# Betelgeuse losing brightness **URL:** \ **Category:** Factual Questions\ **Created:** [December 27, 2019, 11:34pm UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478 "2019-12-27T23:34:54Z")\ **Posts on this page:** 20\ **Page:** 11
**Author:** ![Frodo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/frodo/32/302_2.png) [@Frodo](https://boards.straightdope.com/u/Frodo)\ **Post date:** [July 22, 2025, 1:02pm UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/202 "2025-07-22T13:02:20Z")
Would the eventual absorption by Betelgeuse of the companion star precipitate, delay or have no effect at all on Betelgeuse going supernova? (If Betelgeuse does not go nova before absorbing it’s companion) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 22, 2025, 1:12pm UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/203 "2025-07-22T13:12:11Z")
> [@Northern\_Piper](#): > > Query: the articles say the companion star has not yet started fusing hydrogen at its core. Then what is it doing as a source of heat and light? Contraction. When a star (or any other body) contracts, it decreases its gravitational potential energy, and that energy has to go somewhere. It can be enough to power a star for millions of years. ---
**Author:** ![Northern\_Piper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/northern_piper/32/5304_2.png) [@Northern\_Piper](https://boards.straightdope.com/u/Northern_Piper)\ **Post date:** [July 22, 2025, 2:04pm UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/204 "2025-07-22T14:04:43Z")
Interesting. Thanks. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [July 22, 2025, 7:02pm UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/205 "2025-07-22T19:02:13Z")
Gravitational contraction was once a leading candidate for what powered the Sun itself: > **[Kelvin–Helmholtz mechanism](https://en.wikipedia.org/wiki/Kelvin%E2%80%93Helmholtz_mechanism)** > > The Kelvin–Helmholtz mechanism is an astronomical process that occurs when the surface of a star or a planet cools. The cooling causes the internal pressure to drop, and the star or planet shrinks as a result. This compression, in turn, heats the core of the star/planet. This mechanism is evident on Jupiter and Saturn and on brown dwarfs whose central temperatures are not high enough to undergo hydrogen fusion. It is estimated that Jupiter radiates more energy through this mechanism than it recei... But it can only power a star for millions of years, not billions. And the Sun needs billions. ---
**Author:** ![Jackknifed\_Juggernaut](https://avatars.discourse-cdn.com/v4/letter/j/9de053/32.png) [@Jackknifed\_Juggernaut](https://boards.straightdope.com/u/Jackknifed_Juggernaut)\ **Post date:** [July 22, 2025, 8:31pm UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/206 "2025-07-22T20:31:38Z")
I was going to ask the same question. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [July 22, 2025, 8:45pm UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/207 "2025-07-22T20:45:36Z")
Spitballing like mad here … They’re estimating the companion has a mass very roughly 10% of the primary. So not negligible. This is a cantaloupe dropped in a bucket, not a grain of sand dropped in a bucket. The companion is full of the fuel elements that the primary has already used up. If they could be quickly moved to near the center of the primary, there could be a sort of reverse evolution of the standard stellar element “burning” = transmutation steps. Makes me think of something akin to spraying liquid oxygen into an existing fire. Might get exciting. OTOH, the companion is a ball of gas. Orbiting within the thin outer shells of the primary atmosphere already. So although there’s a lot of relative velocity, it’s tangential to any given shell of the primary, not perpendicular. So the process of spiralling in will be very slow and “colliding” isn’t really a good word for what’s likely going to happen. There is a Roche radius somewhere in here, where the companion is going to get increasingly smeared out into a larger less dense cloud of the same gas it ever was. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 22, 2025, 11:39pm UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/208 "2025-07-22T23:39:03Z")
I don’t think that Roche disintegration will be an issue. Given how diffuse Betelgeuse A is, B will probably survive intact past the point where it crosses A’s photosphere. And if it survives that point, it’ll probably keep on surviving, because as it spirals down from there, it’ll have less and less mass inside its orbit, as well. The only question would be whether Betelgeuse A still has a dense core (at least comparable to B’s density)-- I’m not sure about that. ---
**Author:** ![nearwildheaven](https://avatars.discourse-cdn.com/v4/letter/n/90db22/32.png) [@nearwildheaven](https://boards.straightdope.com/u/nearwildheaven)\ **Post date:** [July 25, 2025, 10:18pm UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/209 "2025-07-25T22:18:34Z")
The more we learn about Betelgeuse, it seems that the less we realize we know, all at the same time. If Betelgeuse A does go supernova, it will cannibalize B. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [July 25, 2025, 11:39pm UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/210 "2025-07-25T23:39:51Z")
