Astronomers have discovered that a scorching hot planet twice the size of Jupiter is orbiting in a death spiral that will drag it towards its parent star. Cosmically speaking, a collision is expected to occur relatively soon.
Researchers have been predicting for some time that this planet, called WASP-12b, would eventually dive towards its star, which is about 1,400 light-years away from Earth. However, these new findings shortened the remaining duration of WASP-12b.
Previous estimates had placed WASP-12b at around 10 million years before its inevitable extinction; But these researchers say the planet is more likely to collide with its star much earlier.
“According to our calculations, the planet will crash into the star [WASP-12] “In just 3 million years, it looks like the star is only 3 billion years old, which is incredibly short considering that it’s only 3 billion years old,” lead author of the study and University of Padova scientist Pietro Leonardi told Space.com.
So this may seem like an incredibly long time, but the fact that stars like the Sun live for about 10 billion years means that this is a very (very) short time on a cosmic scale.
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WASP-12b gets too close for comfort
Overall, the cursed planet WASP-12b orbits its yellow dwarf star so closely that it packs nearly an entire year into a single Earth day. This proximity classifies WASP-12b as an “extremely hot Jupiter” planet; The name is apt, considering that radiation from this star continuously surrounds the planet, giving it a surface temperature of about 4,000 degrees Fahrenheit (2,210 degrees Celsius).
But that’s not the only thing that makes this cursed world an extreme exoplanet unlike anything else in the solar system. The immense gravity that WASP-12b feels just 3.1 million miles from its star creates tidal forces so great that it now takes the shape of an egg.
This gravitational pull also strips material from WASP-12b, which forms a disk of material around the planet’s yellow star.
WASP-12b was the hottest planet ever seen when it was discovered in 2008; He delivered this record to another world called Kelt-9b in 2018. At the time, WASP-12b was also the closest planet to its star, but that record is now held by K2-137b, which is half a million miles away from its red dwarf star, which is about 322 light-years from Earth. .
Although WASP-12b is just one of many hot Jupiter exoplanets discovered since the mid-1990s, there is something that has always set this planet apart.
For example, WASP-12b has been shown to experience changes in the time it takes to orbit its star. Previous theories had attributed this to factors such as the planet’s position relative to Earth and the gradual change in orbit.
Leonardi and his colleagues investigated WASP-12b’s timing variation by looking at 28 observations of the planet as it passed, or “transited,” across the face of its parent star. This was done in collaboration with the Asiago Investigating Transit Timing Variations of Exoplanets (TASTE) project. These observations were collected by the Asiago Observatory in Italy over a 12-year period between 2010 and 2022.
This study not only revealed that WASP-12b’s fiery fate over about 3 million years was the result of a phenomenon called “tidal emission,” but also gave the team the first indication that the planet’s yellow star was very active. During periods of high activity, stars are covered with darker spots called sunspots and experience more extreme explosions of charged particles in the form of plasma. This means the team may have caught WASP-12b because it was undergoing a more violent explosion than usual from its star.
One of the surprises offered by the team’s analysis was some evidence that the dwarf star had reached the end of its main sequence life, a period when stars burn hydrogen in their cores.
For low- to intermediate-mass stars such as WASP-12, whose mass and width are approximately 1.5 times the mass and width of the Sun, the cessation of core hydrogen burning triggers a period of life called the “subgiant phase.” Meanwhile, hydrogen burning moves towards the outer layers of the star.
“According to tidal theory, the emission we see in the system is too strong to be explained by a main sequence star. This could be easily explained if the star had already left the main sequence and entered the subgiant phase.” Leonardi said. “To test this theory, we used high-resolution optical spectra from the High Accuracy Radial Velocity Planet Searcher (HARPS-N) in the Northern Hemisphere to derive the star’s stellar parameters and infer its evolution stage.
“However, according to our results, the star is still in the main sequence and has not yet entered the subgiant phase.”
This means the team still needs to elucidate how quickly tidal emission from a main-sequence dwarf star could cause it to dissipate.
In about 3 million years, when WASP-12b finally dives into its star, it will trigger changes that observers should be able to see from Earth, assuming intelligent life still remains on our planet.
“When the planet inevitably crashes into the star, the first sign will be an explosion of brightness that will make the star hundreds of times brighter than it is today,” Leonardi said. said. “This increase will not last long and will disappear quickly. But maybe future people will be there to see and study it.”
The team’s research is now available in the arXiv paper repository.
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Leonardi thinks the findings about WASP-12b’s doomed state could indicate that other extremely hot Jupiters may also be on a collision course with their stars.
“We still need to understand whether what we observed is a unique scenario or a common occurrence in the universe,” Leonardi said. said. “According to some population studies, when we observe older stars there are fewer hot Jupiters orbiting very close to their stars, so this could be an indication that many planets are experiencing tidal decay and colliding with their stars.”
Leonardi added that he is currently working with the team behind the European Space Agency (ESA) mission characterizing the ExOPlanet Satellite (CHEOPS) to determine the orbital decay rate of other hot Jupiters.
“This study is just the beginning of a long investigation into orbital perturbation,” he concluded.
The team’s research has been published in the arXiv paper repository.