supernovae

[trevorjohnson83]

when a supernovae occurs the star begins fusing heavy elements that collapse on the core in a second and then explode, that's some pretty big chunks of stuff flying at a speed fast enough to escape the black hole it creates? how does that work?

ChatGPT said:​

Thought for 6 seconds
When an ultra‐massive star’s iron core collapses, two seemingly contradictory things happen almost in parallel:

1. The innermost core implodes so violently that it can’t be supported even by neutron degeneracy pressure—and that collapsing remnant becomes a black hole.
2. A powerful shock wave, born in the first few milliseconds of collapse, races outward through the overlying stellar layers and slams into them with 10⁴⁴–10⁴⁵ J of energy, accelerating that material to several thousand km/s.

Because the shock is launched from deep inside before (or as) the black hole is finishing its formation, the outer envelope sees a one‐way push that easily exceeds the local escape velocity—even though the core becomes a black hole seconds later.

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Rough Timeline & Mechanics​

1. Core Collapse (∼0–1 ms)
   Iron core exceeds its Chandrasekhar limit, implodes toward nuclear densities.
2. Core Bounce + Shock Formation (∼1–5 ms)
   The inner core stiffens abruptly, creating an outward “bounce” shock at ∼50 km radius.
3. Neutrino Heating (∼5–100 ms)
   The proto–neutron star floods its surroundings with neutrinos. If enough neutrino energy is deposited behind the shock, it revives the shock that otherwise would stall.
4. Shock Propagation (∼100 ms–1 s)
   The shock travels outward through thousands of kilometers of overlying stellar material, imparting ~10⁴⁴ J and accelerating it to ∼10³–10⁴ km/s.
5. Black Hole Formation (∼0.5–3 s)
   If the proto-neutron star accretes enough fallback material, it collapses into a black hole. But by this time the shock is already kilometers or more away, carrying the outer layers outward.
6. Ejecta Escape
   Those outer layers, now moving faster than the escape velocity at their radius, coast off into space as the visible supernova remnant.

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Why the Ejecta Escapes a Newborn Black Hole​

• Small Schwarzschild Radius: A few solar-mass black hole has rs∼10r_s ∼ 10rs∼10 km—tiny compared to the star’s 10410^4104 km envelope. The shock wave outruns the horizon formation zone by miles in milliseconds.
• Kinetic Energy vs. Gravity: The ejecta’s kinetic energy (12mv2\tfrac12mv^221mv2) far exceeds its gravitational binding energy once it’s been swept up by that revived shock.
• Delayed Collapse: Black hole formation via fallback takes a few hundred milliseconds to seconds—long enough for the shock to clear the outer layers.

So while the core irreversibly collapses into a black hole, its own explosive “bounce” and neutrino-revived shock have already flung the rest of the star outward at speeds high enough to escape—even the deep new gravity well.

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In short: the explosion is powered and launched before the black hole finishes forming, and it carries enough energy to unbind and eject the star’s outer shells.

 

[trevorjohnson83]

who came up with this stuff about supernovae and when?

ChatGPT said:​

Thought for 4 seconds
Here’s a quick historical sketch of how core–collapse supernova theory developed:

1. 1934, Baade & Zwicky
   
   • Walter Baade and Fritz Zwicky first coined the term “super–nova,” and proposed that such explosions mark the collapse of an ordinary star into a neutron star, releasing enormous energy.
2. 1939, Oppenheimer & Snyder
   
   • J. Robert Oppenheimer and Hartland Snyder published the first relativistic calculation showing how a sufficiently massive stellar core can undergo irreversible gravitational collapse.
3. 1966, Colgate & White
   
   • Stirling Colgate and Richard A. White suggested that the core’s bounce and an intense flash of neutrinos could drive a shock wave outward to unbind the star’s envelope.
4. 1985, Bethe & Wilson
   
   • Hans Bethe and James R. Wilson refined the “neutrino–driven” mechanism, showing via detailed simulations how neutrino heating behind the stalled shock can revive it and power the explosion.
5. 1990s–Today, Multi-D Simulations
   
   • Over the last few decades groups led by Adam Burrows, H.-Th. Janka, Christian Ott, and others have used 2D and 3D hydrodynamic simulations to explore instabilities (e.g. SASI) and confirm the neutrino-driven paradigm—while still wrestling with the exact conditions needed for robust explosions.

