Question

1. Explain why the majority of stars visible in a telescope are main sequence stars.
2. What will happen inside the Sun 5 billion years from now when it begins to become a red giant?
3. The concentration of ethyl alcohol in a typical molecular cloud is one molecule per 10⁸ cubic meters. What is the volume of a cloud you would need to make a martini (10 grams)? The molecular weight of an ethyl alcohol is 46 which means that an Avogadro number (6 x 10²³) of molecules weighs 46 grams.

Answer 1

1. If we try to plot the stars around us on H-R diagram most of it would fall in the straight line which is called main- sequencxe stars. So, commnly speaking, most of the stars are found around this region because they spend most of there life (70-90%)  burning hydrogen in their cores than they do producing energy in any other way, so this makes them to be the main sequence stars.

2. Red giant is the dying stage of any star in the stellar evolution. In 5 billion years the Sun will turn into a red giant star, expand and engulf the inner planets, possibly even Earth. The sun will begin the helium-burning process, turning into a red giant star and it would wipe out the life as we know it.

3. Avagadro number of molecule contains 46 g of ethyl alcohol so for 10 gram of it we need.

(Avagadro No. / 46 )x10 = 1.304 x 1023 molecules.

Volume = 1.304 x 1023 x 108 m3

=  140.8 x 1023 m3. (Ans)