Over the last three decades, nearly 4,000 planet-like objects have been discovered to track isolated stars outside the solar system (exoplanets). As of 2011, it was possible to use NASA's Kepler space telescope to observe the first exoplanets in orbit around young binary systems of two live stars with hydrogen still burning in its nucleus.
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 findings 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 pretty solid evidence of the existence of a giant exoplanet with a mass almost 13 times that of Jupiter in a developed binary system. This is the first confirmation on an exoplanet in such a system. "
Almeida is currently a postdoctoral fellow at the Federal University of Rio Grande do Norte (UFRN), with a doctorate at the University of São Paulo Institute of Astronomy, Geophysics and Atmospheric Sciences (IAG-USP), where he was led by Professor Augusto Damineli, co-author of the study.
Variations in eclipse timing (the time taken for each of the two stars to be darkened with the other) and the orbital period led the researchers to discover the exoplanet of the developed binary called KIC 10544976, which is located in the Cygnus constellation of the northern celestial hemisphere .
"Variations in a binary cycle depend on gravity attraction among the three objects that circle around a common mass center," Almeida said.
Orbital variations are not sufficient to prove the presence of a planet in the case of binary, since the magnetic activity of the binary stars fluctuates regularly, just as the solar magnetic field changes polarity every 11 years with turbulence and the number and size of the rays of the sun and then decreases.
"Variations in solar magnetic activity lead to a change in its magnetic field. The same applies to all isolated stars. In binary, these variations also cause a change in the orbital period due to what we call the Applegate mechanism," Almeida says.
To refute the hypothesis that variations in the orbital period of KIC 10544976 were merely due to magnetic activity, analyzed the effect of the eclipse time variation and the magnetic activity cycle of the binary live star.
KIC 10544976 consists of a white dwarf, a dead, low surface temperature low mass star and a red dwarf, a living magnetically active star with a small mass compared to the sun and a 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 for minute.
"The system is unique," says Almeida systems have enough data to enable us to calculate orbital period variation and magnetic cycle activity for the live star. "
With Kepler data, they could estimate the live star's magnetic cycle (red dwarf) based on flow rate and energy (large electromagnetic radiation bursts ) and variations due to spots (areas with cooler surface temperature and thus darkness caused by different concentrations of magnetic field flow).
Analysis of the data showed that the red dwarf magnetic activity cycle lasted 600 days, which is consistent with the magnetic cycles estimated for low mass isolated stars. The orbital period of the binary was estimated at 17 years. "This completely opposes the hypothesis that orbital variability is due to magnetic activity. The most credible explanation is the presence of a giant plane that orbits the binary, with a mass of about 13 times that of Jupiter," Almeida said.
How the planet revolved around the binary was formed is unknown. One hypothesis is that it developed at the same time as the two stars billions of years ago. If so, it is a first generation planet. Another hypothesis is that it was formed by the gas ejected during the death of the white dwarf, making it a second generation planet.
Confirmation of its status as either a first or second generation planet and its direct detection as the paths of bees can be obtained using the new generation of ground-based telescopes with primary mirrors in excess of 20 meters, including the Giant Magellan Telescope (GMT) installed in Chile's Atacama Desert. GMT is expected to see the first light in 2024.
"We are investigating 20 systems where external bodies can show gravitational effects, such as KIC 10544976, and most are only observable from the southern hemisphere. To detect these objects directly and get important responses to formation and development of these exotic environments, as well as the opportunity to live there, Almeida said.
First death of the star confirmed by astronomers
L. A. Almeida et al., Orbital Period Variation of KIC 10544976: Applegate Mechanism vs. Light Travel Time Effect, The Astronomical Journal (2019). DOI: 10.3847 / 1538-3881 / ab0963
Astronomers find evidence of a planet with a mass of almost 13 times that of Jupiter (2019, April 9)
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