Survival After Death: How a Dead Star is Showing Us the Future of Our Solar System

For as long as there have been intelligent beings on Earth, we have observed the star we call our Sun and the neighboring planets encircling it that comprise our solar system. The conditions we see in our planetary neighborhood right now are essentially the way they have been for eons, and they will likely remain this way for many more.

At some point in the future, the Sun will eventually burn out, becoming a mere shadow of its current brightness and, ultimately, fading gradually into darkness. As its light slowly dims, it will also lead to the destruction of several of the planets encircling it, which will very likely include our own.

Questions remain about the extent of the destruction that occurs as a star begins to die and enters its white dwarf phase. Of course, none of us reading this now will be alive when this occurs, but astronomers are still curious about the process, and what it can tell us about the eventual fate of our universe.

However, new research has revealed through observations of a distant star that some planets orbiting white dwarfs may be able to survive this volatile period toward the end of their lifespans.

“Studies have shown that the remnants of destroyed planets and debris-disk planetesimals can survive the volatile evolution of their host stars into white dwarfs,” write the authors of a new paper published in Nature.

However, “few intact planetary bodies around white dwarfs have been detected,” the authors add. On account of the lack of such discoveries, in the past astronomers have had to rely on simulations to help them make predictions about such star systems. According to these simulations, planets possessing orbits similar to our own resident gas giant, Jupiter, do appear to be able to evade destruction when their star enters the white dwarf phase.

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NASA artist’s depiction of an exoplanet orbiting a white dwarf (NASA/Public Domain).

The problem is that there had never been observational confirmation of what these simulations presented; until now.

According to the study, led by J. W. Blackman, the authors “report the non-detection of a main-sequence lens star in the microlensing event MOA-2010-BLG-477Lb12 using near-infrared observations from the Keck Observatory.”

The international research team, with contributors from lead author Blackman’s School of Natural Sciences at the University of Tasmania in Hobart, Australia, as well as contributors from NASA’s Goddard Space Flight Center Laboratory for Exoplanets and Stellar Astrophysics and other locations, says their discovery appears to confirm what earlier simulations had revealed.

“This system is evidence that planets around white dwarfs can survive the giant and asymptotic giant phases of their host’s evolution,” the team writes in the paper’s abstract, adding that it “supports the prediction that more than half of white dwarfs have Jovian planetary companions.”

Not only does the team’s discovery confirm what earlier simulations had suggested, but it also provided the team with a glimpse of what the future of our own solar system will likely be as the Sun burns out over time.

“Located at approximately 2.0 kiloparsecs towards the centre of our Galaxy, it is likely to represent an analogue to the end stages of the Sun and Jupiter in our own Solar System,” the study’s abstract states.

Part of the problem with confirming simulations that addressed the problem of white dwarfs in the past has to do with how little radiation they produce.

“The feeble radiation from white dwarfs makes it difficult to spot exoplanets… which have survived this stellar transformation,” wrote Dimitri Veras, an Associate Professor and STFC Ernest Rutherford Fellow of Astrophysics at the University of Warwick and contributor to the paper, in a recent article for The Conversation.

“[T]hey are literally in the dark,” Veras says, adding that “In fact, of the over 4,500 exoplanets that are currently known, just a handful have been found around white dwarfs – and the location of these planets suggests they arrived there after the death of the star.”

With the new observations of the microlensing event MOA-2010-BLG-477Lb12 described in the team’s Nature paper, astronomers are finally beginning to fill in some of the gaps about how our solar system may begin to look in the distant future, once our nearest neighborhood star finally makes its way into the great white dwarf ever after.

“Although in the system being discussed in the paper, current technology does not allow us to see any exoasteroids,” Veras says, though he adds that “at least now we can piece together different parts of the puzzle of planetary fate by merging the evidence from different white dwarf systems.”

The team’s study, titled “A Jovian analogue orbiting a white dwarf star,” and was published in Nature on October 13, 2021.