Using NASA’s Transiting Exoplanet Survey Satellite (TESS), astronomers are uncovering startling truths about aging stars. They’ve found that stars in their “red giant” phase can be quite harmful to nearby planets, much more than we thought. This leads us to wonder: how might this change affect Earth when our sun transforms in the distant future?
TESS looks for exoplanets by tracking dips in starlight as these planets pass in front of their stars. Starting with nearly half a million planetary systems, researchers narrowed it down to 15,000 potential signals. They focused on stars just entering their red giant phase and identified around 130 candidates, including 33 never seen before.
The data indicates that planets close to red giants are rare. It seems many get destroyed during this transformation. Edward Bryant, a researcher from the University of Warwick, explains the impact: “As stars evolve from their main sequence, they can quickly cause planets to spiral in and be destroyed.” The effectiveness of these stars at engulfing nearby planets surprised the team.
Stars become red giants when they exhaust the hydrogen in their cores. Without this hydrogen, they can’t convert it to helium. When this occurs, the star’s core contracts, while its outer layers expand dramatically, often up to 1,000 times its original size. This expansion means trouble for close-orbiting planets. In about 5 billion years, the sun will grow so large it could potentially engulf Mercury, Venus, and possibly even Earth.
But how does this destruction happen? Bryant mentions a gravitational “tug-of-war” between the star and the planet. As the star expands, this interaction strengthens, pulling the planet closer and sometimes even breaking it apart.
This connection is striking. Research shows that when scientists studied stars in the early stages of expansion, the likelihood of them hosting planets was only about 0.11%. That’s roughly 3% lower than for main-sequence stars. Additionally, older red giants were less likely to have massive planets like Jupiter or Saturn.
What does this mean for Earth? While Earth is at a safe distance compared to other giant planets, the future still looks uncertain. Vincent Van Eylen, another researcher from University College of London, notes, “Earth might survive the sun’s red giant phase, but life on Earth probably would not.”
The researchers plan to investigate further. They want to understand why some planets manage to survive while others meet their demise. Knowing the masses of these planets could provide insights into their fates.
The study’s findings could reshape our understanding of planetary life cycles. As we ponder Earth’s future, the results serve as a stark reminder of how dynamic and unpredictable the cosmos can be.
For a deeper look into this study, see their publication in the Monthly Notices of the Royal Astronomical Society.
