The sight of a bright, colourful ring around the sun caused a stir throughout the country yesterday. The unusual sight, which was visible for several hours, had citizens pausing during their Saturday morning chores and shopping to gaze up at the sky. Several persons were seen taking photos. It even caused an online frenzy, with rapid fire exchanges of text messages and photos via mobiles, as well as postings of pictures and comments on popular networking sites. However, while the appearance of a ring around the sun is not a frequent occurrence, it is not uncommon. What was visible over Trinidad and Tobago yesterday was a halo, also known as a nimbus, icebow or gloriole. It is associated with clouds called cirrostratus which are composed of ice crystals and usually form at altitudes above 20,000 feet.
Dr Shirin Haque, senior lecturer and astronomer in the Department of Physics at the University of the West Indies (UWI), said the halo around the sun is perfectly normal and is due to the ice crystals suspended in the clouds. "The ice crystals act like tiny prisms, refracting the light from the sun and splitting it up into the rainbow colours due to dispersion. The conditions just happened to be right for there to be such a beautiful halo around the sun," she explained. "Halos around the sun do not happen too often but certainly are not an uncommon phenomena at all." She, however, warned: "Looking at the sun directly for any length of time, can cause permanent eye damage. Never attempt to look at a halo directly, or for a long period of time." A halo was last seen in this country in South Trinidad in July 2011. Sightings have been reported in recent days in places as far flung as Malaysia and California in the United States. In folklore, a halo around the sun or the moon means rain is coming. They have been recorded as far back as the beginning of the fourth century.