{"id":968451,"date":"2026-07-30T06:14:28","date_gmt":"2026-07-30T06:14:28","guid":{"rendered":"https:\/\/www.europesays.com\/us\/968451\/"},"modified":"2026-07-30T06:14:28","modified_gmt":"2026-07-30T06:14:28","slug":"after-centuries-of-research-betelgeuse-turns-out-to-be-two-stars-not-one","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/us\/968451\/","title":{"rendered":"After Centuries of Research, Betelgeuse Turns Out to Be Two Stars, Not One"},"content":{"rendered":"

\"\"<\/a>Artistic impression of Betelgeuse and its candidate companion, Betelgeuse B. The smaller blue-white star has been enlarged for visibility; Betelgeuse is estimated to be roughly 400 times wider.<\/p>\n

Betelgeuse is one of the most watched stars in the night sky. People have followed this reddish point on Orion\u2019s shoulder for millennia. Modern astronomers have mapped its enormous surface, watched it pulse, and tracked clouds of dust thrown into the space around it.<\/p>\n

But the famous star may have been hiding something from us: another star.<\/p>\n

Using the European Southern Observatory\u2019s Very Large Telescope in Chile, astronomers have obtained their clearest image yet of a faint source beside Betelgeuse. The object appeared almost exactly where a proposed companion was predicted to be, and two independent image-processing methods recovered it from the red supergiant\u2019s overwhelming glare.<\/p>\n

Meet Betelgeuse B<\/p>\n

The researchers call it Betelgeuse B, and astronomers had suspicions about it for years. It appears to be a young, hot star between 2.6 and 3.1 times as massive as the Sun, orbiting the red supergiant at roughly the distance between Saturn and the Sun. In fact, researchers only spotted it because it\u2019s so big.<\/p>\n

\u201cHonestly, I thought we did not have the sensitivity to detect Betelgeuse B as it was predicted,\u201d explains Miguel Montarg\u00e8s, lead author of the new study, from LIRA at the Observatoire de Paris\u2013PSL. \u201cBecause it is more massive than predicted, we see it!\u201d <\/p>\n

\"Image<\/a>This image shows the location of the red supergiant star Betelgeuse in the constellation of Orion (the Hunter). Betelgeuse can be seen quite easily without the need for a telescope as the right shoulder of Orion, as highlighted in this diagram. Image credits: ESO\/N. Risinger.<\/p>\n

Astronomers have repeatedly suggested that Betelgeuse might have a companion, with claims stretching back to the 20th century. However, none of these claims could provide convincing evidence, largely because Betelgeuse is such a difficult neighbor.<\/p>\n

It is a red supergiant roughly 16.5 to 19 times as massive as the Sun and hundreds of times wider. Its surface heaves with giant convective cells. It pulsates, ejects material and is surrounded by a clumpy, dusty atmosphere. All that changing structure can resemble, obscure or overwhelm the signal from a nearby point of light.<\/p>\n

Originally thought to be about as massive as the Sun, the new observations reveal that Betelgeuse B is instead around two to three times the mass of the Sun. <\/p>\n

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\u201cThe fact that we can still discover a nearby companion, more massive and brighter than the Sun, around such a well-studied star is remarkable,\u201d says Montarg\u00e8s. \u201cThese are among the best moments in science: seeing something new, unexpected.\u201d<\/p>\n

How to Find a Hiding Star<\/p>\n

The strongest recent case for a companion came from Betelgeuse\u2019s peculiar rhythm. The star brightens and fades over several timescales, including a \u201clong secondary period\u201d of roughly 2,200 days \u2014 almost exactly six years. A partner star could explain that observation perfectly.<\/p>\n

An observation with the Gemini North telescope found a possible source at the expected position, but the signal was far too weak to count as a convincing detection. Montarg\u00e8s and his colleagues therefore turned to SPHERE, an instrument on the Very Large Telescope designed to reveal faint objects beside much brighter stars. They observed Betelgeuse on December 3 and 6, 2024.<\/p>\n

