My latest piece for the Jakarta Globe includes 10 things you need to know about total eclipses :)
“The best seat in the solar system”: 10 things you need to know for the March 9 eclipse
Graham Jones | Jakarta Globe | 22 February 2016
A total eclipse is a truly global event. At sunrise on March 9, the darkest part of the moon’s shadow (the ‘umbra’) will strike the earth and trace a ‘path of totality’ that stretches a third of the way around the planet, from the Indian Ocean to the North Pacific.
At the same time, a total eclipse is a truly local event. The path of totality on March 9 will be, at most, a mere 155 kilometres across. And, as if often the case, the umbra seems to be almost deliberately avoiding people: the central line of the eclipse will come within a tantalizing 390 kilometres of Jakarta – but no closer than that.
Five cities that ARE on the path of totality are Palembang, Palangkaraya, Balikpapan, Palu and Ternate. They will have what physicist Brian Cox calls “the best seat in the solar system”. There are about 180 moons in the solar system, “but none of them produce such perfect eclipses as the earth’s moon.”
Here are our ’10 things you need to know’ for anyone hoping to experience totality on the morning of March 9.
1. Location, location, location
Check the eclipse times and duration of totality with NASA’s interactive Google Map. To see totality, you must be somewhere between the two blue lines (which show the northern and southern path limits). Also, the closer you are to the red line (the central line), the longer totality will be.
NEVER observe the partial phase of an eclipse with the naked eye. Even if the sun is 99 percent covered by the moon, the remaining crescent is extremely bright and can cause permanent damage to the eye. The ONLY time it is safe to view an eclipse with the naked eye is during the few short minutes or seconds of totality.
3. Pinhole projectors and solar filters
There are two main ways to safely observe the partial phase of an eclipse. The first is by projection, which can be done very simply with two pieces of card: make a small hole in one card, and use it to project an upside-down image of the sun onto the other. NEVER look at the sun directly through the hole. The second way is to use a specially designed solar filter, such as eclipse glasses or an eclipse viewer. Even when using solar filters, however, NEVER stare at the sun for long periods. NEVER use normal sunglasses, film or smoked glass, and NEVER use solar filters with binoculars or telescopes (unless it is a specialist telescope filter, and is placed on the front, sun-facing end of the instrument).
4. The build-up
Watch the moon waning in the fortnight before the eclipse. It makes a beautiful countdown clock, since a solar eclipse can only occur at new moon, when the moon passes between the earth and the sun. (Why don’t eclipses happen at EVERY new moon? The moon’s orbit around the earth is very slightly tilted to the earth’s orbit around the sun – normally, therefore, the moon passes just above or just below the sun’s position in the sky.)
5. First contact and the partial eclipse phase
‘First contact’ is the moment when the moon takes its first bite out of the sun. It always comes right on schedule, a thrilling demonstration of celestial mechanics, which the science writer Timothy Ferris describes as “a Bach fugue in the sky”. During the partial eclipse phase, look out for natural pinhole projectors: small gaps between the leaves on trees, for example, can project images of the crescent sun onto the ground.
6. The approach of the umbra
About fifteen minutes before totality, observe the changes in light level and temperature, and their effect on the environment around you. About five minutes before totality, notice the moon’s shadow appearing on the western horizon. About one minute before totality, see if you can observe any ‘shadow bands’ – ripples of light on the ground and walls, which are created by the earth’s atmosphere refracting the light from the thin crescent sun.
7. The final seconds
About ten seconds before totality, the solar corona (the outer atmosphere of the sun) becomes visible; seen together with the final jewel of light from the sun, this creates a ‘diamond ring effect’. About five seconds before totality, the final rays of sun can be seen flickering through valleys on the moon, an effect known as ‘Baily’s Beads’.
ONLY now – AFTER Baily’s Beads have completely disappeared – is it safe to view the eclipse with the naked eye. (It is also safe to observe totality through cameras, telescopes or binoculars without any special filters.) However, naked eye observations MUST finish BEFORE Baily’s Beads reappear at the end of totality. Use the interactive Google map to make sure you know how long totality will last at your location.
9. The solar corona
The solar corona, which only becomes visible during a total eclipse, is a luminous plasma of charged particles surrounding the sun. It is about as bright as a full moon, and it is one of the most beautiful sites in the solar system. The late astronomer Frank Orrall told a story about how, when reviewing his observation notes for an eclipse in 1966, he discovered he had written, “the heavens declare the glory of God.” He reflected that his notebooks “normally do not say such things.”
10. The end of totality
Totality ends with the reappearance of Baily’s Beads and the diamond ring effect. The solar corona fades from view and daylight returns. The umbra disappears over the eastern horizon, continuing its dash around the globe at thousands of kilometres per hour. After March 9, the umbra will not strike the earth again for another 18 months…
Graham Jones runs a Global Communication and Science programme that uses solar eclipses as ‘teachable moments’ to connect students in different countries. The programme is sponsored by Garuda Indonesia.