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Observing Sun, the Sun is the only star whose shape can be simply appreciated the view, thanks to its average apparent angular diameter of 32 ’03 “arc, which varies, however, depending on where the Earth is in its orbit: it reaches the maximum value (32 ’35 “) when our planet is at perihelion, while the minimum value (31′ 31”) at aphelion. Such apparent dimensions allow, subject to the use of special equipment and appropriate protections, to observe the details of the surface of our star in order to detect and study the phenomena that characterize it.

Observing Sun, the Sun is the only star. Astronomy.

Such apparent dimensions allow, subject to the use of special equipment and appropriate protections, to observe the details of the surface of our star in order to detect and study the phenomena that characterize it. To the naked eye, you can distinguish the solar disc at sunset or in the presence of fog and clouds, when the light intensity is much lower. These observations allow, albeit in rare circumstances, to observe the particularly large Sunspot.

Then, using a small telescope, equipped with a suitable filter or used to project the image of the star on a white screen, you can easily observe sunspots and Flares.

However, because of the risks to which they may be the eye’s retina, the observation of the sun without the proper protection is harmful to the eye: in fact, the strong radiation can result in death of the cells of the retina, deputies to the vision, or degeneration of some ocular structures, such as crystal. The combination of size and distance from Earth of the Sun and the Moon is such that the two stars appear in the sky with the same apparent diameter or less; this situation is at the origin of periodic occultation of the star by our only natural satellite, which are called solar eclipses; total eclipse, in particular, allow you to view the solar corona and prominences.

Another point to make its apparent motion in the sky. Such motion during the day is used in the scan of hours, with the help of tools provided as sundials. In addition, the star seems to accomplish in one year, a journey of the zodiacal band that varies from day to day. The trajectory of the Sun, measured by determining its location at the same time each day throughout the year, is called the analemma and has a shape similar to the number 8, aligned on a north-south axis. The change in annual solar declination in the north-south direction is about 47 °; There is also a small change in an east-west caused by the different orbital speeds of the Earth, which, in compliance with the laws of Kepler, is maximum at perihelion and aphelion minimum.

Observing Sun, the Sun is the only star. Astronomy.

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Observing Sun, the Sun is the only star. Astronomy.