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The Origin of Stars Professor Michael D. Smith Inaugural Lecture University of Kent 12 November, 2009 The Origin of Stars Professor Michael D. Smith Lecture University of Kent 12 November, 2009 We have problems We now know that we don’t know…… ……… what we thought we knew…… What the Universe is made of How Galaxies form How Stars form Issues and debates We are not familiar with our own Universe. What is the mysterious dark matter and dark energy? What are they and why are they necessary? What came first: galaxies, quasars or stars? A question of evolution: top-down or bottom-up? Was our Universe designed with us in mind? Are there other civilisations, other Universes? The recipe for the Universe begins………IYA2009 We need to know …….. Why do we need to know? Curiosity? Principles? The most fundamental science. Energy Environments Driver for emergence of totally new concepts Driver for pioneering technology We need to create…….. Science is more creative than Art Stumble and then leap Work in the dark But all established laws must be obeyed Teach: making creators Aim: to express the unexpressed. To make explicit what is implicit. Where do stars come from? Science. LoFAR Stamp. Impact? The scene: what is a star? • Ball of gas • Photosphere; corona • Stable phase; nuclear fusion reactors, • gravity, radiation, convection. come from? Centuries: idea of swirling, turbulent gas as the origin of our solar system. Descartes, Kant, Laplace: vortices, nebular hypothesis: importance of angular momentum. Decades: dark patches: black box gas, dust + magnetic field: OBSCURED Is there a problem with clouds? Classical approach: Gravity works alone • Global expansion + local collapse • Giant clouds condense, collapse, fragment • Process is rapid: clouds consumed within few hundred million years • Yet we detect plenty of clouds: clouds exist • Some Unknown Unknown (UU) holds up the clouds Known means of cloud support • Rotation: angular momentum • Magnetic field (standard model) • Turbulence: random supersonic motions • Cloud evolution is delayed • Stars can still form today observations: answer • Rotation: only after collapse • Magnetic field: invisible • Turbulence: supersonic motions: YES • No need to introduce an Unknown Unknown • …although we can’t follow a cloud’s evolution • and can’t be confident of the physics and • dynamics. The Trifid a problem with young stars….. • • • • • Young stars observed – very active, accreting Associated (intimately) with clouds Lifetimes: very short - few million years Rejuvinated old stars? Von Weizsaecker – 1950s Kent SEPnet Astrodome • Something missing in our logic computer simulations….. • My contribution: Supersonic turbulence doesn’t exist • Dissipates immediately in shock waves • Simulations: demonstrated this …even MHD waves interact and dissipate on a ** sound crossing time **. • • • • CLOUDS ARE EPHEMERAL! In a few million years: Young stars condense out of clouds Clouds form, evolve, dissipate Similar properties……….…similar equations… Opaque, condensations (rain, grains), turbulent, ephemeral low efficiency….. • Most of a cloud is dispersed • Only a few per cent is bound into stars • Material is recycled 30 times • Star formation is ongoing ( rate gradually slows ) The Revolution • • • • • Rapid conception - turbulence The Birth: the protostar Feedback from powerful jets: Emerge from giant clouds in clusters Planets and Brown Dwarfs appear ephemeral clouds high accretion strong extraction spatial distribution mass distribution Turbulence v. Gravity Feedback + Regulation + Interaction + Triggering within a Nested System Generates a COMPLEX SYSTEM Out of which stars EMERGE What we know we know…. • There are known knowns. • These are things we know that we know. • There are known unknowns. • That is to say, there are things that we know we don't know. • But there are also unknown unknowns. • There are things we don't know we don't know. Donald Rumsfeld Feb 12, 2002 Philosophy of science…. • UU to KU: pure thought, serendipitous observation, • emergent phenomena ? • KU to KK: systematic scientific methods • Conjecture: • UU = KU/KK • Suggests: there are many • Unknown Unknowns remaining in Star Formation