Portia . Uranus XII - 1986U1 . Portia was named after a rich heiress in Shakespeare's play Merchant of Venice . It is the seventh known satellite of Uranus and was discovered by Voyager 2 . Portia Statistics . Discovered by . ... Equatorial radius (km) . ... Equatorial radius (Earth = 1) . ... Mean density (gm/cm^3) . Mean distance from Uranus (km) . ... Rotational period (days) . Orbital period (days) . ... Mean orbital velocity (km/sec) . ... Orbital eccentricity . ...

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. ...