Date post: | 20-Jun-2015 |
Category: |
Education |
Upload: | pez-amaury |
View: | 184 times |
Download: | 0 times |
From molecular clouds to stars
Amaury Thiabaud – M2 A2P – 14/11/2011
From molecular clouds to stars Amaury Thiabaud - English M2 A2P 2
In this talk…IntroductionRequirements : molecular clouds
CollapseNuclear fire : a star is born
Conclusion
1) Requirements : molecular clouds
2) Collapse
3) Nuclear Fire : a star is born
In this talk…
From molecular clouds to stars Amaury Thiabaud - English M2 A2P 3
What’s needed to form a star ?Why do molecular clouds fulfill these requirements ?
IntroductionRequirements : molecular clouds
CollapseNuclear fire : a star is born
Conclusion
What’s needed to form a star ?
abundant matter : H2, H, He
dense regions
compact regions
What’s needed to form a star ?Why do molecular clouds fulfill these requirements ?
IntroductionRequirements : molecular clouds
CollapseNuclear fire : a star is born
Conclusion
Why do molecular clouds fulfill these requirements ?
From molecular clouds to stars Amaury Thiabaud - English M2 A2P 4
Enough hydrogen : nH ~ 1000 cm-3
One of the most dense object in the Universe
Can be compacted if something breaks its equilibrium :
• shock waves
• encounters with another MC
Formation of a gaseous ringInfluence of magnetic fieldGas fragmentation
IntroductionRequirements : molecular clouds
CollapseNuclear fire : a star is born
Conclusion
Formation of a gaseous ring
From molecular clouds to stars Amaury Thiabaud - English M2 A2P 5
Basic principle : conservation of angular momentum
• rotating object must adjust its speed to its dimensions
• collapsing causes an acceleration centrifugal force spread
Doughnut formation
Formation of a gaseous ringInfluence of magnetic fieldGas fragmentation
IntroductionRequirements : molecular clouds
CollapseNuclear fire : a star is born
Conclusion
Influence of magnetic field
From molecular clouds to stars Amaury Thiabaud - English M2 A2P 6
Everywhere in the Galaxy, but weak
Trapped in the clouds
Contraction increases the magnetic field :
• acts on the ions
• decelerates the gaseous ring
Formation of a gaseous ringInfluence of magnetic fieldGas fragmentation
IntroductionRequirements : molecular clouds
CollapseNuclear fire : a star is born
Conclusion
Gas fragmentation
From molecular clouds to stars Amaury Thiabaud - English M2 A2P 7
Sufficient speed to « explode »
Each resulting fragment takes some angular momentum
A new collapse can happen in this « core »
And so on, until the angular momentum is no longer an obstacle
Proto-starT. Tauri starA new star
IntroductionRequirements : molecular clouds
CollapseNuclear fire : a star is born
Conclusion
Proto-star
From molecular clouds to stars Amaury Thiabaud - English M2 A2P 8
Matter goes in the center of the doughnut, center is growing
This forms a proto-star :
• compression high pressure high temperatures
Around proto-star : proto-planetary disk, « eaten » by energy released
Transparency light can be seen
Proto-starT. Tauri starA new star
IntroductionRequirements : molecular clouds
CollapseNuclear fire : a star is born
Conclusion
T. Tauri star
From molecular clouds to stars Amaury Thiabaud - English M2 A2P 9
Such a star is known as T. Tauri star
Gas contraction : only energy source
Unstable object. Eventually stabilises when contraction ceases
Proto-starT. Tauri starA new star
IntroductionRequirements : molecular clouds
CollapseNuclear fire : a star is born
Conclusion
A new star
From molecular clouds to stars Amaury Thiabaud - English M2 A2P 10
When gravitation = pressure
No more production of energy from the collapse
H fusion prevents the star from cooling too fast
Proto-planetary disk can form planets planetary system
IntroductionRequirements : molecular clouds
CollapseNuclear fire : a star is born
Conclusion
Conclusion
From molecular clouds to stars Amaury Thiabaud - English M2 A2P 11
Thank you for your attention !