How will our solar system end? A distant planet offers hints

A darkened planet circling the feeble remnant of a burned-out star about 6,000 light-years from Earth shows what our own solar system will look like at the end of its existence, according to astronomers.

The distant survivor, described in a study published last week in the journal Nature, seems to be a gas giant similar to Jupiter and provides a snapshot of a planetary system around a dying star, according to the study’s authors.

The star is now a “white dwarf” — a glimmering stellar remnant left over from the “red giant” phase of its demise, when it expanded tens of thousands of times after using up the hydrogen fuel for its nuclear fusion reactions and then collapsed a few hundred million years later.

Any planets closer to the star are likely to have been destroyed — and the same fate is likely to befall our own world when the sun burns up all of its hydrogen after another 5 billion years or so.

“When the sun balloons outwards in what’s known as its red giant phase, it will likely obliterate Mercury and Venus, and possibly Earth,” said Joshua Blackman, an astronomer at the University of Tasmania in Australia and the lead author of the new study.

The sun will have grown too hot for anything on Earth to survive well before then, and its red giant phase will cause lakes of lava, broken continents and devastating blasts of intense ionizing radiation — if it doesn’t fragment our planet entirely, he said in an email.

But it’s not all bad news: Mars and the outer gas giants — Jupiter, Saturn, Uranus and Neptune — are expected to survive the sun’s burning-out. And now the detection of the distant planet orbiting a white dwarf strengthens that idea.

“Our discovery is evidence that the standard picture of how planetary systems evolve as their host star dies is likely to be correct,” Blackman said.

The newly found white dwarf was detected toward the center of our galaxy by a gravitational effect called “microlensing” as it passed in front of an even farther star.

The gravity of the white dwarf caused the distant star to appear to grow brighter for a few years — a brief flash in astronomical time — as its mass focused light through gravitational lensing, said Jean-Phillippe Beaulieu of the Institut d’Astrophysique de Paris, who led the research and is a co-author of the new study. A second flash of light revealed the orbiting planet.

In fact, it’s only due to microlensing that the white dwarf system has been detected at all. Although the team tried to observe it with the giant telescopes at the Keck Observatory in Hawaii, it proved too dim to see.

They hope soon to get better results with the James Webb Space Telescope, which is due to launch in December and which will be able to observe the darkened system directly, Beaulieu said. 

Blackman said the gas giant is about 1.4 times the mass of Jupiter and orbiting 260 million miles to 600 million miles from the white dwarf. 

Although it’s likely to have formed…