{"id":135162,"date":"2025-11-15T19:02:08","date_gmt":"2025-11-15T19:02:08","guid":{"rendered":"https:\/\/www.newsbeep.com\/il\/135162\/"},"modified":"2025-11-15T19:02:08","modified_gmt":"2025-11-15T19:02:08","slug":"alma-just-spotted-a-mysterious-object-orbiting-a-star-in-its-final-days","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/il\/135162\/","title":{"rendered":"ALMA Just Spotted a Mysterious Object Orbiting a Star in Its Final Days"},"content":{"rendered":"

For the first time, astronomers have captured direct evidence of a hidden object orbiting an aging, massive red giant star. The discovery, made using the Atacama Large Millimeter\/submillimeter Array (ALMA), sheds new light on how dying stars interact with their surroundings\u2014and what unexpected dynamics might unfold during the final stages of stellar life.<\/p>\n

The star in question is \u03c01 Gruis, located about 530 light-years from Earth. It\u2019s what\u2019s known as an asymptotic giant branch (AGB) star\u2014an evolved star that was once similar to the sun but has now expanded to a size over 400 times larger. Its brightness is staggering: thousands of times more luminous than our own sun, which has made it nearly impossible until now to observe anything in its immediate neighborhood. That\u2019s precisely what makes this finding, published in Nature Astronomy, so striking.<\/p>\n

A Surprisingly Circular Orbit<\/p>\n

Of all the unexpected aspects of the study published in Nature Astronomy<\/a>, the shape of the companion\u2019s orbit stood out most. Based on earlier models, scientists expected a more elliptical orbit, which would make sense given the chaotic and high-energy environment around an AGB star. Instead, what they observed was a nearly perfect circle.<\/p>\n

A circular orbit suggests that tidal interactions, the gravitational forces that tend to smooth out orbits over time, might be happening more quickly or efficiently than previously thought. That, in turn, could signal the need to recalibrate many existing models of how stars and their companions evolve together.<\/p>\n

This level of detail was only possible because of ALMA\u2019<\/a>s unmatched resolution. The telescope array, made up of 66 radio dishes in Chile\u2019s Atacama Desert<\/a>, was able to visually confirm the motion of the companion despite the overwhelming brightness of \u03c01 Gruis. According to Phys.org<\/a>, this is the first time such an orbit has been directly observed around a red giant of this type.<\/p>\n

\"HydrodynamicHydrodynamic model of the accretion disk surrounding the companion of \u03c01 Gruis. Credit: Nature Astronomy
Pinpointing the Mass to Chart the Orbit<\/p>\n

Before the team could fully interpret their observations, they first had to determine the mass of \u03c01 Gruis\u2014a challenging task given the star\u2019s bloated, pulsating state. This step was carried out by researchers at Monash University, including PhD student Yoshiya Mori<\/a>, who used stellar evolution models to analyze its brightness and pulsation behavior.<\/p>\n

\u201cA key part of understanding the orbit of the companion is knowing the mass of the AGB star,\u201d Mori said. Without that parameter, aligning the observed motion with theoretical models would have been impossible.<\/p>\n

compared their simulations with existing models from the scientific literature, concentrating on the late-stage evolution of red giants. Mori added that introducing a companion into an already unstable system \u201ccould possibly wreak further havoc on the already complicated processes surrounding these stars.\u201d<\/p>\n

Astronomers using ESO\u2019s Very Large Telescope have for the 1st time directly observed patterns on the surface of a star outside the Solar System. The PIONIER instrument reveals the convective cells on the surface of the star (\u03c01 Gruis) whose diameter is 350 times that of the Sun. pic.twitter.com\/qKw3yFk6nv<\/a><\/p>\n

\u2014 bill bold (@bill_bold) January 25, 2018<\/a><\/p>\n

The Case for Revising Late-stage Stellar Models<\/p>\n

Traditional models assumed that orbital circularization takes thousands to millions of years. The case of \u03c01 Gruis shows a companion already in a circular orbit. According to Mats Esseldeurs<\/a>, the project\u2019s lead scientist from KU Leuven, these findings could prompt a broader reassessment of how tidal forces operate and how binary systems evolve over time.<\/p>\n

\u201cUnderstanding 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.\u201d <\/p>\n

And the implications reach far beyond a single star. If similar companions are common around other dying stars<\/a>, current models may need to be reevaluated on a much larger scale.<\/p>\n

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