Today, the path of a total solar eclipse will move across continental USA, an event predicted to be the most photographed of all time. The eclipse occurs as the moon passes between the Sun and the Earth, casting a 70-mile wide shadow and moving across the Earth’s surface at an average speed of 1,651 mph. It will take the shadow a total of 90 minutes to travel across from Oregon to South Carolina, moving over an area home to 12.5 million people. Outside this path of totality, the entirety of North America will still witness an impressive partial solar eclipse; resulting in the most widely viewed solar eclipse since the invention of smart phones. It is this fact that has led experts to predict today’s eclipse to be the most photographed event of all time, dependent on the weather.
Unfortunately, the eclipse will barely be visible from the UK, with the moon’s edge blocking just a small fraction of the sun’s surface. The eclipse will first become visible at around 19:40 BST, before peaking between 19:55 and 20:10, dependent on the location and the weather. To see whether skies will be clear in your area, check our forecast pages or use our app. In most places across the UK, the sun will set before the end of the eclipse, making the sun difficult to see as it sits only a small distance above the horizon. It is important never to look at the sun with the naked eye; methods of producing a homemade pinhole camera are available online.
Past and present, solar eclipses have led to some very important scientific discoveries, including the discovery of helium to the confirmation of Einstein’s theory of general relativity. A new video on the Met Office’s Learn about Weather YouTube feed explores a few of the most significant solar eclipse events.
Despite observing eclipses for thousands of years, there is still a lot to learn from them. During today’s eclipse, NASA will study the reaction of the ionosphere to the sudden drop in solar radiation and temperature. The ionosphere is a thin layer of the Earth’s atmosphere, ionised by radiation from the sun. Additional observations will explore features of the sun’s corona, photographed for the first time during a solar eclipse 166 years ago. Monitoring the sun’s corona is an important aspect of space weather, because it is the source of coronal mass ejections. Ground-based and satellite imagery now replicate the effect of a solar eclipse using an instrument called a coronagraph, enabling the Met Office Space Weather Operations Centre to monitor the sun’s corona 24/7.
A coronal mass ejection (CME) is the large release of material from the sun’s surface. These events are not visible to the naked eye, except in the rare case of a total solar eclipse. In the year 1860, astronomer G. Tempel sketched what he saw during eclipse totality, drawing what we know today to be a coronal mass ejection.
Currently, a large magnetically complex sunspot region AR2671 can be seen in the centre of the sun’s visible disk. Therefore, there is a chance that a coronal mass ejection could occur. Be sure to check our space weather forecast and follow us on Twitter for further space weather updates.
Total solar eclipses happen somewhere in the world at an average rate of once every three years, but unfortunately you’ll have to wait a while to see one from the UK. The UK’s next near-total eclipse will take place in 2026 (96%), but a total eclipse will not be visible in the UK until 2090.
NASA will be live-streaming the event this evening from 17:00 BST at www.nasa.gov/eclipselive
For more information on the eclipse and its significance to space weather, follow @MetOfficeSpace on Twitter.