For the first time, scientists have seen a planet hurtling toward its doom. Kepler-1658b, which is about 1,050 light-years from Earth, is spiraling toward an aging star and is on the brink of death, according to a study published in The Astrophysical Journal Letters. The dying alien planet was first discovered in 2019. Over the past decade, Kepler-1658b’s orbital period around its star has shortened by about 131 milliseconds (thousandths of a second) per year. At that speed, it will likely hit its host star in 2.5 million years, said lead author Shreyas Vissapragada of the Center for Astrophysics, Smithsonian Astrophysical Observatory and Harvard College Observatory.
Furthermore, Kepler-1658b was much warmer than expected, with a daytime temperature of 3,450 Kelvin (3,176.85 degrees Celsius), according to the study. Tidal interactions could warm the planet. “We hypothesized that some of the energy from the falling orbit could be lost inside the planet,” explained Vissapragada. In the future, when an exoplanet collides with its star, that star may witness a temporary increase in chemical elements that are more abundant in the alien world.
The researchers plan to look for other such developed systems. “If they are common, we can learn a lot about the last stages of the life of many planets,” the expert added. This “death by star” fate could also befall Earth. But scientists assume that it is billions of years away. Kepler-1658b is a gas giant exoplanet or ‘hot Jupiter’. These planets are more than twice the diameter of Earth and have enough gravity to hold hydrogen, the most abundant element in the universe, according to the US National Aeronautics and Space Administration (NASA).
According to NASA, the exoplanet takes 3.8 days to orbit and is only 0.0544 AU (roughly the distance from Earth to the Sun) from its star. Vissapragada and his colleagues observed Kepler-1658b with the now-retired Kepler space telescope, the Palomar Observatory in Southern California and the Transiting Exoplanet Survey Telescope (TESS). These instruments recorded transits the dimming of a star’s brightness when an exoplanet passes between it and the telescope for more than 13 years.
Vissapragada said his team looked at the orbital properties of planets orbiting evolving or aging stars. The star Kepler-1658 b is an evolved system as it begins to run out of fuel, hydrogen, and undergoes major structural changes, he added. When a star runs out of hydrogen, it collapses and expands to become a red giant — a dying star, according to NASA. The three telescopes showed that the time it took Kepler-1658b to complete one orbit had steadily decreased over the years.
The star is headed for its demise due to tidal forces. According to scientists, they are generated by gravitational interactions between two orbiting bodies, for example between the Earth and the Moon or Kepler-1658b and its star. Based on rotation rates or orbits, tidal interactions can cause bodies to push each other away (such as between the Earth and the Moon) or toward each other (like Kepler-1658b and its star), the researchers noted.
