Betelgeuse: The Red Supergiant in Orion

Betelgeuse is one of the most fascinating stars visible to the naked eye. This enormous red supergiant marks the shoulder of Orion and has captivated astronomers and the public alike with its dramatic brightness variations and the tantalizing possibility of an eventual supernova explosion. Watch its reddish glow in real time with StarGlobe.

How to Find Betelgeuse

Betelgeuse is the upper-left star of Orion as seen from northern latitudes, marking the hunter's right shoulder. Its distinctly reddish-orange color contrasts sharply with the blue-white Rigel at the opposite corner. The two stars make Orion one of the most colorful constellations in the sky.

Betelgeuse is also part of the Winter Triangle, alongside Sirius in Canis Major and Procyon in Canis Minor. Its red color makes it the most colorful vertex of this large asterism. During winter months, Betelgeuse is easily visible from any location on Earth.

An Enormous Star

Betelgeuse is one of the largest stars known. Its diameter has been estimated at roughly 700 to 1,000 times that of the Sun, depending on the wavelength of observation and the star's current pulsation phase. If placed at the center of our solar system, its outer atmosphere would engulf the orbits of Mercury, Venus, Earth, Mars, and possibly Jupiter.

Despite its enormous volume, Betelgeuse has a mass of only about 15 to 20 times the Sun's mass. This means the star is incredibly diffuse, with an average density far lower than Earth's atmosphere. Its surface temperature of about 3,500 Kelvin is cool compared to most bright stars, giving it the deep red color that makes it so distinctive.

Betelgeuse is located approximately 650 to 700 light-years from Earth, though this distance has been refined through various measurements over the years. Its luminosity is roughly 100,000 times that of the Sun, making it one of the most luminous stars in our region of the galaxy.

The Great Dimming of 2019-2020

In late 2019 and early 2020, Betelgeuse underwent an unprecedented dimming event, fading from its typical magnitude of about 0.5 to an unusually faint 1.6 by February 2020. This dramatic change was visible to the naked eye and sparked widespread speculation that the star might be on the verge of exploding as a supernova.

Subsequent research revealed that the dimming was caused by a combination of a natural pulsation minimum and a cloud of dust ejected from the star's surface that partially blocked its light from our perspective. Hubble Space Telescope observations showed that a large convective plume had erupted from the surface, releasing material that cooled and condensed into dust grains. The star recovered its normal brightness by mid-2020.

Supernova Potential

Betelgeuse is nearing the end of its life and will eventually explode as a Type II supernova. When this happens, it will briefly become extraordinarily bright, potentially reaching magnitude -12 or brighter, rivaling the full Moon in brightness. It would be visible in daylight and would cast shadows at night.

However, the timing is deeply uncertain. "Soon" in astronomical terms could mean anytime within the next 100,000 years. The star is currently fusing heavier elements in its core, progressing through a sequence that ends with iron, at which point the core will collapse and the outer layers will be expelled in a spectacular explosion. At its distance, the supernova would pose no danger to Earth but would be the most dramatic astronomical event in recorded history.

Mythology and Cultural Heritage

Betelgeuse's name is commonly traced to the Arabic "yad al-jawza," meaning the hand of the central one, though the exact etymological path is debated. Pronunciation varies: "beetle juice," "bettle-gerz," and other forms are all used. In Japanese tradition, the star is called Heike-boshi, the star of the Heike clan, associated with the red pennants of the defeated Heike warriors.

Aboriginal Australian cultures recognized Betelgeuse's red color and incorporated it into their traditions. Some nations associated the red star with fire or blood, integrating it into stories connected to the other stars of Orion.

Best Time to Observe

Betelgeuse is best observed from December through March, following the same schedule as Orion. Its brightness and color are easiest to appreciate during January and February evenings when Orion is highest. Comparing Betelgeuse's current brightness against nearby stars like Aldebaran, Rigel, and Procyon is a useful way to monitor its variable behavior over weeks and months.

Neighboring Stars

Rigel sits at the opposite corner of Orion. Aldebaran in Taurus lies to the northwest and shares a similar orange hue, making them an interesting pair to compare. Sirius blazes to the south, and Procyon shines to the east. Explore Betelgeuse's place in the winter sky with StarGlobe.

Quick Facts

Betelgeuse has a variable apparent magnitude averaging about 0.5 (ranging from 0.0 to 1.6), a distance of approximately 650-700 light-years, and a luminosity of roughly 100,000 times the Sun. Its diameter is about 700-1,000 solar radii, and its surface temperature is approximately 3,500 Kelvin. Its right ascension is 5h 55m, and its declination is +7 degrees 24 minutes.