Brazilian astronomers have now found the first evidence of the existence of an exoplanet that revolves around an older or more developed binary where one of the two stars is dead.
The study resulted from a postdoctoral research project and a postgraduate education abroad, both with scholarships from FAPESP. Its results have just been published in The Astronomical Journal, owned by the American Astronomical Society (AAS).
Leonardo Andrade de Almeida, first author of the article, told Agência FAPESP: “We managed to get pretty solid evidence of the existence of a giant exoplanet with a mass almost 13 times that of Jupiter [the largest planet in the Solar System] in a developed binary system. here is the first confirmation of an exoplanet in such a system. “
Almeida is currently a postdoctoral fellow at the Rio Grande do Norte Federal University (UFRN), with a PhD at the University of São Paulo Institute of Astronomy, Geophysics and Atmospheric Sciences (IAG -USP), where he was supervised by Professor Augusto Damineli, co-author of the study.
The clue followed by the researchers to discover the exoplanet in the developed binary called KIC 10544976, which is located in Cygnu’s constellation in the northern celestial hemisphere, included variations in the eclipse (time taken for each of the two stars to be darkened the other ) and the orbital period.
“Variations in a binary orbital period are due to gravity attraction among the three objects that revolve around a common mass center,” said Almeida.
Orbital period variations are not enough to prove the presence of a planet in the case of biaries, since the binary star’s magnetic activity fluctuates regularly, just as the sun’s magnetic field changes polarity every 11 years, with turbulence and the number and size of the sun’s rays peaking and then dropping.
“Variations in solar magnetic activity ultimately cause a change in its magnetic field. The same applies to all isolated stars. In binaria, these variations also cause a change in the orbital period because of what we call the Applegate mechanism, Almeida says.  To disprove the hypothesis that variations in the orbital period of KIC 10544976 were merely due to magnetic activity, the effect of the eclipse time variation and the magnetic activity cycle of the binary star analyzed.
KIC 10544976 consists of a white dwarf a dead low mass star with high surface temperature and a red dwarf, a living (magnetically active) star with a small mass compared to spring Sun and small brightness due to low energy production . The two stars were monitored by ground-based telescopes between 2005 and 2017 and by Kepler between 2009 and 2013, giving data minute by minute.
“The system is unique,” Almeida said. “No similar system has enough data to enable us to calculate the orbital period variation and magnetic cycle activity for the live star.”
With Kepler data, they could estimate the magnetic cycle of the live star (red dwarf) based on the frequency and energy of spots (large bursts of electromagnetic radiation) and variations due to spots (regions with colder surface temperature and thus dark caused of different concentrations of magnetic field flow).
Analysis of the data showed that the red dwarf magnetic activity cycle lasted 600 days, consistent with the magnetic cycles estimated for low mass isolated stars. The binary cycle was estimated at 17 years.
“This completely opposes the hypothesis that orbital variations are due to magnetic activity. The most likely explanation is the presence of a giant plane that orbits the binary, with a mass about 13 times that of Jupiter,” Almeida said.
How the planet orbited the binary was formed is unknown, a hypothesis is that it evolved at the same time as the two stars billions of years ago, if so, it is a first generation planet. formed by the gas ejected during the death of the white dwarf, which made it a second generation planet.
Confirmation of its status as either a first or second generation planet and its direct detection as the Areas binary can be obtained from it new generation of ground-based telescopes with primary mirrors exceeding 20 meters, including the Giant Magellan Telescope ( GMT ) Installed in Chile’s Atacama Desert. GMT is expected to see the first light in 2024.
FAPESP will invest $ 40 million in GMT, or about 4% of the telescope’s estimated total cost. This investment will guarantee 4% of the telescope’s operating time for studies by researchers from the São Paulo State (read more at: agencia.fapesp.br/28569).
We are investigating 20 systems where external bodies can show gravity effects, such as KIC 10544976, and most are only observable from the southern hemisphere. GMT allows us to discover these items directly and get important answers to the formation and development of these exotic environments, as well as the opportunity to live there, Almeida says.
The article “Orbital period variation of KIC 10544976: Applegate mechanism versus light reaction” (DOI: 10.3847 / 1538-3881 / ab0963) by Leonardo A. Almeida, Leandro de Almeida, Augusto Damineli, Claudia V. Rodrigues, Matthieu Castro, Carlos EF Lopes, Francisco Jablonski, José D. Nascimento Jr and Marildo G. Pereira can be downloaded from The Astronomical Journal at iopscience-iop-org-443.webvpn.jxust.edu.cn/article /10.3847/1538-3881/ ab0963 / pdf . & nbsp