宇宙探索中的十大極限物質(下)

est Galaxy

5.最小的星系

Galaxies are immense—countless stars set in an image painted by nuclear processes and gravity. They're so overwhelmingly large and luminous that we can see many of them with the naked eye across great distances. So it's easy to forget that galaxies can be found at the opposite end of the size spectrum as well.

星系無邊無際——那是無數的星星在覈反應和重力的作用下所構成的畫面。他們無限龐大，耀眼無比，以至於我們遠距離就能用肉眼觀察到他們。因此人們很容易忽略能夠找到微小星系的可能性。

'Segue 2' is an example of how something small can take us by surprise, because it only contains about 1,000 stars. For contrast, our galaxy boasts a number in the hundreds of billions. The combined output of the whole galaxy is only about 900 times greater than our Sun, quite underwhelming considering our own star isn't especially large or impressive on a cosmic scale. As the capabilities of our telescopes improve, we might find more outliers like Segue 2, which is great for math, because galaxies of this size were predicted but never observed until recently.

Segue 2矮星系是一個 "小巧玲瓏" 出其不意的典型例子。因爲它只包含1000顆恆星。相反地，我們的星系卻擁有數以億計顆恆星。鑑於我們的星系在浩淼的宇宙中不是特別巨大和突出，而它整個星系的合成輸出僅比我們的太陽系多出900倍，這着實讓人感到失望。隨着望遠鏡性能的不斷提高，我們也許會發現更多像Segue 2一樣的"局外人"。這對於數學的發展無疑是件好事，因爲這樣大小的星系曾被預測過，但直到最近才被觀測到。

est Impact Crater

4.最大的撞擊坑

Ever since we've been studying Mars in appreciable detail, there's been disagreement about what caused the planet's hemispheres to look so dissimilar to each other. A new-ish theory states that the disproportion is due to an immense catastrophic impact that changed the face of the planet. The Borealis Basin offers clues to Mars' tumultuous past, as this is the largest crater (so far) in the Solar System. It covers a large portion of the planet: at least 40 percent, spanning an area 8,500 kilometers (5,300 mi) across. The second largest crater is also on Mars, yet is four times smaller.

自從我們開始研究火星以來，到底是什麼使得火星半球與其他行星大相徑庭，人們對此一直存有爭議。一個最新的學說闡明瞭此差異是因爲一次巨大的災難性的撞擊改變了火星的本來面貌。伯勒里斯盆地——也是迄今爲止太陽系裏最大的撞擊坑，爲火星騷亂的過去提供了線索。它覆蓋了大部分的火星：其面積就佔了至少40%，跨度長達8500公里。第二大的撞擊坑也在火星上，不過比伯勒里斯盆地小四倍。

To have produced such a large crater, the ancient impact must have been absolutely otherworldly, with the offending projectile calculated to have been larger than Pluto.

能夠產生如此龐大的巨坑，早期的那次撞擊必定是空前絕後的，據計算撞擊的拋射體體積比冥王星還要大。

est Perihelion In The Solar System

3.近日點最接近太陽的小行星

While Mercury may be the closest large object to the Sun, there are plenty of smaller things that get even closer. Perihelion is the point in orbit nearest the parent star, and asteroid 2000 BD19 has the smallest orbit, getting incredibly intimate with the giant, hot ball of nuclear explosions that keeps us warm and alive. Since the perihelion is only .092 astronomical units—1 AU is about how far the Earth is from the Sun, on average—HD19 gets hot. Really hot actually, reaching temperatures that could melt zinc and other metals.

雖然水星是離太陽最近的大行星，但還有很多小行星離太陽更近。近日點是最接近母恆星的軌道上的點，而序號爲2000 BD19的小行星擁有最小的軌道，與太陽無限接近。太陽是巨大的伴有核爆炸的火球，它爲人類提供了溫暖和生命。因爲近日點只有0.092個天文單位——一個天文單位是地球跟太陽的平均距離——2000 BD19表面會變得十分炎熱，其高溫度足以使鋅和其他金屬融化。

Studying this asteroid is important because it helps us glean how different factors can shift a body's orbital orientation. One of these factors is Einstein's famous theory of general relativity. Therefore, careful scrutiny of this near-Earth object can help us see how this amazing theory relates to practical observations.

研究這個小行星非常重要，因爲它能夠幫助我們收集一些有關於不同因素改變一個天體的軌道定向的信息。其中一個因素就是愛因斯坦著名的相對論。因此，認真勘察接近地球的天體能夠幫助我們理解這個神奇的理論如何與實際觀測聯繫起來。

emely Old Quasar

2.最古老的類星體

Some black holes are extremely massive, and that's to be expected, because they ingest anything that gets in their way.

人們預測一些黑洞非常龐大，因爲他們能把任何擋道的物體全部吸入。

At two billion solar masses, ULAS J1120+0641 was a huge surprise for astronomers—not necessarily due to its magnitude, but due to its age. ULAS is the oldest quasar (basically a black hole puking into space) ever found. It appeared less than 800 million years after the Big Bang. That's absolutely ancient, and it means that the light from this distant quasar had been on a 12.9-billion-year intergalactic voyage before it arrived here on Earth. No one's sure why the black hole is so big, since there wasn't much of anything for it to eat that long ago.

ULAS J1120+0641 擁有20億倍的太陽質量，對於天文學家來說，它的發現是個"重磅"驚喜。這不僅僅是因爲它的大小，還因爲它的年代。ULAS是迄今爲止人們發現的最古老的類星體（基本上是由一個黑洞噴吐而出）。它在宇宙大爆炸後不到8億年的時候形成。這絕對是非常古老的，因爲這意味着來自這個遙遠類星體的光要經過長達129億年的星際之旅才能到達地球。沒有人知道爲什麼這個黑洞如此之大，因爲早前並沒有很多物質能夠被吞併。

s On Titan

1.土衛六（又稱泰坦）

With spring emerging and winter clouds retreating, the Cassini probe was recently able to get some great snapshots of the lakes littering Titan's north pole topography. Water cannot exist in this alien landscape, but the temperatures are just right for liquid methane and ethane to flow and emerge from the moon's interior.

冬去春來，卡西尼號搜索太空船最近拍到了土衛六北極的地貌圖，其中充滿了湖泊。水無法在這個異域存在，但是溫度卻爲液態甲烷和乙烷從月球內部涌現並且浮動創造了合適的條件。

Oddly enough, this is the first time the clouds have lifted enough to offer a clear view of the pole, even though the Cassini probe has been orbiting Titan since 2004. The main lakes are each hundreds of miles wide, with the largest, Kraken Mare, the size of "the Caspian Sea and Lake Superior combined."The existence of a liquid environment was integral for the formation of life on Earth, but seas full of hydrocarbons are a completely different animal, since material can't dissolve in this substance as well as it can in water.

說來也怪，儘管卡西尼號搜索太空船早在2004年就繞着土衛六觀測，但這是第一次雲層消散天文學家拍到北極的清晰畫面。大部分的湖泊有數百英里寬，最大的可肯拉海是裏海和蘇必略湖的總和。液態環境的存在是構成地球生命的必要條件。但是充滿碳氫化合物的海洋孕育的生命形式和地球不同，因爲有些能在水裏能分解的物質不能在碳氫化合物中分解。

翻譯:高陳影 來源：前十網