Nucleosynthesis
A star's energy comes from the combining of light elements into heavier elements in a process known as fusion, or "nuclear burning". It is generally believed that most of the elements in the universe heavier than helium are created, or synthesized, in stars when lighter nuclei fuse to make heavier nuclei. The process is called nucleosynthesis.
Nucleosynthesis requires a high-speed collision, which can only be achieved with very high temperature. The minimum temperature required for the fusion of hydrogen is 5 million degrees. Elements with more protons in their nuclei require still higher temperatures. For instance, fusing carbon requires a temperature of about one billion degrees! Most of the heavy elements, from oxygen up through iron, are thought to be produced in stars that contain at least ten times as much matter as our Sun. Our Sun is currently burning, or fusing, hydrogen to helium. This is the process that occurs during most of a star's lifetime. After the hydrogen in the star's core is exhausted, the star can burn helium to form progressively heavier elements, carbon and oxygen and so on, until iron and nickel are formed. Up to this point the process releases energy. The formation of elements heavier than iron and nickel requires the input of energy. Supernova explosions result when the cores of massive stars have exhausted their fuel supplies and burned everything into iron and nickel. The nuclei with mass heavier than nickel are thought to be formed during these explosions.
Nucleosynthesis in the News:February 5, 2009: Cosmic dust fountain spotted -- Astronomy.comJanuary 22, 2009: Planetary nebula NGC 2818 -- APOD January 16, 2009: Team detects dust around a primitive star -- Astronomy.com January 6, 2009: Cassiopeia A comes alive across time and space -- NASA's Chandra mission December 29, 2008: NGC 1569: Starburst in a dwarf irregular galaxy -- APOD December 24, 2008: Researcher nabs doubly magic tin isotope, a North American first -- Science Daily December 18, 2008: La Superba -- APOD December 3, 2008: 'Echoes' shine a light on Tycho Brahe's supernova -- Physics World October 2, 2008: 'Little bang' triggered solar system formation -- Carnegie Institution for Science August 29, 2008: Generations of stars in W5 -- APOD July 4, 2008: SN 1006 supernova remnant -- APOD June 10, 2008: Detective astronomers unearth hidden celestial gem -- ESA May 29, 2008: Scientists heat matter to hotter than surface of the sun -- Telegraph May 21, 2008: NASA's Swift satellite catches first supernova in the act of exploding -- NASA GSFC May 18, 2008: On the origin of gold -- APOD April 30, 2008: Stellar ticking time bomb explodes on cue -- NASA GSFC April 14, 2008: A new nova in Cygnus -- Astronomy.com April 7, 2008: Hot, bright, massive stars have complex mixing processes in their great depths -- Science Daily March 27, 2008: The N44 complex -- APOD March 20, 2008: Heavyweight contender -- Physical Review Focus February 29, 2008: Earth is doomed (in 5 billion years) -- Physics World February 17, 2008: M1: The Crab Nebula from Hubble -- APOD January 8, 2008: Hubble finds that "blue blobs" in space are orphaned clusters of stars -- HubbleSite December 20, 2007: Dust in the wind -- Astronomy.com November 21, 2007: Astronomers discover stars with carbon atmospheres -- University of Arizona November 18, 2007: Scientist seeks to understand nuclear reactions on stars deep underground -- Black Hills Pioneer November 15, 2007: Brightest supernova may reignite -- Scientific American October 24, 2007: Massive star's afterlife: A supernova seeds new planets -- Science Daily September 25, 2004: The iron Sun -- NASA GSFC APOD August 18, 2003: New metal-poor galaxies: the youngest in the universe? -- Sloan Digital Sky Survey August 6, 2003: Source for major type of supernova explosions found -- Spaceflight Now April 3, 2003: How the Sun shines -- Space.com March 19, 2003: How does the Sun shine? -- Physics News Update March 6, 2003: Scientists pinpoint stellar production of helium, yielding new insights into the young universe -- EurekAlert October 31, 2002: Old star sheds light on creation of elements -- PhysicsWeb October 31, 2002: Struck by low-metal star finding -- Space News October 23, 2002: Gamma-ray telescope to sleuth for origin of elements -- NASA GSFC July 29, 2002: Dwarf's gift -- HEASARC Picture of the Week July 19, 2002: A solar source for diamond dust? -- Sky & Telescope July 17, 2002: The Sun: A great ball of iron? -- ScienceDaily January 13, 2002: Radioactive decay of elements gives age of stars -- Spaceflight Now January 8, 2002: Sun is mostly iron, not hydrogen -- University of Missouri-Rolla December 1, 2001: Nuclei prompt stellar rethink -- PhysicsWeb October 26, 2001: Elements in the aftermath -- NASA GSFC APOD August 22, 2001: Heavy metal stars -- ESO August 20, 2001: Astrophysicists receive $2 million from Department of Energy to explore supernovae -- LLNL July 23, 2001: Mining aluminum in the Universe -- NASA GSFC HEAPOW July 19, 2001: Iron from meteorites helps probe early solar nebula -- UniSci June 30, 2001: Hydrogen, helium, and the stars of M10 -- NASA GSFC APOD June 5, 2001: Reconsidering interstellar dust and heavy elements -- UniSci May 21, 2001: The universal distribution center -- NASA GSFC HEAPOW April 5, 2001: On the origin of gold -- NASA GSFC APOD January 9, 2001: Unusual mixing in red giants identified as unexpected contributor to mysterious source of lithium -- NOAO January 9, 2001: Evidence presented for new supernova explosion model -- Spaceflight Now January 8, 2001: Rare spherical planetary nebula provides step toward accurate measurement of chemical compositions in stars -- NOAO November 27, 2000: Revealing colorful element formations in ancient stars -- Spaceflight Now March 12, 1999: Hydrogen, helium, and the stars of M10 -- APOD November 9, 1998: WR124: Stellar Fireball (read about Wolf-Rayet stars) -- APOD July 2, 1998: CRIS data indicate a long delay between nucleosynthesis and cosmic ray acceleration -- ACE News Nucleosynthesis ActivitiesGrades 9 - 12: Cosmology and Stellar Evolution -- NASA GSFCGrades 9 - 12: Life Cycle of Stars -- CERES Project Grades 9 - 12: The Sun or the Supernova? -- NASA GSFC Click on images above to
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