A “half-forgotten” drawing of sunspots by Renaissance astronomer Johannes Kepler can tell us more about how the solar cycle works.
“The research group’s discovery is key to resolving an early 17th century debate about the duration of the solar cycle,” writes Nagoya University in Japan. In a statement
This period (1645 to 1715) is known as the Maunder Minimum. Sunspots The temperature is lower than usual, Earth than the standard at the time.
Related : Scientists say the solar maximum will arrive earlier and last longer than previously expected.
Sunspots are cool regions on the Sun’s surface that can give rise to explosive disturbances such as solar flares and coronal mass ejections. (Image courtesy of NASA/SDO)
Kepler did not have a telescope, so instead he observed the Sun using a camera obscura, which “was a small hole in a wall through which an image of the Sun was projected onto a piece of paper,” the statement said. Kepler initially thought he was witnessing a solar transit. Mercury
“This is the oldest sunspot sketch drawn by instrumental observation and projection,” lead author Hisashi Hayakawa, an assistant professor and solar scientist at Nagoya University, said in a statement. He added that the importance of Kepler’s sun drawings has been overlooked throughout the ages. “They have only been discussed in the context of the history of science and have not been used in quantitative analysis of the solar cycle.”
Related: Who invented the telescope?
Key to the researchers’ analysis was tracking how sunspots move throughout the solar cycle. “Sunspot occurrence, frequency, and latitudinal distribution occur in cycles that affect solar radiation and space weather,” the statement said. So the researchers worked to narrow down which latitudes Kepler’s sunspots were observed at.
Johannes Kepler (1571-1630), German mathematician, astronomer and astrologer, oil on panel, Anonymous, 1610. (Image credit: Photo by History/Universal Images Group via Getty Images)
The researchers say their analysis of Kepler’s drawings reveals four major facts.
First, the sunspots were at lower latitudes than previously thought (after taking into account the angle of the sun’s position from his position). Relatedly, subsequent telescopic surveys showed sunspots at higher latitudes, suggesting a “classical transition” between cycles.
The change in latitude suggested that the sunspot group was at the end of one solar cycle, rather than the start of the next, based on the latitude of the sunspots, which led to a third discovery.
Finally, Kepler observations may indicate a transition zone between solar cycles, which this study places between 1607 and 1610.
Some researchers had previously theorised that the Maunder Minimum resulted from an irregular solar cycle that was different to the usual 11 years, but Kepler’s records show that the solar cycle he observed in 1607 showed “regular duration”, the study added.
However, the finding is not without controversy: previous studies of tree ring cycles have suggested normal solar cycles in some studies and abnormal solar cycles in others.
Hayakawa called for further investigation into the issue. “These investigations are extremely important. [tree rings] An independent, preferably observational, documented reconstruction is needed,” he said.
The new study Published in the Astrophysical Journal
