... a positive central nucleus , where most of the atom's mass is concentrated, and . one or more negative electrons . Nucleus and electrons are held together by the electric attraction between positive (+) and negative (-) charges. ... When such processes occur in air, they produce there free ions and electrons, which can move and carry an electric current, something neutral atoms cannot do. ... The next heavier atom is that of helium (chemical symbol He) and it contains two electrons. ...

Lesson Plan #42 http://www.phy6.org/stargaze/Lsun7erg.htm . This long section covers the generation of the Sun's energy through nuclear fusion, as well as some ideas about the evolution of stars like the Sun and their ultimate collapse, leading in some cases to supernova explosions. ... The " weak nuclear force " which tries to balance (equalize) the number of protons and neutrons in the nucleus and can, under suitable conditions, convert one kind to the other. ... Nuclear energy. ...

Titan . ... Hubble Space Telescope Images of Titan's surface . ... Later that year, it will release the European-built Huygens probe for a descent through Titan's atmosphere. ... This artist's rendering shows the European Space Agency's Huygens probe descending into the atmosphere of Saturn's moon Titan after being released by NASA's Cassini spacecraft. ... This artist's rendering shows the Huygens probe on the surface of Saturn's moon Titan after being released by NASA's Cassini spacecraft. ...

... Chandra» (). 17 «Nature» (M.Gilfanov, A.Bogdan, An upper limit on the contribution of accreting white dwarfs to the type Ia supernova rate) 18 2010 . ... Chandra» (), «Spitzer» () - 2MASS. ... Ia, , DES Pan-STARRS. : , +7-495-333-33-77, gilfanov@iki.rssi.ru , 2 - +7-495-333-23-66, pavlinsky@iki.rssi.ru http://hea.iki.rssi.ru/ru/index.php - http://chandra.harvard.edu/press/10_releases/press_021710.html -- «Chandra» http://chandra.harvard.edu http://chandra.nasa.gov , «Nature», 18.02.2010 « ». ...