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A new look at sunspots is helping NASA understand life around other stars


NASAThe large fleet of spacecraft allows scientists to study the Sun in extremely close proximity – one of the agency’s spacecraft is even on its way to fly through the Sun̵

7;s outer atmosphere. But sometimes stepping back can provide new insights.

In a new study, scientists examined sunspots – dark spots on the Sun caused by its magnetic field – at low resolution as if they were trillions of miles away. What resulted was a simulated view of distant stars, which can help us understand stellar activity and life conditions on planets orbiting other stars.

“We wanted to know what a sunspot region would look like if we couldn’t solve it in an image,” said Shin Toriumi, lead author of the new study and scientist at the Institute of Space and Astronautical Science in JAXA. “So, we used solar data as if it came from a distant star to have a better connection between solar physics and stellar physics.”

Sunspots are often precursors to solar flares – intense bursts of energy from the Sun’s surface – so tracking sunspots is important for understanding why and how they occur. Furthermore, understanding the frequency of flares on other stars is one of the keys to understanding their ability to host life. Having some rockets can help build complex molecules like RNA is DNA from simpler building blocks. But too many strong glows can strip entire atmospheres, making a planet uninhabitable.

To see what a sunspot would look like and its effect on the solar atmosphere on a distant star, the scientists started with high-resolution data from the Sun from NASA’s Solar Dynamics Observatory and JAXA / NASA. Hinode mission. By adding up all the light in each image, the scientists converted the high-resolution images into single data points. Putting the successive data points together, the scientists created graphs of how the light changed as the sunspot crossed the rotating face of the Sun. These graphs, which scientists call light curves, showed what a passing sunspot would look like on the Sun. if it were many light years away.

Scientists created light curves using high-resolution images of the Sun to understand what a sunspot would look like on a distant star. They studied different layers of the Sun from the visible surface to the outer atmosphere using 14 different wavelengths, including the six shown here (top left to right: photosphere, photosphere magnetic flux, ultraviolet 304 angstroms; bottom left to right: ultraviolet 171 angstroms, ultraviolet 131 angstroms, X-rays). Credits: NASA / SDO / JAXA / NAOJ / Hinode

“The Sun is our closest star. Using satellites for solar observation, we can resolve signatures on the surface 100 miles wide, “said Vladimir Airapetian, co-author of the new study and astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.” stars you could get a single pixel showing the entire surface, so we wanted to create a model to decode the activity on other stars. “

The new study, published in Astrophysical Journal, looked at simple cases in which there is only one sunspot group visible on the entire face of the Sun. Although NASA and JAXA missions have continuously collected observations of the Sun for over a decade, these cases are quite rare. There are usually several sunspots – such as during the solar maximum, towards which we are now moving – or none. In all the years of data, scientists have found only a handful of cases of just one isolated sunspot group.

By studying these events, the scientists found that the light curves differed when they measured different wavelengths. In visible light, when a single sunspot appears in the center of the Sun, the Sun is weaker. However, when the sunspot cluster is near the edge of the Sun, it is actually brighter due to faculae – bright magnetic features around the sunspots – because, near the edge, the warm walls of their near-vertical magnetic fields become increasingly visible.

The scientists also looked at light curves in X-rays and ultraviolet light, which show the atmosphere above sunspots. Because the atmospheres above the sunspots are magnetically heated, scientists have found that there it glows at certain wavelengths. However, the scientists also unexpectedly discovered that warming could also cause darkening of the light from the low-temperature atmosphere. These results can provide a tool for diagnosing star spot environments.

“So far we have made the best scenarios, where only a sunspot is visible,” said Toriumi. “Next we are planning to do some numerical models to understand what happens if we have more sunspots.”

By studying stellar activity particularly on young stars, scientists can gain insight into what our young Sun may have been like. This will help scientists understand how the young Sun, which was overall weaker but more active, had a impact Venus, Earth and Mars in their early days. It could also help explain why life on Earth began four billion years ago, which some scientists speculate is linked to intense solar activity.

Studying young stars may also contribute to scientists’ understanding of what triggers the superfluous, those that are 10 to 1000 times stronger than the largest seen on the Sun in recent decades. Young stars are typically more active, with the superfluous occurring almost every day. While, on our more mature Sun, they can only occur once every thousand years or so.

Identifying the young lonely who favor the support of habitable planets helps scientists who focus on astrobiology, the study of the evolution of the origin and distribution of life in the universe. Several next-generation telescopes in production, which will be able to observe other stars in X-ray and ultraviolet wavelengths, could use the new results to decode observations of distant stars. In turn, this will help identify those stars with appropriate levels of stellar activity for life – and this can then be followed by observations of other upcoming high-resolution missions, such as NASA’s. James Webb space telescope.

Reference: “Sun-as-a-star Spectral Irradiance Observations of Transiting Active Regions” by Shin Toriumi, Vladimir S. Airapetian, Hugh S. Hudson, Carolus J. Schrijver, Mark C. M. Cheung and Marc L. DeRosa, October 8, 2020, Astrophysical Journal.
DOI: 10.3847 / 1538-4357 / abadf9

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