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Meteor blast over Bering Sea was 10 times size of Hiroshima
白令海上空流星爆炸 威力強達十倍廣島原子彈

A meteorite trail is pictured above a residential apartment block in the Urals city of Chelyabinsk, Russia, on Feb. 15, 2013.
一道隕星痕跡可見於俄國烏拉爾山區城市車里雅賓斯克一棟住宅公寓大樓上方的天空,攝於二○一三年二月十五日。

Photo: AFP
照片:法新社

A meteor explosion over the Bering Sea late last year unleashed 10 times as much energy as the atomic bomb that destroyed Hiroshima, scientists have revealed. The fireball tore across the sky off Russia’s Kamchatka Peninsula on Dec. 18 and released energy equivalent to 173 kilotonnes of TNT. It was the largest air blast since another meteor hurtled into the atmosphere over Chelyabinsk, in Russia’s south-west, six years ago, and the second largest in the past 30 years.

Unlike the Chelyabinsk meteor, which was captured on CCTV, mobile phones and car dashboard cameras, the December arrival from outer space went largely unnoticed at the time because it exploded in such a remote location. NASA received information about the blast from the US air force after military satellites detected visible and infrared light from the fireball.

Lindley Johnson, planetary defense officer at NASA, told BBC News that blasts of this size were expected only two or three times a century. The space agency’s analysis shows that the meteor, probably a few meters wide, barreled into Earth’s atmosphere at a speed of 32km per second and exploded at an altitude of around 26km. The blast released about 40 percent of the energy of the meteor explosion over Chelyabinsk, according to Kelly Fast, NASA’s near-Earth objects observations program manager, who spoke at the 50th Lunar and Planetary Science conference near Houston.

Since the event came to light, meteor researchers have been asking airlines for any sightings of the fireball, which came in close to routes used by commercial carriers flying between North America and Asia. Peter Brown, a meteor specialist at Western University in Canada, spotted the blast independently in measurements made by global monitoring stations. The explosion left its mark in data recorded by a network of sensors that detect infrasound, which has a frequency too low for the human ear to pick up. The network was set up to detect covert nuclear bomb tests.

TODAY’S WORDS
今日單字

1. meteor n.

流星 (liu2 xing1)

2. unleash v.

釋放 (shi4 fang4)

3. atomic bomb phr.

原子彈 (yuan2 zi3 dan4)

4. equivalent adj.

相當於 (xiang1 dang1 yu2)

5. hurtle v.

猛烈衝撞 (meng3 lie4 chong1 zhuang4)

6. infrasound n.

超低頻音 (chao1 di1 pin2 yin1)


The Bering Sea event is another reminder that, despite efforts to identify and track space rocks that could pose a threat to Earth, sizable meteors can still arrive without warning. NASA is working to identify 90 percent of near-Earth asteroids larger than 140m by 2020, but the task could take another 30 years to complete.

The 20m-wide meteor that detonated over Chelyabinsk lit up the morning sky on Feb. 15, 2013. At its most intense, the fireball burned 30 times brighter than the sun. The flash quickly gave way to a shockwave that knocked people off their feet and shattered windows in thousands of apartments. No one was killed but more than 1,200 people were injured, many by flying glass. Some sustained retinal burns from watching the spectacle.

In 1908, the most powerful meteor blast in modern times shook the ground in Russia. The rock exploded over Tunguska, a sparsely populated region in Siberia, and flattened an estimated 80 million trees over an area of 2,000 square kilometers.

(The Guardian)

科學家透露,白令海上空去年底發生一起流星爆炸,釋放出相當於摧毀廣島原子彈的十倍能量。這顆火球在去年十二月十八日劃過俄羅斯的堪察加半島上空,釋放出的能量相當於十七萬三千噸的黃色炸藥。這起事件是繼六年前另一顆流星猛烈衝進俄國西南部車里雅賓斯克上空的大氣層以來,最大的一場空中爆炸,同時也是過去三十年來第二大的爆炸事件。

不同於車里雅賓斯克那顆流星,被閉路電視、手機以及行車記錄器廣泛拍攝到,這位外太空訪客去年十二月抵達時幾乎無人察覺,原因在於爆炸地點實在是人跡罕至。後來因為軍用衛星在十二月偵測到這顆火球發出可見光和紅外線,美國國家航空暨太空總署(NASA)才從美國空軍方面獲得爆炸的相關資訊。

美國太空總署的行星防禦官員林德里‧約翰遜向英國廣播公司新聞網表示,這個規模的爆炸每一百年預期只會發生兩到三次。根據太空總署分析顯示,該顆流星約數公尺寬,以每秒約三十二公里的速度衝進地球的大氣層,並在大約二十六公里的高空中爆炸。美國太空總署的近地天體觀測計畫主管凱莉‧法斯特,近日於休士頓附近召開的第五十屆月球與行星科學研討會中表示,這次爆炸釋放的能量約為車里雅賓斯克上空流星爆炸的百分之四十。

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