4. The table below shows the initial masses of four stars.

\begin{tabular}{|l|c|c|c|c|}
\hline Name of Star & Star 1 & Star 2 & Star 3 & Star 4 \\
\hline Initial mass of star (in Solar mass) & 9 & 0.9 & 5 & 0.3 \\
\hline
\end{tabular}

Which of these stars will stay on the main sequence for the shortest time?

A. Star 1
B. Star 2
C. Star 3
D. Star 4



Answer :

To determine which star will remain on the main sequence for the shortest time, we need to understand the relationship between a star's mass and its main sequence lifetime.

The main sequence lifetime of a star is inversely related to the cube of its mass. This means that a more massive star will have a shorter main sequence lifetime because it burns through its nuclear fuel more quickly.

Given the initial masses of the stars:

- Star 1: 9 Solar masses
- Star 2: 0.9 Solar masses
- Star 3: 5 Solar masses
- Star 4: 0.3 Solar masses

We want to find the star with the largest mass, as that star will have the shortest main sequence lifetime.

Let’s compare the masses:
- Star 1: 9 Solar masses
- Star 2: 0.9 Solar masses
- Star 3: 5 Solar masses
- Star 4: 0.3 Solar masses

Among these values, the largest mass is 9 Solar masses, which belongs to Star 1.

Hence, Star 1 will stay on the main sequence for the shortest time.

So, the correct answer is:
Star 1