Gemini North telescope discovers long-predicted stellar companion of Betelgeuse
41 comments
·July 22, 2025chasil
The companion star "has an estimated mass of about 1.5 times that of the Sun and appears to be an A- or B-type main pre-sequence star, i.e. a hot, young, bluish-white star that has not yet begun to burn hydrogen in its core... The companion is located at a relatively close distance to Betelgeuse, about 4 times the distance between Earth and the Sun. This discovery is the first time a stellar companion has been detected orbiting so close to a red supergiant star. Even more surprising is that the companion orbits inside Betelgeuse's outer atmosphere."
pixl97
Also
>This discovery provides a clearer picture of this red supergiant’s life and future death. Betelgeuse and its companion star were likely born at the same time. However, the companion star will have a shortened lifespan as strong tidal forces will cause it to spiral into Betelgeuse and meet its demise, which scientists estimate will occur within the next 10,000 years.
It's unfortunate our flesh lasts but a blink of cosmic time. That would be something to witness.
tristramb
There are many other red supergiants in the sky, some of which have long secondary periods that could be due to close-in companion stars. For example Mu Cephei has a 12 year periodicity.
colechristensen
>It's unfortunate our flesh lasts but a blink of cosmic time. That would be something to witness.
My preferred solution to the Fermi paradox is that hundred million year long lifespans become trivial relatively soon at which point sublight speed galactic travel becomes no big deal and the differing time scale means that not being contacted by an alien intelligence simply hasn't happened yet, have you tried to establish communication with an ant hill in the last 10 seconds? Everybody else in the galaxy who could talk to us lives so long that they just haven't tried to say hello in the last 10,000 years because they were out to lunch.
adastra22
We should fix that.
AStonesThrow
[dead]
layer8
1-minute video: https://noirlab.edu/public/videos/noirlab2523b/
mkw5053
Wow, so it's currently shining purely from gravitational energy release, not nuclear reactions. I hadn't realized that it was possible or that we'd be able to see something of the sort.
Sharlin
This was how physicists hypothesized the sun and other stars work in the late 19th and early 20th century, before the discovery of nuclear fusion. It presented a conundrum because calculations showed that the sun could only sustain the observed rate of energy release for a few million years – whereas the contemporary geological evidence was indicating that the Earth must be billions of years old.
ByThyGrace
What is "gravitational energy release"? How does that lead to light emission (I suppose heat is generated in the middle)?
mattashii
The mass of a star was at some point a nebula, which collapsed into the star.
That collapse reduced the gravitational potential energy of the mass of that nebula, which through accelleration, friction, and pressure, was turned into heat energy.
That heated mass will emit black-body emissions, and so the gravitational energy is now being radiated as light.
teamonkey
Yes, heat through pressure and friction as the matter tries to collapse under gravity. Not quite enough heat and pressure to trigger a sustained fusion reaction.
One interesting thing is that this star was detected at visual wavelengths, not infrared. While not undergoing fusion, it’s hot enough to glow blue-white.
e23c16
The paper is here: https://arxiv.org/abs/2507.15749
The detection appears to be statistically very marginal, 1.5sigma, and the image contains a very similar bright spot on the opposite side of the star (which, for some reason, does not warrant a detection claim).
ac794
The 'ghost' on the other side is an artifact of the speckle imaging technique.
pavel_lishin
Could this explain why Betelgeuse's brightness seems to vary so much?
edit: apparently, yep, that's why.
arnavpraneet
Could you provide any links as to this? Was not able to find anything
layer8
See here: https://en.wikipedia.org/wiki/Betelgeuse#Variability
And from the original NOIRLab link: “This discovery answers the longstanding mystery of the star’s varying brightness”.
jimmytucson
The system’s brightness decreases when the companion star swings around behind Betelgeuse. It also dips when Betelgeuse goes behind the companion star but much less so because Betelgeuse is so much larger.
anjel
dumb question: If a pre-sequence star is assimilated into a larger EOL star, does all the newly assimilated fuel delay or accellerate the larger star's demise?
bonzini
It may prolong life by a few million years. A red supergiant's outer layers still have a few solar masses worth of hydrogen, and the extra material would delay the collapse of the star onto its core.
On the other hand, if the merger happens after the star has started burning carbon, it would have no effect. The explosions and collapses occurring in a supergiant are driven by successive phases of nuclear fusion in the core (collapse when one kind of fuel is exhausted, explosion as the previous fusion products become fusion ingredients), and they happen on a very short timescale (starting at thousands of years and ending at days before the star goes supernova). The presence of lighter elements billions of km away would not really have any impact on that.
dylan604
At least they got to see it before Betelgeuse went supernovae. Do we have examples of the results of the companion star when the main star lets go?
bongoman42
For all we know, it might have gone supernova in the last few hundred years and we've yet to receive the light from it.
NooneAtAll3
in relativistic terms, anything that we don't observe and hasn't observed us is happening at the same time as we are
so there's no point
the8472
You receive a message from an an alien civilization 1000ly away that they have started a deterministic process that will shoot a death ray at earth in 500 years. Should you act on the information that there's doom heading for earth right now or not?
dylan604
Betelgeuse is approximately 650 to 700 light-years away from Earth, so if you consider a few 300 then that means we have at least ~350 years to continue studying it.
dontlikeyoueith
Wouldn't all Type Ia supernova be examples of at least one possible end state of such an event?
https://science.nasa.gov/resource/type-ia-supernova/
The larger star explodes first in a Type II supernova, becomes a Type Ia.
dylan604
You're asking a question in response to a question. Your Type Ia link suggests this is not what is happening with Betelgeuse though. Its companion star is not a white dwarf. Betelgeuse itself is the start expected to go boom. So what happens to its companion? The anim you linked to shows that the white dwarf's explosion didn't destroy its larger star companion, but Betelgeuse is the opposite with the larger star going boom.
dontlikeyoueith
You're misunderstanding.
I'm not saying Betelgeuse would be a type Ia. Betelgeuse will be a Type II supernova.
I'm wondering whether Type II supernovae with smaller partners later become Type Ia once the larger partner explodes and becomes a white dwarf. The former smaller partner then becomes the relatively larger partner that loses mass to the remnant.
_spduchamp
The sequel wasn't as good.
SirLJ
Any comments from Ford Prefect about this?
dang
The submitted URL was https://noirlab.edu/public/news/noirlab2523/, but for some reason is frequently returning the Spanish version of the article. We replaced it with a link to a third-party article and will include the noirlab.edu link at the top.
layer8
I suspect the following should work to force the English version: https://noirlab.edu/public/news/noirlab2523/?nocache=true&la...
ac794
Gemini also has a press release here: https://www.gemini.edu/news/press-releases/noirlab2523
htrp
Gemini North is a telescope, not some new feature of Google's AI model https://en.wikipedia.org/wiki/Gemini_Observatory
>Gemini North telescope in Hawai‘i reveals never-before-seen companion to Betelgeuse, solving millennia-old mystery
AverageSavage
Is it Beetlejuice, Beetlejuice?
throw432196
As I recall, it means arm pit. For it’s position in the constellation. Update: hmmm, i think i may have misunderstood your joke…
carabiner
Juice of the beetle, yes.
null
https://noirlab.edu/public/news/noirlab2523/