Space Physics: Question 5

Worked solution

Step 1: Identify which fate applies to a massive star

Once a star runs out of hydrogen fuel in its core, what happens next depends on the star’s mass:

• A star with a mass similar to the Sun expands into a red giant, then forms a planetary nebula with a white dwarf at its centre.
• A star much more massive than the Sun instead expands into a red supergiant.

Since this question describes a star much more massive than the Sun, the red giant / white dwarf pathway does not apply here.

Step 2: Follow the massive star’s sequence of stages

For a massive star, the correct sequence after it leaves the main sequence is:

$\text{red supergiant} \rightarrow \text{supernova} \rightarrow \text{neutron star or black hole}$

The star first swells into a red supergiant. When its core can no longer support the star, it collapses suddenly and explodes as a supernova, blasting most of the star’s material into space as a nebula containing hydrogen and heavier elements. Left behind at the centre is an extremely dense remnant. A neutron star, or, if the original star was massive enough, a black hole.

Why the other options are wrong

Final answers

• The massive star’s sequence is red supergiant → supernova → neutron star or black hole, option B