Astronomers discover a planet whose mass is almost 13 times greater than that of Jupiter

Over the last three decades, nearly 4,000 planetary-like objects have been discovered in orbit around isolated stars located outside the solar system (exoplanets). As of 2011, it was possible to use NASA's Kepler Space Telescope to observe the first exoplanets orbiting young binary systems of two living stars with hydrogen burning.

Brazilian astronomers have now found the first evidence of an exoplanet in orbit around an older or more evolved binary in which one of the two stars is dead. The results have just been published in the Astronomical Journal, published by the American Astronomical Society (AAS).

Leonardo Andrade de Almeida, first author of the article, said: "We managed to get some pretty solid evidence of the existence of a giant exoplanet of a mass almost 13 times higher. to that of Jupiter in an evolved binary system.This is the first confirmation of an exoplanet in a system of this type ".

Almeida is currently a postdoctoral fellow at the Federal University of Rio Grande do Norte (UFRN), after conducting postdoctoral research at the Institute of Astronomy, Geophysics and Atmospheric Sciences. from the University of São Paulo (IAG-USP), where he was supervised by Professor Augusto. Damineli, a co-author of the study.

Variations in eclipse synchronization (the time taken by each of the two stars to eclipse the other) and the orbital period have led researchers to discover the exoplanet in the evolved bin called KIC 10544976, located in the constellation of the Swan in the northern celestial hemisphere.

"The variations of the orbital period of a binary are due to the gravitational pull between the three objects, which revolve around a common center of mass," Almeida said.

The variations of the orbital period are not enough to prove the existence of a planet in the case of binaries, because the magnetic activity of the binary stars fluctuates periodically, just as the magnetic field of the sun changes from polarity every 11 years, with turbulence and number and sunspots culminating then declining.

"Changes in the magnetic activity of the sun eventually cause a change in its magnetic field, as do all the isolated stars, and in binary these variations also cause a change in the orbital period because of we call the mechanism of Applegate, "said Almeida.

To disprove the hypothesis that the variations of the orbital period of KIC 10544976 are due only to magnetic activity, the researchers analyzed the effect of the variation of the eclipse time and the of the magnetic activity cycle of the living star of the binary.

KIC 10544976 includes a white dwarf, a dead star, low mass, high surface temperature and a red dwarf, a living star (magnetically active) of small mass compared to that of the sun and poor light due to low energy exit. Both stars were monitored by ground telescopes between 2005 and 2017 and by Kepler between 2009 and 2013, producing minute-by-minute data.

"The system is unique," said Almeida. "No similar system has enough data to allow us to calculate the variation of the orbital period and the activity of the magnetic cycle of the living star."

Using Kepler data, they were able to estimate the magnetic cycle of the living star (red dwarf) based on the rate and energy of light eruptions (large eruptions of electromagnetic radiation) and the variability due to staining. (regions where the surface temperature is colder and therefore dark) caused by different concentrations of magnetic field flux).

The data analysis showed that the magnetic activity cycle of the red dwarf lasted 600 days, which is consistent with the magnetic cycles estimated for insulated low-mass stars. The orbital period of the binary was estimated at 17 years. "This completely refutes the hypothesis that the variation of the orbital period is due to magnetic activity.The most plausible explanation is the presence of a giant planet orbiting the binary , of a mass about 13 times greater than that of Jupiter, "Almeida said.

Training hypotheses

How the planet orbiting the binary has been formed is unknown. One assumption is that it developed together with the two stars billions of years ago. If that's the case, it's a first generation planet. Another hypothesis is that it was formed from the gas ejected at the death of the white dwarf, making it a second-generation planet.

Confirmation of its status as a first- or second-generation planet and direct detection of its orbit around the binary could be achieved with the aid of the new generation of ground-based telescopes with primary mirrors exceeding 20 meters, including the Giant Magellan telescope (GMT) installed in the Atacama desert in Chile. The GMT should see its first fires in 2024.

"We are looking at 20 systems in which external bodies could have gravitational effects, such as KIC 10544976, and most of them are observable only from the southern hemisphere.The GMT will allow us to detect these objects directly and from the outside. get important answers about the formation and evolution of these exotic environments, as well as the possibility of life there, "said Almeida.