Our Sun is known for occasional bursts of energy called solar flares, which can trigger space weather that can disrupt communications and power infrastructure on Earth.
But we should really be grateful that we don’t exist around a star that explodes in so-called “superbursts,” which can be 100 to 10,000 times more energetic than even the most powerful solar flares. A solar superflare could be potentially catastrophic for Earth and cause serious damage to our planet’s atmosphere and the life forms that depend on it. Fortunately, superflares are seen around stars so distant that from our perspective they are just points of light in the sky.
These energetic flares appear to astronomers as sudden, extremely brightening of distant spots, which has led scientists to play star detective in the quest to discover why some stars explode so violently.
Relating to: Scientists study intense ‘superflares’ in 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 the UK have begun examining two leading suspects thought to be responsible. super flares.
To do this, they analyzed 37 superflares seen in the binary star system Kepler-411, as well as five superflares from the star Kepler-396.
Questioning two superflare suspects
A star explosion is thought to occur when magnetic energy accumulated in a star’s atmosphere is suddenly released as a result of the “breaking” and “reconnecting” of magnetic field lines. This is probably true of all types of star flares. So, although there are power differences between solar flares coming from the sun and stellar bursts coming from elsewhere in the universe, the study team was able to use the mechanism that initiates bursts from our star to evaluate more distant, more energetic bursts. .
The researchers were also able to apply the large 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, intensely bright solar flares lasting seconds to hours have been observed at different wavelengths, from radio waves and visible light to ultraviolet and X-rays,” study team member and doctoral student Alexandre Araújo said. candidate at the Mackenzie Center for Radio Astronomy, said in a statement.
The team also had data on starbursts 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 Search Satellite (TESS).
The “usual suspect” model for these violent superflares treats radiation from explosions as “blackbody emission,” referring to electromagnetic radiation in equilibrium with its surroundings. Such emissions also cover a broad spectrum of wavelengths and depend on the temperature of the emitting body. In the case of the superflares studied, the “blackbody emission” would have a temperature of about 17,500 degrees Fahrenheit (9,700 degrees Celsius).
But there is another external suspect that cannot be ignored. This alternative model sees superflares occurring when hydrogen atoms are stripped of their electrons, in other words, “ionized,” and then recombine with those electrons to form neutral hydrogen atoms once again. This external model is preferred as the explanation for superflares in the team’s analysis.
“Given the known energy transfer processes in flares, we argue that the hydrogen recombination model is physically more plausible than the blackbody model for explaining the origin of broadband optical emission from flares,” said Paulo Simões, professor at Mackenzie Presbyterian University. The new study said in a statement. “We conclude that total flare energy estimates based on the hydrogen recombination model are approximately an order of magnitude lower than values obtained using the blackbody radiation model and are in better agreement with known flare processes.”
Simões added that the limitation of the first and more popular blackbody model was related to energy transport. A certain amount of energy must be present in the photosphere of a star to ensure that the plasma in the region is heated enough to cause the extreme brightness associated with superflares. However, none of the energy transport mechanisms normally accepted for solar flares are capable of explaining how such a level and distribution of energy can be achieved.
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“Calculations first made in the 1970s and later confirmed by computer simulations show that most of the electrons accelerated in solar flares fail to pass the chromosphere.” [the sun’s outer atmosphere] and enter the photosphere,” said Araújo. “The blackbody model as an explanation of white light in solar flares is therefore incompatible with the main accepted energy transport process for solar flares.”
The team argues that the hydrogen recombination radiation model is more physically consistent. The unfortunate aspect of all this, the team acknowledged, is the hydrogen reconnection pattern, and its connection to 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 research.
The team’s research was published earlier this year in the journal The Monthly Notices of the Royal Astronomical Society.