The red dwarf star itself emits only about 0.4% of our sun's radiance, so the planet receives about 2% of the intensity that Earth receives from its sun. This is because Barnard's star is in the class of M dwarf stars, cooler and less massive than our sun. It's also an old star that predates our own solar system. The planet is about the same orbital distance from its star as Mercury is from our sun, making a full pass around the star every 233 days. This places it in the "snow line" of the star, where it's cold enough...