The novel observation helps us understand more about Earth’s own final arc. Many astronomers believe that Earth will suffer a similar fate billions of years down the line, when our own evolving Sun consumes fuel, balloons and eats its nearest planets. Humans won’t be around for this event, however, as our growing sun will roast Earth first It is not suitable for life.
“It’s somewhat poetic that everything we see around us, all the stuff we’ve built around us, all of it burns up in a flash when the Sun decides to evolve and swell in 5 billion years,” Kishale D, the study’s lead author and a graduate student at MIT, told a press conference.
Earth’s sober future aside, scientists were impressed by the amazing observation.
“Oh! That was my first reaction,” Amanda Karakas, an astrophysicist at Monash University in Australia who was not involved in the study, said in an email. “It certainly provides clues as to what will happen to our solar system and the planets on Earth many years from now.”
The team stumbled upon this discovery by accident. Dee was initially looking for signs of the explosion of binary star systems, in which two stars orbit each other and periodically brighten as one pulls mass from the other. He began looking at data from the Swicky Transient Facility at Caltech’s Palomar Observatory, which takes images of the sky every night and allows researchers to spot stars that change rapidly in brightness. D observed that a star 12,000 light-years away near the Eagle Cluster in our galaxy grew 100 times brighter in a week.
To further pinpoint the source, he used observations from the Keck Observatory in Hawaii to study the star’s chemical composition, but the results were puzzling. The binary star system he was initially looking for is usually surrounded by lots of hot gas, but he found signs of molecules that exist only at cold temperatures.
Cooler objects tend to shine more brightly at infrared wavelengths, so the team obtained infrared observations of the star a year after the initial observation.
The information stunned the team. Although the star does not appear bright in the light spectrum visible to our naked eyes, the star shines very brightly in the infrared bands. The star must have ejected gas into space, which condensed into dust cool enough to be visible in the infrared—suggesting that the star may have merged with something else and brightened as a result.
Using additional infrared data from NASA’s NeoVice space telescope, the team estimated the total amount of energy released by the star to be very small — about 1,000 times smaller than the stars combined. That means it must be relatively small with whatever star it is conjunct.
“You ask, ‘What’s a thousand times less massive than a star?'” Dee said. “What you have is a star that engulfed the planet.”
Co-author Mansi Ghazliwal says that falling planets are very common, but they are dim and “wimpy”, which makes them difficult to detect. The infrared data illuminated these processes, hidden against much brighter starbursts.
“It’s when a planet joins a star, it’s intrinsically very faint, so it’s hard to find them,” Kasliwal said. “When something is hard to find, all we need is a very powerful camera.”
Other study authors modeled the observations and reconstructed what might be happening. The team said the bright flash they saw at the beginning was the final moments of the planet being eaten by the star. Then when a Jupiter-sized planet fell into the star’s core, the star’s outer layers exploded and settled into cold dust over the next year. The star has more or less returned to its position before the planet fell, except that it is surrounded by the remaining dust. It is now continuing its natural evolution.
Seeing this Jupiter-sized planet being swallowed up by a Sun-like star, it’s only natural to wonder about our own planet’s future. But researchers say Earth’s destruction won’t be as dramatic because of our size.
“I think the difference is very fluid around whether the planet is a gas giant planet, and if it’s close enough in orbit that it’s a big perturbation to a star,” said co-author and graduate student Morgan MacLeod at Harvard. At the news conference. “If it was a rocky planet, it would be too small to cause a dramatic episode.”
The Sun is still a few billion years away from being expected to grow large enough to encompass the Earth. Our host star will first swallow Mercury and Venus before reaching Earth, MacLeod said. But he estimates that it will take tens of thousands of years for the aging Sun to expand from Mercury to Earth. The Sun’s radius does not expand to reach the larger planets in our solar system.
Enrico Ramírez-Ruiz, an astrophysicist who was not involved in the study, called the study’s findings a “fundamental conclusion” but thinks it is not relevant to understanding Earth’s fate and whether it will eventually be engulfed by our sun.
“Whether or not Earth can sink based on its current orbital position remains an open question,” Ramirez-Ruiz, a professor at the University of California Santa Cruz, said in an email.
De said that the planet orbits our galaxy every few years, and since they know what to look for in terms of chemical composition, temperature and infrared signatures, detecting it should be easy.
“The hope is that we can use this new suite of instruments to try to find every planet in our galaxy in real time,” Di said. “This is possible now because of this discovery and the availability of tools.”
