天文學(xué)家首次在另一個星系中發(fā)現(xiàn)了分子氧

天文學(xué)家首次在另一個星系中發(fā)現(xiàn)了分子氧

In a wild galaxy over half a billion light-years away, astronomers have detected molecular oxygen. It's only the third such detection ever outside the Solar System - and the first outside the Milky Way.

在5億光年之外的一個野生星系中，天文學(xué)家已經(jīng)探測到了分子氧。這只是太陽系之外的第三次探測，也是銀河系之外的第一次。

Oxygen is the third most abundant element in the Universe, behind hydrogen (naturally) and helium. So its chemistry and abundance in interstellar clouds are important for understanding the role of molecular gas in galaxies.

氧是宇宙中第三豐富的元素，僅次于氫(自然)和氦。因此，它的化學(xué)性質(zhì)和在星際云中的豐度對于理解星系中分子氣體的作用非常重要。

Astronomers have searched for oxygen again and again, using millimetre astronomy, which detects the radio wavelengths emitted by molecules; and spectroscopy, which analyses the spectrum to look for wavelengths absorbed or emitted by specific molecules.

天文學(xué)家一次又一次地尋找氧氣，他們嘗試了毫米天文學(xué)(探測分子發(fā)射的無線電波長)和光譜學(xué)(分析光譜，尋找特定分子吸收或發(fā)射的波長)這兩種工具。

But these searches have turned up a puzzling lack of oxygen molecules. Which means "a comprehensive picture of oxygen chemistry in different interstellar environments is still missing," wrote a team of astronomers led by Junzhi Wang of the Chinese Academy of Sciences in a new paper.

但是這些研究發(fā)現(xiàn)了一個令人費解的缺乏氧分子的現(xiàn)象，中國科學(xué)院領(lǐng)導(dǎo)的一個天文學(xué)家團隊在一篇新論文中寫道，這意味著“不同星際環(huán)境中氧化物的全面圖像仍然缺失”。

One place molecular oxygen has been detected is the Orion nebula; it's been hypothesised that out in space, oxygen is bound up with hydrogen in the form of water ice that is clinging to dust grains.

已經(jīng)探測到分子氧的一個地方是獵戶座星云，據(jù)推測，那里的氧與氫結(jié)合在一起，以冰的形式附著在塵埃顆粒上。

But the Orion nebula is a stellar nursery, and it's possible that the intense radiation from very hot young stars shocks the water ice into sublimation and splits the molecules, releasing the oxygen.

但獵戶座星云是一個恒星托兒所，因此年輕恒星很有可能發(fā)出的強烈輻射沖擊這些冰，使其升華并分解，釋放氧氣。

Which brings us to a galaxy called Markarian 231.

這些使研究人員想到了名為馬卡里安231的星系。

Markarian 231 is special. It's 561 million light-years away, and powered by a quasar. That's an extremely luminous galactic nucleus with an active supermassive black hole in the centre. They're the brightest objects in the Universe, and Markarian 231 contains the closest quasar to Earth.

馬卡里安231很特別。它距離地球5.61億光年，由類星體提供能量。類星體一個非常明亮的星系核心，中心有一個活躍的超大質(zhì)量黑洞。它們是宇宙中最明亮的天體，而馬爾卡里安231包含了離地球最近的類星體。

In fact, astronomers think Markarian 231 might have two active supermassive black holes in its centre, whirling around each other at a furious rate.

事實上，天文學(xué)家認為馬卡里安231可能在其中心有兩個活動的超大質(zhì)量黑洞，它們以極快的速度相互旋轉(zhuǎn)。

An active galactic nucleus drives molecular outflows, producing continuous shocks of the kind that might release oxygen from water in molecular clouds.

活躍的星系核驅(qū)動分子外流，產(chǎn)生連續(xù)的沖擊，這種沖擊可能會從分子云中的水釋放氧氣。

Using the IRAM 30-metre radio telescope in Spain, they took observations of the galaxy for four days across a number of wavelengths. In those data, they found the spectral signature of oxygen, in line with the shock hypothesis.

他們利用西班牙的IRAM 30米射電望遠鏡，在多個波長上對銀河系進行了為期4天的觀測。在這些數(shù)據(jù)中，他們發(fā)現(xiàn)了氧氣的光譜特征，與沖擊假說一致。

"With deep observations toward Markarian 231 using the IRAM 30 meter telescope and NOEMA, we detected [molecular oxygen] emission in [an] external galaxy for the first time," the researchers wrote in their paper.

研究人員在論文中寫道：“通過使用IRAM 30米望遠鏡和NOEMA對馬卡里安231進行深入觀測，我們首次探測到外部星系中的[分子氧]。”。

"The detected O2 emission is located in regions about 10 kpc (32,615 light-years) away from the center of Markarian 231 and may be caused by the interaction between the active galactic nucleus-driven molecular outflow and the outer disc molecular clouds."

“探測到的分子氧位于距離馬卡里安231中心約32,615光年的區(qū)域，可能是由活躍的星系核驅(qū)動的分子流出物和外圍盤狀分子云之間的相互作用產(chǎn)生的。”

The research has been published in The Astrophysical Journal.

這項研究已發(fā)表在《天體物理學(xué)雜志》上。