Atlas . Saturn XV - 1980S28 . Atlas, the second of Saturn's known satellites, orbits near the outer edge of the A-ring and is about 40 by 20 kilometers (25 by 15 miles) in size. It is probably a shepherd satellite for Saturn's A-ring. Atlas was discovered by R. Terrile in 1980 from photographs taken by Voyager during its encounter with Saturn. Atlas Statistics . ... Mean density (gm/cm^3) . ... Rotational period (days) . Orbital period (days) . ... Credit: Calvin J. Hamilton) . ...

A team of U.S. and German astrophysicists have made the first ever detection of X-rays coming from a comet. ... Following the initial detection, the team reported repeated X-ray emissions from the comet over the next 24 hours. ... One preliminary theory is that X-ray emission from the Sun was absorbed by a cloud of gaseous water molecules surrounding the nucleus of the comet, and then were re-emitted by the molecules in a process physicists call "fluorescence." ... Comets . ...

What follows is a brief list of benchmarks and discoveries that shaped our ideas on atoms and nuclei. ... Discovery of electrons . ... Comparing this to Faraday's results, one could get " Avogadro's number ", the number of (say) hydrogen atoms in one gram of hydrogen--an enormously large number. ... Similarly, energized atoms are only allowed to exist in one of a number of energy levels. ... By the way, Avogadro's number is 602,000,000,000,000,000,000,000 (6.02 10 23 ) molecules in 1 gr hydrogen. ...