Cosmic Distance Ladder – Part 2

How I See It

In this second part of the Cosmic Distance Ladder series, we see how parallax and main sequence fitting help us to know the distance to objects in space. Follow this link to the first in the series if you missed it.

This image shows the path Pluto will take during the next two years, as viewed from Earth. You can’t see Pluto with the naked eye. And, it doesn’t actually move in such a cyclic way. It moves in a smooth elliptical orbit around the Sun. So, why does the path we see in the image look so strange?

There are two reasons. Pluto is actually moving toward the lower left in that part of the sky. And, Earth also is moving around the Sun. It as if you were recording the movement of a slow moving object while riding on a merry-go-round. The merry-go-round motion imparts a back and forth…

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