Stellar Evolution: Low Mass Stars Mass 2-3 M sun But what about - - PowerPoint PPT Presentation

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Stellar Evolution: Low Mass Stars Mass 2-3 M sun But what about - - PowerPoint PPT Presentation

Sep 12, 2023 329 likes •726 views

Stellar Evolution: Low Mass Stars Mass 2-3 M sun But what about High Mass Stars and all of those other elements??? GRAVITY When core T=10 8 K, He fuses into C (& O) What happens when the Helium runs out?? PRESSURE Answer

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Stellar Evolution: Low Mass Stars

Mass ≲2-3 Msun

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  • But what about High Mass Stars

and all of those other elements???

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GRAVITY PRESSURE

  • When core T=108 K, He fuses into C (& O)
  • What happens when the Helium runs out??

Answer Depends on MASS!

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GRAVITY PRESSURE

  • When core T=108 K, He fuses into C (& O)
  • Sun: 100 million yrs
  • Intermediate/High Mass: 100,000 yrs!
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GRAVITY PRESSURE

  • Int/High Mass Stars: Battle continues...
  • T ~600 mil. K, C --> O/Ne/Mg
  • 1,000 yrs
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GRAVITY PRESSURE

  • High Mass Stars: Battle continues...
  • T ~1.5 Billion K! Ne fusion
  • a few yrs!
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GRAVITY PRESSURE

  • High Mass Stars: Battle continues...
  • O (1 year!)
  • Si (1 day!!!)
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Iron - The Nuclear Turnip

  • Requires energy to fuse heavier than Iron
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Iron - The Nuclear Turnip

  • Gravity takes over,
  • uter layers collapse

into iron core and....

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Iron - The Nuclear Turnip BOOM!!

  • Supernova explosion

creates more elements and sends them into space!

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  • But what about High Mass Stars

and all of those other elements???

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Supernovae - Fun Facts

How frequent? How long? 3/100 years in MW tcollapse < 1 second! SN Energy in seconds = Solar output over 1 Billion years!

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Will the Sun ever become a Supernova?

?? BOOM?

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Stellar Evolution: Low Mass vs. High Mass Stars THE ENTIRE EVOLUTION OF A STAR IS DETERMINED BY ITS MASS

Mass ≲2-3 Msun Mass > 3 Msun

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Stellar Evolution: Low Mass vs. High Mass Stars

Where do elements heavier than Fe come from?

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All elements heavier than IRON were created in in Supernova Explosions!

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SN provide raw materials for new generations of stars!!

Galactic Recycling

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SOUPernovae (mmmm)

Early Universe: 75% H, 25% He Supernovae enrich the interstellar medium... Local Universe: 70% H, 28% He, 2% Heavy Elements ISM: 70%H, 28% He, 2% heavy

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How Does SF Happen?

Recall: SF happens in Giant Molecular Clouds GMCs... ...collapse to form stars

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How Does SF Happen?

What causes the clouds to start collapsing? ??

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Triggered Star Formation #1 - Supernova Shocks

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Triggered Star Formation - Supernova Shocks Density Enhancements

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Triggered Star Formation #2 - Winds from Massive Stars W5 NGC 1999

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Triggered Star Formation - Winds from Massive Stars Lagoon Nebula Cavity Excavation

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Plain Old Gravity (example: Bok Globule) Galaxy Collisions (MICE!) Starbursts @ Galactic Center Other Possibilities

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Formation of Stars: Sets the Stage for Planets!

Cloud Protostar Protostar + Disk (T Tauri Star) Star!

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Formation of Stars!

  • 0. Cold Cloud of Gas & Dust

T~30K

  • 1. SN/wind triggers collapse (rotation)

density increases, T increases

  • 2. Protostar forms (more rotation)

density increases, T ~3000K Protostar emits in infrared

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Formation of Stars!

  • 0. Cold Cloud of Gas & Dust

T~30K

  • 1. SN triggers collapse (rotation)

T increases

  • 2. Protostar forms (more rotation)

T ~3000K 3/4. Protostellar Disk forms T ~3000-1 Million K density increases star accretes material from disk Star + Disk emits in infrared T Tauri Stars

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T Tauri Stars - Accretion Disks Protostar accretes material from disk

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T Tauri Stars - Protostars with Disks

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T Tauri Stars - Disks, Jets & Winds Star Formation is Active! (jets move 100-1000 km/s)

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T Tauri Stars: Protostars w/Disks, Jets, Winds Allow rotational energy to escape! (conserve angular momentum) WHY?

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Current Model of Star Formation

  • 0. Cold Cloud of Gas & Dust
  • 1. SN triggers collapse (rotation)
  • 2. Protostar forms (more rotation)
  • 3. Protostellar Disk forms - TTauri Star
  • 4. T reaches 10 Million K - STAR!!
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Current Model of Star Formation

  • 5. T reaches 10 Million K - STAR!! (e.g. Vega)

Stellar Leftovers - DEBRIS DISK

Seeds for Planet Formation!! What happens to the disk??

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How Do Planets Form Out of Debris Disks?? Disks contain DUST Dust ACCRETES

ACCRETION!

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How Do Planets Form Out of Debris Disks?? Slow moving particles collide and stick together

ACCRETION!

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Forming Planets Out of Debris Disks Dust Begins to Accrete forms PLANETESIMALS Planetesimals Collide Small Bodies Break up...

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Forming Planets Out of Debris Disks Leftovers are Asteroids, Comets, Meteoroids, & Dwarf Planets... ...fossil records of SS Formation! Planetesimals grow to form protoplanets... Protoplanets collide to form Planets!