Transcript Folie 1 - University of Kent
The problem of star formation is not how to make stars.
The problem of star formation is how not to make stars.
Canterbury 02.05.2020
The Physics of
Star Formation Dr Dirk Froebrich
University of Kent Canterbury 02.05.2020
Content
- How do we know stars are forming?
- Where do stars form?
- Properties of young stars - Temperature & Turbulence vs. Gravity - Collapse, Discs and Jets Canterbury 02.05.2020
Content
- How do we know stars are forming?
- Where do stars form?
- Properties of young stars - Temperature & Turbulence vs. Gravity - Collapse, Discs and Jets Canterbury 02.05.2020
Inside Stars...
Massive stars are bright and short lived (few Million years) Canterbury 02.05.2020
Gal. Plane The Sky Gal. North Pole Gal. Center Gal. South Pole Gal. Plane Canterbury 02.05.2020
Massive O -Stars Canterbury 02.05.2020
Massive O B -Stars Canterbury 02.05.2020
O B -Stars + Dust Canterbury 02.05.2020
Gal. Plane O B -Stars + Dust Gal. North Pole Gal. Center Gal. Plane Gal. South Pole Canterbury 02.05.2020
The Circinus Cloud Canterbury 02.05.2020
B68
k l b
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Content
- How do we know stars are forming?
- short lived massive stars exist - they must have formed in the last few Myrs - the Universe is 13.7Gyrs old Canterbury 02.05.2020
Content
- Where do stars form?
- in or near Giant Molecular Clouds mostly molecular hydrogen + 1% dust + traces of CO, H 2 O, NH 3 , ...
- these clouds are massive (10 4 -10 6 M SUN ) - these clouds are cold (10-30K) Canterbury 02.05.2020
Content
- How do we know stars are forming?
- Where do stars form?
- Properties of young stars - Temperature & Turbulence vs. Gravity - Collapse, Discs and Jets Canterbury 02.05.2020
Region S106: 150 young stars forming in Cygnus
Subaru Observatory
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Hubble Space Telescope
Region NGC346: young stars forming in the LMC Canterbury 02.05.2020
Hubble Space Telescope
Tarantula Nebula: young stars forming in the LMC Canterbury 02.05.2020
Orion Nebula
Subaru Telescope
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Content
- Properties of young stars - they are ‘social‘ – most form in clusters, some in isolation - single/binary/tripple/multiple – 147/64/9/1 - many low mass and few high mass stars, universal mass distribution Canterbury 02.05.2020
Content
- How do we know stars are forming?
- Where do stars form?
- Properties of young stars - Temperature & Turbulence vs. Gravity - Collapse, Discs and Jets Canterbury 02.05.2020
The Problem:
Betelgeuse MON R2 l Ori NGC2024 ONC OriB NGC2071 OriA 10s of light years
Canterbury 02.05.2020
The Problem:
Betelgeuse MON R2 l Ori NGC2024 ONC OriB NGC2071 OriA 10s of light years
Size: 10 16 m
10 9 m 7 orders of magnitude
Solar Diameter
(x 10.000.000) Density: changes by 21 orders of magnitude (x 1.000.000.000.000.000.000.000) Canterbury 02.05.2020
MON R2 NGC2024
The Problem:
Betelgeuse l Ori
Gravity
NGC2071 OriA ONC OriB 10s of light years
But why has not everything collapsed?
Solar Diameter
Thermal Pressure of gas clouds
critical (Jeans) mass for collapse about 1M SUN for a cloud of 1ly radius Canterbury 02.05.2020
MON R2 NGC2024
The Problem:
Betelgeuse l Ori
Gravity
NGC2071 OriA ONC OriB 10s of light years
Gravity vs. Thermal pressure
Solar Diameter
Almost all clouds are above Jeans limit
should collapse
But we do not observe this!
Solution: Turbulence Canterbury 02.05.2020
MON R2 NGC2024
The Problem:
Betelgeuse l Ori
Gravity
NGC2071 OriA ONC OriB 10s of light years
Turbulence: random bulk motion of material at supersonic velocities v>sound speed (200m/s) creation of shocks increasing density
Solar Diameter
Canterbury 02.05.2020
MON R2 NGC2024
The Problem:
Betelgeuse l Ori
Gravity
NGC2071 OriA ONC Solar Diameter OriB 10s of light years
Gravity vs. Thermal pressure + Turbulence
Star Formation is the interplay of Gravity and supersonic turbulence in Molecular Clouds
Gravoturbulent Fragmentation Canterbury 02.05.2020
Content
- How do we know stars are forming?
- Where do stars form?
- Properties of young stars - Temperature & Turbulence vs. Gravity - Collapse, Discs and Jets Canterbury 02.05.2020
Now, how does it work?
Stage 1 Stage 2 Stage 3
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Now, how does it work?
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Orion Nebula: Discs seen in silhouette Canterbury 02.05.2020
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HH 46/47 Canterbury 02.05.2020
HH 212
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HH 46/47 HST 1994 - 1997 Canterbury 02.05.2020
HH 46/47 HST 1994 - 1997 Canterbury 02.05.2020
HH 34 HST 1994 - 1997 Canterbury 02.05.2020
HH 34 HST 1994 - 1997 Canterbury 02.05.2020
MON R2 NGC2024
The Problem:
Betelgeuse l Ori
Gravity
NGC2071 OriA ONC Solar Diameter OriB 10s of light years
Gravity vs. Thermal Pressure + Turbulence + angular Momentum + magn. Fields Spin
accretion disc formation
ejection of jets (accelerated and collimated by magnetic fields)
feedback from outflows and radiation
turblence Canterbury 02.05.2020
Planet Formation
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The end
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