• Anthelion: What is this optical phenomenon in the sky?

    The optical phenomenon of anthelion

Have you ever been in an aeroplane and seen a kind of glowing halo as you drifted through a fine cloud of tiny water droplets? Today we’re going to find out what it is: known as the anthelion or glory.

Stay tuned for an exploration of one of the most amazing optical phenomena.

What exactly is an anthelion?

Derived from the Greek word meaning “opposite the sun”, an anthelion is an atmospheric optical and rare occurrence. It appears as a luminous halo visible under certain atmospheric conditions, mainly around or close to the sun.

This natural spectacle appears as a circle of light or a circular rainbow surrounding the sun at a certain angular distance.

How does it happen? It happens when the sun’s rays interact with ice crystals in high clouds, such as cirrus clouds.

These crystals act as prisms, refracting and reflecting sunlight in a process that disperses the different colours of the spectrum. Each colour is refracted at a slightly different angle, creating the mesmerising rainbow effect.

The discovery of the anthelion

Back in 1947, Hendrik Christoffel van de Hulst was researching the aviator’s halo and theorised that it could be caused by surface waves. So how do these rings form?

Van de Hulst suggested that one explanation might be the deflection of light rays by surface waves on water droplets. But this remains a hypothesis. The exact process behind these auroras is still unknown.

Anthelion, an optical phenomenon based on a solar halo

The anthelion effect in aviation

In aviation, the anthelion is of great importance for several reasons. For pilots, it’s more than just a beautiful display; it’s an indicator of atmospheric conditions during flight, particularly the presence of ice crystals in high clouds, which is crucial for route planning and flight safety.

And, as you might imagine, by helping to predict the weather, it also signals areas of turbulence or changes in flight conditions. In case that you don’t know what is turbulence, here you have the explanation.

Surprisingly, yes, the aviator’s halos ensure a safe and enjoyable flight.

  • Anthelion, an optical phenomenon

Anthelion: A visual spectacle and more

The anthelion, or aviator’s halo, is more than just an optical effect; as you’ve seen, it serves a significant purpose in aviation.

Phenomena such as halos have gradually helped to make aviation a well-rounded sector, where even a small halo can reveal a great deal about the sky and enhance flight safety.

If you’d like to learn more about weather facts such as cloud formation and other aspects of aviation, our aviation blog is the place to be.

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