So, the basic picture you described—a core collapse, bounce-generated shock, neutrino heating and envelope ejection before the nascent black hole swallows the inner core—was built up over roughly fifty years of work, with key milestones in 1934, 1939, 1966 and 1985.

 

[trevorjohnson83]

are supernovae remnants visibly different than planetary nebulae? are supernovae based on a star's size, is size based on parallax view?

ChatGPT said:​

Thought for 10 seconds
1. Visual Differences: Supernova Remnants (SNR) vs. Planetary Nebulae (PN)

• Morphology & Symmetry
  • PN are typically small (∼0.1–1 pc), symmetric shells or rings blown off by low-mass stars. They often show smooth, rounded shapes (spherical, elliptical or bipolar).
  • SNR are larger (several pc), highly irregular and filamentary—shocked ejecta plowing into the interstellar medium produces tangled filaments and arcs. nisenet.orgAstronomy Notes
• Central Object
  • PN harbor a hot white dwarf in their center, often visible in optical/UV images.
  • SNR may contain a neutron star or pulsar (or a black hole) that is usually faint against the bright, shock-heated shell. Astronomy Stack Exchange
• Emission Mechanism
  • PN glow primarily by photo-ionization (UV light from the white dwarf excites the shell—strong O III, H α lines).
  • SNR shine by shock-heating and synchrotron emission (high [S II]/H α ratios; strong radio and X-ray signatures). Astronomy Notes

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2. What Governs a Star’s Supernova Type & How “Size” Is Determined

• Progenitor Mass (“Size”)
  • Core-collapse (Types II, Ib/c): Stars with initial masses ≳ 8 M☉ end their lives in a supernova once fusion can no longer support the iron core.
  • Type Ia: A 1.4 M☉ white dwarf in a binary accretes mass until runaway carbon fusion detonates it.
• Measuring Stellar “Size” via Parallax
  1. Parallax → Distance: Missions like Hipparcos/Gaia measure a star’s annual parallax angle to determine its distance, ddd.
  2. Brightness + Distance → Luminosity: Observed flux FFF yields absolute luminosity L=4πd2FL=4\pi d^2FL=4πd2F.
  3. Luminosity + Temperature → Radius: Using the Stefan–Boltzmann law,
     L=4πR2σTeff4⟹R=L4πσTeff4 . L = 4\pi R^2\sigma T_{\rm eff}^4 \quad\Longrightarrow\quad R = \sqrt{\frac{L}{4\pi\sigma T_{\rm eff}^4}}\,.L=4πR2σTeff4⟹R=4πσTeff4L.
  Thus, “size” (radius) depends on distance from parallax, measured brightness, and spectroscopic temperature.

---

So yes—a star’s mass (and thus “size”) determines which kind of supernova it can undergo, and we infer that size through parallax-based distance measurements combined with photometry and spectroscopy.

Sources
o4-mini

You said:​

why do supernovae remnants surround the core remnant if the shockwave should carry it all away pretty darn quick?

ChatGPT said:​

Thought for 13 seconds
Because the explosion’s blast starts from the collapsing core itself and pushes the star’s envelope outward, the expelled material naturally expands as a shell centered on the new compact remnant. Here’s why that shell remains visible around the core:

1. Shock Launches Inside Out
   • The core collapse and bounce create a shock right at the boundary between the proto–neutron star and the overlying mantle. That shock plows outward, accelerating the envelope while the core stays put. Wikipedia
2. Core Receives Only a Small “Kick”
   • Neutron stars often get a natal kick of a few hundred km/s, but the ejecta travels at thousands of km/s. The bulk of the mass is thrown off symmetrically, so it always expands in a roughly spherical shell around the (nearly stationary) remnant. A&A
3. Deceleration by Interstellar Medium
   • As the ejecta runs into surrounding gas, it slows and piles up into a thin, dense shell—what we observe as the supernova remnant (SNR). That shell continues to surround the central neutron star or black hole as it coasts outward. Wikipedia
4. Reverse Shock
   • A reverse shock — formed when the forward shock slows in the ISM — propagates back inward, heating inner ejecta and further defining the hollow shell structure that keeps the remnant’s “wall” around the core. HEASARC

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So even though the material is driven away at high speed, it is always launched around the core. From our vantage, we see that expanding shell still centered on the compact remnant—just like a balloon being inflated around a seed.are supernovae remnants visibly different than planetary nebulae? are supernovae based on a star's size, is size based on parallax view?

