“According to our calculations, the planet will crash into the star in just 3 million years.”

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

Key takeaways

  • The hot planet WASP-12b, twice the size of Jupiter, will collide with its parent star in 3 million years.
  • The planet’s close orbit causes extreme tidal forces, shaping it into an egg-like form and pulling material into a debris disk.
  • New calculations show WASP-12b’s collision is much sooner than the previously estimated 10 million years.
  • Observations indicate the star is highly active, possibly influencing the planet’s rapid orbital decay.
  • The crash will cause a bright outburst observable from Earth, offering valuable data for future studies on hot Jupiters.

Astronomers found that a faraway, burning hot planet twice the size of Jupiter is on a death spiral that will collide with its parent star. A crash is likely to occur rather soon, cosmically speaking.

Researchers have long projected that this planet, known as WASP-12b, will ultimately collide with its star, which is around 1,400 light years away from Earth. However, these new results have reduced the time WASP-12b has remaining.

Previous estimations put WASP-12b’s certain doom at roughly 10 million years, but these astronomers believe the planet will collide with its star far sooner.

“According to our calculations, the planet will crash into the star [WASP-12] in just 3 million years, an incredibly short amount of time considering the star only appears to be 3 billion years old,” Pietro Leonardi, research lead author and University of Padova scientist, told Space.com.

In other words, while this may appear to be an extremely lengthy time, the fact that stars like the sun survive for about 10 billion years makes it a very (very) brief period on cosmic scales.

WASP-12b gets too close for comfort

In general, the doomed planet WASP-12b circles its yellow dwarf star so closely that one Earth day is nearly equivalent to a full year. This closeness characterizes WASP-12b as a “ultra-hot Jupiter” planet, a suitable moniker given that radiation from this star continuously belts the planet, giving it a surface temperature of roughly 4,000 degrees Fahrenheit (2,210 degrees Celsius).

That isn’t the only characteristic that distinguishes this doomed world from other exoplanets in our solar system. WASP-12b’s tremendous gravity, although being only 2.1 million miles from its star, causes so powerful tidal forces that it has taken on an egg-like form.

This gravitational force also removes material from WASP-12b, forming a disk of debris around the planet’s yellow star.

When it was found in 2008, WASP-12b was the hottest planet ever observed, a record it lost in 2018 to another world known as Kelt-9b. At the time, WASP-12b was also the nearest planet to its star, but that record is currently held by K2-137b, which is just over half a million miles from its red dwarf star, which is 322 light-years distant from Earth.

WASP-12b is one of numerous hot Jupiter exoplanets found since the mid-1990s, yet something has always distinguished this planet.

For example, WASP-12b’s orbital time appeared to vary. Previous ideas ascribed this to variables such as the planet’s location relative to Earth and a gradual shift in orbit.

Leonardi and colleagues studied the temporal variation of WASP-12b by analyzing 28 observations of the planet as it crossed, or “transited,” the face of its parent star. This work was done in conjunction with the Asiago Search for Transit Timing Variations of Exoplanets (TASTE) project. The Asiago Observatory in Italy gathered these observations during a 12-year period.

Not only did this analysis indicate that WASP-12b’s fiery fate in roughly 3 million years is the consequence of a phenomena known as “tidal dissipation,” but it also provided the scientists with the first clues that the planet’s yellow star is extremely active. During periods of high activity, stars are covered in more black patches known as sunspots, and they undergo more intense outbursts of charged particles in the form of plasma. This suggests that the scientists may have caught WASP-12b during an even more powerful explosion by its star than typical.

The team’s investigation revealed several unexpected findings, including evidence that the dwarf star had already reached the end of its main-sequence existence, a phase during which stars burn hydrogen in their cores.

For low to intermediate-mass stars, such as WASP-12, which has a mass and width around 1.5 times that of the sun, the end of core-hydrogen burning initiates a period of life known as the “sub-giant phase,” during which hydrogen burning shifts to the star’s outer layers.

“According to tidal theory, the system’s dissipation is too strong to be explained by a main sequence star.” “If the star had already left the main sequence and entered its sub-giant phase, this could be easily explained,” Leonardi added. “To verify this notion, we employed high-resolution optical spectra from the High Accuracy Radial Velocity Planet Searcher in the Northern Hemisphere (HARPS-N) to determine the star’s stellar characteristics and evolutionary stage.

“However, according to our results, the star is still in the main sequence and has not yet entered its sub-giant stage.”

This implies that the team has yet to explain how a main sequence dwarf star might produce fast tidal dissipation.

When WASP-12b ultimately plunges into its star in roughly 3 million years, it will cause changes that watchers on Earth should be able to notice – provided sentient life still exists.

“When the planet inevitably crashes into the star, the first indication will be an outburst of luminosity, which will see the star become hundreds of times brighter than it is today,” according to Leonardi. “This spike will not stay long and will rapidly subside. But perhaps future people will be able to observe and analyze it.

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

Leonardi believes that the data about WASP-12b’s hopeless fate may imply that additional ultra-hot Jupiters are also on crash trajectories with their stars.

“We still have to figure out if what we observed is a unique scenario or a common event in the universe,” Leonardi told the crowd. “According to some population studies, the number of hot Jupiters orbiting very close to their stars decreases when we observe older stars, so this could be an indication that many planets experience tidal decay and crash into their stars.”

Leonardi also stated that he is now collaborating with the team behind the European Space Agency’s (ESA) project Characterising ExoPlanet Satellite (CHEOPS) to estimate the orbital decay rate of additional hot Jupiters.

“This study is just the beginning of a long search for orbital decay,” the scientist said.

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

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