Key Takeaways:

  1. WASP-12b, a scorching hot planet twice the size of Jupiter, is hurtling towards its parent star, with astronomers predicting a collision within 3 million years.
  2. WASP-12b’s close orbit around its yellow dwarf star results in surface temperatures of around 4,000 degrees Fahrenheit, shaping it into an egg-like form due to immense gravitational forces.
  3. Through meticulous analysis spanning over a decade, researchers observed variations in WASP-12b’s orbit, indicating heightened stellar activity and potential signs of the star’s evolutionary stage.
  4. Discoveries regarding WASP-12b’s fate prompt further investigation into the fate of other ultra-hot Jupiter exoplanets and their potential collision courses with stars.
  5. Collaboration with projects like the European Space Agency’s CHEOPS mission aims to delve deeper into understanding orbital decay rates, marking the beginning of an extensive exploration into celestial phenomena.

Astronomers have made a significant discovery concerning a distant planet, larger than Jupiter and extremely hot, indicating that it is on a trajectory towards its parent star, ultimately leading to its destruction. This catastrophic collision is anticipated to occur relatively soon, considering the vastness of cosmic time.

For some time now, researchers have been anticipating the inevitable fate of this planet, named WASP-12b, which orbits a star located approximately 1,400 light years away from Earth. However, recent findings have accelerated the timeline for WASP-12b’s demise.

An illustration shows the egg-shaped planet WASP-12b on a death spiral towar its yellow dwarf parent star (Image credit: Robert Lea)

Previously, estimates suggested that WASP-12b had roughly 10 million years left before its inevitable collision with its star. Nonetheless, new calculations indicate a much shorter timeframe for this cataclysmic event.

Lead researcher Pietro Leonardi, a scientist from the University of Padova, explained, “Based on our calculations, we expect the planet to collide with the star [WASP-12] in a mere 3 million years, a remarkably brief period considering the star’s estimated age of 3 billion years.”

While this may appear lengthy from a human perspective, in cosmic terms, where stars like the sun endure for approximately 10 billion years, it represents an exceedingly short duration.

WASP-12b’s perilous proximity

In general, WASP-12b, the ill-fated planet, orbits its yellow dwarf star in such close proximity that it completes nearly an entire orbit in a single Earth day. This closeness categorizes WASP-12b as an “ultra-hot Jupiter” planet, aptly named due to the relentless bombardment of radiation from its star, resulting in surface temperatures of around 4,000 degrees Fahrenheit (2,210 degrees Celsius).

However, what distinguishes this doomed world as an extreme exoplanet, unlike anything within our solar system, is not solely its searing temperatures. The immense gravitational pull experienced by WASP-12b, situated just 2.1 million miles from its star, generates powerful tidal forces, contorting the planet into an egg-like shape.

Additionally, this gravitational influence causes material to be stripped from WASP-12b, forming a disk of matter around the planet’s yellow star.

Discovered in 2008, WASP-12b once held the title of the hottest known planet, a record later surpassed by another world named Kelt-9b in 2018. WASP-12b also held the distinction of being the closest planet to its star, although this record has since been claimed by K2-137b, located just over half a million miles from its red dwarf star, positioned some 322 light-years away from Earth.

Despite the discovery of numerous hot Jupiter exoplanets since the mid-1990s, WASP-12b has always stood out.

The planet exhibited variations in its orbital period, a phenomenon previously attributed to factors such as its position relative to Earth and a gradual orbital shift.

Leonardi and his team investigated these variations by analyzing 28 observations of WASP-12b as it transited its parent star, conducted in collaboration with the Asiago Search for Transit Timing Variations of Exoplanets (TASTE) project. These observations, spanning 12 years from 2010 to 2022, were collected by the Asiago Observatory in Italy.

This study not only revealed that WASP-12b’s impending collision in approximately 3 million years is due to tidal dissipation but also suggested heightened activity in the planet’s yellow star. During periods of increased activity, stars exhibit more dark patches called sunspots and experience more intense outbursts of charged particles in the form of plasma. Consequently, the team may have observed WASP-12b experiencing an exceptionally violent onslaught from its star.

One surprising outcome of the team’s analysis was evidence indicating that the dwarf star may have already reached the end of its main-sequence lifespan, during which stars burn hydrogen in their cores.

“For a star like WASP-12, which is of low to intermediate mass and approximately 1.5 times the mass and width of the sun, the cessation of core-hydrogen burning signals the onset of the ‘sub-giant phase,’ characterized by hydrogen burning in the star’s outer layers,” explained Leonardi.

“According to the tidal dissipation theory, the level of dissipation observed in the system exceeds what would be expected from a main-sequence star. If the star had already transitioned to the sub-giant phase, this discrepancy could be readily explained,” Leonardi added. “To test this hypothesis, we utilized high-resolution optical spectra from the High Accuracy Radial Velocity Planet Searcher in the Northern Hemisphere (HARPS-N) to determine the stellar parameters and infer its evolutionary stage.”

“However, our results indicate that the star remains in the main sequence and has not yet entered the sub-giant phase.”

Consequently, the team must further investigate how rapid tidal dissipation can be induced by a main-sequence dwarf star.

Approximately 3 million years from now, when WASP-12b finally collides with its star, this event will trigger observable changes from Earth, assuming intelligent life still exists on our planet.

“As the planet inevitably collides with the star, the initial sign will be a surge in luminosity, causing the star to become hundreds of times brighter than it is presently,” noted Leonardi. “While this increase will be brief and transient, future generations may witness and study this phenomenon.”

Leonardi believes that the revelations concerning WASP-12b’s doomed fate could imply that other ultra-hot Jupiters may also be on collision courses with their stars.

“We must ascertain whether what we’ve observed is an isolated occurrence or a common phenomenon in the universe,” remarked Leonardi. “Population studies suggest that the number of hot Jupiters in close proximity to their stars diminishes as stars age, potentially indicating that many planets undergo tidal decay and collide with their stars.”

Leonardi disclosed that he is collaborating with the team behind the European Space Agency (ESA) mission CHaracterising ExOPlanet Satellite (CHEOPS) to ascertain the rate of orbital decay for other hot Jupiters.

“This study marks the initial phase of an extensive investigation into orbital decay,” he concluded.

The team’s research is accessible on the arXiv paper repository.

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