Betelgeuse eruption

Betelgeuse Ejected a Mass Weighing Several Times the Moon’s Weight

An enormous part of the star Betelgeuse erupted into space in December 2019, the first time such a phenomenon has been observed. NASA says the star “quite literally blew its top” in a “catastrophic upheaval.”


As one of the closest massive stars to Earth, the star is 530 light years away and easily observable with the naked eye in the night sky. It forms the shoulder of the constellation Orion and would extend to Jupiter if it were to replace our Sun in the center of the solar system.

Betelgeuse in the Orion constellation
Left: Orion constellation map by Torsten Bronger via Wikipedia, CC BY-SA 3.0. Right: Image showing Betelgeuse (top left) and the dense nebulae of the Orion molecular cloud complex Images via Wikipedia by Rogelio Bernal Andreo, (CC BY-SA 3.0)

At the time, people noticed a considerable dimming, but only now are we learning exactly why.

Instead of something resembling a coronal mass ejection as we see routinely with the Sun, Betelgeuse lost a blob of plasma weighing several times as much as the Moon. It was 400 billion times the mass of a typical coronal mass ejection on our Sun.

Betelgeuse’s Dimming Finally Explained

After the glowing red supergiant star, 1 billion miles in diameter, lost the huge chunk of its photosphere, it grew dimmer for several months, as seen by observers with average telescopes. According to Wired, the star dulled by 35 percent from mid-February until it began becoming brighter again in April 2020. 

“Telescopes pointed at the giant were able to determine that—rather than a tidy, uniform drop in luminance—Betelgeuse’s dimming was unevenly distributed, giving the star an odd, squished shape when viewed from Earth,” Wired reported in 2021.

At the time, astronomers thought the star in the Orion constellation could go supernova, but on the other hand, research indicates that may not happen for 100,000 years. (If it does, it wouldn’t harm Earth but could make a light show visible even during the daytime.)

The dimming event was among the first times scientists could observe a star changing in real-time in such a short time period.

After months of observation, scientists suggested there might be a massive dust cloud causing Betelgeuse to look dimmer, or there was a temporary cold patch like a sunspot at the southern pole. Then, a 2021 study in Nature determined that dust was the most likely reason for the dimming. Such massive dust clouds could later form into planets, they suspected.

Mystery solved,” but now, we find out that the cosmic burp was more dramatic than expected.

Video by Insane Curiosity:

Hubble Space Telescope Observes Betelgeuse 

Fortunately, the Hubble Space Telescope observed Betelgeuse before, during, and after the strange event. They discovered the star had lost a huge part of its visible surface using Hubble’s data and data from numerous other observatories. 

“The eruption blew off a chunk of the star’s lower atmosphere, the photosphere, leaving behind a cool spot that was further occluded by the dust cloud from the blowout,” reported LiveScience. 

Before the plasma eruption, a plume reaching 1 million miles long may have formed inside the star.

“We’ve never before seen a huge mass ejection of the surface of a star. We are left with something going on that we don’t completely understand,” said astrophysicist Andrea Dupree from the Harvard & Smithsonian Center for Astrophysics.

“It’s a totally new phenomenon that we can observe directly and resolve surface details with Hubble. We’re watching stellar evolution in real time.”

Video by thebhp:

Betelgeuse is Still Acting Strange

Following the eruption, Betelgeuse stopped pulsing the way it had been for 200 years of observed history. Scientists believe the star’s interior convection cells are still reverberating from the blast. Dupree compared it to “sloshing around like an imbalanced washing machine tub.”

These cells drive a pulsation rate that has always been on a 400-day oscillation period up until the blast.

Meanwhile, the outside may be “jiggling like a plate of gelatin dessert,” NASA says. However, the photosphere is rebuilding itself.

Now that the James Webb Space Telescope is in operation, the astronomers will have a chance to observe what happened to the mass ejected into space.

Featured image credits: NASA, ESA, Elizabeth Wheatley (STScI)