\"Astronomy<\/a>This image, taken with ESO\u2019s Very Large Telescope (VLT), shows the clearest image ever of what likely is Betelgeuse B, a star orbiting Betelgeuse. The image was taken with the SPHERE instrument in December 2024, when the companion was predicted to be furthest apart from Betelgeuse as seen from Earth. The circle indicates the size of Betelgeuse, which has been removed. The bright source to the left, marked with a crosshair, is consistent with being Betelgeuse B. Image credits: ESO\/M. Montarg\u00e8s et al.<\/p>\n

The companion wasn\u2019t visible in the raw images. Researchers had to model and subtract the shifting patterns created by Betelgeuse, Earth\u2019s atmosphere and the telescope itself. Two independent processing techniques then revealed a compact source in almost the same location.<\/p>\n

One method found the companion with a confidence of 6.1 sigma<\/a>, while a second reached 5.1 sigma. In plain terms, both signals are strong enough to be very unlikely to come from random noise. They also placed the object just 0.052 arcseconds from Betelgeuse \u2014 roughly the apparent width of a human hair viewed from about 400 meters away. Even one of the world\u2019s most powerful telescopes struggled to separate the two.<\/p>\n

There is still an important caveat. The team has observed the object clearly at only one point in its probable orbit. Astronomers must see it move around Betelgeuse before they can formally prove that the two stars are gravitationally bound.<\/p>\n

But there is now, as Montarg\u00e8s put it, \u201cvery little space left for doubt.\u201d<\/p>\n

A Hot Young Star Beside an Ancient Giant<\/p>\n

After figuring out where it is, the researchers tried to see what kind of star it might be. <\/p>\n

Its brightness best matches a young main-sequence star with 2.6 to 3.1 times the Sun\u2019s mass. Its surface temperature is probably between 11,200 and 12,000 Kelvin, about twice that of the Sun, and it may shine dozens of times more brightly.<\/p>\n

A very young star still pulling in surrounding material often produces strong hydrogen-alpha emission, along with ultraviolet and X-ray radiation. Previous observations with the Hubble Space Telescope and the Chandra X-ray Observatory found no such signals from Betelgeuse B.<\/p>\n

Betelgeuse and its companion probably formed together eight to 10.5 million years ago. But Betelgeuse, being much more massive, raced through its fuel and expanded into a red supergiant. Betelgeuse B appears to have only just reached the main sequence, the long stable phase during which stars fuse hydrogen in their cores.<\/p>\n

Why This Finding Matters<\/p>\n

In addition to solving a mystery from one of the most-studied stars, this would also offer astronomers important clues about how solar systems form and emerge.<\/p>\n

Most massive stars are thought to form in binary or multiple systems. Yet only around 20% to 40% of red supergiants are known to have companions. Some close systems probably merge before either star reaches this swollen stage, while others become almost impossible to detect inside the giant star\u2019s glare and complex atmosphere.<\/p>\n

Betelgeuse suggests that long secondary periods could offer another way to find them. Around a quarter of red supergiants show similar slow variations, and some may be hiding companions of their own. That could change how astronomers interpret their winds, mass loss and eventual explosions.<\/p>\n

The study was published<\/a> in Astronomy & Astrophysics.<\/p>\n","protected":false},"excerpt":{"rendered":"Artistic impression of Betelgeuse and its candidate companion, Betelgeuse B. The smaller blue-white star has been enlarged for…\n","protected":false},"author":3,"featured_media":968452,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_share_on_mastodon":"0"},"categories":[8],"tags":[388886,388887,85002,388888,103314,388889,159,56332,67,132,68,79241],"class_list":["post-968451","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-betelgeuse","tag-betelgeuse-b","tag-binary-stars","tag-companion-stars","tag-european-southern-observatory","tag-red-supergiants","tag-science","tag-stellar-evolution","tag-united-states","tag-unitedstates","tag-us","tag-very-large-telescope"],"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@us\/117007463329198990","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts\/968451","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/comments?post=968451"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts\/968451\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/media\/968452"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/media?parent=968451"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/categories?post=968451"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/tags?post=968451"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}