Rare Nacreous Clouds
Also called polar stratospheric clouds or mother of pearl clouds, nacreous clouds are mostly visible within two hours after sunset or before dawn. They blaze unbelievably bright with vivid, iridescent colors. These clouds are rare and occur in the polar stratosphere at altitudes of 15,000–25,000 meters. They are so bright because at those heights, they are still sunlit.
Although incredibly beautiful, they have a negative impact on our atmosphere. They create ozone holes by supporting chemical reactions that produce active chlorine which catalyzes ozone destruction.
In the heart of the mythical Elqui Valley in Pisco, surrounded by the Andes Mountains, 500km north of Santiago in central Chile, lies a magical place that allows for star-spangled dreams beneath the clear pure sky. Combining stargazing and specialized astronomic tours with night-time horseback riding, meditation and even tarot readings, Elqui Domos is a hotel quite like no other.
It was completed in 2005 to fulfil its owners’ desire to observe and enjoy the grandeur of the one of the world’s most star-filled skies. It is one of only seven astronomic hotels around the world and the only one in the Southern Hemisphere, offering breathtaking views of the magic skies draped over the Elqui Valley (the valley is renowned for its sharp, clear skies, as it happens to sit under one of the clearest atmospheres in the world). The lack of rain and pleasant weather all year round set the perfect conditions for astronomic tourism, where guests can gather to enjoy a unique chance to liaise with the stars.
This composite image of a galaxy illustrates how the intense gravity of a supermassive black hole can be tapped to generate immense power. The image contains X-ray data from NASA’s Chandra X-ray Observatory (blue), optical light obtained with the Hubble Space Telescope (gold) and radio waves from the NSF’s Very Large Array (pink).
This multi-wavelength view shows 4C+29.30, a galaxy located some 850 million light years from Earth. The radio emission comes from two jets of particles that are speeding at millions of miles per hour away from a supermassive black hole at the center of the galaxy. The estimated mass of the black hole is about 100 million times the mass of our Sun. The ends of the jets show larger areas of radio emission located outside the galaxy.
The X-ray data show a different aspect of this galaxy, tracing the location of hot gas. The bright X-rays in the center of the image mark a pool of million-degree gas around the black hole. Some of this material may eventually be consumed by the black hole, and the magnetized, whirlpool of gas near the black hole could in turn, trigger more output to the radio jet.
Most of the low-energy X-rays from the vicinity of the black hole are absorbed by dust and gas, probably in the shape of a giant doughnut around the black hole. This doughnut, or torus blocks all the optical light produced near the black hole, so astronomers refer to this type of source as a hidden or buried black hole. The optical light seen in the image is from the stars in the galaxy.