This Friday large parts of the globe will go darker for a couple of hours, as a result of an eclipse of the Sun.
RTÉ's Science and Technology Correspondent Will Goodbody previews the event
WHAT IS A SOLAR ECLIPSE?
An eclipse is defined as the temporary obscuring of one body by another, or its shadow.
A solar eclipse, like we’ll see on Friday, is caused by the moon passing between Earth and the Sun, causing a shadow to fall on the Earth’s surface in certain places.
Areas on the margins of the shadow experience a partial eclipse. While along a narrower strip of the Earth, the moon completely obscures the Sun, causing a total eclipse.
SO WHAT WILL WE EXPERIENCE IN IRELAND?
Because Ireland will be in a zone where the Sun is almost entirely but not totally obscured by the moon, it will only experience a partial eclipse.
However, at least 90% of the Sun will be covered by the moon, meaning it will still be quite the spectacle.
An area off the west coast of Ireland, running north through the middle of the Atlantic, over the Faro Islands and up over the Arctic will experience the full solar eclipse.
SO WHERE ARE THE BEST PLACES TO WATCH IT?
Ireland and Scotland are the best places in these islands to see the eclipse, with Mayo and Donegal getting the best view of the eclipse in the Republic of Ireland (weather permitting).
It will reach 95.5% in northwest Donegal, and almost 95% in Derry.
All of Ulster will see at least 93% eclipse, and nowhere in Ireland will experience less than 91%.
HOW LONG WILL IT LAST?
The exact timing of the eclipse will vary slightly depending on where in Ireland you are watching it from.But in Dublin the phenomenon starts at 8:24am, and runs until 10:36am.
The peak of the eclipse will be reached at 9:28am (9:22am in southwest Kerry or 9:31am in the northeast). So in effect there is a two hour window during which a partial eclipse will be visible here – weather permitting.
WHAT WILL WE SEE?
Of course, everything is weather dependent. If it is cloudy, it won’t be possible to see the eclipse although its effect will be felt as it will get a little duller or darker as the process unfolds. It will also feel colder.
If the weather is good, it will be possible to see the distinct outline of the moon pass slowly from right to left over the edge and across the shape of the Sun, eventually almost completely covering it, before it slowly moves off it again.
HOW CAN WE SEE IT?
YOU MUST NEVER LOOK DIRECTLY AT THE SUN EITHER WITH THE NAKED EYE OR WITH DEVICES LIKE TELESCOPES OR BINOCULARS – as it can severely damage your eyes, even leading to blindness. Luckily, there are a number of safe options.
First, you might be able to get your hands on a pair of (CE approved) special eclipse viewers, which have filters on them that protect your eyes from the harmful effects of the Sun.
You could also make yourself a simple pinhole projector. You can do this by getting a piece of card or stiff paper, punching a hole in it, and then holding it in front of a second piece of paper.
The image of the Sun will be projected through the hole onto the second piece of paper, and as the eclipse takes place you will be able to watch it without damaging your eyes.
Alternatively, you can go to one of the many viewing events being run by astronomy club and other organisations around the country to watch the eclipse.
At many of these experienced astronomers will be on hand with specially adapted telescopes through which it will be possible to view the eclipse safely.
There will also be some livestreams available online through which you can watch the event.
HOW UNUSUAL IS THIS?
Eclipses happen once or twice every year around the world, but are often only visible in very inaccessible remote places.
The last time one was visible from Ireland was in 1999 and it will be 2026 before another partial one is seen here again. While it will be 2090 before a total solar eclipse is next visible from this part of the world.
They are unusual though as the plane of the moon’s orbit is tilted relative to the Earth’s, and so most of the time the moon appears above or below the Sun. When an eclipse happens the moon crosses a lunar node – one of two places where the orbits cross each other.
WHAT CAN WE LEARN FROM ECLIPSES?
Eclipses have been a source of fascination for astronomers, physicists and other scientists for millennia. Indeed in modern times, their study has led to the development and proof of important theories, like Einstein’s theory of general relativity.
On this occasion, astronomers here will be particularly keen to use the event to highlight this fascinating area of scientific study.
But astrophysicists from Trinity College Dublin and other foreign institutions will also travel with an Air Corps maritime patrol aircraft out into the Atlantic Ocean to an area where a total eclipse will be visible, in order to study and take scientific images of the event. In particular they will be interested in viewing the corona – the outer atmosphere of the Sun.
It is a swirling mass of gas extending into space, which can have a damaging impact on things like communication systems and power grids on Earth when it is particularly active.
Scientists will use the occasion to try to understand better why the corona is considerably hotter than the surface of the Sun.
IF THE WEATHER IS BAD HERE, WHERE WILL IT BE BEST TO WATCH THE ECLIPSE?
The Norwegian Arctic islands of Svalbard are one location. But the residents are discouraging last-minute visitors, saying its hotels are full, it will be freezing cold and polar bears are on the prowl!
More than 1500 visitors are due to join the 2,500 residents of the archipelago for the event, pushing the capacity of the town to its maximum safe limit. It’s reported, however, that there are a few beds left in the Faroe Islands, including in private homes, if you can get there!
SOLAR ECLIPSE ORGANISED VIEWING EVENTS:
Trinity College Dublin – Front Square – 8am-10.30am
Blackrock Castle Observatory Cork – 8.30am-10.30am
Astronomy Ireland headquarters Blanchardstown, Dublin – 8am-11am
Queens Belfast, outside Whitla Hall – 8.15am-10.45am
Galway Astronomy Club, Toft Park, Salthill – 7.30am-10.30am
Dunsink Observatory, Castleknock - 8.30am - 10.30am
Scopes and Space at the Papal Cross, Phoenix Park, Dublin - from 8am
St Cronan's Stargazers at St Cronan's National School Bray Co Wicklow
Midlands Astronomy Club at Athlone Castle Co Westmeath
Shannonside Astronomy Club at The Stone Circle Grange Co Limerick
DEISE Astronomy Club at Dungarvan Square Co Waterford