For the first time, astronomers saw a planet being engulfed by its host star in May 2020. They thought the planet would perish as the star grew larger at the end of its life and became a red giant, based on the information available at the time.
As a kind of postmortem, new findings from the James Webb Space Telescope show that the planet’s demise occurred in a different way than first believed. According to researchers, the planet appears to have come to the star rather than the star coming to it, with disastrous results. This is a death plunge that occurs when the orbit of this alien globe erodes over time.
The end was quite dramatic, as evidenced by the aftermath documented by Webb. The orbiting telescope, which was launched in 2021 and became operational in 2022, observed hot gas likely forming a ring around the star following the event and an expanding cloud of cooler dust enveloping the scene.
“We do know that there is a good amount of material from the star that gets expelled as the planet goes through its death plunge. The after-the-fact evidence is this dusty leftover material that was ejected from the host star,” said astronomer Ryan Lau of the U.S. National Science Foundation’s NOIRLab, lead author of the study published in the Astrophysical Journal.
The star is located in our Milky Way galaxy about 12,000 light-years from Earth in the direction of the constellation Aquila. A light year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km). The star is slightly redder and less luminous than our sun and about 70% of its mass.
The planet is believed to have been from a class called “hot Jupiters” – gas giants at high temperatures owing to a tight orbit around their host star.
“We believe it probably had to be a giant planet, at least a few times the mass of Jupiter, to cause as dramatic of a disturbance to the star as what we are seeing,” said study co-author Morgan MacLeod, a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics.
Jupiter is our solar system’s largest planet.
The researchers believe that the planet’s orbit had gradually deteriorated due to its gravitational interaction with the star, and hypothesized about what happened next.
“Then it starts grazing through the atmosphere of the star. At that point, the headwind of smashing through the stellar atmosphere takes over and the planet falls increasingly rapidly into the star,” MacLeod said.
“The planet both falls inward and gets stripped of its gaseous outer layers as it plows deeper into the star. Along the way, that smashing heats up and expels stellar gas, which gives rise to the light we see and the gas, dust and molecules that now surround the star,” MacLeod said.
But they cannot be certain of the actual fatal events.
“In this case, we saw how the plunge of the planet affected the star, but we don’t truly know for certain what happened to the planet. In astronomy there are lots of things way too big and way too ‘out there’ to do experiments on. We can’t go to the lab and smash a star and planet together – that would be diabolical. But we can try to reconstruct what happened in computer models,” MacLeod said.
None of our solar system’s planets are close enough to the sun for their orbits to decay, as happened here. That does not mean that the sun will not eventually swallow any of them.
About five billion years from now, the sun is expected to expand outward in its red giant phase and could well engulf the innermost planets Mercury and Venus, and maybe even Earth. During this phase, a star blows off its outer layers, leaving just a core behind – a stellar remnant called a white dwarf.
Webb’s new observations are giving clues about the planetary endgame.
According to our studies, it is possible that planets would eventually spiral in towards their host system rather than the star becoming a red giant and consuming them. However, it appears that our solar system is rather stable, so our major concern is that the sun may turn into a red giant and engulf us,” Lau stated.