The James Webb Space Telescope (JWST) has already proven adept at peering into the past by imaging objects at great distances; But a new breakthrough may have seen the powerful instrument act almost like a scientific crystal ball, peering into Earth’s distant future. Solar system.
JWST made its prediction possible by enabling the rare direct orientation of two extrasolar planets, or “exoplanets,” orbiting two different dead stars, or “white dwarfs.”
Not only do the planets strongly resemble the gas giants Jupiter and Saturn in the solar system, but white dwarfs also serve as analogues of the fate of the Sun. When the Sun collapses into a white dwarf, the change will likely destroy the inner planets of the solar system, all the way down to Jupiter.
“Very few planets have been discovered around white dwarf stars. What is extraordinary about these two candidate planets is that they are more similar to planets in our outer solar system in terms of temperature, age, mass and orbital separation than any planets found before.” Mullaly, lead author of the study, which has not yet been peer-reviewed, and an astronomer at the Space Telescope Science Institute, told Space.com. “This offers our first chance to see what a planetary system looks like after its star dies.”
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A snapshot of our future
The planet candidates were directly observed by JWST’s Mid-Infrared Instrument (MIRI) as they orbited white dwarfs WD 1202-232 and WD 2105-82. An exoplanet candidate is located at a distance from its white dwarf host equal to approximately 11.5 times the distance between the Earth and the Sun. The other candidate is located about 34.5 times the distance from its dead star parent as the distance between our planet and our star.
The masses of the planets are currently uncertain; Mullaly and his colleagues estimate that these are between 1 and 7 times the size of Jupiter, the largest planet in the solar system.
When the Sun consumes the fuel necessary for the nuclear fusion processes occurring in its core in about 5 billion years, it will swell into a red giant. However, nuclear fusion will continue in the outer layers. This will see our star’s outer layers extend all the way to Mars, swallowing Mercury, Venus, Earth, and possibly the Red Planet itself. Eventually, these outer layers will cool, leaving a smoldering stellar core (now a white dwarf) surrounded by a planetary nebula of exhausted stellar material.
But these exoplanet detections provide clues about what might happen to planets beyond Mars and the gas giants Jupiter and Saturn when the sun dies.
“Our Sun is expected to turn into a white dwarf star within 5 billion years,” said Mullaly. “After a star dies, we expect planets to drift outward into wider orbits. So if you turn back time on these candidate planets, you’d expect them to have orbital separations similar to Jupiter and Saturn.”
“If we can confirm these planets, they will provide direct evidence that planets like Jupiter and Saturn can survive the death of their host stars.”
What’s more, the white dwarfs at the center of this discovery are contaminated with elements heavier than hydrogen and helium, which astronomers call “metals.” This may provide clues as to what will happen to objects in the asteroid belt between Mars and Jupiter after the Sun dies.
“We suspect giant planets drive comets and asteroids onto the surfaces of stars, causing metal pollution,” Mullaly said. “The presence of these planets strengthens the link between metal pollution and planets. Since 25 to 50 percent of white dwarfs show such pollution, it means that giant planets are common around white dwarf stars.”
Therefore, any asteroid that managed to survive the death of the sun could attack the corpses of Jupiter and Saturn.
This dual discovery is impressive beyond its predictions for the future of our planetary system; It also represents a rare scientific achievement.
A rare direct exoplanet detection
Since the discovery of the first exoplanets in the mid-1990s, astronomers have discovered nearly 5,000 worlds orbiting stars outside the solar system. As of April 2020, only 50 of these exoplanets had been discovered by direct imaging, according to the Planetary Society.
This is because any light from a planet at such great distances is usually drowned out by the intense light from that planet’s host star; This makes direct detection of an exoplanet akin to seeing a firefly sitting on the glowing lamp of a lighthouse.
As a result, exoplanets are often seen through their influence on the light of their star, either by causing a drop in light output as they pass across the face of the star, or by “transitioning” across the face of the star, or through a “wobbling” motion created by the star’s surface. The planet is gravitationally attracted to the star.
“We directly imaged these two exoplanets, which means we took pictures of them and saw the light produced by the planet itself,” Mullaly said. “Most discovered exoplanets are found using the transit method or by measuring the motion of the star. These indirect methods tend to favor planets that are much closer to the star. Direct imaging is better at finding planets farther from the star, with wider orbital separations.”
He explained that JWST detects these planets directly, opening up the opportunity to further study these worlds; Scientists can now begin to investigate things like the composition of planets’ atmospheres and directly measure their masses and temperatures.
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Mullaly added that everything he and his team discovered about these exoplanets was unexpected, and that these oddities could change the way astronomers think about exoplanets like these in general.
Alternatively, the peculiar properties of targeted worlds may offer tantalizing clues toward long-sought economons.
“If these are planets, it is surprising that they are not as red in the mid-infrared as we would expect. The amount of light collected by JWST at 5 and 7 microns is brighter than we expected for both exoplanet candidates, given their age and how bright they are at 15 microns,” Mullaly concluded. “This could challenge our understanding of the physics and chemistry of exoplanet atmospheres.
“Or perhaps this could mean there is another light source, such as a warmed moon orbiting the planet.”
The team’s research is available as a preprint on the arXiv research repository.