Skip navigation

Celestial mechanics

warning: Creating default object from empty value in /var/www/vhosts/ on line 33.
Original author: 
(author unknown)

This was a weekend of the Sun and Moon -- a coincidence of the summer solstice and the "Supermoon". Friday was the summer solstice (in the northern hemisphere), welcomed by humans for thousands of years as the longest day of the year. In ancient times, people celebrated this day as the center point of summer. Some still observe the solstice with ceremonies and prayers, gathering on mountaintops or at spiritual landmarks. Over the weekend, skywatchers around the world were also treated to views of the so-called Supermoon, the largest full moon of the year. On Sunday, the moon approached within 357,000 km (222,000 mi) of Earth, in what is called a perigee-syzygy of the Earth-Moon-Sun system (perigee: closest point of an elliptical orbit; syzygy: straight line made of three bodies in a gravitational system). Photographers across the globe set out to capture both events, and collected here are 24 images of our two most-visible celestial neighbors. [24 photos]

The largest full moon of 2013, a "supermoon" scientifically known as a "perigee moon", rises over the Tien Shan mountains and the monument to 18th century military commander Nauryzbai Batyr near the town of Kaskelen, some 23 km (14 mi) west of Almaty, Kazakhstan, on June 23, 2013. (Reuters/Shamil Zhumatov)     

Your rating: None

Galaxy clusters are the largest objects in the Universe that are held together by their own gravity. They're so big that the expansion rate and distribution of matter within the Universe affects their formation and evolution. As a result, their numbers, sizes, and motion record the history of the cosmos on its largest scales. 

One of the places galaxy clusters leave their imprint is on the Universe's cosmic microwave background (CMB). As the CMB's photons scatter off hot gas in a cluster, its relative motion adds a very slight shift to the photon's wavelength, an effect known as the kinematic Sunyaev-Zel'dovich effect (kSZ). The kSZ effect has now been observed for the first time, as described in a forthcoming paper by Nick Hand et al. 

Read the rest of this article...

Read the comments on this post

Your rating: None