What is the curved line on the Hertzsprung diagram showing??

Question

and another question it is important for life on Earth that the Sun is, in fact, a second generation star why?

Answer 1

Wikipedia likely explains it better than I can.

I assume by the curved line you are referring to the main sequence of stars.

They mapped almost all the stars they could on a graph with brightness or size and temperature or colour.

The main sequence happens to cluster about a curved diagonal line on the graph.

There are a couple of ways of classifying the stars. They generally look about the same.

Because all of the elements on earth that are heavier than lithium were created inside a star we would not have the chemical elements available to form life if there were only first generation stars.

Because Sol was formed out of a cloud of star dust our planets have the heavier elements like iron.

Answer 2

If you mean the line that runs from the upper left to the lower right, that is the "Main Sequence" where stars spend the main part of their lives.  They move off the main sequence as their nuclear fuel runs low.

If the Sun was only a "first generation star" then the cloud it formed from would only contain hydrogen and helium, no carbon, aluminium, silicon and oxygen (or elements like iron and uranium.)  However, the Sun formed from a cloud of gas that had been seeded by the ashes of other stars and thus contained these heavier elements that make us and the world we know.

Answer 3

You should ask this question to any scientist.Do you read me?