Which statement about red dwarfs is true?

• A. They are hotter than the Sun
• B. They are as bright as the Sun
• C. They are rare
• D. They are cooler, fainter, and much less massive than the Sun

Answer: (D)

Red dwarfs are small, cool stars on the main sequence. Their surface temperatures are much lower than the Sun’s, which makes them appear red. Because they have small radii and cooler temperatures, their luminosity is much lower than the Sun’s, so they are faint. They also have far less mass than the Sun, typically only a fraction of it. So the true statement is that red dwarfs are cooler, fainter, and much less massive than the Sun. They aren’t hotter, they aren’t as bright as the Sun, and in fact they’re among the most common types of stars in our galaxy.