每日跟讀#699: Water found in atmosphere of planet beyond our solar system

Scientists for the first time have detected water in the atmosphere of an Earth-like planet orbiting a distant star, evidence that a key ingredient for life exists beyond our solar system, according to a study published on Wednesday.

根據週三發表的一份研究指出，科學家首次在某顆行星的大氣層中偵測到水的存在，該星體與地球相似，不過它環繞的恆星距離相當遙遠。這項發現證明，生命的關鍵要素也存在於太陽系之外。

Water vapor was found in the atmosphere of K2-18b, one of hundreds of “super-Earths” — worlds ranging in size between Earth and Neptune — documented in a growing new field of astronomy devoted to the exploration of so-called exoplanets elsewhere in the Milky Way galaxy. More than 4,000 exoplanets of all types and sizes have been detected overall.

科學家在「K2-18b」的大氣層中發現水汽，這顆行星是數百顆「超級地球」──大小介於地球和海王星之間的星體──的其中之一，記錄在持續成長的天文學新領域中。該領域研究致力於探索我們銀河系內其他星系的「太陽系外行星」。目前，科學家已偵測到超過四千顆不同類型和大小的太陽系外行星。

The latest discovery was reported in research by a team of scientists at University College London (UCL) published in the peer-reviewed journal Nature Astronomy. “We found water,” UCL astrophysicist Ingo Waldmann told Reuters of the breakthrough, revealed from observations made with the Hubble Space Telescope, which analyzed starlight filtered through K2-18b’s atmosphere.

這項最新發現來自倫敦大學學院一組科學家團隊的研究，並發表在經過同儕審查的期刊《自然‧天文學》上。倫敦大學學院的天體物理學家印哥‧瓦爾德曼向路透表示：「我們發現水了」，並說明這項突破來自於哈伯太空望遠鏡的觀察，分析星光經過「K2-18b」大氣層過濾後的變化。

More precisely, it marks the first time scientists have found water in the atmosphere around a super-Earth — as opposed to a gas giant — orbiting a star within its “ habitable zone,” just the right distance for liquid water to potentially exist on the surface.

更精確地說，這是科學家首次在恆星「適居帶」內運行的超級地球──而非氣體巨行星──其大氣層中發現水。「適居帶」與恆星的距離剛好能讓液態水有可能存在於行星表面。

Angelos Tsiaras, an astronomer at UCL, said the team is focusing its attention on identifying exoplanets with conditions similar to those on Earth. “But of course this is not in order to find a place where we could go. This is still science fiction,” Tsiaras said, noting that K2-18b orbits a dwarf star in the constellation Leo that lies 100 light years from Earth.

倫敦大學學院的天文學家安傑洛斯‧齊阿拉斯表示，研究團隊正聚焦於辨認環境與地球表面相似的太陽系外行星。齊阿拉斯說：「但當然，這不是為了尋找我們可以前往的地方。目前這種事情仍然只會出現在科幻小說中。」他也提到，「K2-18b」位於獅子座中，繞著一顆白矮星運行，距離地球一百光年。

While light from the sun takes several minutes to reach Earth, light from K2-18b’s star takes a century to reach our planet, “so for us to travel there is impossible,” he said. “Given it’s so far away we don’t really have any other choice but stay on our own Earth, so it’s important to make Earth great again rather than looking for an alternative to go to,” Tsiaras said.

相對於太陽光只要花幾分鐘的時間就會抵達地球，「K2-18b」所繞行的恆星，其光線要花上一個世紀才會抵達我們的行星。齊阿拉斯說：「所以，對我們而言，前往那裡是不可能的。」他並進一步指出：「鑑於這顆行星實在太過遙遠，我們除了留在自己的地球上別無選擇。也因此，重要的是讓地球再度偉大，而不是找出另一個替代行星後飛向那邊。」

Aside from the tremendous distance separating Earth from K2-18b, the exoplanet is likely exposed to far more radiation than Earth, diminishing the prospects for life evolving there. However, the discovery brings astronomers closer to answering the fundamental question of how unique Earth is in the universe, the scientists said.

除了分隔地球和「K2-18b」行星的極大距離之外，這顆太陽系外行星可能曝露在遠高於地球接收的輻射線中，更加削弱生命在該地發展的前景。不過，科學家們表示，這項新發現，讓天文學家更加接近解答「地球在宇宙中有多獨特」的根本性問題。

Source article: http://www.taipeitimes.com/News/lang/archives/2019/09/15/2003722288