Recent observations using NASA’s Transiting Exoplanet Survey Satellite (TESS) have revealed a startling truth: aging stars in their red giant phase are significantly more destructive to orbiting planets than previously thought. This discovery has profound implications for our understanding of planetary systems and raises crucial questions about the fate of Earth as the Sun itself evolves.
The Red Giant Transformation: A Stellar Makeover
Stars like our Sun spend most of their lives in a stable phase known as the “main sequence,” where they generate energy through nuclear fusion – converting hydrogen into helium. However, this process eventually comes to an end. When a star exhausts its core hydrogen supply, it begins to transform into a “red giant.”
This transformation is dramatic. The core contracts, while the outer layers expand significantly, potentially growing to as much as 1,000 times the star’s original size. For planets orbiting close to the star, this expansion poses a severe threat. Scientists estimate that our Sun will enter this red giant phase in roughly 5 billion years, potentially engulfing Mercury, Venus, and possibly Earth.
Uncovering Planetary Demise with TESS
To understand the frequency of this planetary destruction, a team of astronomers used TESS to observe a massive sample of planetary systems. They began with nearly half a million potential signals indicating the presence of exoplanets. Through careful analysis, including the application of a computer algorithm, they narrowed this down to 15,000 candidate planets orbiting stars just beginning to evolve into red giants. Of these, around 130 were identified as potential planets, including 33 newly detected candidates.
The findings revealed a striking pattern: planets are much less likely to be found orbiting close to red giant stars. This suggests that many planets are eliminated as stars undergo this transformation. “This is strong evidence that, as stars evolve off their main sequence, they can quickly cause planets to spiral into them and be destroyed,” stated Edward Bryant, a University of Warwick researcher involved in the study.
Tidal Interactions: A Gravitational Tug-of-War
The primary mechanism behind this planetary destruction is believed to be “tidal interaction,” a gravitational tug-of-war between the planet and the star. As a star expands into a red giant, the strength of this interaction increases dramatically.
Just like the Moon pulls on Earth’s oceans to create tides, a planet exerts a gravitational pull on its star. This interaction slows the planet down and causes its orbit to shrink, ultimately leading it to spiral inwards towards the star, where it either breaks apart or falls in.
The study confirmed this theory: when researchers focused on stars already expanding, the likelihood of them hosting a planet dropped to a mere 0.11%. This represents a roughly 3% decrease compared to the chances of hosting a planet around a star in its main sequence phase. The researchers also observed a decline in the probability of red giants hosting giant planets like Jupiter or Saturn as the star’s age increased.
Earth’s Fate: A Mixed Outlook
Given these findings, what does this mean for Earth’s chances of survival as the Sun transitions into a red giant? While Earth is undoubtedly safer than the giant planets examined in the study, which are much closer to their star, the researchers emphasize that their observations only cover the initial stages of this evolution – the first one to two million years.
Unlike the missing giant planets observed in the study, Earth itself may survive the Sun’s red giant phase. However, the conditions on Earth during this period would likely be unsustainable for life.
The team is now pursuing additional data to better understand why some planets are consumed by elderly stars while others escape this fate. This research could provide crucial insights into Earth’s potential long-term survival and the challenges it may face as our own star transforms.
