A new look at sunspots

Helping NASA scientists understand major flares and life around other stars


Research News


NASA’s extensive fleet of spacecraft allows scientists to study the Sun extremely close-up – one of the agency’s spacecraft is even on its way to fly through the Sun’s outer atmosphere. But sometimes taking a step back can provide new insight.

In a new study, scientists looked at sunspots – darkened patches 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 the conditions for life on planets orbiting other stars.

“We wanted to know what a sunspot region would look like if we couldn’t resolve it in an image,” said Shin Toriumi, lead author on the new study and scientist at ?the Institute of Space and Astronautical Science at JAXA. “So, we used the 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 outbursts of energy from the surface of the Sun – so monitoring sunspots is important to understanding why and how flares occur. Additionally, understanding the frequency of flares on other stars is one of the keys to understanding their chance of harboring life. Having a few flares may help build up complex molecules like RNA and DNA from simpler building blocks. But too many strong flares can strip entire atmospheres, rendering a planet uninhabitable.

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

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

The new study, published in the Astrophysical Journal, looked at simple cases where there is just one group of sunspots visible across the entire face of the Sun. Even though NASA and JAXA missions have continually gathered observations of the Sun for over a decade, these cases are quite rare. Usually there are either several sunspots – such as during the solar maximum, which we are now moving toward – or none at all. In all the years of data, the scientists only found a handful of instances of just one isolated sunspot group.

Studying these events, the scientists found the light curves differed when they measured different wavelengths. In visible light, when a singular sunspot appears at the center of the Sun, the Sun is dimmer. However, when the sunspot group is near the edge of the Sun, it’s actually brighter due to faculae – bright magnetic features around sunspots – because, near the edge, the hot walls of their nearly vertical magnetic fields become increasingly visible.

The scientists also looked at the light curves in x-ray and ultraviolet light, which show the atmosphere above the sunspots. As the atmospheres above sunspots are magnetically heated, the scientists found brightening there at some wavelengths. However, the scientists also unexpectedly discovered that the heating could also cause a dimming in the light coming from the lower temperature atmosphere. These findings may provide a tool to diagnose the environments of spots on the stars.

“So far we’ve done the best-case scenarios, where there’s only one sunspot visible,” Toriumi said. “Next we are planning on doing some numerical modeling to understand what happens if we have multiple sunspots.”

By studying stellar activity on young stars in particular, scientists can glean a view of what our young Sun may have been like. This will help scientists understand how the young Sun – which was overall more dim but active – impacted Venus, Earth and Mars in their early days. It could also help explain why life on Earth started four billion years ago, which some scientists speculate is linked to intense solar activity.

Studying young stars can also contribute to scientists’ understanding of what triggers superflares – those that are 10 to 1000 times stronger than the biggest seen on the Sun in recent decades. Young stars are typically more active, with superflares happening almost daily. Whereas, on our more mature Sun, they may only occur once in a thousand years or so.

Spotting young suns that that are conducive to supporting habitable planets, helps scientists who focus on astrobiology, the study of the origin evolution, 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 that can then be followed up by observations from other upcoming high-resolution missions, such as NASA’s James Webb Space Telescope.


From EurekAlert!

14 thoughts on “A new look at sunspots

  1. One big limitation of the “data” they have simulated with the resolution:pixel reduction exercise by wavelength is that is may only apply to G class star (temperature is spectrum) with rotation rates similar to the Sun. Extrapolating to stars outside those narrow parameters can be fraught with lots of caveats to explain dips in apparent light curves.

  2. There is really nothing learnt from this [yet?]. All they say is that some numerical modeling [send more money] are needed that ‘may’ provide insight into this or that. This is thin gruel, indeed, considering that it comes from luminaries of the field.

    • “luminaries of the field” are indeed funding farmers. If only the average taxpayer knew what was going on with their remittances!

