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The Life and Death of Stars Dr Martin Hendry University of Glasgow How do stars and planets form? from Nebulae How do stars and planets form? from Nebulae The Orion Nebula Forming stars Forming stars versus Gas pressure trying to expand the cloud Forming stars versus Gravity trying to collapse the cloud Collapse often caused by the shock wave from a Supernova Hydrogen fusion – fuelling a star’s nuclear furnace H = Hydrogen He = Helium E = mc 2 Repulsive Potential Energy Nuclear fusion only occurs at very high temperatures, because atomic nuclei tend to repel each other Coulomb Barrier 0 Distance Starlight is electromagnetic radiation The Electromagnetic Spectrum Stars of different colours have different temperatures Temperature and colour of a star are related by Wien’s Law 4000K 5000K 6000K 7000K Surface temperature (K) 25000 10000 8000 6000 5000 4000 3000 106 -10 Supergiants -5 102 0 Giants 1 +5 10-2 +10 10-4 +15 O5 B0 A0 F0 G0 Spectral Type K0 M0 M8 Absolute Magnitude Luminosity (Sun=1) 104 We can plot the temperature and luminosity of stars on a diagram Stars don’t appear everywhere: they group together, and most are found on the Main Sequence Surface temperature (K) 25000 10000 8000 6000 5000 4000 3000 106 -10 Supergiants -5 102 0 Giants 1 +5 10-2 +10 10-4 +15 O5 B0 A0 F0 G0 Spectral Type K0 M0 M8 Absolute Magnitude Luminosity (Sun=1) 104 Stars found on the Main Sequence convert hydrogen into helium. Stars like the Sun can do this for many billions of years, using the P-P chain of nuclear reactions Surface temperature (K) 25000 106 10000 8000 6000 . 5000 4000 3000 . . . . .. . . . . .. . . .. .. . ... .. . .... .. . .. ..... ... . . .. . ... . . ... ........ . .. .... . .. . . ..... ...... ...... .. .. ..... . ...... . . ... . . . ... ... .. Deneb -10 Rigel Betelgeuse Antares Luminosity (Sun=1) Arcturus 102 Aldebaran Regulus Vega Procyon A Altair 10-2 Pollux Sun Procyon B O5 B0 +5 +10 Barnard’s Star Sirius B 10-4 0 Mira Sirius A 1 -5 A0 F0 G0 Spectral Type K0 M0 M8 +15 Absolute Magnitude 104 Stars found on the Main Sequence convert hydrogen into helium. Stars like the Sun can do this for many billions of years, using the P-P chain of nuclear reactions The P-P chain: converting hydrogen to helium Surface temperature (K) 25000 106 10000 8000 6000 . 5000 4000 3000 . . . . .. . . . . .. . . .. .. . ... .. . .... .. . .. ..... ... . . .. . ... . . ... ........ . .. .... . .. . . ..... ...... ...... .. .. ..... . ...... . . ... . . . ... ... .. Deneb -10 Rigel Betelgeuse Antares Luminosity (Sun=1) Arcturus 102 Aldebaran Regulus Vega Procyon A Altair 10-2 Pollux Sun Procyon B O5 B0 +5 +10 Barnard’s Star Sirius B 10-4 0 Mira Sirius A 1 -5 A0 F0 G0 Spectral Type K0 M0 M8 +15 Absolute Magnitude 104 Stars found on the Main Sequence convert hydrogen into helium. Hotter stars burn their hydrogen much faster, via the CNO Cycle Interior of a solar-type star Interior of a red giant star When the fuel runs out: formation of a red giant White dwarfs: earth-sized stellar relics Surface temperature (K) 25000 106 10000 8000 6000 . 5000 4000 3000 . . . . .. . . . . .. . . .. .. . ... .. . .... .. . .. ..... ... . . .. . ... . . ... ........ . .. .... . .. . . ..... ...... ...... .. .. ..... . ...... . . ... . . . ... ... .. Deneb -10 Rigel Betelgeuse Antares Luminosity (Sun=1) Arcturus 102 Aldebaran Regulus Vega Procyon A Altair 10-2 Pollux Sun Procyon B O5 B0 +5 +10 Barnard’s Star Sirius B 10-4 0 Mira Sirius A 1 -5 A0 F0 G0 Spectral Type K0 M0 M8 +15 Absolute Magnitude 104 Stars on the Main Sequence turn hydrogen into helium. Blue stars are much hotter than the Sun, and use up their hydrogen in a few million years Interior of a very massive star Crab Nebula: supernova of 1054 Supernova 1987A, in the Large Magellanic Cloud Supernovae Putting the Iron in Irn Bru