Professor Michael D. Smith Inaugural Lecture University of Kent 12 November, 2009 The Origin of...
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Professor Michael D. Smith
Inaugural LectureUniversity of Kent
12 November, 2009
The Origin of Stars
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Professor Michael D. Smith
LectureUniversity of Kent
12 November, 2009
The Origin of Stars
Ignorable
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We now know that we don’t know……
We have problems
……… what we thought we knew……
What the Universe is made ofHow Galaxies form
How Stars form
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• Issues and debatesWe 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
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Why do we need to know?
We need to know ……..
Curiosity? Principles? The most fundamental science.
EnergyEnvironments
Driver for emergence of totally new conceptsDriver for pioneering technology
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We need to create……..
Science is more creative than ArtStumble and then leap
Work in the darkBut all established laws must be obeyed
Teach: making creators
Aim: to express the unexpressed.To make explicit what is implicit.
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Where do stars come from?
Science. LoFAR Stamp. Impact?
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The scene: what is a star?
• Ball of gas• Photosphere; corona• Stable phase; nuclear fusion reactors, • gravity, radiation, convection.
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The Mystery: Where do stars 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
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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
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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
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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
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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
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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
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Similar properties……….…similar equations…
Opaque,
condensations (rain, grains),
turbulent,
ephemeral
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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 )
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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
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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
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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