Possible model of exoplanets with a rocky core andgaseous atmosphere (artist's impression)
具有巖石核心和氣態大氣層的系外行星可能具有的模型（來自藝術家的印象）
Is therea second Earth out there in space? Our knowledge of planetary systems far, faraway is increasing constantly, as new technologies continue to sharpen our gazeinto space. To date, 3,700 planets have already been discovered outside oursolar system. The planetary masses and radii of these exoplanets can be used toinfer their mean density, but not their exact chemical composition andstructure. The intriguing question about what these planets could look like isthus still open.
太空中有第二個地球嗎？隨著新技術不斷擴大，我們對太空的注視，我們對遠距離行星系統的了解不斷增加。迄今為止，已經在太陽系外發現了3,700顆行星。這些系外行星的行星質量和半徑可用於推斷它們的平均密度，但不能確定它們的確切化學成分和結構。因此，關於這些行星看起來像什麼的有趣問題仍然沒有答案。
"Theoretically, we can assume various compositions,such as a world of pure water, a world of pure rock, and planets that havehydrogen-helium atmospheres and explore what radii are expected" explainsMichael Lozovsky, a doctoral candidate in the group of Prof. Ravit Helled atthe Institute for Computational Science at the University of Zurich.
「從理論上講，我們可以假設各種成分，例如純淨水世界，純巖世界，以及具有氫 - 氦氣的行星，並探索預期的行星半徑」，蘇黎世大學計算科學研究所Ravit教授組博士候選人Michael Lozovsky解釋道。
Thresholds for planetary composition行星組成的閾值
Lozovsky and collaborators have used databases andstatistical tools to characterize exoplanets and their atmospheres. These arefairly common and surrounded by a volatile layer of hydrogen and helium.However, the directly measured data previously didn't allow the researchers todetermine the exact structure, since different compositions may lead to thesame mass and radius. In addition to the accuracy of the data relating to massand radius, the research team thus also investigated the assumed internalstructure, temperature and reflected radiation in 83 of the 3,700 knownplanets, for which the masses and radii are well-determined.
Lozovsky和合作者使用資料庫和統計工具來描述系外行星及其大氣層。這些是相當常見的並且被揮發性的氫和氦層包圍。然而，之前直接測量的數據不允許研究人員確定確切的結構，因為不同的成分可能導致相同的質量和半徑。除了與質量和半徑有關的數據的準確性之外，研究小組還調查了3,700個已知行星中83個的假定內部結構，溫度和反射輻射，其質量和半徑是確定的。
"We used a statistical analysis to set limits onpossible compositions. Using a database of detected exoplanets, we found thatevery theoretical planetary structure has a 'threshold radius', a planetaryradius above which no planets of this composition exist," explains MichaelLozovsky. The amount of elements in the gaseous layer that are heavier thanhelium, the percentage of hydrogen and helium, as well as the distribution ofelements in the atmosphere are important factors in determining the thresholdradius.
「我們使用統計分析來對可能的成分進行限制。使用檢測到的系外行星的資料庫，我們發現每個理論上的行星結構都有一個'閾值半徑'，一個行星半徑，在此之上不存在這種成分的行星，」Michael Lozovsky解釋道。氣體層中比氦重的元素的量，氫和氦的百分比以及大氣中元素的分布是確定閾值半徑的重要因素。
Super-Earths and mini-Neptunes超級地球和迷你海王星
The researchers from the Institute for ComputationalScience found that planets with a radius of up to 1.4 times that of Earth(6,371 kilometers) can be earth-like, i.e. they have a composition similar toEarth. Planets with radii above this threshold have a higher share of silicatesor other light materials. Most of the planets with a radius above 1.6 radii ofthe Earth must have a layer of hydrogen-helium gas or water in addition totheir rocky core, while those larger than 2.6 Earth radii can't be water worldsand therefore might be surrounded by an atmosphere. Planets with radii largerthan 4 Earth radii are expected to be very gaseous and consist of at least 10percent hydrogen and helium, similarly to Uranus and Neptune.
來自計算科學研究所的研究人員發現，半徑達地球半徑（6,371公裡）的1.4倍的行星可以是地球狀的，即它們的成分與地球相似。半徑超過此閾值的行星具有更高比例的矽酸鹽或其他輕質材料。大多數半徑超過地球半徑1.6倍的行星除巖石核心外還必須有一層氫氦氣或水，而大於地球半徑2.6倍的行星不能成為水世界，因此可能被同一種氣體圍繞。半徑大於地球半徑4倍的行星預計是非常氣態的，由至少10％的氫和氦組成，類似於天王星和海王星。
The findings of the study provide new insights into thedevelopment and diversity of these planets. One particularly interestingthreshold concerns the difference between large terrestrial-like planets --otherwise known as super-Earths -- and small gaseous planets, also referred toas mini-Neptunes. According to the researchers, this threshold lies at a radiusof three times that of Earth. Below this threshold, it is therefore possible tofind earth-like planets in the vast expanse of the galaxy.
該研究的結果為這些行星的發展和多樣性提供了新的見解。一個特別有趣的閾值是大型類地行星（也稱為超級地球）和小型氣體行星（也稱為迷你海王星）之間的差異。根據研究人員的說法，這個閾值的半徑是地球的三倍。低於這個閾值，因此可以在廣闊的星系中找到類似地球的行星。
Exoplanet 太陽系外行星
Rocky 巖石的
Gaseous 氣體的
Gaze 注視
Radii （radius的複數）半徑
Intriguing 有趣的
Helium 氦
Threshold 閾值
Radiation 輻射
Hydrogen 氫
Neptune 海王星
Composition 組合
Silicate 矽酸鹽
Uranus 天王星
Atmosphere 氣圈
Terrestrial 地球上的
Vast 巨大的
本期：迷你數獨
每個謎題都由一個在不同位置給與提示數字的4x4或6x6網格組成。遊戲的目的是將空方格填上數字1到4（對於4x4大小的謎題）或者1到6（對於6x6的謎題），使得每一行，每一列以及每一個宮都沒有重複的數字出現。
本期難度：Moderate
（答案見下期）
上期互動答案
上期文章：研究人員教計算機去看視錯覺
註： 數獨是一種源自 18 世紀末的瑞士數學家歐拉所創造的拉丁方塊遊戲。傳數獨源起於拉丁方陣（ Latin Square ）， 1970 年代在美國發展，改名為數字拼圖（ Number Place ）、之後流傳至日本並發揚光大，以數學智力遊戲智力拼圖遊戲發表。在 1984 年一本遊戲雜誌《パズル通信ニコリ》正式把它命名為數獨，意思是「在每一格只有一個數字」。後來一位前任香港高等法院的紐西蘭籍法官高樂德（ Wayne Gould ）在 1997 年 3 月到日本東京旅遊時，無意中發現了。他首先在英國的《泰晤士報》上發表，不久其他報紙也發表，很快便風靡全英國，之後他用了 6 年時間編寫了電腦程式，並將它放在網站上，使這個遊戲很快在全世界流行