T Coronae Borealis nova, animation
Animation of a T Coronae Borealis nova. Located 3,000 light-years away, T Coronae Borealis consists of two stars that orbit each other: a red giant nearing the end of its life and an Earth-sized stellar remnant known as a white dwarf. In this system, the gravity of the white dwarf pulls in some of the gas that flows off the red giant, creating a flattened cloud of gas around the dwarf. Over time, this gas gradually accumulates on the surface of the white dwarf, forming a layer of material. As decades pass, the pressures and temperatures within this layer increase until reaching a critical point. This triggers a runaway thermonuclear reaction, resulting in an explosion known as a nova (white burst). The explosion only affects the surface material, leaving the white dwarf intact, which means the entire process can repeat over and over again. For a few days, this eruption brightens the system so much that it becomes visible from Earth with the unaided eye.