Star Tau Ceti Has Two Planets in Habitable Zone
VOA News
August 13, 2017 2:58 AM (source)
Star Tau Ceti Has Two Planets in Habitable Zone
天文新發現:恆星天倉五有兩顆位於「適居帶」的行星
August 13, 2017 2:58 AM
George Putic
WASHINGTON —
Scientists from U.S. and Britain have found four planets, slightly larger than Earth, orbiting a star visible with a naked eye.
Using a technique so sensitive that it can measure tiny changes in the light emitted by stars, scientists at University of California Santa Cruz and the University of Hertfordshire detected the planets orbiting the star Tau Ceti, which is 12 light-years from Earth. Two of the planets orbit in the so-called habitable zone, meaning the surface water could possibly exist.
The changes in light are caused by gravitational pull of the planets orbiting the star.
Tau Ceti, in the south of the constellation Cetus, emits light spectrum similar to our sun but is about 25 percent smaller.
The two planets in its habitable zone are larger than Earth, but frequent bombardment by asteroids and comets from the star's massive debris ring make them improbable candidates to sustain life.
Observations were done from the Keck Observatory in Hawaii and the European Southern Observatory's Very Large Telescope in Chile.
美國和英國的科學家發現了四個比地球還大上一些的行星(planet),它們繞行著(orbit)一個我們肉眼即可見的(with a naked eye)恆星(star)。
美國加州大學聖塔克魯茲分校(University of California Santa Cruz)和英國赫特福德大學(University of Hertfordshire)的科學家們使用一種非常敏銳的(sensitive)測量技術,可以測量出恆星發射(emit)的光線的微小變化。他們偵測到(detect)繞行著距離地球12光年(light-year)的恆星天倉五(Tau Ceti)的行星。其中的兩個行星在所謂的適居帶(habitable zone)繞行,這意味著行星上可能存在著地表水。
科學家們偵測到的光線變化是由行星繞行恆星時的重力(gravitational pull)所致。
位在鯨魚星座(constellation Cetus)南方的天倉五所發射出光線的光譜(spectrum)與我們的太陽相似,但天倉五的體積較太陽小了約25%。
這兩個位於適居帶的行星比地球大,但自天倉五恆星龐大的岩屑環(debris ring)而來的小行星(asteroid)與彗星(comet)所造成的頻繁撞擊(bombardment),使得這兩個行星不太可能(improbable)成為可維持(sustain)生命發展的候選者。
此天文觀測是由夏威夷(Hawaii)的凱克天文台(Keck Observatory)和智利(Chile)的歐洲南方天文台的甚大望遠鏡(European Southern Observatory's Very Large Telescope)所執行。
Language Notes
orbit [`ɔrbɪt] (v) 繞軌道運行,沿軌道圍繞(行星或恆星)運行
emit [ɪ`mɪt] (v) 發出,射出,散發(光、雜訊、氣味或氣體)
habitable (a) 適合居住的,可以居住的
* inhabit (v) 居住於. . . . . .。與本字相關的幾個易混淆的字須注意:形容詞 "inhabitable" 是在動詞 "inhabit" 字尾加 "-able"而來,意思仍為「可居住的」,所以 "habitable"、"inhabitable" 是同樣的意思,而加上 "un-" 字首後形成的 "uninhabitable" 才是指「不適合居住、不能居住的」。另外,"habitual" 是名詞 "habit"「習慣」的形容詞,意思為「通常的、習慣性的」
gravitational [ˏgrævə`teʃənḷ] (a) 重力的,引力的
* gravitation [ˏgrævə`teʃən] (n) 重力,引力
constellation [ˏkɑnstə`leʃən] (n) 星座;星座區域
* 本字的字根為 "stella",即 "star"「星星」之意
bombardment [bɑm`bɑrdmənt] (n) 砲擊;轟炸
* bombard [bɑm`bɑrd] (v) 砲擊;轟炸
debris [də`bri]/[`debri] (n) 碎片,殘駭
* 須注意本字為「不可數名詞」,且字尾 "s" 不發音;在發音上可分兩種:美式發音,重音在第二音節;英式發音,重音在第一音節
improbable [ɪm`prɑbəbḷ] (a) 不大可能發生的;未必確實的
* 本字由表否定的字首 "im-" 和形容詞 "probable"「很可能真實的;很可能發生的」組成
Check your vocabulary!
Debris from the aircraft was scattered over a large area.
It's highly improbable that Norris will agree.
A lot of improvements would have to be made before the building was habitable.
On this mission the Shuttle will orbit the Earth at a height of several hundred miles.
The machine emits a high-pitched sound when you press the button.
編譯:簡嘉呈
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