The star with the lowest surface temperature known is AC 79 3888, a red dwarf star located in the constellation of Aquarius. This star is estimated to be around 300 to 500 million years old, and is only about one-third the size of our Sun. It is classified as an M-type star, which is the coolest type of star, and has a surface temperature of around 2,700 Kelvin (2,400 Celsius).
This is much cooler than the surface temperature of our Sun, which is around 5,778 Kelvin (5,500 Celsius). The low surface temperature of this star is due to its very low mass, which is only about one-tenth that of our Sun. The lower mass means that the star has a much lower energy output, and therefore a lower temperature.
The red dwarf star AC 79 3888 is one of the faintest stars known, with an apparent magnitude of 18.6. This means that it is too faint to be seen with the naked eye, and can only be seen with a large telescope.
The low surface temperature of AC 79 3888 makes it an ideal target for astronomers looking to study low-energy stars. Because it is so faint, it is easier to observe than brighter stars, and its low temperature allows astronomers to study the effects of lower stellar temperatures on the formation and evolution of planetary systems.
The location of AC 79 3888 is also of particular interest to astronomers. Because it is located in the constellation of Aquarius, it is located in an area of the sky that is known to contain a number of other stars of similar size and temperature. This makes it an ideal target for studying the effects of stellar density and clustering on the formation of planetary systems.
Overall, the star AC 79 3888 has the lowest surface temperature of any known star. Its low mass and faintness make it an ideal target for astronomers looking to study low-energy stars, and its location in the constellation of Aquarius makes it an ideal target for studying the effects of stellar density and clustering on the formation of planetary systems.