Astronomers witness never-before-seen asteroid break-up

Astronomers witness never-before-seen asteroid break-up

天文學家首次"目睹"小行星分裂

Astronomers said Thursday they have witnessed for the first time the breakup of an asteroid, disintegrating into as many as 10 smaller pieces at a "leisurely" speed.

天文學家3月6日報告稱,他們首次觀測到一顆小行星分裂正以"慢悠悠的"速度裂解成差不多10塊碎片. 

The crumbling asteroid, designated P/2013 R3, was first noticed as an unusual, fuzzy-looking object by ground-based telescopes in Arizona on September 15, 2013, the researchers reported in the US journal Astrophysical Journal Letters.

這顆編號為P／2013　R3的小行星是2013年9月首次被亞利桑那州的地面望遠鏡發現的, 它看上去有些"模模糊糊、不同尋常".這一發現發表在新一期《天體物理學雜志通訊》上. 

A follow-up observation on Oct. 1 with the W. M. Keck Observatory on the summit of Mauna Kea, a dormant volcano on the island of Hawaii, revealed three bodies moving together in an envelope of dust nearly the diameter of Earth.

天文學家們在10月1日利用夏威夷的凱克天文臺進一步觀測發現,在一團直徑與地球相當的塵埃中,有3塊碎片.

Astronomers then looked at it with the Hubble Space Telescope, which soon showed there were really 10 embedded objects, each with comet-like dust tails, said David Jewitt of the University of California at Los Angeles, who led the astronomical forensics investigation.

研究負責人、美國加州大學洛杉磯分校教授戴維·朱伊特說,他們認為值得進一步研究,于是改用精度極高的哈勃太空望遠鏡進行觀測,很快發現這顆小行星正在裂解成約10塊碎片,而且每塊都有彗星一樣的尾巴.

The four largest rocky fragments are up to 400 yards (365.76 m) in diameter, about four times the length of a football field, Jewitt said. "Seeing this rock fall apart before our eyes is pretty amazing."

其中最大的4塊碎片直徑近365米,有4兩個足球場那么長.朱伊特說："看著這顆小行星在我們眼前分裂,感覺真是非常奇妙！" 

The asteroid began coming apart early last year, and the researchers said the fragments are drifting away from each other at a leisurely pace of one mile (about 1.6 kilometer) per hour.

這顆小行星從去年年初開始分裂,遠離彼此的相對速度只有"慢悠悠的每小時1.6公里".

The researchers said the rare event is not caused by a collision with another asteroid, or the pressure of interior ices warming and vaporizing. 

研究人員還表示這顆小行星發生分裂不是因為與另一顆小行星發生碰撞, 也不可能是因為有內部冰層升溫揮發導致小行星承受不住壓力而分裂. 

They suspected the break-up is a result of sunlight, which causes the rotation rate of the asteroid to gradually increase. Eventually, its component pieces succumb to centrifugal force and gently pull apart, "like grapes on a stem", they said. 

他們猜測,這顆小行星發生分裂是由于吸收陽光后自轉速度逐漸加快,最后在離心力作用下,小行星開始緩慢分裂.  

The possibility of disruption in this manner, known as the YORP effect, has been discussed by scientists for several years, but never reliably observed. 

多年來,科學家一直猜想小行星會以這種"亞爾科夫斯基效應"的方式分裂,但此前從未觀測到這種情況發生. 

The asteroid's remnant debris, weighing about 200,000 tons, will in the future provide a rich source of meteoroids, Jewitt said. 

朱伊特表示,這顆總重20萬噸的小行星最終將會成為流星體的豐富來源. 

Most will eventually plunge into the sun, but a small fraction of the debris may one day blaze across our skies as meteors, he added.