This one’s for the folks down under. And, interestingly, the path of this eclipse crosses the path of the total eclipse that swept across Australia in November 2012, giving some lucky communities the rare chance to experience a solar eclipse two years in a row. The eclipse begins in Australia on the morning of May 10, local time, but in many parts of the world it will still be May 9.

What's an Annular Eclipse?

An annular eclipse occurs when the moon blocks out the center of the sun, leaving a glowing ring called an annulus around the moon’s dark silhouette. This is often called the “ring of fire.” It’s a lovely sight and well worth seeing, although it doesn’t compare to the wonder of a total eclipse.

We experience both total and annular eclipses because the distance between the earth and the moon varies. When the moon is close to the earth, it appears as large as the sun and we see a total solar eclipse. When it’s further away, it appears smaller than the sun and we see an annular eclipse.

The moon casts a complex shadow during an eclipse. If the umbral shadow touches the earth, there’s a total solar eclipse. But sometimes, as shown in the diagram, the umbral shadow doesn’t quite reach us. Instead, an antumbral shadow falls on the earth, creating an annular eclipse. Areas within the much larger penumbral shadow experience a partial eclipse.

The Path of Annularity

The path of annularity—the area from which the complete ring of the sun is visible—will begin in Western Australia, where the eclipse will be in progress as the sun rises. The moon’s shadow will travel northeast across the Northern Territory, where Tennant Creek will see an annular phase of just over three minutes. Then it will reach the west coast of Cape York, a peninsula at the northernmost part of Queensland, where it will intersect the 2012 eclipse path. It will leave Australia after crossing Cape York.

The antumbral shadow will subsequently make landfall in eastern Papua New Guinea, the Solomon Islands, and the Gilbert Islands (part of the Republic of Kiribati). Tarawa atoll, the most populous of the Gilberts, will experience an annular phase of six minutes. After that, the shadow will essentially fall on open ocean until it ends its journey of more than 8,000 miles (13,00 km).

The red area on the map shows the path of annularity. The blue and green lines indicate areas that will see a partial eclipse, and the pink shows areas that will see only a part of the eclipse because the sun is rising or setting.

Image credit: Fred Espenak, NASA/GSFC.

Weather Prospects

According to Jay Anderson’s Eclipser website, the area around Tennant Creek in the Northern Territory may be the best place to see the eclipse under cloud-free skies, but Australia in general has good weather prospects. Once the eclipse path leaves Australia, however, the weather is likely to be mostly cloudy.

Links

• The UK Hydrographic Office’s’s Annular Eclipse of the Sun: 2013 May 09-10 site has local circumstances and animations for 105 locations.

• Jay Anderson’s website Eclipser provides detailed maps, climate information, and weather predictions for eclipse chasers.

• The NASA Eclipse Web Site has an abundance of information about solar eclipses, lunar eclipses, and transits.