chapter 12 the deaths of stars. what do you think? will the sun explode? if so, what is the...
TRANSCRIPT
![Page 1: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/1.jpg)
Chapter 12The Deaths of Stars
![Page 2: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/2.jpg)
What do you think?
• Will the Sun explode? If so, what is the explosion called?
• Where did carbon, silicon, oxygen, iron, uranium, and other heavy elements on Earth come from?
• What is a pulsar?
• What is a nova?
![Page 3: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/3.jpg)
Low-mass stars expand into the giant phase twice before becoming planetary
nebulae
![Page 4: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/4.jpg)
Stages in the evolution of low-mass stars beyond the helium flash:
• Movement to horizontal branch
• Core helium fusion
• Asymptotic GIANT branch (AGB)
• Planetary nebula formation
![Page 5: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/5.jpg)
Low-mass stars expand into the supergiant phase before expanding
into planetary nebulae
![Page 6: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/6.jpg)
![Page 7: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/7.jpg)
![Page 8: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/8.jpg)
![Page 9: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/9.jpg)
The burned-out core of a low-mass star becomes a white dwarf
white dwarf
![Page 10: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/10.jpg)
white dwarf
Sirius and its white dwarf companion
![Page 11: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/11.jpg)
The burned-out core of a low-mass star becomes a white dwarf
• Stable stars are supported by– gas pressure– radiation pressure– electron degeneracy pressure
• Star loses hydrostatic equilibrium
• Gravitational contraction of the core
• Temporary, nuclear fusion-based stability
• Surrounding planetary nebula disperses
• Remaining core is WHITE DWARF
![Page 12: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/12.jpg)
The starting MASS
determines the exact pathway
Mass-loss causes the end-state, a planetary nebula and a white dwarf, to have substantially less mass than the original red supergiant.
![Page 13: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/13.jpg)
What’s a nova?
• A nova is a relatively gentle explosion of hydrogen gas on the surface of a white dwarf in a binary star system.
• It occurs when the white dwarf steals mass from its companion and the external layers quickly ignite and shine brightly.
• This process does not damage the white dwarf and it can repeat.
![Page 14: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/14.jpg)
Yeah, but what about the really
BIG stars?
![Page 15: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/15.jpg)
A series of different types of fusion reactions in high-mass stars lead to
luminous supergiants
![Page 16: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/16.jpg)
![Page 17: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/17.jpg)
A series of different types of fusion reactions in high-mass stars lead to
luminous supergiants• When helium fusion ceases in the core, gravitational
compression increases the core’s temperature above 600 million K at which carbon can fuse into neon and magnesium.
• When the core reaches 1.5 billion K, oxygen begins fusing into silicon, phosphorous, sulfur, and others
• At 2.7 billion K, silicon begins fusing into iron• This process immediately stops with the creation of iron
which can not fuse into larger elements and a catastrophic implosion of the entire star initiates.
![Page 18: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/18.jpg)
High-mass stars die violently by blowing themselves apart in supernova explosions
![Page 19: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/19.jpg)
Remnants of supernova explosions can be detected for millennia afterward
![Page 20: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/20.jpg)
The most famous “before and after” picture
Supernova 1987 A
![Page 21: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/21.jpg)
![Page 22: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/22.jpg)
Supernova 1987A offers a close-up look at a massive star’s death
![Page 23: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/23.jpg)
![Page 24: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/24.jpg)
Consider the change in brightness with time for some supernovae ….
There are at least two distinctly different types of
brightness fall-off
observed.
![Page 25: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/25.jpg)
white dwarf
Accreting white dwarfs in close binary systems can also explode as supernovae
![Page 26: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/26.jpg)
white dwarf
White dwarfs in close binary systems can rapidly gain mass from a companion and
create powerful explosions
![Page 27: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/27.jpg)
White dwarfs in close binary systems can create powerful explosions if it
exceeds 1.4 solar masses (Chandrasekar limit)before after
Called a TYPE I supernova
![Page 28: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/28.jpg)
After an initial brightening, there is a slow drop-off in brightness
![Page 29: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/29.jpg)
Let’s again consider the end state of very large stars
![Page 30: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/30.jpg)
The cores of may Type II supernovae become neutron stars• When stars between 4 and 9 times the mass
of the Sun explode as supernovae, their remnant cores are highly compressed clumps of neutrons called neutron stars.
• These tiny stars are much smaller than planet Earth -- in fact, are about the diameter of a large city.
• Spinning neutron stars are called pulsars.
![Page 31: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/31.jpg)
Neutron Star
![Page 32: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/32.jpg)
Pulsars• first detected in 1967 by Cambridge University
graduate student Jocelyn Bell
• Radio source with an regular on-off-on cycle of exactly 1.3373011 seconds
![Page 33: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/33.jpg)
Pulsars• first detected in 1967 by Cambridge University graduate
student Jocelyn Bell• Radio source with an regular on-off-on cycle of exactly
1.3373011 seconds• Some scientists speculated that this was evidence of an alien
civilization’s communication system and dubbed the source LGM
Little Green Men
• Today, we know pulsars are rapidly spinning neutron stars.
![Page 34: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/34.jpg)
THE LIGHT HOUSE MODEL
A rotating magnetic field explains the
pulses from a neutron star
![Page 35: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/35.jpg)
Pulsating X-ray sources are neutron
stars in close binary
systems
![Page 36: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/36.jpg)
Other neutron stars in binary systems emit powerful jets of gas
![Page 37: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/37.jpg)
Neutron stars in binary systems can also emit powerful isolated bursts of X-rays
X-ray bursters probably arise from mass transfer in binary star systems where one
star is a neutron star rather than a white dwarf. A helium layer 1km thick would be
enough to cause a flash across the surface that emits X-rays
Recently discovered gamma-ray bursters, which happen over fractions of seconds, might have a similar origin.
![Page 38: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/38.jpg)
![Page 39: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/39.jpg)
What did you think?• Will the Sun explode? If so, what is the explosion called?
The Sun will explode as a planetary nebula in about five billion years.
• Where did carbon, silicon, oxygen, iron, uranium, and other heavy elements on Earth come from?These elements are created by supernovae.
• What is a pulsar?A pulsar is a rotating neutron star in which the magnetic field does not pass
through the rotation axis.
• What is a nova?A nova is a relatively gentle explosion of hydrogen gas on the surface of a white
dwarf in a binary star system.
![Page 40: Chapter 12 The Deaths of Stars. What do you think? Will the Sun explode? If so, what is the explosion called? Where did carbon, silicon, oxygen, iron,](https://reader036.vdocuments.net/reader036/viewer/2022062407/56649c9b5503460f9495a0e9/html5/thumbnails/40.jpg)
Self-Check1: List the stages in the evolution of low-mass stars beyond the helium flash.
2: List the stages in the evolution of high-mass stars beyond the initial red giant or supergiant stage.
3: Name the objects that represent the end phases of evolution for main-sequence stars and indicate the mass range for each.
4: Compare and contrast the physical and observable properties of Type I and Type II supernovae.
5: Describe the properties of gas clouds that are produced by late stages of stellar evolution and indicate from which type of stars they are formed.
6: Review the observational evidence that links pulsars with neutron stars.
7: Compare and contrast pulsars with X-ray sources that pulsate.
8: Compare and contrast the physical processes that occur in supernovae with those in novae and bursters.