Parhelios are an atmospheric phenomenon caused by the Sun (therefore, they can also be considered a phenomenon of astronomical origin).
In the following image you can see what they may look like:
These are two small glows that form on both sides of the Sun when there is a certain type of cloud (cirrus clouds, those clouds that look like “filaments” or “cotton flakes”). These clouds contain ice crystals that act like small prisms that are, refracting the rays of the Sun, that is, diverting part of those rays to another place and thus forming the parhelios. These then look like a Sun behind the clouds , although less bright than the real Sun.
The two parhelios are not always seen; many times there are only cirrus clouds on one side of the Sun and only one is formed . Actually, as can be seen in the photo, the parhelios are only the most luminous points of an iridescent halo that surrounds the Sun (formed by the same cause as the parhelios), but the halo is rarely seen in its entirety.
They don’t always look the same. Sometimes the parhelios appear as a round luminous spot , like a less bright Sun; other times they appear more elongated vertically and / or decompose in the colors of the rainbow. Sometimes they look like small fragments of a rainbow (but they should not be confused with this, since the parhelion always appears next to the Sun, while the rainbow appears on the side of the sky opposite the Sun).
| Photos of parhelios made by members of our Association | ||
| Parhelio “right”. Taken at a Grouping outlet, near Reinosa, August 2004. | Parhelio “left” (to the left of the image). On the right the Sun. Taken by Javier García-Oliva in Fregeneda, April 2005. | |
When one learns of the existence of parhelios and begins to be aware of them, one realizes that they are seen more often than expected. They can be seen especially at sunset or in the morning , when the Sun is low over the horizon.
The parhelion appear exactly 22 ° from the Sun, due to the angle at which the light rays are refracted . To find this point in the sky, we can do the following: we place the arm fully extended forward and open the hand. When we cover the Sun with the tip of the thumb, the parhelion should be approximately where the tip of the little finger indicates ( as if we were measuring a “span” in the sky ). If cirrus clouds are present at this point, a sheath may form. (This, both to the left and to the right of the Sun).
The word parhelio comes from the Greek (para-helios) and can be interpreted as “similar to the Sun” .
On quite rare occasions a lunar parhelion occurs , which is formed similarly but at night and with the full Moon instead of the Sun. (Actually, a lunar parhelion should be called “paraselenium” … although, after all , the moonlight comes from the Sun). We recently saw one …
The phenomenon has been documented since ancient times . For example, in the first book of La República (De re publica) by Cicero , the characters engage in a dialogue of a philosophical and political nature. The dialogue must take place in the year 129 BC. At the beginning of it, one of the characters asks his companions what they think of the phenomenon that has been observed in Rome in those days , called “parhelion”, which they refer to as the phenomenon that allows to observe, with the naked eye, “two suns” (without a doubt, the true one and a parhelion)
