Doomed Exoplanet Spiralling into Star May Give Us a Glimpse of Earth’s End
Astronomers have identified a planet that is spiraling towards a cataclysmic collision with its aging sun for the first time, potentially providing a glimpse into how Earth might end one day.
A team of mostly US-based researchers said in a new study published on Monday that they hope the doomed exoplanet Kepler-1658b can shed light on how worlds die as their stars age.
Kepler-1658b is a “hot Jupiter” planet located 2,600 light-years from Earth.
While the planet is similar in size to Jupiter, it orbits its host star an eighth of the distance between our Sun and Mercury, making it far hotter than our own Solar System’s gas giant.
According to the study published in The Astrophysical Journal Letters, Kepler-1658b’s orbit around its host star takes less than three days and is getting shorter by around 131 milliseconds per year.
“If it continues spiraling towards its star at the observed rate, the planet will collide with its star in less than three million years,” said Shreyas Vissapragada, the study’s lead author and a postdoc at the Harvard-Smithsonian Center for Astrophysics.
“We’ve never seen direct evidence of a planet spiraling towards its evolved star before,” he told AFP.
An evolved star has reached the “subgiant” stage of the stellar life cycle, when it begins to expand and brighten.
The tides are shortening Kepler-1658b’s orbit, which is similar to how the Earth’s oceans rise and fall every day.
This gravitational push-pull can work in both directions; for example, the Moon is slowly spiraling away from Earth.
Could Earth face a similar fate?
“Death by star is a fate that many worlds are thought to face, and it could be the Earth’s ultimate goodbye billions of years from now as our Sun grows older,” the Center for Astrophysics said in a statement.
“The Sun will evolve into a red giant star in five billion years or so,” said Vissapragada.
While the tidally-driven processes observed on Kepler-1658b “will drive the decay of the Earth’s orbit towards the Sun,” he believes that effect could be counterbalanced by the Sun losing mass.
“The Earth’s ultimate fate is somewhat uncertain,” he added.
Kepler-1658b was the first exoplanet discovered using the Kepler space telescope, which was launched in 2009. However, it took nearly a decade of work before the existence of the planet was confirmed in 2019, according to the Center for Astrophysics.
Astronomers were able to observe the slow but steady change in the planet’s orbit as it crossed the face of its host star over a period of 13 years.
According to Vissapragada, one “big surprise” was that the planet itself is quite bright.
Previously, it was thought that this was due to the planet’s high reflectivity, he explained.
However, the researchers now believe that the planet is far hotter than previously thought, possibly due to the same forces that are pushing it towards its star.
