Two years ago, a distant star dying in a system 12,000 light-years from Earth was initially accused of consuming a planet. However, recent findings have exonerated this aging star from any wrongdoing, as described in observations from the James Webb Space Telescope, a collaborative effort by NASA and its European and Canadian space partners. The team discovered that while the planet did succumb to its stellar companion, the circumstances differed from previous assumptions. Instead of the star expanding into a red giant and engulfing the planet, the planet’s orbit gradually diminished, resulting in its eventual collision with the star.
This development shifts the focus on responsibility, suggesting the planet effectively propelled itself into the star. Ryan Lau, an astronomer at the National Science Foundation’s NOIRLab, commented on this revelation, noting that the star indeed consumed the planet, just not as previously believed, attributing more fault to the planet itself.
An artistic rendering illustrates a planet skimming near a star shortly before being entirely engulfed. Credit for this depiction goes to K. Miller and R. Hurt from Caltech/IPAC. Earlier studies have documented instances of stars devouring planets, with evidence often gleaned from post-mortem analyses of the star’s remains. However, prior research published in Nature detailed the first direct observation of a star swallowing a planet in real time. The event, first detected five years ago as a bright flash labeled ZTF SLRN-2020, revealed the star’s infrared glow a year prior, indicating the presence of dust from a destroyed planet.
Initially, astronomers suspected the star had transformed into a red giant, capable of engulfing nearby planets, a fate expected for the Earth when the sun eventually meets its end. New data from the Webb telescope, however, indicated that the star remained the same size, and it was the Jupiter-sized planet that drew closer over millions of years until it collided with the star. These findings, along with new conclusions, have been published in The Astrophysical Journal.
The collision resulted in a massive explosion, forming a swirling disk of gas and dust, with molecules such as carbon monoxide detected by the Webb telescope following the aftermath. Morgan MacLeod from the Harvard-Smithsonian Center for Astrophysics explained that the planet, upon grazing the star’s atmosphere, initiated an irreversible process of spiraling inwards.
In contrast to massive stars that end as supernovae or black holes, medium-sized stars like the sun undergo a slower demise, forming a "planetary nebula" from the shed layers of the star, despite the misnomer. These phenomena are composed of gas and dust from a decaying star, expected to be the eventual outcome for our sun in approximately 5 billion years. While scientists have made strides in understanding these events, much remains to be learned.
Observing a single star through its entire lifecycle is impracticable due to the vast amount of time required, as noted by Paul Sutter, a professor at Stony Brook University, who was not involved with the recent study. Instead, by studying numerous stars at different stages and their interactions with their surroundings, researchers can piece together the life cycle of stars.
The Webb telescope’s exploration of the aftermath’s gases raises further questions about the specifics of the planet’s engulfment, motivating scientists to investigate additional similar occurrences to gather more information.