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Fig.2. Planetary Nebula WeSb1. It glows mainly in hydrogen emission lines (red) and oxygen (blue and green). The central star is slightly offset upwards in the center. Image (by Klaus Bernhard) is based on observations from NOT and INT telescopes on the Canary Islands

A Star That Destroyed Its Own Planetary System

15. 1. 2025 | 364 visits

An international team of astrophysicists, including researchers from the Astronomical Institute of the Slovak Academy of Sciences (SAS), has discovered a unique star that likely destroyed its own planetary system. The research team examined about 2,000 stars surrounded by so-called planetary nebulae. One of them, named WeSb1, displayed peculiar and suspicious behavior. The findings were recently published in the renowned journal Nature Astronomy.

“Its brightness frequently drops randomly, sometimes by as much as tenfold. These changes could last for days or even weeks, as though something dark was obscuring it. Subsequently, we observed the object using multiple telescopes on the Canary Islands, employing various methods, the TESS satellite, and even a 1.3-meter telescope at Skalnaté Pleso for one night. We determined that the star is not obscured by other stars or planets, but by large dust clouds. These clouds are not located in its atmosphere but orbit around the star,” stated researchers Klaus Bernhard and Dave Jones.

PhD student James Munday adds that the situation is more complex. The actual central star cannot be observed as it is too hot and emits ultraviolet radiation. Instead, they observe its companion star, which is similar to the Sun but slightly hotter and larger. This companion star is being obscured by the dust clouds. Scientists are now asking where such large and dense dust clouds originate.

“The most plausible explanation is that these dust clouds result from the disintegration or collisions of larger objects, such as planets or asteroids. When the dwarf star became a giant AGB star, it likely engulfed the surrounding planets. Losing most of its mass, the AGB star destabilized planets farther away. This caused orbital chaos, collisions of objects, and some of them strayed toward the companion star, where collisions and disintegration could continue, forming massive dust clouds. Planets and dust near the central star likely did not survive, but those near the companion star possibly did. This allows us to witness this spectacle,” said Ján Budaj, the lead author of the study from the Astronomical Institute of SAS.

Astronomers explain that over 5,000 exoplanets have been discovered to date. These are planets orbiting stars other than the Sun, much like the planets in our Solar System. Most exoplanets orbit normal stars known as dwarfs. During the evolution of such stars, a dwarf transforms into a giant, then an even larger AGB star, and eventually, paradoxically, into a very small white dwarf. It turns out that nearly every star has planets or more complex planetary systems, including smaller objects like asteroids or comets. Such objects have been detected around dwarf stars, giants, and white dwarfs. Unfortunately, we still know very little about what happens to planets and planetary systems around AGB stars when the massive, cool AGB star transforms into a tiny, hot white dwarf.

“There is a transitional phase between the AGB star and the white dwarf called the planetary nebula. This is a sort of envelope around the central star, which has nothing to do with planets—it’s just an unfortunate name. The massive AGB star loses most of its mass, which later forms the planetary nebula. We can observe this nebula only because it is illuminated by the hot central star. This scenario suggests that planets and planetary systems persist even in the planetary nebula stage, undergoing a fairly wild and often violent evolution,” the researcher added.

The full article

 

Research Team Members:

Ján Budaj  (Astronomical Institute of SAS, Tatranská Lomnica, Slovak Republic)

Klaus Bernhard (Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne e.V. , Berlin, Germany)

David Jones (Instituto de Astrofísica de Canarias, La Laguna, Spain, Departamento de Astrofísica, Universidad de La Laguna, La Laguna, Spain, Nordic Optical Telescope, Breña Baja, Spain)

James Munday (Department of Physics, University of Warwick, Coventry, UK)

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