Betelgeuse Dimming: Is It About to Explode?

For casual stargazers and professional astronomers alike, the constellation Orion is a winter staple. However, its bright orange shoulder, the star Betelgeuse, has been acting strangely. Following a historic dimming event in 2019 and a surprising brightening in 2023, speculation about an imminent supernova has reached a fever pitch. This article examines the latest theories regarding the red supergiant’s erratic behavior and what science says about its explosive future.

The "Great Dimming" of 2019: What Really Happened?

Between late 2019 and early 2020, Betelgeuse captured global attention when its brightness plummeted by roughly 35% to 40%. Typically one of the top 10 brightest stars in the night sky, it fell out of the top 20, noticeably changing the appearance of Orion.

At the time, many speculated that this dimming was the “pre-explosion” phase. However, rigorous data from the Hubble Space Telescope (HST) and the European Southern Observatory (ESO) revealed a different culprit.

The leading theory, confirmed by the Center for Astrophysics | Harvard & Smithsonian, attributes the event to a Surface Mass Ejection (SME). Here is the timeline of that event:

  • The Ejection: The star blew out a massive chunk of its surface material into space.
  • The Cooling: As this gas moved away from the star, it cooled down significantly.
  • The Dust Cloud: The cooled gas condensed into solid dust. From Earth’s perspective, this dust cloud formed directly in front of the star, blocking its light and causing the apparent dimming.

Andrea Dupree, a senior astrophysicist at the Center for Astrophysics, described the event as the star “recovering from a traumatic injury.” This suggests the dimming was not a sign of death, but rather a violent burp of stellar material.

Why Is Betelgeuse Behaving Erratically Now?

While the dimming event is now understood, Betelgeuse has not returned to normal. In 2023 and continuing into 2024, the star began pulsating differently.

Typically, Betelgeuse follows a 400-day cycle of brightening and dimming. Recently, astronomers have observed a new, shorter rhythm:

  1. Increased Brightness: In mid-2023, Betelgeuse became roughly 50% brighter than usual, claiming the title of the 7th brightest star in the sky for a short period.
  2. The “185-Day” Cycle: The star appears to be pulsating on a shorter timeline of roughly 185 to 200 days, rather than its standard 400-day heartbeat.

Astronomers believe this erratic behavior is the aftermath of the 2019 Surface Mass Ejection. The star is effectively “sloshing” around as its outer layers attempt to regain equilibrium. The interior convection cells are unbalanced, causing the surface to oscillate faster than normal. Think of it as a bell that is still vibrating chaotically after being struck hard.

The Supernova Timeline: Decades or Millennia?

The ultimate question remains: When will Betelgeuse go supernova?

A red supergiant like Betelgeuse explodes when it runs out of fuel. It burns through elements in stages: Hydrogen, Helium, Carbon, Neon, Oxygen, and finally Silicon. Once the core turns to Iron, fusion stops, gravity wins, and the star collapses and explodes.

The Mainstream Consensus

Most astrophysicists estimate that Betelgeuse is still in the Helium-burning phase or perhaps early Carbon burning.

  • Timeframe: 10,000 to 100,000 years.
  • Evidence: Models of stellar evolution suggest the star still has significant mass to burn through before reaching the Iron core collapse.

The Controversial “Decades” Theory

A recent study led by Hideyuki Saio at Tohoku University in Japan proposed a more alarming timeline. Their research argued that the new 185-day pulsation period represents the star’s “fundamental mode.” If this is true, it implies the star is much larger and further along in its life cycle than previously thought.

  • The Theory: Betelgeuse is currently burning Carbon at its core.
  • The Conclusion: If accurate, the star could explode within a few decades.
  • The Rebuttal: Many experts dispute this, arguing the 185-day cycle is an “overtone” (a secondary vibration) caused by the recent surface trauma, not the fundamental heartbeat of the star.

What Will the Explosion Look Like?

When Betelgeuse eventually does go supernova, it will be a spectacular astronomical event for Earth, though it poses no danger to us.

  • Brightness: It will likely shine as bright as the half-moon (magnitude -10 to -12).
  • Visibility: It will be clearly visible during the day for several weeks.
  • Duration: It will remain visible to the naked eye at night for months before fading.
  • Aftermath: Orion will lose its left shoulder, changing the constellation forever.

Distance and Danger

One reason for the intense scrutiny is the star’s proximity. While 650 light-years sounds far, it is practically next door in galactic terms.

However, we are in the “safe zone.” For a supernova to strip Earth’s ozone layer and cause a mass extinction event, the exploding star would need to be within 50 light-years. At 650 light-years, the radiation will be negligible by the time it reaches us. The main impact on Earth will be a fantastic light show and a flood of neutrinos that will excite particle detectors worldwide.

Frequently Asked Questions

Is Betelgeuse currently dimming again? Betelgeuse varies in brightness constantly. While it is not undergoing a “Great Dimming” like in 2019, it continues to cycle through bright and dim phases. You can track its current magnitude via the American Association of Variable Star Observers (AAVSO).

Will we get a warning before it explodes? Yes. Current neutrino detectors (like Super-Kamiokande in Japan) would detect a burst of neutrinos hours before the visible light reaches us. The core collapse releases neutrinos instantly, while the shockwave takes time to reach the star’s surface.

Can I see Betelgeuse tonight? If it is winter in the Northern Hemisphere (or summer in the Southern Hemisphere), yes. Look for the three stars of Orion’s Belt. Betelgeuse is the bright, reddish star located up and to the left of the belt.

How big is Betelgeuse compared to the Sun? It is massive. If you placed Betelgeuse in the center of our solar system, its surface would extend past the orbit of Jupiter, engulfing Mercury, Venus, Earth, and Mars.