Nick Fritzsche - Stellar Evolution 1 Stellar Evolution Nick Fritzsche IKTP-Proseminar „Understanding the universe“

Nick Fritzsche - Stellar Evolution 2 Stellar Evolution - Basic properties - Hertzsprung-Russell diagram - Birth of stars - Pre-main-sequence stars - Main sequence - Endpoints of Stellar Evolution - Actual research

Nick Fritzsche - Stellar Evolution 3 Basic properties - Wien's displacement law: - Stefan-Boltzmann-Law: - Mass-luminosity relation: Mass-luminosity: burro.cwru.edu

Nick Fritzsche - Stellar Evolution 4 Hertzsprung-Russel-Diagram -Luminosity as a function of temperature - Remember: surface properties like color, type of spectrum give temperature H-R-diagram: Wikipedia

Nick Fritzsche - Stellar Evolution 5 Stellar Evolution: Wikipedia

Nick Fritzsche - Stellar Evolution 6 Birth of stars - Gas clouds collapse to stars, when gravitational is higher than thermal energy - - Smaller clouds (solar nebula) require violent external influence (shock wave) to increase density → gravitation overcomes pressure Young stars in gas cloud: jumk.de Shock wave: astronomynow.com

Nick Fritzsche - Stellar Evolution 7 Pre-main-sequence stars - Thermal energy transported via convection first - Temperature increases rapidly when thermal radiation starts -Nuclear fusion due to high temperatures start at main sequence area

Nick Fritzsche - Stellar Evolution 8 Main sequence - Protostars get visible blowing of their dust envelope - Main sequence: long period with small changes in size, temperature or luminosity - „Hydrogen burning“: nuclear energy generated in central regions, flows to the surfaces and radiates into space Protostars: mpg.de Main sequence star: starformation.synthasite.com

Nick Fritzsche - Stellar Evolution 9 Endpoints of Stellar Evolution: Low mass stars M < 0.1M sun : -Never reach the main sequence - Evolve directly into brown dwarfs Wikipedia: Brown Dwarf

Nick Fritzsche - Stellar Evolution 10 Endpoints of Stellar Evolution: Moderate mass stars 0.1M sun < M < 1.4M sun : - High temperature in degenerated core ignites helium inside the hydrogene burning shell → brighter, more voluminous, lower surface temperature, slight red shift, helium flashes 1.4M sun < M < 8M sun : - Helium burning starts before core contraction → burns to carbon without helium flashes Red Giant: astronomycafe.net Helium flash: Wikipedia

Nick Fritzsche - Stellar Evolution 11 Endpoints of Stellar Evolution Moderate mass stars - Fuel burnt: core becomes white dwarf and ejcts outer layers forming planetary nebula, → low luminosity, small, low temperature, high density White Dwarf: bbc.co.uk Planetary nebula: Wikipedia „Future of the earth“

Nick Fritzsche - Stellar Evolution 12 Endpoints of Stellar Evolution Massive stars M >8M sun : - H-, He-, C-, Ne-, O-, Si-burning possible - Iron core collapse because of energy loss after fuel is exhausted - Explosive, reflecting wave pushes star shells away, after core contraction reaches the density of atomic nuclei (Supernova) Supergiant: nasa.gov Supernova: Wikipedia

Nick Fritzsche - Stellar Evolution 13 Endpoints of Stellar Evolution Massive stars - Star is destroyed except possibly a high-density central core (black hole or neutron star) -Particles and electro-magnetic waves (light) cannot escape from the black hole's gravity - Neutron stars are smallest and densest known stars (11–11.5 km (7 miles) radius, M~2M sun ) - rotating, highly magnetized neutron stars emitting electro-magnetic waves (pulsars) send periodic signals Black Hole: Wikipedia Pulsar: nrao.edu

Nick Fritzsche - Stellar Evolution 14 Actual research - Astroseismology: Pulsation periods give hints on internal structure of stars (e.g. density profile) - 3D core collapse supernova explosion simulation Astroseismology: astroseismology.org supernova: mpa-garching.mpg.de/

Nick Fritzsche - Stellar Evolution 15 Thanks for your attention!

Nick Fritzsche - Stellar Evolution 16 Literature „Cauldrons in the Cosmos – Nuclear Astrophysics“ by Claus E. Rolfs and William S. Rodney „Neutrino Astrophysics“ by John N. Bahcall „An Introduction to Nuclear Astrophysics“ by Richard N. Boyd „Experimentalphysik 4 – Kern-, Teilchen-, und Astrophysik“ by Wolfgang Demtröder „Der neue Kosmos“ by Albrecht Unsöld and Bodo Baschek

Nick Fritzsche - Stellar Evolution 17 Images H-R-diagram: Russell_diagram Young stars in gas cloud: a/junge-sterne.shtml Shock wave: tsunami-wakes-up-comatose-galaxies/ Main sequence star: Protostar: dust Red Giant: White Dwarf: pre_2011/space/theoriginsoftheuniverserev3.shtml Astroseismology: Simulation: garching.mpg.de/mpa/institute/news_archives/news1005_janka/ news1005_janka-de.html Supergiant: stars.html Supernova: Ring nebula: Helium flash: Black hole: Neutron star: Pulsar: Mass-luminosity: cademics/Astr221 /StarProp/masslum.html