This article was originally published in Eos. The publication contributed the article to Space.com. Expert voices: opinion articles and opinions.
Our sun is approximately halfway through its life, which means Land it is too. After a star exhausts its nuclear hydrogen fuel, its diameter expands more than a hundredfold, enveloping any unfortunate planets into nearby orbits. For us, that day is at least 5 billion years away. solar system, But scientists have discovered a possible preview of the fate of our world.
Using data from the TESS Observatory (Transiting Exoplanet Study Satellite)astronomers Edward Bryant from the University of Warwick and Vincent Van Eylen at University College London compared systems with stars in the main sequence of their lives (fusing hydrogen, like the Sun) with post-main sequence stars closer to the end of their lives, with and without planets.
“We saw that these planets are becoming rarer. [as stars age]”Bryant said. In other words, Planets are disappearing as their host stars age. Comparing planetary systems with younger and older stars makes it clear that the discrepancy is not due to the fact that the planets did not exist in the first place: older stars are simply hungry.
“We’re pretty sure it’s not due to a training effect,” Bryant explained, “because we don’t see big differences in the mass and [chemical composition] of these stars versus the populations of main sequence stars.”
Total immersion isn’t the only way giant stars can destroy planets. As they grow, giant stars also exert increasing tidal forces on their satellites that cause their orbits to decay, strip them of their atmospheres, and may even tear them apart entirely. The orbital decay aspect is potentially measurable, and this is the effect that Bryant and Van Eylen considered in their model of how planets die.
“We’re looking at how common planets are around different types of stars, with the number of planets per star,” Bryant said. Bryant and Van Eylen identified 456,941 post-main sequence stars in the TESS data and, from them, found 130 planets and planet candidates with close orbits. “The fraction [of stars with planets] “It becomes significantly smaller for all shorter period stars and planets, which is very much in line with the theory’s predictions that tidal decay becomes very strong as these stars evolve.”
Astronomers use TESS to find exoplanets by looking for the dimming of light as they pass in front of their host stars, a miniature eclipse known as transit. As with any exoplanet detection method, transits are best suited for large, Jupiter-sized planets in relatively small orbits lasting less than half an Earth year, sometimes a lot less. So these solar systems are not much like our own in that sense. The study of planets orbiting post-main sequence stars poses additional challenges.
“If you have a planet the same size but a larger star, you have a smaller transit,” Bryant said. “That makes it harder to find these systems because the signals are much shallower.”
However, although the stars in the sample data have a much larger surface area, they are comparable in mass to that of the Sun, and that is the most important thing, the researchers said. A star with the same mass as the Sun will go through the same stages of life and die in the same way, and that similarity is what helps reveal the future of our solar system.
“The processes that take place once the star evolves [past main sequence] can tell us about the interaction between the planets and the host star,” he said Sabine Reffertastronomer at Universität Heidelberg who was not involved in the study. “We have never seen this kind of difference in planet occurrence rates between [main sequence] and giants before because before we did not have enough planets to statistically see this difference. “It’s a very promising approach.”
Planets: Part of a balanced stellar breakfast
Exoplanet science is one of astronomy’s greatest successes in the modern era: since the first discovery of exoplanets 30 years ago, astronomers have confirmed more than 6,000 planets and identified many more candidates for follow-up observations. At the same time, the job can be difficult when it comes to planets orbiting post-main sequence stars.
A complicated aspect of this work is related to the age of stars, which formed billions of years before our sun. Older stars have a lower abundance of chemical elements heavier than helium, a measurement astronomers call “metallicity.” Observations have found a correlation between high metallicity and exoplanet abundance.
“A small difference in metallicity…could potentially double the rate of occurrence,” Reffert said, emphasizing that the paper’s general conclusions would be valid, but the details would need to be refined with better metallicity data.
Future observations to measure metallicity using spectra, along with the mass of stars and planets, would improve the model. Furthermore, the European Space Agency‘s PlatoMissionscheduled for launch in December 2026, it will add more sensitive data to TESS observations.
Earth’s proud fate is far in the future, but researchers have taken a big step toward understanding how dying stars could devour their planets. With more data from TESS and Plato, we might even glimpse the tiny orbital changes that indicate a planet spiraling toward its doom: a grim end for that world but a wonderful discovery for our understanding of the coevolution of planets and their host stars.