> [@nearwildheaven](#): > > The more we learn about Betelgeuse, it seems that the less we realize we know, all at the same time. You can substitute [darn near whatever] for “Betelgeuse” in that sentence and it still works. Science is like that. Each time we peel back an onion layer of ignorance, we find … a larger onion with more layers underneath. Sure, there are a few areas where we’ve mostly drained the swamp of ignorance. But not many. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 26, 2025, 12:00am UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/211 "2025-07-26T00:00:50Z")
> [@LSLGuy](#): > > Each time we peel back an onion layer of ignorance, we find … a larger onion with more layers underneath. Or sometimes, another, smaller onion orbiting it. ---
**Author:** ![mbh](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@mbh](https://boards.straightdope.com/u/mbh)\ **Post date:** [July 26, 2025, 8:47pm UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/212 "2025-07-26T20:47:12Z")
Hanging from Orion’s belt . . . ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [July 26, 2025, 9:06pm UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/213 "2025-07-26T21:06:05Z")
> [@Northern\_Piper](#): > > Astronomers say they have found Betelgeuse’s small companion: a blue A or B star, hot but not yet on the main sequence, orbiting Betelgeuse at about 4 AU. This means Betelgeuse B is very young (a few million years at most), and that implies that Betelgeuse A is also very young. It must be going through its stellar cycle very quickly indeed. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [July 26, 2025, 10:27pm UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/214 "2025-07-26T22:27:47Z")
> [@eburacum45](#): > > This means Betelgeuse B is very young (a few million years at most), and that implies that Betelgeuse A is also very young. It must be going through its stellar cycle very quickly indeed. The more massive the star, the faster it consumes its fuel. I believe the most massive O-type stars go through their lives in something like one or two million years, maybe less. Betelgeuse was either a late O or an early B star when it was main sequence, which is not the most massive. ---
**Author:** ![DesertDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desertdog/32/11503_2.png) [@DesertDog](https://boards.straightdope.com/u/DesertDog)\ **Post date:** [July 26, 2025, 10:54pm UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/215 "2025-07-26T22:54:20Z")
> [@LSLGuy](#): > > You can substitute [darn near whatever] for “Betelgeuse” in that sentence and it still works. Knowledge is fractal. John M. Ford, the sf writer said something like, “Every time we solve a mystery God says, ‘Oh, you got that one now? Here’s another mystery.’” ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 26, 2025, 11:03pm UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/216 "2025-07-26T23:03:28Z")
> [@dtilque](#): > > Betelgeuse was either a late O or an early B star when it was main sequence, which is not the most massive. Not the most massive, but definitely on the high end. Big stars live fast, die young, and leave beautiful corpses. > [@DesertDog](#): > > Knowledge is fractal. John M. Ford, the sf writer said something like, “Every time we solve a mystery God says, ‘Oh, you got that one now? Here’s another mystery.’” Another two, at least. ---
**Author:** ![Northern\_Piper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/northern_piper/32/5304_2.png) [@Northern\_Piper](https://boards.straightdope.com/u/Northern_Piper)\ **Post date:** [July 26, 2025, 11:09pm UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/217 "2025-07-26T23:09:44Z")
> [@eburacum45](#): > > This means Betelgeuse B is very young (a few million years at most), and that implies that Betelgeuse A is also very young. It must be going through its stellar cycle very quickly indeed. The articles say that A and B likely formed around the same time, but that B hasn’t even started fusion yet, with its much smaller size. But for A, it would have a long lifetime ahead. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [July 26, 2025, 11:37pm UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/218 "2025-07-26T23:37:32Z")
> [@Northern\_Piper](#): > > The articles say that A and B likely formed around the same time, but that B hasn’t even started fusion yet, with its much smaller size. But for A, it would have a long lifetime ahead. Based on it’s estimated mass of 1.5 solar masses, BetelBuddy would be an F-type star when it settled down to main sequencehood. That’d give it a lifespan of around 4 to 5 billion years. Of course, that all goes out the window when the big guy supernovas. ---
**Author:** ![nearwildheaven](https://avatars.discourse-cdn.com/v4/letter/n/90db22/32.png) [@nearwildheaven](https://boards.straightdope.com/u/nearwildheaven)\ **Post date:** [July 27, 2025, 12:48am UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/219 "2025-07-27T00:48:21Z")
This describes exactly how I feel about diabetes and cancer research, and no, folks, Big Pharma isn’t hiding the cure from us because it’s more profitable to keep people sick. ---
