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2012-07-20 17:45

Oldest spiral galaxy in universe discovered



Compiled from news reports

Astronomers have discovered the universe's most ancient spiral galaxy yet, a cosmic structure that dates back roughly 10.7 billion years, a new study reveals.

The galactic find, discovered by researchers using NASA's Hubble Space Telescope, comes as something of a surprise. Other galaxies from such early epochs are clumpy and irregular, not strikingly symmetrical like the newfound spiral, which broadly resembles our own Milky Way.

"The fact that this galaxy exists is astounding," study lead author David Law, of the University of Toronto, said in a statement. "Current wisdom holds that such ‘grand-design’ spiral galaxies simply didn’t exist at such an early time in the history of the universe."

A team reporting in Nature says the galaxy BX442 got the gravitational "kick" it needed to form a spiral from a smaller "dwarf galaxy" orbiting it.

They first spotted BX442 as the one and only spiral-looking object in a survey of 300 galaxies carried out by the Hubble space telescope, when they were shocked to see what looked to be a spiral galaxy.

"What we've learned when we look at galaxies at that epoch is that they're very dynamically hot," explained Law.

"Even though we see some discs existing at that time, they're very thick and puffy, whereas the Milky Way has an... amount of random motion only about a tenth or so the amount of ordered rotation, giving rise to a very thin disc," he told BBC News.

To get a closer look at BX442, the team went on to use the OH-Suppressing Infrared Integral Field Spectrograph at the Keck observatory in Hawaii -- which can subtract the effect of all the water that lies between the Earth and galaxies at such astronomical distances.





관련 한글기사


107억살 최고령 나선은하 발견

지금까지 발견된 어떤 나선은하보다도 나이가 많은 약 107억년 전의 나선은하가 발견됐다고 BBC 뉴스와 스페이스 닷컴이 19일 보도했다.

캐나다 토론토 대학 과학자들은 미항공우주국(NASA)의 허블 우주망원경을 이용해 지구에서 약 107억 광년 거리에 있는 나선은하 BX442를 발견했다고 네이처지에 발표했다.

연구진은 "이런 은하가 이 시기에 존재했다는 것은 놀라운 일"이라면서 은하 형성에 관한 이론에 따르면 빅 뱅 후 겨우 30억년이 지났을 때 우주는 너무도 혼돈 상태여서 이처럼 완벽한 나선 형태를 가진 은하가 형성될 수 없는 것으로 알려져 있다고 지적했다.

학자들 사이에 `위대한 설계'(Grand Design)로 불리는 확실한 나선형 팔을 가진 얇고 가지런한 원반 형태로 물질이 모이려면 중력의 작용이 더 오랫동안 지속돼야만 할 것으로 생각됐던 것이다.

우주 탄생 초기에는 지금보다 훨씬 다양한 형태의 은하들이 존재했으며 대부분은 불규칙한 모양을 갖고 있었다.

연구진은 먼 거리에 있는 나선은하 300개 가량을 촬영해 그 특성을 분석했으나 이 가운데 나선은하로 확인된 것은 BX442 뿐이라고 밝혔다. (연합뉴스)




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