Solar games at Paranal

ESO staff Guillaume Blanchard was able to capture the rather rare blue flash while observing the sunset on Christmas eve from the Paranal Residencia. The image was taken with a... Click here for more information.

ESO staff Stéphane Guisard has been chasing green flashes for many years and has been able to capture them on many occasions. The picture shown above is one of many examples from his collection. "The most challenging is to capture the green flash while still seeing the rest of the Sun with all its colours," says Guisard.

His colleague Guillaume Blanchard was even luckier. On Christmas Eve, as he was one of the few to follow the tradition of looking at the sunset, he had the chance to immortalise a blue flash using his hobby telescope.

ESO astronomer Yuri Beletsky also likes to take photographs from Paranal, but he prefers the night views. This allows him to make use of the unique conditions above the site to make stunning images. On some of these, he has captured other extremely interesting effects related to the Sun: the so-called Zodiacal light and the 'Gegenschein'.

Both the Zodiacal light and the Gegenschein (which is German for "counter shine") are due to reflected sunlight by interplanetary dust. These are so faint that they are only visible in places free from light pollution.

Most of the interplanetary dust in the Solar System lies in the ecliptic, the plane close to which the planets are moving around the Sun, and the Zodiacal light and Gegenschein are thus seen in the region centred around the ecliptic. While the Zodiacal light is seen in the vicinity of the Sun, the Gegenschein is seen in the direction opposite to the Sun.

Each of the small particles of dust, left over from comets and asteroids, acts as a small Moon reflecting the light coming from our host star. "If you could see the individual dust particles then you would see the ones in the middle of the Gegenschein looking like very tiny full moons, while the ones hidden in the faint part of the dust band would look like tiny crescent moons," explains ESO astronomer Colin Snodgrass. "But even the VLT cannot see such tiny individual dust particles out in space. Instead we see the combined effect, in photos like these, of millions of tiny dust particles reflecting light back to us from the Sun."