**Author:** ![PastTense](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pasttense/32/14550_2.png) [@PastTense](https://boards.straightdope.com/u/PastTense)\ **Post date:** [January 25, 2026, 6:37pm UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/220 "2026-01-25T18:37:23Z")
> Using new observations from NASA’s [Hubble Space Telescope](https://science.nasa.gov/mission/hubble/) and ground-based observatories, astronomers tracked the influence of a recently discovered companion star, Siwarha, on the gas around Betelgeuse. The research, from scientists at the Center for Astrophysics | Harvard & Smithsonian (CfA), reveals a trail of dense gas swirling through Betelgeuse’s vast, extended atmosphere, shedding light on why the giant star’s brightness and atmosphere have changed in strange and unusual ways… > > The team detected Siwarha’s wake by carefully tracking changes in the star’s light over nearly eight years. These changes show the effects of the previously unconfirmed companion as it plows through the outer atmosphere of Betelgeuse. This discovery resolves one of the biggest mysteries about the giant star, helping scientists to explain how it behaves and evolves while opening new doors to understanding other massive stars nearing the end of their lives. > **[NASA Hubble Helps Detect 'Wake' of Betelgeuse’s Elusive Companion Star - NASA...](https://science.nasa.gov/missions/hubble/nasa-hubble-helps-detect-wake-of-betelgeuses-elusive-companion-star/)** > > New Hubble and ground-based observations allowed astronomers to track the influence of a recently discovered companion star around Betelgeuse. Preprint at: > **[Betelgeuse: Detection of the Expanding Wake of the Companion Star](https://arxiv.org/abs/2601.00470)** > > Recent analyses conclude that Betelgeuse, a red supergiant star (HD 39801), likely has a companion object with a period of about 2000 days orbiting at only 2.3 stellar radii, deep in the chromosphere of the supergiant. A probable detection of such a... However I came across this negative comment: > Astronomer here! This result is actually NOT as clear as the press release makes it out to be and in fact I’m surprised NASA is doing a press release saying it’s a direct detection when it’s very much not. Heck they don’t even link the paper- [here](https://arxiv.org/abs/2601.00470) it is. > > Now, multiple teams have been searching with HST, Chandra, and a bunch of other telescopes to find the companion of Betelgeuse, and have been for a few years now. There are two major teams, one of which got non detections with Hubble that mean “if we didn’t detect it the companion had to be under 1.5x the mass of the sun.” The second team, Howell et al, used a ground based telescope called Gemini North and had a 2.5 sigma detection of a companion- short of the minimum gold standard in science of a [3 sigma](https://kipac.stanford.edu/highlights/how-special-3-sigma) detection used to determine if a signal is real. (This has to do with statistics if you’re not familiar with the terminology- the odds of how real a signal actually is.) the Howell et al team placed a limit of a 2 solar mass companion. > > So to be clear- HST is NOT capable of directly detecting Betelgeuse’s companion star. This is VERY misleading in the press release… > **[Reddit - The heart of the internet](https://www.reddit.com/r/space/comments/1q82egi/nasa_hubble_helps_detect_wake_of_betelgeuses/nym2jbp/)** ---
**Author:** ![PastTense](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pasttense/32/14550_2.png) [@PastTense](https://boards.straightdope.com/u/PastTense)\ **Post date:** [July 28, 2026, 9:18pm UTC](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478/221 "2026-07-28T21:18:09Z")
> **[Scientists get best-yet glimpse of Betelgeuse’s companion star](https://www.scientificamerican.com/article/scientists-get-best-yet-glimpse-of-betelgeuses-companion-star/)** > > After decades of hints and speculation, scientists have at last unveiled the hidden companion to the iconic star Betelgeuse > **[Astronomers find strongest evidence yet that Betelgeuse has a companion](https://phys.org/news/2026-07-astronomers-strongest-evidence-betelgeuse-companion.html)** > > At long last, astronomers have firm evidence that Betelgeuse, one of the most famous stars in the night sky, is not alone. Using the European Southern Observatory's Very Large Telescope (ESO's VLT), a team led by French researcher Miguel Montargès... The actual scientific paper: > **[eso2611a.pdf](https://www.eso.org/public/archives/releases/sciencepapers/eso2611/eso2611a.pdf)** > > 894.93 KB [![](https://scx1.b-cdn.net/csz/news/800a/2026/astronomers-find-stron.jpg) ](https://scx1.b-cdn.net/csz/news/800a/2026/astronomers-find-stron.jpg) [Previous page](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478.md?page=10) [Next page](https://boards.straightdope.com/t/betelgeuse-losing-brightness/845478.md?page=12)