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(CNN) — If you want to see the epic total solar eclipse that will cross the skies of North America on Monday, you should try to travel as close as possible to the center of the celestial spectacle’s path.
New cartographic calculations have raised some concern that the path of totality (where it is possible to see the moon completely blocking the sun) is slightly narrower than NASA calculated. This means some roadside towns that were expecting to experience a second or two of total darkness could be left out.
NASA has not changed its predictions, but the space agency warns that there is some uncertainty when it comes to plotting the path of the eclipse.
“Calculations using a slightly larger radius for the size of the Sun yield an eclipse path that is slightly narrower,” NASA spokesperson Karen Fox said in an emailed statement. “This difference would only affect cities at the very edge of the path of totality, where general predictions are difficult anyway; a few city blocks one way or another could mean 20, 10, or 0 seconds of the totality”.
In any case, NASA scientists and other experts recommend spectators head to the center of the trajectory, rather than the perimeter.
“I would never go near the edge of totality, because it’s the difference between day and night,” says Edward Guinan, professor of astronomy and astrophysics at Villanova University.
Cartography of the moment
The latest questions about the possible change in trajectory have focused on a new map calculated by software developer John Irwin, of Guildford, England, and published on a website called Besselian Elements.
The research has not been thoroughly reviewed by scientists, Guinan said. And even if NASA’s map is wrong, Irwin’s calculations indicate that it only differs by a couple thousand meters at the edges.
A woman looks at a map showing the path of the eclipse during the Solar Eclipse Festival at the California Science Center in Los Angeles, California, on August 19, 2017, two days before the total eclipse on August 21. Credit: Frederic J. Brown/AFP/Getty Images
Irwin did not immediately respond to an email request for comment on Friday.
But few things in science are certain. And NASA also acknowledges that exact measurements of the eclipse’s path are difficult to pin down.
“The accurate prediction of the eclipse has brought new attention to a small but real uncertainty about the size of the Sun,” the NASA statement says. “Uncertainty in Earth’s rotation can also affect eclipse predictions at this level.”
Guinan explained that it is extremely difficult to determine an exact measurement of the size of the Sun because “it is a fuzzy surface.”
He noted that the Sun might be slightly enlarged right now because our star is going through a period of maximum magnetic activity, which “could cause the Sun to swell a little.”
But the uncertainty is only a few hundred meters, while the Moon is millions of kilometers in diameter.
Still, even slight adjustments to the Sun’s size could gently alter the edges of the Moon’s shadow on Monday.
Edge effects
The Besselian Elements website states that the alternative map of the Irwin eclipse should be consulted if one expects to travel to the edge of the path, where the duration of total darkness may be very brief, but observers may have a prolonged view of other phenomena related to the eclipse.
Guinan notes that eclipses offer “edge effects.”
“You wouldn’t see the total eclipse, but you would see this diamond ring effect: flashes of the Sun entering and leaving behind the mountains and crossing the valleys of the Moon,” he explains. “It would be a really cool thing if you’ve seen a lot of eclipses.”
The solar eclipse creates the effect of a diamond ring during the 2017 solar eclipse, as seen from Clingmans Dome, which at 2,025 meters is the highest point in the Great Smoky Mountains National Park in Tennessee. Credit: Jonathan Ernst/
“But I don’t recommend people do this,” he said.
NASA also said in its statement: “Traveling toward the center of the path of totality, even a mile or two, will quickly increase the length of totality that people can see.”
And the totality is the real spectacle, Guinan stressed.
This phase of the eclipse will plunge the area into darkness. The temperature will drop. The animals will behave as if it were night. You can see the solar corona, that is, its fiery outer atmosphere. Stars and planets will shine in the surrounding sky.
“When you see the total eclipse, you can’t go back,” Guinan says. “It is spectacular”.
