宇宙的奧秘總是令人嚮往，人們不斷發現探索出新的信息。
The universe holds so many mysteries for us human beings. Its enormous size invites people to keep learning and finding out new information about it.
本短文將介紹宇宙中存在著的三種物質。首先是星系一個受引力束縛系統包括恆星,恆星殘骸,星際氣體和塵埃,暗物質。宇宙中可觀測到的大約有1700億個星系。想像宇宙是多麼巨大!
Today, we will learn about three basic structures in the universe. Let’s start with number one: galaxies. A galaxy is a gravitationally bound system consisting of stars, stellar remnants, interstellar gas and dust, and dark matter. There are approximately 170 billion galaxies in the observable universe. Can you imagine how huge that is?
數以億計的星系總稱為銀河系，其中就包括了我們的太陽系。銀河系的英語是Milky Way ，因為它看上去就像打翻的牛奶(Milk）。銀河系中有數以億計的星球，比地球大的就至少有170億。
Of those billions of galaxies, one is called the Milky Way. It is the galaxy that contains our solar system, where Earth is located. It is called the Milky Way because the disk of the galaxy runs across the sky as a band of glowing light, like spilled milk. Astronomers estimate that there are between 100 and 400 billion stars in the Milky Way, and think that each star has at least one planet. So there are likely hundreds of billions of planets in the Milky Way, and at least 17 billion of those are the size and mass of Earth.
我們的太陽位於銀河系主要兩條旋臂的其中一條：獵戶臂。太陽系是以太陽為中心，和所有受到太陽的引力約束天體的集合體。太陽離銀河系中心大約2.4萬光年。
The Sun is located in the Orion Arm, a region of space in between the two major arms of the Milky Way. The Sun and all the objects that orbit it, either directly or indirectly, form the solar system. It takes the Sun about 240 million years to orbit the Milky Way once.
因此，我們可以想像太陽繞著銀河系轉，我們的地球他、繞著太陽轉。宇宙中的所有物質都是圍繞的另一個物質轉的。是不是很神奇？
So imagine this: the Sun orbits around the Milky Way, and Earth orbits around the Sun. Everything in the universe orbits around something, or is orbited around by something else … or both! It paints a huge, complex, beautiful picture, doesn’t it?
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