Betelgeuse

Spectral class: M2
Diameter: 1.3 billion kilometers

Also known as Alpha Orionis, Betelgeuse is a massive red supergiant star in the Alpha Quadrant. Pulsating with slight irregularity with a period of 2070 days, it is nearing the end of its life and will soon become a supernova.

Betelgeuse is the central component of the Betelgeuse system, a multiple star system.

The dust envelope

The star is surrounded by an asymmetric circumstellar structure at 1-1.5 stellar radii from the surface of the star, revealed to be an extensive dust envelope. Another much fainter feature exists at 2-2.5 stellar radii; an outward-expanding residue of the dust structure.

Future

For particularly massive stars like Betelgeuse, the core continues to produce elements heavier than carbon in its core. Carbon fuses into oxygen and neon, then oxygen to silicon and sulfur, then finally silicon and sulfur fuses to iron. Each reaction occurs in quicker succession, with layers of previous reactions still happening on the outer parts of the core. The supergiant generally swells up more and more during the final stages in its life, often becoming variable in brightness and throwing off material explosively. The star color may change also, varying from being a blue supergiant to being a red supergiant, depending upon speed and amount of stellar wind outflow. The last reaction of silicon and sulfur fusing to iron takes less than a week to complete. Once the core has been converted to iron, the star no longer has a way to hold back gravity.

The star cannot use iron to sustain itself or hold back the pressure gravity is exerting. For atoms the size of or heavier than iron, fusion absorbs instead of releases energy. (This is the same reason why we can get energy out of splitting uranium nuclei in a process called fission.) Gravity causes the core to collapse catastrophically and the outer layers cave in. Then these layers are ripped apart by an immense shock wave, forming a supernova. Neutrons set free by the collapse bombard material forming elements heavier than iron, such as gold, silver, bromine, iodine, mercury, lead, and uranium. The outrushing material sends shock waves through space which can ignite further star formation in nearby nebulas. The supernova becomes as bright as an entire galaxy for a period of weeks.