Betelgeuse, a luminous star, has long captivated observers with its striking presence in the night sky. As a red supergiant, it stands out. Its visibility from Earth makes it a frequent subject of curiosity.
Finding Betelgeuse
Locating Betelgeuse in the night sky begins with identifying the constellation Orion. Orion is easily recognizable by its “belt,” a distinct line of three bright stars. Betelgeuse is positioned above and to the left of these stars, marking Orion’s right shoulder. Another bright star, Rigel, is found to the lower-right of the belt.
Betelgeuse is known for its distinct reddish-orange hue, which helps distinguish it from other stars. This color is a key visual cue for identification. The best time to observe Betelgeuse in the Northern Hemisphere is during winter, particularly from mid-September to mid-March, with optimal viewing in mid-December, as it rises in the east after sunset. It is visible from nearly all inhabited regions of the globe during these months.
Understanding Betelgeuse
Betelgeuse is classified as a red supergiant, a type of star that has expanded significantly as it nears the end of its life cycle. This immense star is roughly 640 to 764 times the size of our Sun. If Betelgeuse were placed at the center of our solar system, its outer surface would extend beyond the orbit of Mars, and possibly even past Jupiter.
Its luminosity is also remarkable, shining approximately 7,500 to 14,000 times brighter than the Sun. The star’s characteristic reddish-orange color is due to its relatively cool surface temperature, which is around 3,300 to 3,800 degrees Celsius (6,000 degrees Fahrenheit). Betelgeuse is located approximately 400 to 700 light-years from Earth, meaning the light we see left the star centuries ago.
Betelgeuse’s Dynamic Nature
Betelgeuse is a semiregular variable star, meaning its brightness fluctuates over time, though not always with strict periodicity. It typically varies between magnitude 0.0 and +1.6, with a main period of around 400 days and a longer secondary period near 2,100 days. This variability is due to changes in its size and temperature.
A notable event occurred between late 2019 and early 2020 when Betelgeuse experienced an unprecedented dimming. This “Great Dimming” was attributed to a massive ejection of gas from the star’s surface, which then cooled and condensed into a dust cloud, obscuring its light. While this event led to speculation about an imminent supernova, it was later understood as a phenomenon of mass loss.
As a red supergiant nearing the end of its life, Betelgeuse is expected to end its existence in a supernova explosion. This is considered a certainty, a “when” rather than an “if,” though the precise timing remains uncertain. Estimates suggest it could occur within the next 10,000 to 100,000 years. When it explodes, it could briefly appear as bright as a half-moon and be visible even during daylight hours.