Even though dark places like Sark are becoming more and more rare, when fewer and fewer people seem to take some time to look up at the stars, human beings have always been fascinated by the sky, using it to navigate, measure time or just enjoy the view.

And when it comes to enjoying the view, the sky sometimes becomes an extraordinary source of amazement. Out of all the wonderful displays the sky has to offer, I decided to draw up a list of the five most beautiful astronomical events, visible to the naked eye.

Total Lunar Eclipse

When the Moon passes behind the Earth, the Sun’s rays cannot strike the Moon (they are perfectly aligned); our satellite’s color completely changes. The change is really amazing, as if the Moon was glowing with a blood red color. The eclipses usually last a few hours and are visible from anywhere on the night side of the Earth.

The next total lunar eclipse will occur on June 15, 2011. It will be visible completely over Africa, and Central Asia, visible rising over South America, western Africa, and Europe, and setting over eastern Asia. In western Asia, Australia and the Philippines, the lunar eclipse will be visible just before sunrise.

© Martin Pugh

Meteor shower

Meteor showers are pretty common: a number of meteors are observed to radiate from one point in the sky. They are caused by streams of cosmic debris, called meteoroids, entering the Earth’s atmosphere at extremely high speeds on parallel trajectories. There are many notable meteor showers, among others the Perseids (the most visible) and the Leonids (the most spectacular).

The Perseids are active between July and August, with a peak around August 12, during which you can observe 60 meteors or more per hour.

The Leonids are active in November, with a peak changing every year. Approximately every 33 years, Leonids produce a “meteor storm”, with more than 1,000 meteors per hour (they actually gave birth to the term meteor shower)!

Aurora

An aurora, also known as Northern Lights, is a natural phenomenon, particularly observable in polar regions: “curtains” of light shining in different colors are slowly dancing across the night sky. Depending on the nature of the ionized particles, different colors will be visible: green, red and blue. They are caused by the collision of charged particles, coming from the solar wind, directed by the Earth’s magnetic field. They are also quite common, visible every year, provided you are somewhere close to the polar circles: if someday you happen to be in these areas, this is definitely a must see.

Comets

Comets are another famous celestial event: they are small icy bodies made of rock, dust and frozen gases which, when they come close to the sun, heat up and spew dust and gases into a giant glowing head. The dust and gases form a tail that stretches away from the sun for millions of kilometers.

Halley’s Comet is probably the best known one. It is a short-period comet and it is visible from Earth every 75 to 76 years: it will appear in our sky in 2061.

There are of course many other comets, unfortunately most of them are not visible to the naked eye. However, Great Comets (a comet bright enough to be noticed by a casual observer – Comet Hale-Bopp was one of them) are visible about every decade or so, but they are unpredictable. The last one observed was Comet McNaught in January and February 2007: it was the brightest comet for over 40 years.

© Robert H. McNaught

Total solar eclipse

A total solar eclipse is probably the most spectacular event you can witness: the Moon passes between the Sun and the Earth, and fully covers the Sun from a location on Earth (there are of course also partial solar eclipses, but these are much more common, and less spectacular). During the eclipse, the Sun’s faint corona will be visible, and the chromosphere, solar prominences, even a solar flare may be seen – the sky is then completely dark, except near the horizon.

As the Sun’s photosphere completely disappears, tiny specks of light remain visible for a few seconds; they are the last rays of sunlight shining through lunar valleys. They are called Baily’s beads, after the astronomer Francis Baily who first provided the explanation of the phenomenon. The last flash of sunlight before totality, called the diamond ring effect, occurs when only one point of sunlight remains. At the end of totality, the same effects will occur in reverse order, on the opposite side of the Moon. Unlike lunar eclipses, totality is visible only along a narrow path on the Earth’s surface traced by the Moon’s umbra.

The next total solar eclipse will occur on November 13, 2012, and it will be visible from northern Australia and the southern Pacific Ocean. So, if you have planned some holidays then, Australia would be a place of choice!


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