Recently, NASA and NOAA announced that the Sun has officially reached solar maximum, but what does that mean?
The Sun goes through an 11-year cycle of activity in which we see all types of solar phenomena (sunspots, flares, prominences, eruptions) reach a maximum level of activity, dwindle to a minimum level about 5-6 years later, and then reach a maximum level of activity once again, making a total cycle of 11 years or so. The solar cycle has been observed for roughly two centuries as astronomers first noted how the number of sunspots increased and decreased at a fairly regular interval. Later observations showed that other types of activity such as solar flare frequency also correlated to the apparent sunspot cycle. We now know that the solar cycle involves global changes throughout the Sun’s magnetic field with the magnetic field flipping during solar maximum; however, the finer details of this are still topics of heliophysics researchers.
What does solar maximum mean for us?
For the most part, it means there is more activity that astronomers (amateur and professional) can observe and record with properly filtered solar telescopes, more solar flares that have the potential to cause radio blackouts, and a greater potential for large eruptions, known as coronal mass ejections or “CMEs,” to impact our planet.
Lately, CMEs have caught the attention of many due to the auroras (“northern lights”) they can generate. As particles from Earth-directed eruptions reach us, Earth’s magnetic field deflects and funnels them toward the poles. The molecules of our atmosphere interact with them and emit characteristic colors. For example, the reds and greens often seen in auroras are usually due to oxygen. Particularly large eruptions or multiple eruptions arriving around the same time can initiate auroras at lower latitudes. With the Sun being at solar maximum, the chances of Tennesseeans and others at low latitudes observing additional auroras are definitely not out of the question over the next couple of years. On May 10, 2024, virtually every state in the U.S. saw an aurora of some kind, and a strong eruption triggered auroras on October 10 (though not quite as intense) in many southern states including Tennessee. Wondering when the next aurora might pop up over your area? NOAA has a convenient website for forecasting aurora. Pay close attention to where the thin red line is situated.
What can we see on the Sun?
Auroras and sunspots are not the only solar activity we can observe. Large plumes of gas known as prominences can be seen dancing around the limb of the Sun. Though they don’t look particularly large, keep in mind that the disk of the Sun is about 110 times wider than our planet, making some of these clouds of gas more than 10 times the width of Earth. To be able to view the prominences you must have a special solar telescope known as a hydrogen-alpha telescope. These telescopes completely block all light from the Sun except one very narrow portion of the red – the 656.28 nanometer wavelength (“hydrogen alpha”) that is only produced by hydrogen atoms. One can also sometimes see dark streaks snaking across the disk of the Sun – these are filaments, which are prominences seen from above.
Two glorious prominences were spied on October 22 as students from Brentwood Academy visited the observatory during a field trip. Between trips, observatory director Billy Teets acquired 30-second videos at one-minute intervals over a span of two hours, which were later processed to create an intriguing timelapse showing how the prominences gradually morphed over time.
IMPORTANT NOTE: Do NOT attempt to view the Sun with the type of hydrogen alpha filter that is used for deep sky imaging as this will not provide the necessary filtration for visual observation or photography. If you don’t have a solar telescope, you can still follow what the Sun is up to. The National Solar Observatory (NSO) has numerous telescopes around the world that image the Sun in “white light,” which provide a good view of sunspot activity, as well as hydrogen alpha and makes those images available online.