtesy of Youtube
Here is the video from CBS News:

 Picture from: APTOPIX_Russia_Meteorite-0d778

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