Our sun is known for its occasional outburst of energy called a solar flare, which can cause space weather that can disrupt communications and energy infrastructure here on Earth.
But we should really be grateful that we don’t exist around a star that erupts with so-called “superflares” that can be 100 to 10,000 times more energetic than even the most powerful solar flares. A superflare from the sun could be potentially catastrophic for Earth, causing serious damage to our planet’s atmosphere and the life forms that depend on it. Fortunately, superflares around stars are seen so far away that they are just points of light in the sky from our perspective.
These energetic bursts appear to astronomers as a sudden and extreme brightening of those distant dots, and this has led scientists to play star detective on a quest to discover why some stars erupt so violently.
Related: Scientists study violent “superflares” on stars thousands of times brighter than the Sun
And now a team of researchers from the Mackenzie Center for Radio Astronomy and Astrophysics at Mackenzie Presbyterian University in Brazil and the School of Physics and Astronomy at the University of Glasgow in Britain have begun investigating the two main suspects believed responsible esteemed for these super flares.
To do this, they analyzed 37 superflares seen in the binary star system Kepler-411, as well as another five coming from the star Kepler-396.
I’m interrogating two superflare suspects
A stellar outburst is thought to erupt when magnetic energy built up in a star’s atmosphere is suddenly released due to magnetic field lines ‘snapping’ and ‘reconnecting’. This probably applies to every type of stellar flare. So despite the fact that there are power differences when it comes to solar flares from the Sun and stellar outbursts from elsewhere in the cosmos, the research team was able to use the mechanism that launches solar flares from our star to assess distant, energetic outbursts. .
The researchers were also able to apply the vast amount of data collected on solar flares since they were first described in the scientific literature by astronomers Richard Carrington and Richard Hodgson, who independently observed the same solar flare on September 1, 1859.
“Since then, solar flares have been observed with intense brightness lasting from seconds to hours and at different wavelengths, from radio waves and visible light to ultraviolet and X-rays,” said Alexandre Araújo, a member of the research team and a Ph.D. candidate at the Mackenzie Center for Radio Astronomy, said in a statement.
The team also had data on stellar outbursts from observations of other stars made by observatories designed to look for signs of orbiting planets, such as the Kepler Space Telescope and the Transiting Exoplanet Survey Satellite (TESS).
In the ‘usual suspect’ model for these violent superflares, the radiation from a burst is treated as a ‘blackbody emission’, referring to electromagnetic radiation that is in equilibrium with the environment. Such emissions also cover a broad spectrum of wavelengths and depend on the temperature of the emitting body. The ‘blackbody emission’ in the case of the superflares studied would have a temperature of about 17,500 degrees Fahrenheit (9,700 degrees Celsius).
Yet there is still an external suspect that cannot be ruled out. In this alternative model, superflares are generated as a result of hydrogen atoms being stripped of electrons, or becoming ‘ionized’, and then recombining with these electrons to form neutral hydrogen atoms again. It is this external model that the team’s analysis favors as an explanation for superflares.
“Given the known processes of energy transfer in solar flares, we argue that the hydrogen recombination model is physically more plausible than the blackbody model to explain the origin of the broadband optical emission from solar flares,” said Paulo Simões, a professor at Mackenzie Presbyterian University who led gave to the new study, said in a statement. “We concluded that estimates for total solar radiation energy from the hydrogen recombination model are approximately an order of magnitude lower than the values obtained using the blackbody radiation model and better fit the known solar flare processes.”
Simões added that the limitation of the first and most popular blackbody model concerns energy transport. A certain amount of energy is required on a star’s photosphere to ensure that the plasma in the region is heated enough to lead to the extreme brightening associated with superflares. Yet none of the energy transport mechanisms normally accepted for solar flares has the power to explain how this kind of energy level and distribution can be achieved.
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‘Calculations first performed in the 1970s and later confirmed by computer simulations show that most of the electrons accelerated in solar flares fail to pass through the chromosphere. [the sun’s outer atmosphere] and enter the photosphere,” Araújo said. ‘The blackbody model as an explanation for white light in solar flares is therefore incompatible with the main energy transport process accepted for solar flares.’
The team claims that the hydrogen recombination radiation model, on the other hand, is more consistent from a physical point of view. However, the team admitted that the unfortunate aspect of all this is the hydrogen reconnection model and that the link with superflares cannot yet be confirmed by observations.
Still, the researchers conclude that their study at least provides a strong argument in favor of the hydrogen reconnection model, which they say has been neglected in most superflare studies to date.
The team’s research was published earlier this year in the journal The Monthly Notices of the Royal Astronomical Society.