A solar eclipse takes place when the moon passes in front of the sun during daylight hours. The shadow of the moon blocks the sun’s light either partially (a partial solar eclipse) or completely (a total solar eclipse).
A solar eclipse isn’t a particularly rare phenomenon; in fact, around the world each year there can be as many as five solar eclipses. So what makes the total solar eclipse of 2017 so special?
Let’s find out by looking at total eclipses around the world and what to expect in 2017 when a truly historic total eclipse happens right above our heads.
A Little Light
While the total solar eclipse occurs when the moon moves completely in front of the sun blocking the light of the sun from hitting the surface of the earth, there is a little light which escapes, giving the appearance of a “halo” or corona around the moon itself which makes for a vivid, memorable image.
What’s Special about the Solar Eclipse in 2017?
Great question. The solar eclipse of 2017 will be the first time in 99 years that there has been a solar eclipse visible from the United States from one coast to the other. And the last time a total solar eclipse was visible over North America was 40 years ago. It will take roughly 3 minutes for the path of the eclipse to pass over the whole country.
But Don’t Look
It’s important to remember that you should never, ever look directly at the sun – especially during a total solar eclipse. Doing so can lead to permanent eye damage or even blindness. The best way to observe a solar eclipse is using a pinhole camera which projects the image of the eclipse without any of the dangerous rays of light hitting the eye. You can also purchase special viewing goggles to protect your eyes.
Watch out for “Baily’s Beads”
When there is a total eclipse of the sun, there are often little bead-like dimples of light seen around the corona. These are caused by the fact that the moon isn’t a perfect sphere and there are both mountains and valleys which can allow more (or less) light to pass through. They were named after Francis Baily who was the person to explain their existence in 1836.
Solar Eclipses weren’t always seen on Earth
For a solar eclipse to be visible from earth, the sun, the moon and the earth must line up in a fairly precise arrangement in 3-D space. For a long period of the earth’s history, the moon wasn’t aligned with the earth to make a solar eclipse visible but the lunar orbit changes at a rate of about 2 cm every year and now you can see solar eclipses. In about 600 million years, the moon’s orbit will have changed enough that the eclipse will no longer be visible from the earth.
Annular Solar Eclipses
A total solar eclipse is one where the moon passes directly in front of the sun blocking nearly all the light from the sun. However, there are times when the moon’s orbit makes the shape of the moon too small to cover the sun’s surface area (from our perspective) and this is known as an “annular” eclipse. It looks like a bright ring of sunlight surrounding the moon.
The Date for the 2017 Total Eclipse
The solar eclipse in 2017 will take place on the 21st of August. If you’re planning to take some time off to see it – book your vacation early; it’s expected to be the most popular day of the year for Americans to request some time off in 2017.
How often will there be a Solar Eclipse?
While you’ll find that there’s a solar eclipse somewhere in the world every 5-6 years, a total eclipse of the sun is somewhat rarer. Total eclipses occur roughly every 1-2 years and are thus quite exciting phenomena to witness because of their relative scarcity in the world.
How Long does a Total Eclipse Last?
A total eclipse can, depending on the exact positions of the sun, moon, and earth, last for a couple of minutes up to a maximum of about 7 and a half minutes. That means if you want to observe an eclipse, you’ll need to be prepared and outside waiting to do so.
The Path of a Solar Eclipse
While the sight of a solar eclipse is incredibly dramatic, the path of the solar eclipse is quite restrained – the width is often only 100 miles across on the earth’s surface but the length of the sweep of an eclipse (again on the surface of the earth) can be up to 10,000 miles.
Watching a Solar Eclipse
If you’re going to watch a solar eclipse directly, you should use special glasses which prevent damage to the eyes. They’re not expensive (a few bucks) and they should have either #14 Welder’s Glass or optical Mylar as the material for the lenses. Always make sure that you have the right material for the lenses before staring at the sun.
Don’t Forget to Look Around During a Solar Eclipse
Make sure that you take a little time to NOT look at the solar eclipse when it happens too. If you turn away from the sun, you’ll find that the whole world appears to be experiencing a sunset all at the same time from every direction. It’s quite beautiful.
What’s the Path of the Eclipse in 2017?
The total eclipse will only be visible on a narrow path across the United States (though from quite a bit more of the U.S.A. you will be able to witness what appears to be a partial eclipse). The path begins near Salem in Oregon (at about 10:15 a.m.) and finishes near Charleston in South Carolina.
You will Never See a Total Solar Eclipse at the Poles
Viewing a solar eclipse requires an alignment of the earth, the moon and the sun. The poles are currently in a position where the alignment for a total solar eclipse is impossible to achieve; so you can only ever expect to witness a partial eclipse at the North or South Pole.
The Eclipse Pattern – The Saros Cycle
Most, but not all, eclipses have an identical repeat eclipse roughly 18 years and 11 days after the first eclipse. This periodicity of solar eclipses is known as the Saros Cycle – it also applies to lunar eclipses. The precise calculations used to arrive at these figures are very complicated though their accuracy is easy to observe.
Solar eclipses aren’t the only unusual astronomical phenomena; there are many others. For example, you can find (using a very big telescope) “ultra-diffuse” galaxies; which contain just 1% as many stars as an ordinary galaxy. Nobody knows why these galaxies exist though some believe they’re bits that fell off of other galaxies.
You’re not likely to see suicidal comets yourself, but they can be found using the Hubble Space Telescope – these are comets which are destroyed simply by the rays of the sun. The radiation from the sun causes the comet to spin and eventually it spins so fast that it pulls itself apart.
Triple Eclipses on Jupiter
If you were lucky enough to be able to see an eclipse from the surface of Jupiter (which has a lot of moons) occasionally you’d find that three of the moons (Io, Europa and Callisto) lined up to block the view of the sun as they did in January 2015.
Antennae galaxies are full of gas and from that gas we expect stars to be born. Millions and millions of stars. It’s like looking at a hatchery designed to bring forth burning balls of gas. These galaxies only exist in this state for about 1 million years before they have created all the stars that they can create.
Meteor Strikes on the Moon
The moon has no atmosphere for meteors to burn up in (unlike the earth) and as such it is regularly pelted by space debris. The phenomenon has been observed about 100 times by NASA since 2005. They have the same impact as about 100lbs of TNT which makes them rather explosive to watch.