Astronomers have used observations by a 17th-century German mathematician to determine the state of the solar cycle in 1607, which could help solve the mystery of the Sun’s period of minimum activity.
An international team of scientists has deciphered 400-year-old astronomical drawings, helping to unravel the mystery of solar activity at the time. The researchers used observations by German mathematician Johannes Kepler, made in 1607, to determine the state of the Sun’s 11-year cycle.
Johannes Kepler, born in 1571, is best known for his laws of planetary motion. However, his contributions to astronomy go far beyond that. Kepler also made careful observations of the Sun, using a primitive but effective method.
Johannes Kepler in 1610
Kepler used the Sun to observe the Sun. camera obscura. This is a simple device consisting of a small hole in the wall through which sunlight passes and falls on a sheet of paper. In this way, the scientist could safely study the image of the Sun and sketch its features.
The dark spots that Kepler detected on the Sun’s surface are actually temporary phenomena in the photosphere, the visible layer of the Sun’s atmosphere. These areas appear darker because they are cooler than the surrounding areas — about 3,800 K (3,500 °C) versus 6,000 K (5,700 °C). The spots are caused by the complex interactions between the Sun’s magnetic field and its plasma as the star rotates.
Image of a sunspot from the GREGOR telescope
A team of researchers led by Hisashi Hayakawa from Nagoya University (Japan) applied modern methods of analyzing Kepler’s images. The scientists used Spörer’s law, which describes the change in latitudes of the formation of active regions of the Sun during the solar cycle. The results showed that Kepler’s observations occurred at the end of the solar cycle, which preceded a period of significant reduction in solar activity.
The data obtained may help astronomers better understand long periods of minimal solar activity, in particular the so-called Maunder Minimum (1645-1715). This mysterious stage in the history of the Sun still raises many questions among specialists. The new information brings scientists closer to unraveling the causes of long-term changes in the behavior of our star and their impact on the Earth’s climate.
Let us recall that archaeologists discovered traces of tungsten in the laboratory of the Danish astronomer Tycho Brahe, although this element was officially discovered only in the 18th century.
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Source: Sciencealert, Universetoday
