When our sun enters its death throes in about five billion years, it will burn our planet and then collapse dramatically into a dead ember known as a white dwarf. But the fate of distant planets such as Jupiter or Saturn is less clear.
Wednesday in nature magazine, astronomers report observing a tantalizing preview of our solar system’s afterlife: a Jupiter-sized planet orbiting a white dwarf 6,500 light-years from here.
Known as MOA-2010-BLG-477Lb, the planet occupies an orbit similar to Jupiter. This discovery not only offers a glimpse into our cosmic future, but also increases the possibility that any life in “survivor” worlds could withstand the death of its stars.
“While there is plenty of evidence for rocky planetary debris orbiting white dwarfs, we have very few data points for intact planets,” said Joshua Blackman, a postdoctoral researcher at the University of Tasmania and lead author of the study.
“It is likely that the fate of our solar system will be similar to MOA-2010-BLG-477Lb,” he added in an email. “The sun will become a white dwarf, the inner planets will swallow up, and the planets with a wider orbit such as Jupiter and Saturn will survive.”
The planet was first observed due to the effects of gravitational field deflection of light, a phenomenon known as microlensing. After searching for years for the host star with the Keck II telescope in Hawaii, Dr. Blackman and his colleagues concluded that it was orbiting a white dwarf too faint to be directly observed.
Astronomers use a different method I mentioned last year Another intact Jupiter-like planet discovered, known as WD 1856 b, orbits closely around a white dwarf. But MOA-2010-BLG-477Lb orbits its hidden stellar crust at a distance of three times the distance between Earth and the Sun, making it the first known planet to occupy a Jupiter-like orbit around a white dwarf. By contrast, WD 1856 b orbits its white dwarf every 1.4 days, indicating that it migrated to its current location after its star’s death, despite the exact mechanics of that flight. It is still fragmented.
Andrew Vanderberg, the assistant professor of physics at MIT who led the team that discovered WD 1856 b, said the new study’s conclusions appear solid. He also noted that planets with wide orbits around white dwarfs are probably more abundant than those in narrow orbits, but the latter group is easier to spot.
“If I had to guess, I’d say their people are a lot more common because it just has to stay there and nothing happens to them,” said Dr. Vandenburg. “That sounds to me like the most likely outcome, at least at this point in the history of the universe.”
New discoveries could yield insights into the search for extraterrestrial life and the potential habitability of white dwarf systems. Lisa Kaltenegger, director of the Carl Sagan Institute at Cornell University, has suggested that some life-bearing star systems may even encounter what she calls “Second Configuration” New creatures appear in the reconfigured Fallout of the white dwarf system.
Dr. Kaltenegger, who was part of the team that discovered WD 1856b, said in an email. “If planets can survive the death of their stars, can life also?”
Dying stars emit harmful radiation as they grow to a stage called red giants, causing disruption to their systems that can kill life. But there are some speculative scenarios that might preserve the habitability of white dwarf systems.
“There are a lot of things that have to go well,” Dr. Vanderberg said. It imagines a planet away from a red giant star that then moves inward after the star becomes a white dwarf and retains “enough water to be a nice place to live” when the star turns into a white dwarf.
Because white dwarfs are small and faint, such a planet would have to be in a very close orbit in order for liquid water to exist. However, if life appeared on a world like Jupiter’s moon Europa, which may have a subsurface ocean pushed by Jupiter’s tidal forces, it would likely live at a greater distance from the star.
“If humanity is somehow still around in five billion years, we probably have a better chance of surviving the sun’s red giant phase on Jupiter’s moon than on Earth,” Dr. Blackman said.
Although the existence of life around white dwarfs is still a matter of speculation, next-generation observatories, such as James Webb Space Telescope and the Nancy Grace Roman Space Telescope, can help provide specific answers to some of these evocative questions. As more healthy planets are observed orbiting white dwarfs, scientists will get a clearer picture of the life and afterlife of these mysterious systems.
Dr Blackman concluded, “This is the first detection of a planet orbiting a white dwarf using microlensing technology, but certainly not the last.”