The Atacama Large Millimeter/submillimeter Array (ALMA) has been invaluable in studying distant protoplanetary disks and nebulae, which are very cold regions of the universe, and it is now used to also study the hottest thing in the neighborhood – the Sun.
ALMA’s ability to look between infrared and radio waves makes it ideal to study the chromosphere, the region of the Sun’s atmosphere just above the Sun’s visible surface. Over 30 months of observations have produced a never-before-seen view of the Sun, including a spot that looks like a turtle.
You might laugh at the pareidolia of the astronomers, but whether you see a turtle pattern or not, this particular find is incredible. The sunspot is twice as wide as the Earth and it’s darker than the surrounding regions because it’s colder. ALMA has delivered a temperature map of the atmosphere of the Sun, which will help scientists understand how the heat is propagated.
"We’re accustomed to seeing how our Sun appears in visible light, but that can only tell us so much about the dynamic surface and energetic atmosphere of our nearest star,” Tim Bastian, an astronomer with the National Radio Astronomy Observatory, said in a statement. “To fully understand the Sun, we need to study it across the entire electromagnetic spectrum, including the millimeter and submillimeter portion that ALMA can observe."
ALMA view of the whole solar disk. ALMA (ESO/NAOJ/NRAO)
ALMA has 66 high-precision antennas, but only one was used for this experiment. The antenna had to be adapted for the observations. The Sun is many billion times brighter than the usual ALMA target, so several precautions had to be put in place to not completely destroy the tech.
And while the preparation was laborious, the results are a success. The single antenna can make a low-resolution map of the Sun in just a few minutes, or produce more sophisticated views of particular regions.
Being so close, the Sun is our best option to understand how stars work, and there’s plenty that we still don’t know. Hopefully, ALMA can provide a unique view on the solar mysteries.