This Plucky Planet Outlasted Its Star’s Death

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Artist's impression of a giant gas planet that survived its star's death.

W. M. Keck Observatory/Adam Makarenko

Just in time for Hallowe’en, astronomers spotted a ghost of our solar system’s barren future.

Astronomers spotted a planetary system some 6,500 light-years from us, orbiting a dead or “white dwarf” star. It’s a glimpse of what our own neighborhood may look like after the sun dies in about five billion years.

So far the team found a Jupiter-like planet, coincidentally moving in an orbit similar to Jupiter’s distance from the sun in our own solar system. They found this world using the W. M. Keck Observatory on Maunakea in Hawaiʻi, a veteran exoplanet observatory. So we have firm evidence now that distant planets may be able to survive the death of a star, although inner planets like ours may not be so lucky.

“This evidence confirms that planets orbiting at a large enough distance can continue to exist after their star’s death,” says Joshua Blackman, an astronomy postdoctoral researcher at the University of Tasmania in Australia and lead author of the study, in a Keck statement. “Given that this system is an analog to our own solar system, it suggests that Jupiter and Saturn might survive the sun’s red giant phase, when it runs out of nuclear fuel and self-destructs.”

As for Earth? In the long term, we may want to move planets. As the sun approaches the end of its life, it is expected to balloon into a red giant star, which would either roast our planet or eat it alive depending on how big it grows. Eventually the “balloon” will deflate as the sun sloughs off its gas, leaving behind a cooling core known as a white dwarf star.

“Earth’s future may not be so rosy because it is much closer to the sun,” said co-author David Bennett, a senior research scientist at the University of Maryland and NASA’s Goddard Space Flight Center, in the same statement. “If humankind wanted to move to a moon of Jupiter or Saturn before the sun fried the Earth during its red supergiant phase, we’d still remain in orbit around the sun, although we would not be able to rely on heat from the Sun as a white dwarf for very long.”

The research team plans to continue their search for white dwarf “ghost” systems to see how many other planets survived the turbulence. NASA has a new mission that will likely give an assist, too. The forthcoming Nancy Grace Roman Telescope (formerly known as WFIRST) is expected to launch in the mid-2020s.

“Roman will be capable of doing a much more complete survey of planets orbiting white dwarfs located all the way into the galactic bulge at the center of the Milky Way,” Keck stated. “This will allow astronomers to determine whether it is common for Jupiter-like planets to escape their star’s final days, or if a significant fraction of them are destroyed by the time their host stars become red giants.”

A study based on the research appeared in Nature.

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