... The atoms of oxygen, for instance, contain electrons with negative electric charges and protons which are positive, but the two charges balance each other andthe electric and magnetic forces cancel. Magnetic forces have almost no effect on neutral atoms. ... It can be shown that such free electrons and ions will be guided by the magnetic field lines (or "lines of force") which rise from near the southern (magnetic) pole and enter the Earth again near the northern pole. ...

If you look up at the night sky with your naked eye all you see is a black void with a few points of white light. ... Types of Nebulae . ... NGC 7023 . ... Orion Nebula . Horsehead Nebula . ... NGC 2440 . ... Dumbbell Nebula . Little Dumbbell Nebula . Cat's Eye Nebula . ... The Vela Supernova Remnant . ... Supernova 1987a . ... NGC 1976 (Orion Nebula) . ... NGC 6514 (Trifid Nebula) . ... NGC 6853 (Dumbbell Nebula) . NGC 650-1 (Little Dumbbell Nebula) . NGC 6543 (Cat's Eye Nebula) . ...

Next: 2--Dimensional Images Up: Test Data Previous: Test Data . Modern solid-state detectors produce data which differ in two main aspects from classical photographic images: (a) a much higher S/N (signal to noise ratio) and (b) the rigid spatial digitisation of the incoming flux. ... The usage of the programs and images that we provide as a reference test package should also facilitate documentation of possible application software malfunctions and their subsequent repair. ...

Cardiff is the capital of Wales since 1955. It is a city of the broad Severn estuary which extends into the Bristol Channel. ... It is both the cultural centre (with a university) and the economic centre of principality. ... The foundation of the National Museum of Wales in 1907 and of the Walsh University of Wales in 1893 helped Cardiff become a cultural centre. ... Cathay's Park is the centre of the civic life of the city with its exceptionally fine group of municipal buildings. ...

XMM-Newton Science Analysis System . omichain (omichain-1.51) [xmmsas_20080701_1801-8.0.0] . ... For ODFs with Engineering 2/4 data (ie images of dimension 1024x1024 and 2048x2048, respectively), the time taken to process the data may become considerable (in excess of one hour). If time is of importance to you, and you are only interested in the ``brighter sources'', a considerable reduction in processing time can be achieved by setting the parameter `` omdetectnsigma '' to 2.01. ...

... ARTICLE: The Adventurous Search For The Astronomical Unit . ... Kepler himself had suggested to use the rare occasions of Venus transiting (crossing) the solar disk to measure our distance to the planet. ... Due to the orbital inclination of Venus against the ecliptic of 3.5°, a Venus transit is so rare that it happens only at intervals of 121.5 years, 8 years, 105.5 years, 8 years and so on. ... Crabtree witnessing the transit of Venus 1639 . ... Transits of Venus - The Quest for the Solar Parallax...