The main representative of the working group of variable stars, in which there are sudden drops in brightness at irregular intervals by several stellar classes. The apparent brightness of this luminous giant remains at 5.8 mag for most of the time, then drops to 13.8 mag or sometimes even to 15 mag within a few weeks and remains so for several months. The giant star ejects a huge cloud of carbon-rich gas into the surrounding area through thermonuclear reactions, which obscures the star's light and causes the sharp drop in brightness that we observe. When the cloud disperses, the star shines again with undiminished light.