Perched atop the Atacama desert in northern Chile, the Atacama Large Millimeter/submillimeter Array (ALMA) is known for peering deep into the cosmos. Revealing distant galaxies and the birth of planets orbiting far away stars.
Now, scientists are expanding what ALMA looks at. Instead of the faintest objects billions of light-years away, ALMA can now train its antennas on the Sun. Just 0.00001581 light-years away.
Why study the Sun with ALMA? Tim Bastian, an astronomer with the National Radio Observatory in Charlottesville, Virginia explains. “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,” says Bastian. “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.”
Here’s an image ALMA captured in December 2015.
It was captured at a wavelength of 1.25 millimeters. What this image is showing us is the temperature differences in a piece of the Sun’s atmosphere called the chromosphere. It sits just above the visible surface of the Sun, or photosphere.
The exact wavelength used to observe the Sun probes different parts of the chromosphere. The image above was at a wavelength of 1.25 millimeters. Here’s another one at 3 millimeters.
By observing the Sun at slightly different wavelengths, astronomers hope to learn more about the dynamics inside the chromosphere.
The images captured by ALMA will only get better. The pair above were part of a testing campaign to get the observatory ready for solar observations for astronomers across the world.
You wouldn’t think observing the closest star would bring many challenges, but special procedures were needed. Remember, ALMA was designed to catch glimpses of faint objects far away. Not a blinding star at our doorstep. Astronomers will soon conduct observations of a star billions of times brighter than ALMA usually observes.
ALMA will continue to probe mysteries in the far reaches of the universe. But it might just help answer a few closer to home too.