Robert's Quartet is a compact galaxy group approximately 160 million light-years away in the constellation Phoenix. It is a family of four very different galaxies whose proximity to each other has caused the creation of about 200 star-forming regions and pulled out a stream of gas and dust 100,000 light years long. Its members are NGC 87, NGC 88, NGC 89 and NGC 92, discovered by John Herschel on the 30 September 1834.The quartet is one of the best examples of compact galaxy groups. Because such groups contain four to eight galaxies in a very small region they are excellent laboratories for the study of galactic interactions and their effects, in particular on the formation of stars. The quartet has a total visual magnitude of almost 13. The brightest member of the group is NGC 92, having the blue magnitude of 13.8. On the sky, the four galaxies are all within a circle of radius of 1.6 arcmin, corresponding to about 75,000 light-years. It was named by Halton Arp and Barry F. Madore, who compiled A Catalogue of Southern Peculiar Galaxies and Associations in 1987. Arp and Madore named Robert's Quartet after Robert Freedman who generated many of the updated positions...

Horsepower (hp) is a unit of measurement of power, or the rate at which work is done, usually in reference to the output of engines or motors. There are many different standards and types of horsepower. Two common definitions used today are the mechanical horsepower (or imperial horsepower), which is about 745.7 watts, and the metric horsepower, which is approximately 735.5 watts. The term was adopted in the late 18th century by Scottish engineer James Watt to compare the output of steam engines with the power of draft horses. It was later expanded to include the output power of other types of piston engines, as well as turbines, electric motors and other machinery. The definition of the unit varied among geographical regions. Most countries now use the SI unit watt for measurement of power. With the implementation of the EU Directive 80/181/EEC on 1 January 2010, the use of horsepower in the EU is permitted only as a supplementary unit. History The development of the steam engine provided a reason to compare the output of horses with that of the engines that could replace them. In 1702, Thomas...

Gemasolar is a concentrated solar power plant with a molten salt heat storage system. It is located within the city limits of Fuentes de Andalucía in the province of Seville, Spain. Design and specifications The plant is of the solar power tower type CSP and uses concepts pioneered in the Solar One and Solar Two demonstration projects, using molten salt as its heat transfer fluid and energy storage medium. Originally called Solar Tres, it was renamed Gemasolar.The project, which has received a subsidy of five million euros from the European Commission and a loan of 80 million euros from the European Investment Bank, makes use of the Solar Two technology tested in Barstow, California, but is approximately three times the size. It makes use of several advances in technology after Solar Two was designed and built. Gemasolar is the first commercial solar plant with central tower receiver and molten salt heat storage technology. It consists of a 30.5-hectare (75-acre) solar heliostat aperture area with a power island and 2,650 heliostats, each with a 120-square-metre (1,300 sq ft) aperture area and distributed...