Planetary nebulae form during the late stages of evolution for low-to-medium mass stars. As a star expands into a red giant, it ejects its outer layers through pulsations and stellar winds. The hot core ionizes the ejected gas, causing it to glow brightly. This energized shell of nebulous gas appears as a planetary nebula. Examples are the Helix Nebula and Ring Nebula. More massive stars may explode as supernovae, leaving behind neutron stars or black holes, depending on the star's original mass. The document discusses these stages of stellar evolution and death that give rise to different astronomical phenomena like planetary nebulae and neutron stars.

1. PLANETARY NEBULA
FORMATION
SARANYA V.S
Department of Space Engineering and Rocketry

2. STELLAR EVOLUTION- MAIN
STAGES
 The Collapse of an Interstellar Cloud
 Fragmentation into smaller clumps — Stars
 Hydrogen Burning -Main Sequence
 Helium Burning - Red Giant
 Higher “nuclear” fuels (depending on mass)
 Death, depending on mass:
 Planetary Nebula — White Dwarf
 Supernova — Neutron Star
 Supernova — Black Hole

3. DARK NEBULA
 Ninety-nine percent of the material in the Universe
is hydrogen and helium. Some of that is locked up
in stars but the vast portion floats in the spaces that
lay between them.
The distances between stellar bodies is huge, the
density of this material is exceedingly thin. some of
it is shepherded by gravity and exploding stars into
enormous nebulous clouds,

4. COLLAPSE OF INTERSTELLAR CLOUD
 Interstellar Medium Contains Clouds.
 T~10-100°K, M~10’s-1000’s of Msun
 If gravitational pull exceeds gas (and B) pressure, gas
collapses.

5. PROTOSTARFORMATION

6. EVOLUTION OF STARS / GROSS
FEATURES:
 M < 0.08 Msun – Brown Dwarf (no nuclear
burning)
 0.08 Msun < M < 0.5 Msun – Central hydrogen
burning. Formation of a degenerate core. No
helium ignition –End as a He white dwarf
 0.5 Msun < M < 2 Msun – Central Hydrogen
burning, Helium flash, Helium burning - End as
CO White dwarf.

7.  2 Msun < M < 8 Msun – Central Hydrogen burning,
Helium ignites non degenerately _ End as CO
White dwarf.
 8 Msun < M < 20 Msun – Numerous burning stages
after Helium burning. Type II Supernova - ends as
Neutron Star.
 20 Msun < M – As above, but ends as a Black
Hole.
 Note: High masses are inaccurately known due to
large wind mass loss during evolution

8. HYDROGEN BURNING
Brown dwarfs
Sub brown dwarfs
Red dwarfs
Super giants

9. HELIUM BURNING
 Low mass star
becomes white dwarf after about 100 billion years
 Mid size star
• red giant branch star (inert He core)
• asymptotic giant branch star (inert C core)
formation of planetary nebulae and further becomes
white or black dwarf.
 Massive star
undergo supernova explosion and transforms into
neutron star or black hole

10. RED GIANT EXPANSION

11. Asymptotic Giant Branch Stars
& Planetary Nebulae
Once He is exhausted in core, core continues to
contract, He & H burn in shells, envelope
expands.
 At some point, envelope becomes unstable, and
starts to pulsates, each time shedding some material.
 Envelope ejected at ~ 30 km/s, and core contracts
and cools
Envelope becomes planetary nebula
Core becomes white dwarf

12. PLANETARY NEBULA
 During the red giant phase, the outer layers of the
star are expelled via pulsations and strong stellar
winds.
 The exposed hot, luminous core emits ultraviolet
radiation that ionizes the ejected outer layers of the
star.
 This energized shell of nebulous gas reradiates the
absorbed ultraviolet energy at visible frequencies and
appears as a planetary nebula.

13. Planetary nebula formation

14. Ring nebula
Lemon slice nebulaNecklace nebula
Crab nebula

15. Eskimo nebula

16. Helix nebula

17. Formation of helix nebula

18. Cats eye nebula

20. Bipolar nebulae

21. Formation of bipolar nebulae

22. ADVANCED BURNING IN MASSIVE
STARS
Shells:

23. SUPERNOVAE
 One Iron photodisintegration takes place,
core collapses on time scale of 10’s of ms.
 At “Low” masses, Neutron star is formed,
and shock appears.
 As long as there is large fluxes of infalling
material, shock cannot “leave” the core.
Once shock does propagates outwards
(perhaps using n heating) it:
 Heats the envelope (fast nuclear
processes take place (making Trans-
Iron isotopes).
Accelerates the envelope, and it is
ejected with speeds of order 10,000’s
km/s

24.  Cloud Gravitationally Unstable And Starts
Collapsing. Flow Limited By Formation Of Shock
Waves

25. LEFT OVERS OF MASSIVE STARS
 The remnant left can be
either a Neutron Star:
Or a Black Hole!
 Neutron stars are held
by degeneracy pressure
of neutrons (and not
electrons)
sun

26. Neutron star Black hole
If the collapsing stellar core at the
center of a supernova contains
between about 1.4 and 3 solar
masses, the collapse continues until
electrons, protons neutrons are
expelled, producing a neutron star
If the collapsed stellar core is larger
than three solar masses, it collapses
completely to form a black hole: an
infinitely dense object whose gravity
is so strong that nothing can escape its
immediate proximity, not even light

27. CONCLUSION
Man’s inquisitiveness to know about the outer space has
led to the discovery of several secrets of space. The
formation, evolution and the death of the stars and
nebulae is discussed in this seminar. This topic has
become an interesting topic of research by the scientists
all over the world and covers a vast area of astronomy.
The outer space is limitless…….
And hence the discussion goes on…

28. Thank you