1·Rather, they are dark because of interstellar dust that hides the stars behind it.
相反，它们之所以是黑暗的，是因为星际尘埃将恒星隐藏在它的后面。
2·Optical astronomy is most directly affected, for although interstellar gas is perfectly transparent, the dust is not.
光学天文学受到最直接的影响，因为虽然星际气体是完全透明的，但尘埃却不是。
3·The average density of interstellar material in the vicinity of our Sun is 1,000 to 10,000 times less than the best terrestrial laboratory vacuum.
在我们的太阳附近，星际物质的平均密度比最好的地球实验室真空还要低1000到10000倍。
4·But for other astronomers, interstellar dust is useful in its own right.
但对于其他天文学家而言，星际尘埃自身确是有用的。
5·My conclusions are that the 'safe bet' for predicting when the first interstellar mission will occur will always lie hundreds of years into the future.
我的结论是对于预测第一个星际使命什么时候发生下个“安全的赌注”这将永远会是在几百年后的未来。