{"id":263392,"date":"2025-11-15T00:40:07","date_gmt":"2025-11-15T00:40:07","guid":{"rendered":"https:\/\/www.newsbeep.com\/uk\/263392\/"},"modified":"2025-11-15T00:40:07","modified_gmt":"2025-11-15T00:40:07","slug":"alma-resolves-close-companion-orbiting-giant-red-star","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/uk\/263392\/","title":{"rendered":"ALMA resolves close companion orbiting giant red star"},"content":{"rendered":"

\"Scientists<\/p>\n

Hydrodynamic simulation of the accretion disk around companion \u03c01 Gru C. Credit: Nature Astronomy (2025). DOI: 10.1038\/s41550-025-02697-2<\/p>\n

Close companions can influence stellar evolution in many ways. While some companions can be detected around young stellar objects, direct observational evidence of companions around asymptotic giant branch (AGB) stars or aging stars, has remained elusive.<\/p>\n

\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tUnveiling the mysteries of \u03c01 Gruis<\/p>\n

At some 530 light-years from Earth, a red giant star<\/a> called \u03c01 Gruis (affectionately known as pi-one-Gru by astronomers and scientists) has long been a mystery for scientists. Known as an asymptotic giant branch<\/a> (AGB) star, \u03c01 Gruis, was once like the sun but is now an aging star at the end of its life, having cooled as it swelled to over 400 times the size of the sun, it has now become a red giant star.<\/p>\n

These stars can make new elements, undergo pulsations on the timescale of days to years, and lose a lot of their mass\u2014throwing off an Earth-mass equivalent of material over a four-year period\u2014before ending their lives as planetary nebulae or, in layman’s terms, ionized gas ejected from red giant stars late in their lives.<\/p>\n

\u03c01 Gruis shines a few thousand times more brightly than our sun. Which makes detecting any close companion objects to these stars exceptionally difficult, since they can outshine them and also vary in brightness.<\/p>\n

ALMA reveals a hidden companion<\/p>\n

In a paper published<\/a> in Nature Astronomy, an international team of scientists have been able to directly show the orbit of a companion around \u03c01 Gruis using the resolving power of the Atacama Large Millimeter\/submillimeter Array (ALMA)\u2014an astronomical interferometer of 66 radio telescopes<\/a> in the Atacama Desert of northern Chile.<\/p>\n

Yoshiya Mori, Ph.D. Candidate in Astrophysics at Monash University was responsible for making detailed comparisons between the observed properties of \u03c01 Gruis and state-of-the-art Monash University stellar evolution<\/a> models, along with models from existing literature that predict how these stars pulsate.<\/p>\n

“A key part of understanding the orbit of the companion is knowing the mass of the AGB star. Our team helped better constrain this mass by using its observed luminosity and pulsation characteristics to find the best suited stellar model,” Mr. Mori said.<\/p>\n

“This research is especially interesting, as throwing a close companion into the mix could possibly wreak further havoc on the already complicated processes surrounding these stars.”<\/p>\n

\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tChallenging previous models of stellar evolution<\/p>\n

Despite earlier predictions of an elliptical orbit for the companion star<\/a>, the research has observed an almost perfectly round orbit. This suggests the orbit evolves faster than previously thought. The result calls for adjustments to existing models of the final life stage of giant stars with companions.<\/p>\n

Project lead, Mats Esseldeurs from KU Leuven, says our sun will one day go through such a stage as well.<\/p>\n

“Understanding how close companions behave under these conditions helps us better predict what will happen to the planets around the sun, and how the companion influences the evolution of the giant star itself,” said Mr. Esseldeurs.<\/p>\n

The analysis suggests that model-predicted circularization rates may have been underestimated. Researchers believe this will open avenues for our understanding of tidal interaction physics and binary evolution.<\/p>\n

More information:
\n\t\t\t\t\t\t\t\t\t\t\t\tMats Esseldeurs et al, Evidence for the Keplerian orbit of a close companion around a giant star, Nature Astronomy (2025). DOI: 10.1038\/s41550-025-02697-2<\/a><\/p>\n

\n\t\t\t\t\t\t\t\t\t\t\t\t\tProvided by
\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tMonash University<\/a>
\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/p>\n

\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/p>\n

\n\t\t\t\t\t\t\t\t\t\t\t\tCitation:
\n\t\t\t\t\t\t\t\t\t\t\t\tALMA resolves close companion orbiting giant red star (2025, November 14)
\n\t\t\t\t\t\t\t\t\t\t\t\tretrieved 14 November 2025
\n\t\t\t\t\t\t\t\t\t\t\t\tfrom https:\/\/phys.org\/news\/2025-11-alma-companion-orbiting-giant-red.html\n\t\t\t\t\t\t\t\t\t\t\t <\/p>\n

\n\t\t\t\t\t\t\t\t\t\t\t This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
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