Astronomers have discovered a giant exoplanet larger than Jupiter, but with an extremely low mass for this class of planets. But first of all, the object attracts interest in itself with its composition, similar in density to polystyrene, which made it even jokingly nicknamed the "fluffy planet".
The team that discovered KELT-11b (the planet's name), whose orbit is about 320 light years from Earth, says that this "in all respects unusual" world is the third most dense among the planets, which have been accurately determined their mass and radius … And this strange sphere from all sides is able to tell us more about how such unusual exoplanets generally appear and develop.
“She's very bloated. At just 1 / 5th the mass of Jupiter, it is nearly 40 percent larger, making it similar in density to a giant foam wrapped in a dense atmosphere,”says astronomer Joshua Pepper of Lehigh University of Pennsylvania.
In addition to its unusual density, the planet KELT-11b is also distinguished by the fact that it orbits the super-bright star KELT-11, which is in the process of transforming into a red giant. This may indicate that, as part of the thermonuclear process, the star began to burn hydrogen located outside its core. Scientists say that over the next 100 million years or so, the outer layers of KELT-11's atmosphere will expand and eventually the star will completely engulf KELT-11b. The absorption will not take long, since the planet is very close to the star. The exoplanet makes a complete revolution around its star in less than 5 Earth days.
But before its death, this "world of foam", thanks to the brightness of the star itself KELT-11, will be able to tell scientists about the composition of its atmosphere. Astronomers note that the star of this system is the brightest in the sky of the Southern Hemisphere among the known stars in which planets were discovered thanks to the method of transit search.
The transit method of searching for new exoplanets is one of the most popular among astronomers. Indeed, due to the passage of the planet between the star and our telescopes, the brightness of the observed star decreases. This indicates to scientists that an exoplanet may be in front of the star at this moment. However, in the case of the superbright star KELT-11, the decrease in its luminosity during the passage of the planet turned out to be so insignificant that astronomers could not immediately confirm the existence of the planet using KELT (Kilodegree Extremely Little Telescope) - two robotic telescopes operating in unison and located in Arizona and South Africa.
“It was quite difficult to open it. The initial observation of the star with KELT showed only a slight change in the light curve on the diagram,”Pepper told Phys.org last year, when astronomers first announced their discovery and awaited critical analysis of their research from the outside.
"Since the transition had such a small impact (the star's brightness dropped below 0.3 percent), it was difficult to get verified and fully validated data from those observations."
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However, new observations were able to confirm the existence of the exoplanet KELT-11b in this system, and now those parameters of the star's luminosity, which initially made it difficult for scientists to prove its presence, can be used to determine its atmosphere. Using these data, the researchers plan to find out why this "foam" world is so bloated in size. It is almost twice as large as one would expect given its mass and distance from the star.
“I think KELT-11b offers us a great chance to better understand the mechanisms that cause planets to swell so much,” Pepper says.
“In addition, since the star of the system is in its transitional state, on the basis of this data we plan to better understand the behavior of planetary systems, whose luminaries are at the end of their life cycle.”
NIKOLAY KHIZHNYAK