Discovery of a planet spiraling into its star could foreshadow Earth’s ultimate fate : ScienceAlert

For the first time, astronomers have identified a planet heading for a catastrophic collision with its aging sun, potentially offering a glimpse of Earth’s end one day.

In a new study published Monday, a team of mostly US-based researchers said they hope the doomed exoplanet Kepler-1658b can help shed light on how worlds die when their stars grow older.

Kepler-1658b, located 2,600 light-years from Earth, is known as the “hot Jupiter” planet.

Although the planet is similar in size to Jupiter, it orbits its parent star one-eighth the distance between our Sun and Mercury, making it far hotter than the gas giant in our own solar system.

Kepler-1658b’s orbit around its parent star lasts less than three days — and it’s getting shorter by about 131 milliseconds a year, according to the study published in The Letters of the Astrophysical Journal.

“If it continues to spiral toward its star at the observed rate, the planet will collide with its star in less than three million years,” said Shreyas Vissapragada, a postdoctoral researcher at the Harvard-Smithsonian Center for Astrophysics and lead author of the study.

“This is the first time we’ve seen direct evidence of a planet spiraling toward its evolved star,” he told AFP.

An evolved star has entered the “subgiant” phase of the stellar life cycle when it begins to expand and brighten.

Kepler-1658b’s orbit is shortened by the tides, much like the way Earth’s oceans rise and fall each day.

This gravitational push-and-pull can work in both directions – for example, the moon spirals away from the earth very slowly.

Earth’s “Ultimate Adios”?

So, could Earth be heading for a similar fate?

“Death-by-Star is a fate thought to await many worlds and could be Earth’s ultimate adios billions of years from now as our sun ages,” the Center for Astrophysics said in a statement.

Vissapragada said that “in about five billion years, the sun will evolve into a red giant star.”

While the tidal-driven processes observed on Kepler-1658b “drive the decay of Earth’s orbit toward the Sun,” that effect could be offset by the Sun’s mass loss, he said.

“Earth’s ultimate fate is somewhat unclear,” he added.

Kepler-1658b was the first exoplanet ever observed by the Kepler space telescope, launched in 2009. However, it took nearly a decade of work to confirm the planet’s existence in 2019, the Center for Astrophysics said.

For 13 years, astronomers have observed the slow but steady change in the planet’s orbit as it crosses the face of its host star.

A “big surprise” was that the planet itself is quite bright, Vissapragada said.

This was previously thought to be because it’s a particularly reflective planet, he said.

But now researchers think the planet itself is much hotter than expected, possibly due to the same forces propelling it toward its star.

© Agence France-Presse

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