Stellar Characteristics
As a red dwarf star, Gliese 876 is much less massive than our Sun: estimates suggest it has only 32% of the mass of the Sun. The surface temperature of Gliese 876 is cooler than our Sun and the star has a smaller radius. These factors combine to make the star only 1.24% as luminous as the Sun, and most of this is at infrared wavelengths.
Estimating the age and metallicity of cool stars is difficult due to the formation of diatomic molecules in their atmospheres, which makes the spectrum extremely complex. By fitting the observed spectrum to model spectra, it is estimated that Gliese 876 has a slightly lower abundance of heavy elements compared to the Sun (around 75% the solar abundance of iron). Based on chromospheric activity the star is likely to be around 6.5 to 9.9 billion years old, depending on the theoretical model used. However, the low rotational period of the star as well as its membership among the young disk population suggest that the star is between 0.1–5 billion years old.
Like many low-mass stars, Gliese 876 is a variable star. Its variable star designation is IL Aquarii and it is classified as a BY Draconis variable. Its brightness fluctuates by around 0.04 magnitudes. This type of variability is thought to be caused by large starspots moving in and out of view as the star rotates. Gliese 876 emits X-rays.
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