Science Behind Halos around the Sun and Moon

What is a halo?

Halo is the optical phenomena created by light from the Moon or Sun interacting with ice crystals suspended in the atmosphere. Halos can have many patterns, varying from colored or white rings to arcs and spots in the air. Many of these surface near the Moon or Sun, but others happen elsewhere or even in the other part of the sky.

What are the different types of Halos?

There are different types of halos that typically depend upon the kind of light available and the number of ice in the air.

Different kinds of Halos, and the science behind them

22-degree halo or the Circular Halo: Among the most common halos is the 22° halo, which resembles a big ring around the Moon or Sun with a radius of about 22°. The ice crystals that create the 22° halo are faced semi-randomly in the atmosphere, in opposition to the horizontal orientation required for other halos, which we will explore next. As a result of the properties of the ice crystals associated, no light is returned towards the center of the ring, leaving the sky darker than the atmosphere around it, and giving it the hypothesis of a “hole in the sky.” The 22° halo is not mixed with the corona, which is a strange optical phenomenon caused by water droplets rather than ice crystals, and which has the form of a multicolored wheel rather than a ring.

Bottlinger’s ring: A rare halo formation in the sky, Bottlinger’s ring is elliptical rather than circular. It has a small radius, making it very challenging to observe in the Sun’s glare and more likely to be detected around the fainter Sun, often seen from hilltops or planes. Bottlinger’s rings are not well explained yet. It is proposed that they are formed by very flat pyramidal ice crystals with appearances at remarkably low angles, hung horizontally in the atmosphere. These specific and problematic conditions would reveal why the halo is very rare.

Light pillar Halos: They are strange and beautiful. A light pillar resembles an upright pillar or column of light emanating from the Sun near sunrise or sunset, though it can develop below the Sun, mainly if the observer is at a high altitude. Hexagonal plate- and column-shaped ice crystals cause the wonder. Plate crystals usually cause pillars only when the Sun is within 6 degrees of the horizon; column crystals can create a pillar when the Sun is as high as 20 degrees above the horizon. The crystals tend to orient themselves near-horizontally as they float or fall through the air, and the breadth and clarity of a sun pillar depend on crystal arrangement.

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