The James Webb Space Telescope has imaged two alien worlds still orbiting the bodies of their dead stars: ScienceAlert

The James Webb Space Telescope has imaged two alien worlds still orbiting the bodies of their dead stars: ScienceAlert

No star dies quietly. Even the most peaceful stellar deaths involve earthquakes, explosions, and the fall of enormous amounts of mass into the surrounding space.

This will be the Sun’s ultimate fate, as it will swell into a red giant that may extend as far as Mars before its outer matter is washed away and its core collapses into an ultra-dense white dwarf.

So what happens to the remaining planets? Will their turbulent orbits send them wandering the galaxy, or will they be swallowed by a white dwarf? Could it even remain quiet and undisturbed, orbiting a dead star as it slowly cooled over trillions of years into a cold, inert mass?

Now, a new discovery provides insight into the possible fate of the solar system’s planets. Using the James Webb Space Telescope, astronomers have obtained direct images of what appear to be two gas giant exoplanets orbiting white dwarf stars.

“If confirmed, these will be the first directly imaged planets that are similar in both age and separation to the giant planets in our solar system,” wrote a team led by astronomer Susan Mulally of the Space Telescope Science Institute (STScI). They will prove that widely separated giant planets like Jupiter survive stellar evolution.

The photos are so great for a number of reasons. Normally, we do not see exoplanets directly. Although more than 5,500 exoplanets have been confirmed at the time of writing (and thousands more have been discovered), most of these discoveries are indirect. Astronomers observe the effects of an exoplanet on its host star, and infer its properties based on those effects.

This is because exoplanets are very small and very far away, and any light they reflect or emit is tiny compared to that of a star; Our current technology, although improving, simply cannot detect it.

But the James Webb Space Telescope is the most powerful space telescope ever built, so Mulally and her team used it to search for white dwarf exoplanets.

They found what appear to be giant gas exoplanets orbiting two different white dwarf stars called WD 1202-232 and WD 2105-82 at a distance of 34 and 53 light-years from Earth, respectively. It’s unclear exactly how massive the exoplanets are, but images put them somewhere between 1 and 7 times the mass of Jupiter. More precise masses can be obtained by studying the subtle oscillations of stars, known by their name Radial velocity.

JWST images reveal exoplanet candidates. (Mulally et al., ArXiv, 2024)

Even more interesting is the orbital separation between white dwarfs and their planets.

The exoplanet orbiting WD 1202-232 appears to be located at a distance of 11.47 astronomical units; This is slightly further than Saturn, which orbits the Sun at a distance of 9.5 astronomical units. The exoplanet orbiting WD 2105-82 has an apparent orbital separation of 34.62 AU, similar to Neptune’s orbital distance of 30 AU.

If exoplanets are the same age as their host stars, this means that exoplanets with distances similar to those of the outer planets in the solar system can survive the violent death of their stars and remain in orbit.

Only a few white dwarf exoplanets have been discovered so far, which means we don’t have a great deal of information to rely on when predicting the fate of the solar system when the sun dies. We know, based on analysis of white dwarf atmospheres, that this dense stellar remnant can eat up nearby planets, polluting their atmospheres with planetary material.

This discovery has not yet been confirmed. It is possible that the two objects are distant background galaxies, although researchers believe this is unlikely. This means that the two candidate worlds represent an important and key piece of the puzzle about what happens to a planetary system like ours when a star reaches the end of its life.

The team recommends follow-up surveys to determine the nature of their remarkable discovery.

“If confirmed using combined integer motion, these giant planets would represent the first directly imaged planets that are similar in age, mass, and orbital separation to the giant planets in our solar system,” they wrote.

“Future spectroscopy and multi-scale imaging of these systems may be possible using the James Webb Space Telescope, which would improve observational constraints on physics and a variety of fascinating giant planet models.”

The research has been accepted for publication in Astrophysical Journal Letterswhich is available on arXiv.

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