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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?

The closest stars to our solar system are

about 4.3 light-years away from Earth

But how do we know that distance?

It seems like measuring a star’s distance should be impossible.

It’s not like we can stretch out a cosmic tape

from here to Aldebaran,

a giant red star that’s over 400 trillion miles away.

Fortunately, we have triangles.

Try this.

Shift to the left.

Then to the right.

Everything in front of you appears to moveback and forth.

But objects that are farther away move less than stuff that’s nearby.

This effect is called parallax,

and we can use it to measure large distances.

As our planet goes around the sun,

the stars appear to shift back and forth

relative to more distant stars.

The farther away a star is, the less it moves.

This shifting is incredibly tiny.

The closest star to our sun moves no more

than the width of a soccer ball seen from

40 miles away.

By looking at a star in January

and then again in July,

we can draw a triangle.

The base is the diameter of earth’s orbit.

The opposite angle is how far the star appears to shift.

Dig up some high school trigonometry,

and you can calculate the triangle’s height,

which in this case is the distance to thestar.

Knowing these distances lets us measure other things,

like the brightness of stars

or the size of galaxies.
2013年这一年非常关键
It’s so essential that in 2013,

the European Space Agency launched a telescope called Gaia

to measure parallax with more precision thanwe’ve ever seen.

Above the turbulence of Earth’s atmosphere,

Gaia has been plotting the distances to over

a billion stars,

creating a map of the Milky Way and some of its galactic neighbors.

All that from the lowly triangle.

For Scientific American, I’m Deboki Chakravarti.