Observations with the European Southern Observatory's SPHERE instrument have identified Betelgeuse B with a significance level of 6.1 sigma. According to the researchers, it is a young star with a mass of 2.6–3.1 times that of the Sun, orbiting the red supergiant about once every six years.
After about a century of speculation and searching, astronomers have obtained the strongest evidence yet thatBeetlejuice is not a single star. A team led by Miguel Montreger of the Paris Observatory processed observations made with the European Southern Observatory's Very Large Telescope Array (ESO VLT), and revealed a light source corresponding to the companion star Beetlejuice B.
The finding was published in the journal Astronomy & Astrophysics. The researchers emphasize that further observations are still needed to show that the object is moving along the expected path around Betelgeuse. However, the measured location, brightness, and characteristics leave little room for an alternative explanation, they say.
“We have shown that Betelgeuse is not alone, but is accompanied by a pale star,” said Montrez. He said the discovery concludes a search that began about a century ago. He said he jumped out of his chair when he first saw the processed images.
Much stronger detection than the previous observation
In August 2025, the news website reported a possible detection of the companion star using the ʻAlopeke instrument on the Gemini North telescope in Hawaii. That detection matched the predicted location well, but its significance was only 1.5 sigma – a level that is usually not sufficient to determine that it is a solid discovery.
The new study is based on observations made in December 2024 using an instrument Sphere-ZIMPOL of the VLT in the Atacama Desert in Chile. The researchers used two different methods to process the images and separate the faint light of the companion from the bright light of the Betelgeuse.
The PACO ASDI method identified the source at a significance level of 6.1 sigma, while an independent principal component analysis identified it at a significance level of 5.1 sigma. The agreement between the two methods, along with the agreement with the early observation from Gemini, greatly strengthens the possibility that this is indeed a companion star.
The source is located at an angular distance of 52.32 milliarcseconds from Betelgeuse. According to the distance the researchers adopted for the system, this figure represents a projected separation of about 8.8 astronomical units – slightly less than the average distance between Saturn and the Sun.
Despite this distance, the companion star moves within Betelgeuse's vast outer atmosphere. The red supergiant's radius is hundreds of times greater than the Sun's, and its chromosphere and stellar wind extend far beyond its visible surface.
A larger and brighter companion than expected
Previous studies estimated that the companion may have a mass close to that of the Sun. The new images indicate a larger star: its estimated mass is 2.6–3.1 times that of the Sun.
According to the analysis, Betelgeuse B is likely a young star of spectral type B8.5V to B9.5V, which has only recently entered the main sequence – the stage where stars generate energy by fusing hydrogen in their cores. Its estimated age is similar to Betelgeuse’s, between eight and ten million years, consistent with the hypothesis that the two stars formed together.
The companion is very faint compared to Betelgeuse. In the filter in which the detection was made, its light intensity was less than a thousandth of that of the red supergiant. Revealing it required adaptive optics and processing methods originally developed for imaging planets outside the solar system.
“It is impressive to see how SPHERE and the advanced processing methods developed for planet detection are also successful in identifying a companion around a massive and evolved star like Betelgeuse,” said Anthony Bucaletti of the Paris Observatory, one of the authors of the study.
The six-year cycle
Betelgeuse is a variable star with several brightness cycles. The three shorter cycles, lasting hundreds of days, are mainly attributed to the star's pulsations. In contrast, the origin of a long secondary cycle lasting about 2,200 days—about six years—remains unexplained.
Studies published in 2024 suggested that the long cycle is caused by the influence of a companion star. According to the scenario, the companion moves within the material surrounding Betelgeuse and influences the dust, gas and stellar wind. The distance measured in the VLT images corresponds to an orbit lasting at least about 5.5–5.9 years, a figure very close to the long luminosity cycle.
The researchers note that the companion alone probably cannot destroy enough dust to explain the full change in brightness. Its gravitational effect on the atmosphere and the flow of material around Betelgeuse may be the main factor.
The lender is also known as Siwara (Siwarha), which means “her bracelet” in Arabic. The name refers to the Arabic origin of the name Betelgeuse, “the hand of Al-Jawza’,” a female figure associated with Orion. In the new paper, the researchers continue to use the cautious scientific name “Candidate Betelgeuse B.”
No sign of an imminent supernova
The discovery of the companion does not indicate that Betelgeuse is about to explode anytime soon. The great dimming of 2019–2020, which sparked speculation of an impending supernova, was explained by local cooling of the star's surface and the formation of a dust cloud that blocked some of its light.
However, the companion may have long-term effects on the mass loss, rotation, and evolution of the Betelgeuse. Since many massive stars are born in binary systems, understanding the interactions in the nearby system may help decipher the evolution of Red supergiants Others and the stars exploding as Type II supernovae.
To complete the confirmation, the team plans to observe the system again and see if the position of Betelgeuse B changes according to the predicted orbit. Such a movement would show that the two stars are gravitationally bound and allow for more precise measurements of their orbits and masses.
Questions and Answers
Has the companion star of Betelgeuse been discovered for sure? The new detection is very strong and was obtained by two separate processing methods, but the researchers are still calling it a “candidate.” Further observation that shows orbital motion would strengthen the evidence that it is gravitationally bound to the Betelgeuse.
How big is Betelgeuse B? Its estimated mass is 2.6–3.1 times that of the Sun. It is probably a young, hot main sequence star, but it is very faint compared to the Betelgeuse.
Did the escort cause Betelgeuse's great fading? No. The great dimming of 2019–2020 is attributed to a dust cloud formed after material was ejected from the star's surface. The companion may explain another brightness cycle, lasting about six years.
Does the discovery mean that Betelgeuse will explode soon? No. Betelgeuse will indeed end its life as a supernova, but the new finding does not indicate that the explosion is expected in the near future.
For the original publication: Opening the original publication
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