Supernova Explosions and Remnants

stellar structure

For a 25 solar mass star, theduration of each stage is

stellar corpses: the core

When the central iron core continues to grow and approaches M , two processes begin: nuclear photodisintegration and neutronization.

Nuclear photodisintegration: The temperature is high enough for energetic photons to be abundant and get absorbed in the endothermic reaction:

with an energy consumption of 124 MeV. The Helium nuclei are further unbound:

consuming 28.3 MeV(the binding energy of a He nucleus). The total energy of the star is reduced per nucleon by

With about 10 protons in a Chandrasekhar mass, this corresponds to a total energy loss of

ch

57

stellar corpses: the core

Neutronization: The large densities in the core lead to a large increase in the rates of processes such as

This neutronization depletes the core of electrons and their supporting degeneracy pressure, as well as energy, which is carried off by neutrinos.

The two processes lead, in principle, to an almost total loss of thermal pressure support and to an unrestrained collapse of the core of a star on a free-fall timescale:

In practice, at these high densities, the mean free path for neutrino scattering becomes of order the core radius. This slows down the energy loss, and hence the collapse time to a few seconds.

core collapse supernovae

As the collapse proceeds and the density and the temperature increase, the reaction

becomes common, and is infrequently offset by

leading to a equilibrium ratio of densities

Thus most nucleons become neutrons

core collapse supernovae

type Ia supernovae. If it were not for radioactive heating, adiabaticexpansion of the debris would cool it to near invisibility in less thanan hour. Type Ia supernovae are about ten times less prevalent thancore-collapse supernovae, but yield about ten times as much iron,are often more than ten times brighter at peak light, and arespectacular sources of nuclear g-ray lines and continuum8. It iswith these bright supernovae that observers are now obtaining thebest and, perhaps, the most provocative information about thegeometry of the Universe.

Astronomers use observational, not theoretical, criteria to typesupernovae. A type I supernova (such as a type Ia) is one with nohydrogen in its spectrum, while the spectrum of a type II supernovahas prominent hydrogen lines. The epochal supernova in the LargeMagellanic Cloud (LMC), SN1987A, was a core-collapse supernova,because it exploded as a!15–20M! blue supergiantwith a radius of!4 ! 107 km (ref. 9) and not as the canonical red supergiant with a

radius of !109 km; however, it was dimmer than a typical type IIand early relied on 56Ni to power its muted optical light curve. Yetthere is no reason to suspect that the explosion itself was not of thecommon core-collapse variety. The light curve and spectrum of asupernova reflect more its progenitor’s radius, chemical makeup,and expansion velocities than the mechanism by which it exploded.To the theorist, the achievement of the critical Chandrasekharmassunites the types; the supernovamechanism is either by implosion tonuclear densities and subsequent hydrodynamic ejection, or bythermonuclear runaway and explosive incineration.There is approximately one supernova explosion in the Universe

every second. In our galaxy, there is one supernova every !30–50years and one type Ia supernova every !300 years. Supernovahunters, peering deeply with only modest-aperture telescopes, cannow capture a dozen or so extragalactic supernovae per night,mostly the bright type Ias. Approximately 200 supernova remnantshells are known in theMilky Way and these are radio, optical, andX-ray echoes of only the most recent galactic supernova explosions.Within the last millennium, humans have witnessed and recordedsix supernovae in our galaxy (Table 1).

Supernovae from massive starsA star’s first thermonuclear stage is the fusion of hydrogen intohelium in its hot core. With the exhaustion of core hydrogen, moststars then proceed to shell hydrogen burning, and then to corehelium burning. The ashes of the latter are predominantly carbonand oxygen and low-mass stars do not proceed beyond this stage.However, stars withmasses from !8M! to !60–100M! (the upperlimit depending upon the heavy-element fraction at birth) proceedto carbon burning, with mostly oxygen, neon, and magnesium asashes1,2. For starsmoremassive than !9–10M!, the ashes of carbonburning achieve sufficient temperatures to ignite and they burnpredominantly to silicon, sulphur, calcium, and argon. Finally, theseproducts ignite to produce iron and its congener isotopes near thepeak of the nuclear binding energy curve. Fusion is exothermic onlyfor the assembly of lighter elements into elements up to the irongroup, not beyond. Hence, at the end of a massive star’s thermo-nuclear life, it has an ‘onion-skin’ structure in which an iron oroxygen–neon–magnesium core is nestedwithin shells comprised ofelements of progressively lower atomic weight at progressivelylower densities and temperatures. The outer zone consists ofunburned hydrogen and ‘primordial’ helium. A typical nesting isFe → Si → O → He → H. The oxygen in the ‘oxygen’ zone is themajor source of oxygen in the Universe, for little oxygen survives inthe ejecta of the rarer type Ia supernovae. These shells are not pure,

review article

728 NATURE |VOL 403 | 17 FEBRUARY 2000 |www.nature.com

FeF e O - SiOHH eH e

C ollapse of C ore(~1.5 M )

~1sec.

