What’s a surprising way to figure out what an exoplanet is made of? Wait until it gets torn apart by its star!
Recently, astronomers at the W. M. Keck Observatory in Hawaiʻi observed a fascinating event: a dead star devouring the remains of a shattered planet. This destructive feast occurred more than 3 billion years after the star had turned into a white dwarf.
This finding is important. According to astrophysicist Érika Le Bourdais, the lead author of the study, this challenges our understanding of how planetary systems evolve.
More intriguingly, this discovery provides insight into what might happen in our own Solar System over 5 billion years from now, when our Sun will shed its outer layers and become a white dwarf.
The researchers found 13 heavy elements in the atmosphere of the white dwarf, which is the most ever recorded for a hydrogen-rich white dwarf. This suggests the remnants of an ancient planet that was at least 200 kilometers wide. It had a rocky mantle and a metallic core, similar to Earth.
The specific white dwarf is identified as LSPM J0207+3331, located 145 light-years away in the constellation Triangulum.
Unexpectedly, the presence of so many heavy elements in a cold, hydrogen-rich white dwarf challenges previous assumptions. Typically, these heavy elements sink quickly, leading scientists to expect only a few would be detected.
In contrast, elements are easier to find in warmer, helium-rich white dwarfs, where they take longer to settle. Given that hydrogen-rich stars are quite common and among the oldest in the Milky Way, this study offers a fresh perspective on the long-term evolution of planetary bodies around dead stars.
Interestingly, astronomers can uncover details about exoplanets by observing how white dwarfs consume them. Normally, it’s hard to know a planet’s chemical makeup directly. However, when a planet is devoured, its elements create unique chemical signatures in the white dwarf’s hydrogen atmosphere.
The destroyed planet exhibited a core mass fraction of about 55%. For context, Mercury has a core mass fraction of around 70%, while Earth has about 32%. This ratio reveals important information about a planet’s structure.
The study also highlights the ongoing change in planetary systems. Astronomer John Debes noted that something must have disturbed this system long after the star’s death. As stars age and lose mass, they can destabilize the orbits of planets. It’s possible that larger planets nudged the shattered planet into a fatal path. This long-term instability is still not fully understood.
Researchers aim to find evidence of larger planets, like massive gas giants, that might have influenced the smaller planets. However, locating them can be tricky due to their low temperatures and distance.
Using data from the now-retired Gaia space telescope and infrared readings from NASA’s James Webb Space Telescope, scientists are hopeful to uncover the culprits behind this cosmic event.
Studying these kinds of planetary interactions will further our understanding of exoplanet formation and evolution on a larger scale, shedding light on how planets, including Earth-like ones, form, grow, and ultimately meet their end.
This exciting research is published in The Astrophysical Journal. For more on the study, you can check out the full paper here.
These insights not only broaden our knowledge of distant worlds but also invite us to reflect on the fate of our own Solar System.
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