A Star Is Observed to Be on or Close to the Main-Sequence

question 113

Multiple Choice

A star is observed to be on or close to the main-sequence region of the Hertzsprung-Russell diagram. What particular feature of stellar behavior can be inferred by this observation?

• A) The star is generating internal energy by hydrogen fusion.
• B) The star is generating energy by helium fusion, having stopped hydrogen "burning."
• C) The star is slowly shrinking and thereby releasing gravitational potential energy as it slides down the main sequence from top left to bottom right across the H-R diagram.
• D) Stars that have reached the main sequence have ceased nuclear "burning" and are simply cooling down by emitting radiation.

---

Definitions:

Equilibrium Quantity

The quantity of goods or services supplied and demanded at the equilibrium price, where market supply and demand balance.

Excise Tax

A tax on the production, sale, or consumption of a commodity in a country.

Demand Curves

A graphical representation showing the quantity of a good that consumers are willing and able to purchase at various price levels, holding other factors constant.