A solar halo seen over Mexico on May 21 has a lot of people making jokes about the phenomenon, with some suggesting it's a sign of UFOs from outer space. The phenomenon was witnessed by observers in and around several of the country's largest urban centers, including Mexico City.
Solar halos, also known as sun halos, are a fairly common occurrence, which result from the presence of large quantities of ice crystals in the atmosphere. These particles break white light up into its constituent colors – much as a prism does – while reflections of the light result in the halo shape that appears to encircle the sun.
"I have received some 30 phone calls from people who are scared and think that it's a bad omen, others think it means it will rain more than expected," said Juan Manuel Caballero, coordinator of the National Weather Service. "I've had to repeat several times: 'No, it doesn't hurt if you don't look at it directly.'"
People across large areas of Mexico trained their smartphones and cameras on the display and shared the images on social media outlets.
"The aliens have finally arrived! Prepare the sandwiches for the trip!" one commentator wrote in a Facebook post quoted by several media outlets.
In addition to the people preparing for an alien visit, other observers took their theories in the opposite direction, saying it could be man-made. More than one person suggested the phenomenon was part of a government conspiracy to blind voters ahead of an election scheduled for June 7.
"A sun halo days before elections. Coincidence? I don't believe it," one commenter wrote on Twitter.
In addition to sun halos, a similar phenomenon can often be seen at night, with light rings forming around the moon. The most common of these events is known as a 22-degree halo, for the angle at which the light is refracted from the sun or moon in order to produce the rings.
A popular myth holds that rings seen around the moon are a sign of storms to arrive in the near future — but meteorologists dismiss the notion. These events can be driven by thin cirrus or cirrostratus clouds in the atmosphere, which can sometimes be associated with storm fronts. However, they often occur without any consequent change in weather.
Corona, which resemble halos but are smaller and more colorful, are caused by water droplets in the sky.
Astronomers are reassuring the public that solar halos are a relatively common phenomenon that viewers miss most of the time because people just don't spend enough time gazing at the sky.
Photo: Javier Armas | Flickr
