Immediately after turning telescopes on the heavens, astronomers discovered spots on the Sun. The Englishman Thomas Harriot was perhaps the first to see sunspots in December 1609, but others like the more famous Galileo soon followed. Don’t try this at home, seriously, until you have the proper equipment and have read instructions. But, don’t be discouraged. It’s rather easy, just keep reading.
Our Sun is now about 4.5 billion years old. It was created from a swirling cloud of hydrogen, helium, and a smattering of heavier elements. As the cloud collapsed gravitationally, the center of this protostar became dense and hot enough for fusion to begin. And, there was light. Our Sun continues to fuse the lighter elements into heavier elements like a continuous hydrogen bomb. Astronomers pieced this puzzle together by observing stars in all phases of life; from birth, to middle age, through violent death.
The Sun is not as unchanging as it might seem. Our Sun will burn for another 6 billion years. It is swelling and growing warmer, but at a pace too slow for us to notice. But, there are other changes occurring at an observable rate. Solar magnetic activity causes storms visible on the Sun’s surface. These sunspots are cooler areas on the Sun that appear black because the surrounding areas are brighter. Sunspots rotate with the Sun from East to West, disappearing off the western edge. The Sun takes roughly 28 days to complete a rotation. Longer lasting sunspots may survive to be observed reappearing on the eastern edge.
The number of observable sunspots varies with an 11-year cycle, called the solar cycle. These cycles have been observed since 1610, and accurately recorded since 1750. Cycles after 1750 are numbered. We are entering cycle 25 which began in December 2019. During the decades from 1640 to 1700, few sunspots were observed. It is called the Maunder minimum, and it coincided with the “little ice age” in Europe. Periods of high sunspot activity coincide with a slightly hotter Sun.
The peak in cycle 25 sunspot numbers is predicted to occur sometime before 2026. Now is a great time for observing sunspots. Sunspots are spectacular in small telescopes equipped with a solar filter. Without a filter, the telescopic Sun would be instantly blinding. Larger sunspots are naked-eye visible without the magnification of a telescope. However, a filter is still required. Inexpensive cardboard eclipse viewers work fine for observing larger sunspots. Two pairs of Celestron Eclipsmart X2 binoculars are available on Amazon for $12. The X2 magnification makes finding small sunspots a little easier. These cardboard binoculars will also work well for the upcoming October 2023 and April 2024 eclipses. Stay tuned for stories about those eclipses as they approach.