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The life cycle of a star

Presentation General Science

Joep ten Wolde

on 8 June 2011

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Transcript of The life cycle of a star

The life cycle of stars general info Birth and Death Life Videos The relation between us and stardust Examples of the creation of stars The types of stars definition 2 facts about stars A star is a massive, luminous ball of plasma held together by gravity sun Spectroscopy Luminosity, brigthness and magnitude blue giant (main sequence) (light echoe) Red supergiant (later phase) Neutron star (final state) yellow dwarf (main sequence) red gaint (later phase) white dwarf (later phase) brown dwarf (final phase) Cepheid variable star (example) binary stars Stars radiate power total power radiated by star = luminosity (Watts) Total power received by observer on earth = Brightness (W/m2) Scale to compare brightness = magnitude scale
The lower on the scale, the brighter the star. Magnitude scale if stars were 3.26 light years away (difference of distance is not taken into account) = absolute magnitude H - R diagram Stars emit energy In short Birth of star Death Our real ancestor Light is received through prism

Spectrum is formed

Spectrum can be analysed

Conclusions about the composition and conditions of a star The capturing and anlysing of a specturm Spectroscopy allows the determination of the composition and conditions of a star process Composition Conditions Presence of different elements in a star each element has a unique signature This signature can be identified in the spectrum of a star every different element absorbs a different part of the wavelength The emission lines can tell temperature, luminosity and velocity This has to do with the strength of absorption, which is dependant on temperature Concluded in a table.... stars range in size from 20 km to 0.9 billion km stars appear to us as points of light The human eye is relatively insensitive to colours of point sources The visible diameter of stars is nearly zero Energy is produced by fusion of hydrogen into helium ('hydrogen burning') Stars lose energy (and Hydrogen) surface temperature luminosity surface temperature luminosity surface temperature luminosity surface temperature blue giant (high mass) red supergiant neutron star yellow dwarf (lower mass) red giant white dwarf brown dwarf All hydrogen is gone gravity contracts the star No hydrogen fusion possible temperature increases helium fusion is possible expansion the same story, no hydrogen, it expands Duration !!The whole life cycle of a star is decided by its mass!! Lower mass = yellow dwarf Larger mass = blue giant nebula gravity due to mass contraction causes heat heat makes hydrogen burning possible Rest of loose matter is either blown away or forms planets usually referred to as the birth of the star A cloud of dust and gas Hydrogen runs out Gravity contracts the star Increased temperature allows helium fusion Helium runs out Star continuous to fuse until all iron has ran out less than 4 solar masses greater than 4 solar masses higher mass lower mass red gaint forms planetary nebula and becomes white dwarf Red supergiant experiences supernova. Eventually becomes neutron star or black hole is formed Planets are made of the gasses and dust in the nebula Nebulae are formed when lower mass star dies We are made of the gasses and dust from the nebula supernova observed by hubble
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