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我们如何测量星体之间的距离

How Do We Measure the Distance to Stars?

离我们太阳系最近的恒星
The closest stars to our solar system are
大约距离地球4.3光年
about 4.3 light-years away from Earth
但我们是怎么知道那个距离的呢?
But how do we know that distance?
测量星体的距离似乎是不可能的
It seems like measuring a star’s distance should be impossible.
我们也不能从这里伸出宇宙级的卷尺
It’s not like we can stretch out a cosmic tape
到毕宿五
from here to Aldebaran,
一颗超过四百万亿英里以外的红巨星
a giant red star that’s over 400 trillion miles away.
幸运的是 我们有三角形
Fortunately, we have triangles.
试试这样做
Try this.
先往左边移动
Shift to the left.
然后再往右边移动
Then to the right.
这样一来 你面前的一切似乎都在来回移动
Everything in front of you appears to moveback and forth.
但是在远处的物体比附近的东西移动的少
But objects that are farther away move less than stuff that’s nearby.
这种效应被称为视差
This effect is called parallax,
我们可以用它来测量很远的距离
and we can use it to measure large distances.
当我们地球绕着太阳转时
As our planet goes around the sun,
相对于更远的星体
the stars appear to shift back and forth
近处的星体似乎在来回移动
relative to more distant stars.
而星体越远 它移动的幅度就越小
The farther away a star is, the less it moves.
这种移动非常微小
This shifting is incredibly tiny.
距离太阳最近的恒星的移动距离
The closest star to our sun moves no more
不超过从40英里外
than the width of a soccer ball seen from
看到的足球的宽度
40 miles away.
通过在一月观测一个星体
By looking at a star in January
然后七月再次观测它
and then again in July,
我们就可以画一个三角形
we can draw a triangle.
它底边是地球运动轨迹的直径
The base is the diameter of earth’s orbit.
所对的角就是星体出现的移动距离
The opposite angle is how far the star appears to shift.
再用些高中的三角函数知识
Dig up some high school trigonometry,
然后你就可以计算三角形的高
and you can calculate the triangle’s height,
这就是地球距离星体的距离
which in this case is the distance to thestar.
知道了这些距离我们就能测量其他参数
Knowing these distances lets us measure other things,
像是恒星的亮度
like the brightness of stars
或是星系的大小
or the size of galaxies.
2013年这一年非常关键
It’s so essential that in 2013,
欧洲航天局发射了一台名为“盖亚”的电子望远镜
the European Space Agency launched a telescope called Gaia
用比我们见过的更精确的方式来测量视差
to measure parallax with more precision thanwe’ve ever seen.
在地球大气层的湍流之上
Above the turbulence of Earth’s atmosphere,
盖亚一直在测绘地球到其他恒星的距离
Gaia has been plotting the distances to over
其数量超过10亿颗
a billion stars,
绘制了银河系及其周边星系的地图
creating a map of the Milky Way and some of its galactic neighbors.
所有这些都归功于不起眼的三角形
All that from the lowly triangle.
这里是《科学美国人》 我是德博基·查克拉瓦蒂
For Scientific American, I’m Deboki Chakravarti.

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视频概述

看用高中数学测量星体间距离

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https://www.youtube.com/watch?v=KD9dAJ7MWrU

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