ChatGPT said:​

Thought for 10 seconds
1. Visual Differences: Supernova Remnants (SNR) vs. Planetary Nebulae (PN)

• Morphology & Symmetry
  
  • PN are typically small (∼0.1–1 pc), symmetric shells or rings blown off by low-mass stars. They often show smooth, rounded shapes (spherical, elliptical or bipolar).
  • SNR are larger (several pc), highly irregular and filamentary—shocked ejecta plowing into the interstellar medium produces tangled filaments and arcs. nisenet.orgAstronomy Notes
• Central Object
  
  • PN harbor a hot white dwarf in their center, often visible in optical/UV images.
  • SNR may contain a neutron star or pulsar (or a black hole) that is usually faint against the bright, shock-heated shell. Astronomy Stack Exchange
• Emission Mechanism
  
  • PN glow primarily by photo-ionization (UV light from the white dwarf excites the shell—strong O III, H α lines).
  • SNR shine by shock-heating and synchrotron emission (high [S II]/H α ratios; strong radio and X-ray signatures). Astronomy Notes

---

2. What Governs a Star’s Supernova Type & How “Size” Is Determined

• Progenitor Mass (“Size”)
  
  • Core-collapse (Types II, Ib/c): Stars with initial masses ≳ 8 M☉ end their lives in a supernova once fusion can no longer support the iron core.
  • Type Ia: A 1.4 M☉ white dwarf in a binary accretes mass until runaway carbon fusion detonates it.
• Measuring Stellar “Size” via Parallax
  
  1. Parallax → Distance: Missions like Hipparcos/Gaia measure a star’s annual parallax angle to determine its distance, ddd.
  2. Brightness + Distance → Luminosity: Observed flux FFF yields absolute luminosity L=4πd2FL=4\pi d^2FL=4πd2F.
  3. Luminosity + Temperature → Radius: Using the Stefan–Boltzmann law,
     
     L=4πR2σTeff4⟹R=L4πσTeff4 . L = 4\pi R^2\sigma T_{\rm eff}^4 \quad\Longrightarrow\quad R = \sqrt{\frac{L}{4\pi\sigma T_{\rm eff}^4}}\,.L=4πR2σTeff4⟹R=4πσTeff4L.
     Thus, “size” (radius) depends on distance from parallax, measured brightness, and spectroscopic temperature.

---

So yes—a star’s mass (and thus “size”) determines which kind of supernova it can undergo, and we infer that size through parallax-based distance measurements combined with photometry and spectroscopy.

Sources

o4-mini

You said:​

why do supernovae remnants surround the core remnant if the shockwave should carry it all away pretty darn quick?

ChatGPT said:​

Thought for 13 seconds
Because the explosion’s blast starts from the collapsing core itself and pushes the star’s envelope outward, the expelled material naturally expands as a shell centered on the new compact remnant. Here’s why that shell remains visible around the core:

1. Shock Launches Inside Out
   
   • The core collapse and bounce create a shock right at the boundary between the proto–neutron star and the overlying mantle. That shock plows outward, accelerating the envelope while the core stays put. Wikipedia
2. Core Receives Only a Small “Kick”
   
   • Neutron stars often get a natal kick of a few hundred km/s, but the ejecta travels at thousands of km/s. The bulk of the mass is thrown off symmetrically, so it always expands in a roughly spherical shell around the (nearly stationary) remnant. A&A
3. Deceleration by Interstellar Medium
   
   • As the ejecta runs into surrounding gas, it slows and piles up into a thin, dense shell—what we observe as the supernova remnant (SNR). That shell continues to surround the central neutron star or black hole as it coasts outward. Wikipedia
4. Reverse Shock
   
   • A reverse shock — formed when the forward shock slows in the ISM — propagates back inward, heating inner ejecta and further defining the hollow shell structure that keeps the remnant’s “wall” around the core. HEASARC

---

So even though the material is driven away at high speed, it is always launched around the core. From our vantage, we see that expanding shell still centered on the compact remnant—just like a balloon being inflated around a seed.

 

[trevorjohnson83]

planetary nebulae

 

[trevorjohnson83]

supernovae