The James Webb Space Telescope (JWST) has made a groundbreaking discovery, providing a glimpse into the future of our solar system. The powerful instrument has made a rare direct detection of two exoplanets orbiting dead stars, known as white dwarfs. These exoplanets bear a striking resemblance to Jupiter and Saturn, our own gas giants, and offer a snapshot of what our planetary system might look like after the sun dies.
The planet candidates were observed by the JWST’s Mid-Infrared Instrument (MIRI) as they orbited the white dwarfs WD 1202-232 and WD 2105-82. One exoplanet candidate is located at a distance from its white dwarf host that is about 11.5 times the distance between Earth and the sun, while the other candidate sits further away at a distance of about 34.5 times the separation between our planet and star.
While the masses of these planets are still uncertain, estimates suggest they could be between 1 and 7 times the mass of Jupiter, the largest planet in our solar system. These exoplanet detections provide valuable insights into what might happen to gas giants like Jupiter and Saturn when the sun transforms into a white dwarf in approximately 5 billion years.
“Our sun is expected to turn into a white dwarf star in 5 billion years,” says Susan Mullaly, lead author of the research and an astronomer at the Space Telescope Science Institute. “We expect planets to drift outward, into wider orbits, after a star dies. So, if you wind back the clock on these candidate planets, you would expect these to have had orbital separations similar to Jupiter and Saturn.”
Confirmation of these planets would provide direct evidence that gas giants can survive the death of their host star. This discovery also sheds light on the fate of the planets beyond Mars when our own sun dies.
The white dwarfs at the center of this discovery are also found to be polluted with elements heavier than hydrogen and helium, known as “metals.” This pollution suggests that giant planets like Jupiter and Saturn could be responsible for driving comets and asteroids onto the surface of white dwarf stars. It strengthens the connection between metal pollution and planets, indicating that giant planets are common around white dwarf stars. This finding offers insights into what might happen to the asteroids in our own asteroid belt between Mars and Jupiter after the sun’s demise.
The detection of these exoplanets is not only significant for predicting the future of our planetary system but also represents a rare scientific achievement. Since the mid-1990s, astronomers have discovered around 5,000 exoplanets orbiting stars outside our solar system. However, only 50 of these exoplanets have been directly imaged, making this a remarkable breakthrough.
Direct imaging of exoplanets is challenging due to the overwhelming light emitted by their parent stars. Typically, exoplanets are detected through their effects on starlight, such as causing a dip in light output as they transit the star’s face or through gravitational tugs that create a wobble motion in the star. However, the JWST’s direct imaging capabilities allow scientists to study these exoplanets in greater detail, including their atmospheres, masses, and temperatures.
Susan Mullaly and her team were surprised by some unexpected features of these exoplanets, which could potentially challenge our understanding of exoplanet atmospheres. The brightness of these planets at certain wavelengths was brighter than expected, suggesting there may be another source of light, such as a heated moon orbiting the planet. These peculiarities could also offer clues about the existence of exomoons, a long-sought-after phenomenon.
The research conducted by Mullaly and her team has been made available as a preprint on the research repository site arXiv. This groundbreaking discovery not only provides insights into the future of our solar system but also pushes the boundaries of our knowledge about exoplanets and their atmospheres. The James Webb Space Telescope continues to revolutionize our understanding of the universe, acting as a scientific crystal ball that allows us to peer into the far future of our cosmic neighborhood.
