Early astronomers used only their eyes to look at the stars.

When astronomers use their telescopes to look at stars, things are different.

Astronomers sometimes use light that can't be seen by humans to learn more about objects in space.

There are a great many instruments besides those which the astronomers use.

The resulting image is permanent, so many astronomers can use the same data.

Now, astronomers using an Australian radio telescope have found the 1,000th.

Astronomers use red shifts to figure out the distance of objects from Earth and thus their age.

So astronomers use some more indirect methods beyond a few thousand light years.

The point is, the astronomers were using Earth as a norm.

At the high end of the temperature spectrum, astronomers use a different trick.