2024-01-11 11:43:56
Composite image illustrating the 51 Pegasi system and its measured magnetic field. The detected “weak magnetic braking” of 51 Peg represents a relatively sudden change that makes the magnetic environment more stable. – AIP/J. FOHLMEISTER
MADRID, 11 Ene. (EUROPA PRESS) –
The current magnetic environment around the star 51 Pegasi, where the first exoplanet was discovered in 1995, may be particularly favorable for the development of complex life.
It’s the conclusion of new research that suggests cosmic hotspots for finding extraterrestrial neighbors could be around stars going through their midlife crisis and beyond. This groundbreaking study, which sheds light on magnetic phenomena and habitable environments, has been published in The Astrophysical Journal Letters.
Stars like the Sun are born spinning rapidly, which creates a strong magnetic field that can explode violently, bombarding their planetary systems with charged particles and harmful radiation. Over billions of years, the star’s rotation gradually slows as its magnetic field is swept away by a wind flowing from its surface, a process known as magnetic braking. The slower rotation produces a weaker magnetic field and both properties continue to decrease, each feeding off the other.
Until recently, astronomers had assumed that magnetic braking continues indefinitely, but new observations have begun to question this assumption.
“We are rewriting the textbooks on how rotation and magnetism in older stars like the Sun “they change beyond half their life”says team leader Travis Metcalfe, senior research scientist at White Dwarf Research Corporation. “Our results will have important consequences for stars with planetary systems and their prospects for the development of advanced civilizations.”
Klaus Strassmeier, director of the Leibniz Institute for Astrophysics in Potsdam, Germany, and co-author of the study, adds it’s a statement: “This is because the weakened magnetic braking also strangles the stellar wind and makes devastating eruptive events less likely.”
The team of astronomers from the United States and Europe combined observations of 51 Pegasi from NASA’s Transiting Exoplanet Survey Satellite (TESS) with cutting-edge measurements of its magnetic field made by the Large Binocular Telescope (LBT) in Arizona using the instrument PEPSI (Potsdam Echelle Polarimetric and Spectroscopic Instrument).
Although the exoplanet orbiting 51 Pegasi does not pass in front of its parent star as seen from Earth, the star itself shows subtle variations in brightness in TESS observations that can be used to measure the radius, mass and age of the star.a technique known as asteroseismology.
Meanwhile, the star’s magnetic field imprints a small amount of polarization on the starlight, allowing PEPSI at the LBT to create a magnetic map of the stellar surface as the star spins, a technique known as Zeeman imaging. Doppler. Together, these measurements allowed the team to assess the current magnetic environment around the star.
Previous observations from NASA’s Kepler space telescope already suggested that magnetic braking could weaken substantially beyond the age of the Sun, breaking the close relationship between rotation and magnetism in older stars. However, the evidence for this change was indirect and based on measurements of the rotation rate of stars with a wide range of ages. It was clear that the rotation stopped slowing at some point around the age of the Sun (4.5 billion years). and that weakened magnetic braking in older stars could reproduce this behavior.
However, only direct measurements of a star’s magnetic field can establish the underlying causes, and the targets observed by Kepler were too faint for LBT observations. The TESS mission began collecting measurements in 2018, similar to Kepler observations, but for the closest and brightest stars in the sky, including 51 Pegasi.
In recent years, the team began using PEPSI at the LBT to measure the magnetic fields of several TESS targets, gradually building a new understanding of how magnetism changes in stars like the Sun as they grow. The observations revealed that magnetic braking changes suddenly in stars that are slightly younger than the Sun, becoming more than 10 times fainter at that point and dimming further as the stars continue to age.
The team attributed these changes to an unexpected change in the strength and complexity of the magnetic field, and to the influence of that change on the stellar wind. The newly measured properties of 51 Pegasi show that, like our own sun, it has already gone through this transition to weakened magnetic braking.
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