1. Size and Mass:
* Red dwarfs: Are the smallest and least massive stars, with about 8% to 50% the mass of our Sun.
* Main sequence stars: Can range in size and mass from about 0.08 to 100 times the mass of our Sun.
2. Temperature and Color:
* Red dwarfs: Have much lower surface temperatures than main sequence stars, ranging from 2,400 to 3,500 K. This low temperature gives them their red appearance.
* Main sequence stars: Have a wider range of temperatures and colors, with hotter stars appearing blue and cooler stars appearing orange or yellow. Our Sun is a yellow main sequence star.
3. Luminosity:
* Red dwarfs: Are much fainter than main sequence stars, with only about 0.01 to 0.001% of the Sun's luminosity.
* Main sequence stars: Have a range of luminosities depending on their mass.
4. Lifetime:
* Red dwarfs: Have extremely long lifespans, estimated to be trillions of years. This is due to their slow rate of hydrogen fusion.
* Main sequence stars: Have shorter lifespans that vary depending on their mass. Larger, hotter stars have shorter lives (millions to billions of years).
5. Nuclear Fusion:
* Red dwarfs: Fuse hydrogen into helium very slowly due to their lower temperatures and pressures.
* Main sequence stars: Fuse hydrogen into helium at a much faster rate, depending on their mass.
6. Activity:
* Red dwarfs: Can be very active stars, with frequent flares and coronal mass ejections. These events can be powerful, potentially impacting any planets orbiting the star.
* Main sequence stars: Also exhibit activity, but typically less frequent and intense than red dwarfs.
In Summary:
Red dwarfs are smaller, cooler, fainter, and longer-lived than most main sequence stars. Their slow fusion rate and low temperatures make them interesting objects for studying stellar evolution and the potential for life on exoplanets.