A solitary white dwarf will eventually a. brighten and explode. b. accrete mass from other objects. c. implode to become a black hole. d. become cold and dim.

Stellar evolution is the process by which a star changes over the course of time. The lifecycle of a star is dictated by its mass. For stars similar to our Sun, this journey begins from a protostar formed in a molecular cloud. After the protostar stage, it becomes a main sequence star, where it spends the majority of its life fusing hydrogen into helium in its core.

Once the hydrogen is exhausted, the star enters the red giant phase, and it undergoes changes as fusion processes shift to its outer layers. Eventually, stars like our Sun will shed their outer layers, forming a planetary nebula, leaving behind a hot core that will become a white dwarf.

This remnant no longer has nuclear fusion but shines initially due to the residual thermal energy from its earlier stages.

White dwarf cooling describes the process by which a white dwarf loses its residual heat over time. At the beginning of this stage, a white dwarf is extremely hot, being around 100,000 degrees Fahrenheit or more. However, without nuclear reactions to generate new energy, it slowly radiates its remaining heat into space.

As white dwarfs cool, they emit less light and gradually become less luminous. This process can take billions of years. Over this extended period, the white dwarf will pass through various stages of cooling until it becomes almost invisible to us.

Theoretical models predict that we would eventually see these objects as black dwarfs. However, since the Universe is not yet old enough, no black dwarfs have been observed.

The end stages of stars vary significantly based on their initial mass. For low-to-medium mass stars, like our Sun, the final stage involves becoming a white dwarf. After spending a long period as a white dwarf, the star will continue to cool until it becomes a cold, dim object.

High-mass stars, on the other hand, end their lives quite dramatically. Once they exhaust their nuclear fuel, they undergo supernova explosions, which may leave behind neutron stars or black holes depending on the remaining mass.

Understanding these end stages helps us comprehend the cosmic lifecycle and the fate of different stars in our Universe. For solitary white dwarfs, like in the mentioned exercise, the natural path is towards cooling and dimming, following their long luminous journey.