New evidence suggests red novas are caused by planets being engulfed by their parent stars

In 2020, astronomers made an intriguing observation of a red nova, a relatively moderate energetic event in the grand scale of the universe. However, recent research has shed light on this phenomenon, suggesting that what we witnessed was a star annihilating its own planet.

These cosmic events are scientifically referred to as intermediate luminosity optical transits (ILOTs), and they are exceedingly rare to observe due to their moderate energy output. This makes it challenging for us to detect and study them. Nevertheless, astronomers suspect that such occurrences are actually quite common throughout the universe.

For years, scientists have pondered whether red novas were caused by planets being consumed by their parent stars. Several potential ILOT candidates have been meticulously examined with this hypothesis in mind. However, it has proven difficult to reconcile theoretical predictions with actual observational data.

The latest observation, named ZTF SLRN-2020, might provide a breakthrough. Unlike previous suspected star-planet interactions that occurred in young systems, where planets were on tumultuous paths colliding with each other and occasionally plunging into their stars, this event involved a star in its main sequence—a typical, middle-aged star. The study, published on the arXiv preprint server, presents the findings of an astronomer who conducted a detailed analysis of the event.

Based on theoretical calculations, the astronomer concluded that the planet’s journey towards its star was not a simple case of slipping into the star’s atmosphere. Instead, it underwent several violent phases as it was torn apart, ultimately resulting in the red nova flare.

As the planet approached the star, it heated up, causing its outer layers to transform into a plasma state. The complex interplay of electricity and magnetism within this plasma led to the emission of twin jets from the planet while it orbited the star. However, these jets lacked sufficient power to entirely overcome the star’s gravitational pull, causing the material to rain back down.

Although the planet regained some of its lost mass through this jet process, it was once again subjected to intense energies near the star’s surface, resulting in further mass loss. Prior to being entirely engulfed, the planet likely formed an accretion disk around the star, with material from the destroyed planet gradually seeping into the star. Eventually, the cataclysmic event came to a conclusion. The accretion disk itself could have generated its own jets, propelling away from the star and creating a nebula that expanded into space.

Undoubtedly, the interaction between the planet and its star during the engulfment process unleashed an astonishing amount of energy, culminating in the red nova. We still lack precise details about the system and the unfortunate circumstances that led to the planet’s fate. Astronomers aspire to discover more of these lower energy transient events, as they hold the potential to deepen our understanding of the intricate dynamics between planets and their parent stars.

Source: Universe Today

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