Tuesday, December 20, 2022

An exoplanet six times the size of Jupiter is crashing into its star

For the first time, astronomers have observed a planet orbiting ever closer to its star. This means that, one day, this world will be so close to its luminous star that it will be swallowed by it — a fate also reserved for Earth , which will be swallowed by the Sun in the distant future.

 The discovery of the exoplanet Kepler-1658b was announced in 2019 and it orbits an F-type star (class of stars between 1 and 1.4 solar masses). Its mass is just under 6 times that of Jupiter and it takes just 3.8 days to complete an orbit around its star.

In addition, Kepler-1658 is an evolved star, that is, it has already taken the initial steps to become a red giant — the final stage of small stars like this one, which also includes our Sun.

Already the exoplanet, belonging to the class of hot Jupiters (because it is a gaseous giant very close to its star), is only 0.0544 AU away from its bright star (1 AU is the average distance between the Earth and the Sun) , but that distance gets smaller and smaller.

Scientists have previously detected evidence of other worlds shortening their orbital periods, falling into their stars, but this is the first time they've found this happening in an evolved star.

However, the star did not swallow the planet overnight. In fact, its orbital period is shrinking at a minuscule rate of 131 milliseconds per year, so there's still plenty of life left for this gaseous world to enjoy.

To detect such a small decline took years of observation with several powerful telescopes. The first of these was Kepler, the space observatory that discovered this star system (hence the name Kepler-1658). Then the Hale Telescope at the Palomar Observatory in Southern California and the Transitioning Exoplanet Survey Telescope (TESS) completed the study.

The cause of the spiral orbit is the gravitational interactions between the planet and the star. The consequences of these interactions, known as tides, are similar to the Moon's effects on planet Earth's seas. In the case of Kepler-1658b, tidal movements steal its orbital energy, leading to an ever-inward orbit.

 This study will be very useful for understanding stellar systems in the final stage of their star evolution. Astronomers calculate that the same will happen to the Sun and the three innermost planets - Mercury, Venus and Earth - in 4.5 billion years. But to understand how this works, and even if it will happen or not, you need to analyze worlds like Kepler-1658.

The paper describing the findings is lead author by exoplanet scientist Shreyas Vissapragada of the Harvard and Smithsonian Center for Astrophysics and was published in the Astrophysical Journal Letters .

Source: Astrophysical Journal Letters , Center for Astrophysics | Harvard and Smithsonian

Illustration of the exoplanet Kepler-1658b (Image: Reproduction/Kepler-1658b)

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