    • Agree, the above new look at sunspots did not reveal much if anything new.
      However, an old look at sunspots might reveal a bit more
      Leif Svalgaard October 28, 2018 at 3:32 pm
      “Even the 11-year Schwabe cycle is not a ‘cycle’ but an ‘eruption’. Around the statistical solar minimum two eruptions run in parallel: one at low latitudes and one in high to mid-latitudes.The length of an eruption is typically 17 or so years. Each eruption leaves behind the debris of which the next eruption will develop”
      I had a look at sunspot magnetic data, it changes polarity every 11 years, hence a strong ~22 spectral component, but what of Dr. Svalgaard’s 17 years, not there but there is a strong-ish ‘bump’ at just above 18 years as the second strongest component and about 3 x as strong as the rest of the noise.
      It might be of interest that the ratios of intensity of the spectral components for the solar magnetic and global temperature’s data for both 18 and 22 years are exactly the same, an incidental conformation of a causal link between the two.

  3. I’ve often puzzled/wondered about the term ‘active’ as applied to Sol.

    Wouldn’t most laypersons take that to mean it to be ‘expending more energy’? Isn’t that the definition of ‘activity’?

    Yet Sol doesn’t, total solar power/temp/irradiance (seem to) stay within very tight limits – plus/minus a few 10th Watts/sqm.
    Thus the Stefan formula as used/abused by Climate Science says that Sol’s average temperature stays The Same

    Bring that Down to earth, literally, don’t that imply Earth’s atmosphere can become more/less active without *its* temperature changing

    Thus we’re left with the result that ‘temperature is *entirely* The Wrong Metric with which to measure ‘Climate’ – climate being= Activity within Earth’s atmosphere, as it is on El Sol.

  4. “…on other stars you might only get one pixel.” The problem of pixel size limitation can be addressed by “re-sampling”, wherein the processor looks at adjacent pixels for some small influence of the target pixel, then utilizes these small differences to adjust the view of the target. For example, in the early days of Landsat, average pixel size around 30 meters, we wanted to georeference the pixel to allow us to be inside of the data in the field (where we utilized a short wave infrared spectrometer to analyze what was controlling reflectence in a given pixel, which chosen pixel had gold mineralization within it). So we found a farmers green field against a background of natural brown, with a pixel faintly tinged by the brown influence, then position ourselves where we estimated the center of the pixel was, maybe plus or minus 4 or 5 meters? then surveyed the spot and corrected the georeference of the pixel. The same technique, now aided by very fast computers, can easily resolve to a quarter pixel by this resampling technique.

    • Interesting Ron. I was with HP in the late 80s. Testing sub-micron optical microscopes. One was by IVS, who was doing satellite imaging for NASA. I wasn’t involved in that end, but they were doing pixel interpretation to define the edge of our .9 micron +/- linewidths for measurement.

      • Steve: “I was with HP in the late 80s.” I utilized one of your workstations to process imagery, as per above. Worked great. Now a dinosaur. Soon maybe collector value?

        • Ron
          It sounds like we have similar backgrounds. I got into multispectral remote sensing in the ’80s. By the time I retired a decade ago, I had become an expert in imaging polarimetry. My optical mineralogy/petrology courses were a big help in getting a handle on the issues. Actually, I’m doing research at the moment on the optical constants of opaque minerals, which uses elliptically polarized light; the process is known as ellipsometry.

        • Ron; I have no idea about the value of one of those workstations. We made the first 32 bit CPU, finally making it to high yield production circa ’83-4. That was the 8111 chip, so something containing that might be sought after. I would guess most old electronic equipment gets destroyed, so something that old could be rare. I’m still using my 15C calculator after thirty -five years, and have a 41CX and 70B handheld programable models from the 80s. I think the astronauts used the 41CX early on as their computer.

  5. Why take pictures of such an insignificant object in the solar system? Everyone knows it has no impact on the climate models and modelers. This debate was also declared ended. Move along.

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