肥皂泡泡和水母星系
Using the detailed eyes of the Atacama Large Millimeter/submillimeter Array (ALMA) and ESO’s Very Large Telescope (VLT), astronomers have mapped the intense tails of a cosmic jellyfish: a number of knotty streams of gas spewing outwards from a spiral galaxy named ESO 137-001. This celestial cnidarian is shown here in beautiful detail. The various elements making up this image were captured by different telescopes. The galaxy and its surroundings were imaged by the NASA/ESA Hubble Space Telescope; its tails, which trace streams of hydrogen and show up in hues of bright purple, by the MUSE instrument mounted on the VLT; and bright hotspots of carbon dioxide emission from within the system, which show up as flares of orange-red, were spotted by ALMA. These tails are caused by a dramatic phenomenon known as ram-pressure stripping. The space between galaxies in a cluster is not empty, but full of material that acts like a viscous fluid. As a galaxy travels through this resistant environment, gas is stripped out of the galaxy to form a wake that creates beautiful, intricate systems such as that seen here around ESO 137-001 (which resides in the Norma galaxy cluster). The direction and position of the tail shed light on the way in which the galaxy is moving — with galaxies usually falling towards the centre of the cluster itself. This image offers the first high-resolution map of the cold molecular gas lurking within a ram-pressure stripped system. ESO 137-001 is one of the nearest jellyfish galaxies to Earth, and is particularly interesting because its long, extended tails of gas contain features known as ‘fireballs’: bursts of star formation. The precise mechanisms governing how stars form within jellyfish tails are mysterious, and this map thus provides a new window onto the conditions needed for new stars to form in such intense, changeable environments.  The ALMA array comprises 66 antennas, and is located on the Chajinator plateau in the Chilean Atacama Dese

肥皂泡泡和水母星系

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大家知道怎麼製作肥皂泡嗎?首先,你把一個塑膠或金屬的圓環,放進肥皂水裡,然後輕輕把環拿起來,這時候,圓環裡佈滿一層薄薄的肥皂,如果你不去動那個環,什麼事情都不會發生。但要是你開始走路,或是做個把環舉到頭頂的動作等等,隨著你的運動,環後面就拖曳出一長串美麗的肥皂氣泡了。
這背後的原因當然是空氣的壓力。你在空氣中移動環,是絲毫不覺得困難的事。然而,薄薄的肥皂膜很容易被環所穿過去的空氣向後推,所以肥皂泡泡很容易被從環中吹出去。
天文學家在一個遙遠的星系團中,研究了一個宇宙中的肥皂泡玩具。那個星系團中的星系之間的空間裡,充滿極熱稀薄的氣體——我們暫時把這些氣體當作是「空氣」吧。星系團中有個星系正以相當高的速度穿過了這團氣體——我們且把這星系當成你手上拿的「環」。結果,星系中稀薄的氣體——「肥皂膜」——就會被朝外推,變成拖曳在後方了。天文學家稱這個過程為「衝壓力剝離」。
哈伯太空望遠鏡已經對這樣的星系及宇宙版「肥皂泡」做了詳細的成像。合在一起看,它們滿像水母,後面拖著一條細細的尾巴。利用位於智利的一座「甚大望遠鏡」,天文學家還探測到水母尾巴那邊灼熱的氫氣發出的輝光。
現在凹瑪望遠鏡也對水母星系做了研究。在凹瑪的偵測裡發現,氣體流(圖像中橘色的節點)裡面,有一氧化碳分子發出來的次毫米波輻射。這是我們第一次在衝壓力剝離星系裡偵測到冷分子氣體!
對於想了解該星系怎麼運動的人,以及想更了解星系和星系團中稀薄氣體間交互運動的科學家來說,新觀測幫他們提供了一些以前沒有的資訊。另外,關於水母星系尾巴部分發生的原因不明星暴增(在短時間内形成很多星星的現象,被稱為「星暴增」),以後還可以繼續做更多調查。


發現了什麼?

凹瑪望遠鏡觀測到的水母星系,正式名稱為ESO 137-001。南半球有個「矩尺座」,水母星系是「矩尺座星系團」的一部分,距離地球約2億2000萬光年。矩尺座星系團裏有好幾百個星系。其中之一的這個水母星系ESO 137-001,以時速700萬公里朝向銀河的中心移動。由於這種快速的運動,所以氣體被從該星系向外推出,長出一條25萬光年長的尾巴。

誰發現的?

用凹瑪望遠鏡觀測了在水母星系ESO 137-001裡面的一氧化碳的,是捷克科學研究院的天文學家Pavel Jáchym和他的9位團隊伙伴,包括美國、加拿大、英國、澳大利亞、葡萄牙、法國等天文學家。這項研究發表在天文學專業雜誌《天文物理期刊》上。

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