Stay informed with free updates
Just sign up to Science myFT Digest: delivered straight to your inbox.
Millions of people are expected to watch a total solar eclipse on Monday that will stretch across Central and North America, offering rare views of the star that supports life on Earth.
The alignment of the Moon and Sun began marking a dark trail starting off the Pacific coast of Mexico around 11:00 am local time. It is forecast to leave the continent 5,400 km northeast in Newfoundland, Canada, just after 5pm local time and head towards the Atlantic Ocean.
Total eclipses occur about once every 18 months, but this one is notable because it travels over the rotating Earth near many densely populated areas, at a time of high solar activity. The rolling shadow entered the United States in Texas and will pass over Oklahoma, Arkansas, Missouri, Illinois, Kentucky, Indiana, Ohio, Pennsylvania, New York, Vermont, New Hampshire and Maine, according to NASA, the American space agency.
“Part of the reason for the excitement is that it is spreading over a populated area,” said Robert Massey, deputy executive director of the Royal Astronomical Society of the United Kingdom, who worked as a tour guide in Iran during the 1999 total eclipse which overwhelmed Europe. . “Eclipses have become much more public events because there is public transportation and it is easier for people to travel long distances to see them.”
Eclipses occur when the Moon appears to viewers on Earth directly in front of the Sun, blocking its light. The full effect is localized in a so-called “path of totality,” which this time is less than 200 km wide.
The event will give observers the primordial experience of daytime darkness, and NASA says the effect will last up to four minutes and 28 seconds in Torreón, northern Mexico.
It should offer spectacular views of the Sun’s normally invisible outer atmosphere, including the reddish ring known as the chromosphere and the bright envelope called the corona.
The sun is near the peak of its 11-year cycle of changing magnetic activity, which has led to an increase in disturbances such as solar flares and sunspots.
Eclipse viewers could be treated to the sight of prominences – huge rings of plasma comprising charged hydrogen and helium – exploding outward from the sun’s surface.
“There will be a lot of activity to see,” Massey said. “The corona will take on a radial appearance – and there is more chance of seeing these eruptions at the edge of the sun.”
It is not safe to look at the sun without special protective glasses for the eclipse, except during the brief total phase, NASA warns.
This eclipse, like its modern predecessors, fueled merchandising opportunities ranging from T-shirts to mugs featuring the Simon & Garfunkel phrase “Hello darkness, my old friend.”
There won’t be another total solar eclipse over the United States for more than 20 years — and it’s predicted that one day the phenomenon will no longer be visible anywhere on Earth. The Moon is slowly moving away from the planet and one day it will no longer be able to completely cover the light of the solar sphere.
That moment, however, is still far away: scientists predict that it won’t happen for hundreds of millions of years.