Shortly after European astronomers developed the first telescope in the early 17th century , they observed dark spots on the surface of the sun. They also leave their modern-day successors a mystery. From about 1645 to 1715, these blobs, now known as indicators of solar activity, all but disappeared. Gathering sunspot counts and other historical observations, astronomer John Eddy concluded nearly 50 years ago that the sun has essentially been napping for 70 years, which he called Mond The minimum is named after a couple of astronomers who had previously studied it.
It now appears that the sun isn’t the only one that needs a long nap. Building on a decades-long record of tracking stellar activity from observations of dozens of stars at specific wavelengths, a team of astronomers has determined that another is experiencing its own The Maunder minimum . “I’m more convinced than anything I’ve ever seen that this is a Mond minima,” said astronomer Jennifer van Saders of the University of Hawaii at Manoa.
The discovery, reported in a preprint on arXiv last month, may help explain what triggered the sun’s strange behavior 400 years ago, and suggests More such incidents are likely to occur. “It’s a way to study the sun’s past and future,” Van Sardes said. She added that the finding supports a theory she and her colleagues have put forward: that these events are accidental symptoms of a key shift in the magnetic field of Sun-like stars in about half their life — a midlife crisis. Some astronomers speculate that the sun’s transition helped the emergence of life on Earth, and that finding stars at a similar stage could help identify other solar systems that favor complex life.
For decades, scientists have known that our sun’s activity ebbs and flows in cycles of about 11 years, which flips the direction of its magnetic poles corresponding to the frequency. During solar maximums, sunspots spread, marking weak spots in the magnetic field where plasma from the sun’s atmosphere can violently circulate jets. Astronomers have discovered young Sun-like stars with similar periods, as well as older stars with completely stable activity. But no one noticed a cycling star suddenly flattened.
In 2018, as part of undergraduate research at Penn State University Park, Anna Baum set out to pair the Mount Wilson Observatory and the WM Keck Observatory with the Observations at the apparent wavelengths of 59 stars were combined to produce a 50-year chronology of stellar evolution. During the seven-year data gap when Keck upgraded the probe, one star appeared to show dramatic changes. Its activity went from a 17-year cycle to almost flat, and it has remained that way for the past 18 years.
Baum thought she had made a mistake at first; maybe the observatory was even looking at two different stars. But earlier this year, her colleagues found additional observations filling the gaps in the data, capturing the radiation from the star as it transitioned from an active to a quiet state. The recovered dataset “hit the jackpot,” said Jacob Luhn, an astronomer at the University of California, Irvine and lead author of the preprint.
This finding reinforces a popular theory as to why these prolonged periods of quiescence occur. Stars spin more slowly with age because their solar wind acts as a “magnetic brake,” like a child reaching out for an arm while spinning in a chair. In 2016, van Saders of the White Dwarf Research Corporation and her colleague Travis Metcalfe noticed that at some point, stars stop braking and their velocity stabilizes – they propose that this transition stems from changes in the star’s magnetic field. Then, last year, Dibyendu Nandi and colleagues at the Indian Centre of Excellence for Space Science confirmed the idea through computer simulations linking the stabilization of spin rates to weakened magnetic fields . During this transition, Nandi said, as the star moves toward an “inert” state, where its activity is flat rather than cyclic, random perturbations in its magnetic field can lead to something like a Maunder minima The temporary loop closes.
The theory predicts that this transitional state will occur in middle-aged stars – like our sun and this newly discovered Doze like stars. “Everything about this discovery actually confirms what we’ve been talking about for the past 5 years,” Metcalfe said. “We certainly know about stars that don’t cycle, but we don’t know how they got there — it’s like the missing link in that evolutionary picture.”
It may not be a coincidence that our sun’s magnetic transition may have started around the same time that life on Earth first crawled out of the sea, Metcalfe believes. Incoming particles and radiation from active stars can damage DNA and promote mutations that accelerate evolution. They “may be part of the necessary ingredients to start life,” he said. But at some point, the vibrant space weather can pose a threat to complex life — “like a giant cosmic reset button that shuts off forever,” he added.
The star that is transitioning from riding to stable provides the ideal balance of spark and protection to nourish life. “If we’re looking for technological civilizations,” Metcalfe said, “maybe the best place to look is around stars in the second half of [their] lives” — in other words, just entering a midlife crisis.