G, K, M, and L type stars are classifications based on the spectral characteristics of stars. These classifications are part of the Morgan-Keenan (MK) system, which categorizes stars based on their surface temperature and spectral lines. Here are the main differences between these star types:
G-Type Stars (Yellow Dwarf):
- G-type stars, also known as yellow dwarfs, have surface temperatures ranging from approximately 5,000 to 6,000 Kelvin (K).
- Our Sun is a G-type star (specifically, it is classified as a G2V star).
- G-type stars have a moderate energy output and appear yellowish in color.
- They are typically main-sequence stars, fusing hydrogen into helium in their cores.
- These stars are known to be relatively stable and have a longer lifespan compared to more massive stars.
K-Type Stars (Orange Dwarf):
- K-type stars have surface temperatures ranging from approximately 3,500 to 5,000 K.
- They are cooler and slightly smaller than G-type stars.
- K-type stars emit a reddish-orange light.
- These stars have a longer lifespan than G-type stars and tend to be less luminous.
- K-type stars are also known to exhibit higher levels of magnetic activity, such as flares and sunspots.
M-Type Stars (Red Dwarf):
- M-type stars are the most common type of star in the universe.
- They have surface temperatures ranging from approximately 2,400 to 3,500 K.
- M-type stars are small and relatively cool, with a reddish color.
- They have a low energy output and are much less luminous than G and K-type stars.
- Red dwarfs have exceptionally long lifespans, potentially lasting trillions of years.
- Many exoplanets have been discovered orbiting M-type stars, and they are considered promising candidates for habitable worlds.
L-Type Stars (Brown Dwarfs):
- L-type stars, also known as brown dwarfs, are not true stars but rather objects that fall between stars and gas giant planets in terms of mass.
- They have surface temperatures below 2,400 K.
- L-type stars emit primarily in the infrared part of the electromagnetic spectrum and appear relatively dim.
- They are unable to sustain stable hydrogen fusion in their cores, which is a defining characteristic of true stars.
- Brown dwarfs are often referred to as "failed stars" because they lack sufficient mass to ignite sustained nuclear fusion.
It's worth noting that the MK system encompasses a broader classification scheme with additional types, such as O, B, and A-type stars, which are hotter and more massive than G-type stars.