Sunspots may be visible during the March 29 partial solar eclipse. Here's how to spot them.

Observing an eclipse of the sun is always fascinating, but on March 29, 2025 — when a partial solar eclipse is visible in the Northern Hemisphere — there will be an extra reason to do so.

As well as up to 94% of the sun being blocked by the moon, sky-watchers will see sunspots on the solar surface.

Sunspots are indicative of magnetic disturbances in our star, they appear as dark patches on the surface of the sun and can be as big as Earth. Their presence is a clue to where the sun is in its 11-year solar cycle, with astronomers counting them every day since 1610. During the solar cycle, the number of sunspots waxes and wanes. In October 2024, NOAA and NASA announced that the solar maximum had arrived after astronomers observed a peak in sunspots.

Tracking the progress of the eclipse

As well as a bonus sight for anyone watching through solar eclipse glasses, there's a good reason to look for sunspots. So far in the solar maximum period, most sunspots have occurred in the sun's southern hemisphere. Most solar cycles have two peaks, so astronomers expect a flurry of sunspots in the sun's northern hemisphere. On March 29, you can look for yourself — and see the moon slowly cover up, then reveal whatever sunspots there are on the sun. It's a great way to track the eclipse's progress while doing some serious solar observing.

If you can't wait for the eclipse, you can get a preview of what the sun looks like right now from NASA's Solar Dynamic Observatory.

Why you need to use solar filters during the eclipse

Remember, NEVER look at the sun without proper eye protection and never use regular sunglasses to observe the sun. It is never safe to look directly at the sun's rays, even if the sun is partly obscured, because they contain harmful ultraviolet (UV) and infrared (IR) rays that can damage your eye's retina and even cause blindness. The only safe way to look directly at the sun is through specifically designed solar filters, using solar eclipse glasses for direct viewing and solar filters for telescopes and binoculars.

Besides, the only way you'll see sunspots on the sun is through solar filters. If you have solar eclipse glasses left over from previous eclipses, inspect them for any scratches or damage, as even a tiny pinhole can damage your eyes. Indirect eclipse viewing methods, such as a pinhole projector, also show sunspots.

Read more: How to observe the sun safely

Editor's Note: If you snap a photo of the partial solar eclipse and would like to share it with Space.com's readers, send your photo(s), comments, and your name and location to spacephotos@space.com.