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 The Origin of Stars Ignorable
We now know that we don’t know…… We have problems ……… 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
Why do we need to know? 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.
Centuries: idea of swirling, turbulent gasas 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 The Mystery: Where do stars come from?
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 • Something missing in our logic • Kent SEPnet Astrodome
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
Opaque, condensations (rain, grains), turbulent, ephemeral Similar properties……….…similar equations…
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 ephemeral clouds • The Birth: the protostar high accretion • Feedback from powerful jets: strong extraction • Emerge from giant clouds in clusters spatial distribution • Planets and Brown Dwarfs appear 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 RumsfeldFeb 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