双语小知识:寻宝仙女座

Amateur Astronomer - - CONTENTS -

Deep Vision 远望

If you gaze long enough into a dark, starry sky — a sky that’s not polluted by streetlights or the Moon — it seems like you can see forever. That’s not quite the case, but you can come pretty close: The most distant object that’s easily visible to the unaided eye is two-and-a-half million light-years away. 如果你久久凝望黑暗而布满星斗的夜空——一片没有被路灯或是月光污染的天空,仿佛你就能一直看下去。这样说并不准确,但其实也很接近了:裸眼能看到的最远天体距离我们250万光年。 M31 is a giant galaxy in the constellation Andromeda. It looks like a skinny smudge of light that’s wider than the Moon. M31是仙女座中一个巨大的星系。它看起来像是一块比月亮还要宽大一些的模糊的光斑。 That smudge is the combined glow of hundreds of billions of stars — a cosmic pinwheel that’s even bigger than our own galaxy, the Milky Way. We’re viewing it from just above the edge, so it looks a bit like a fat cigar. 光斑由几千亿颗恒星的光芒汇聚而成,那是一个比我们的银河系更大的宇宙中的“大风车”。我们从它边缘上方观察它,所以它看起来有点像一根粗粗的雪茄烟。 We’re also seeing M31 as it looked far in the past. It takes the galaxy’s light two-and-a-half million years to reach us, so we see it as it looked two-and-a-half million years ago. Millions of stars that contribute to the galaxy’s glow have expired since then — some with titanic explosions that briefly shine brighter than billions of “normal” stars. We won’t know which ones, though, until their light reaches Earth — perhaps millions of years in the future, or perhaps as early as tonight. 我们也看到了M31在很久以前的样子。这一星系的光要花费250万年才能到达我们这里,所以我们看到的是它大概250万年前的样子。在那之后,曾在星系中闪耀的数百万颗恒星走向了死亡,有的伴随着剧烈的爆发,在短时间内比几十亿颗“正常的”恒星还要闪亮。当然,直到它们的光芒抵达地球,我们并不知道它们中哪些会爆发,或许在未来几百万年之后,也或许就在今晚…… We do know that M31 and the Milky Way are moving closer together, so over the next few billion years the galaxy will grow larger and brighter. Eventually, it and the Milky Way may merge — and some other galaxy will take M31’s place on the edge of forever. 我们确实知道M31和银河系正在靠近,所以再过几十亿年,M31会变得更大也更亮。最终它会和银河系融合在一起——那就又有其他的星系会取代M31处于“永恒”边缘的位置了。

图片中就是仙女座中的M 31,确切地说,应该是大约250万年以前的M 31。并不是摄影师乘坐了某种神秘的时间机器回到了从前,而是M 31距离我们太远,我们看见的是它在250万年前发出的光。250万光年这一遥远的距离,也使M 31成为肉眼可见的最远的地方。图片来源:A dam Evans/W ikipedia.

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