Chapter 34, Problem 14TE

No galaxy found so far is made of less than $25\%$ helium. If not from the stars, where did this helium come from?

To determine

The source of helium in the galaxy.

Answer to Problem 14TE

Helium in the galaxies is the product of Big Bang explosion.

Explanation of Solution

Helium has a more complex structure than hydrogen. The fusion between hydrogen and helium happens in the stars. But it was seen that the existing stars are not capable of making that much helium and thus, this helium is not from stars.

The presence of helium, which is not from the stars, supports the Big Bang model. Big Bang model suggests that the early universe would have been favourable to the formation of helium, but not the formation of other elements. A detailed study gives the suggestion that the amount of helium created just after the Big Bang should be about that which is observed today.

Conclusion:

Therefore, helium in the galaxies is the product of Big Bang explosion.