30,0

00- 60,000 km /s Bounce

Shock

Hot, e xtendedmantle

D E N S E

D E N S E

C O RE

C O RE

ν

ν

ν

ν

ν

ν

ν

ν

νν

M

M

M

~0.1-1sec

M

ν

ν

Prog en it or St ar

Iro n Cor e

Early Pro t o n eu t ro n S t ar

Early Su p ern ov a

Lat e P rot on eu t ro n S t a r

6x10 km8

6x10 km3

2x10 km3

2x10 km2

30 km

Figure 1 The sequence of events in the collapse of a stellar core to a nascent neutron star.It begins with a massive star with an ‘onion-skin’ structure, goes through white-dwarf coreimplosion, to core bounce and shock-wave formation, to the protoneutron-star stagebefore explosion, and finally to the cooling and isolated-neutron-star stage afterexplosion. This figure is not to scale. The wavy arrows depict escaping neutrinos and thestraight arrows depict mass motion.

Table 1 Supernovae that have exploded in our Galaxy and the LargeMagellanic Cloud within the last millennium

Supernova Year (AD) Distance (kpc) Peak visual magnitude.............................................................................................................................................................................SN1006 1006 2.0 −9.0

Crab 1054 2.2 −4.0

SN1181 1181 8.0 ?

RX J0852-4642 !1300 !0.2 ?

Tycho 1572 7.0 −4.0

Kepler 1604 10.0 −3.0

Cas A !1680 3.4 !6.0?

SN1987A 1987 50 " 5 3.0.............................................................................................................................................................................These ‘historical’ supernovae are only a fraction of the total, because the majority were shroudedfrom view by the dust that pervades the Milky Way. Thus, it is estimated that this historical cohortrepresents only about 20% of the galactic supernovae that exploded since AD1000. Included areSN1987A, which exploded not in the Milky Way but in the Large Magellanic Cloud (one of itsnearby satellite galaxies), RX J0852-4642 (ref. 77, ref. 11), a supernova remnant whose recent(!AD1300) and very nearby birth went unrecorded, perhaps because it resides in the SouthernHemisphere (but in fact for reasons that are as yet unknown), and Cas A, a supernova remnant thatwas born in historical times, but whose fiery birth was accompanied by a muted visual display thatmay have been recorded only in the ambiguous notes of the seventeenth-century astronomer JohnFlamsteed (ref. 78). The distances and peak visual magnitudes quoted are guesses at best, exceptfor SN1987A. Astronomical magnitudes are logarithmic and are given by the formula MV ¼#2:5log10ðbrightnessÞ þ constant. Hence, every factor of ten increase in brightness represents adecrease in magnitude by 2.5. For comparison, the Moon is near −12magnitudes, Venus at peak is−4.4 magnitudes, and good eyes can see down to about +6 magnitudes.

© 2000 Macmillan Magazines Ltd

type Ia supernovae. If it were not for radioactive heating, adiabaticexpansion of the debris would cool it to near invisibility in less thanan hour. Type Ia supernovae are about ten times less prevalent thancore-collapse supernovae, but yield about ten times as much iron,are often more than ten times brighter at peak light, and arespectacular sources of nuclear g-ray lines and continuum8. It iswith these bright supernovae that observers are now obtaining thebest and, perhaps, the most provocative information about thegeometry of the Universe.

Astronomers use observational, not theoretical, criteria to typesupernovae. A type I supernova (such as a type Ia) is one with nohydrogen in its spectrum, while the spectrum of a type II supernovahas prominent hydrogen lines. The epochal supernova in the LargeMagellanic Cloud (LMC), SN1987A, was a core-collapse supernova,because it exploded as a!15–20M! blue supergiantwith a radius of!4 ! 107 km (ref. 9) and not as the canonical red supergiant with a

radius of !109 km; however, it was dimmer than a typical type IIand early relied on 56Ni to power its muted optical light curve. Yetthere is no reason to suspect that the explosion itself was not of thecommon core-collapse variety. The light curve and spectrum of asupernova reflect more its progenitor’s radius, chemical makeup,and expansion velocities than the mechanism by which it exploded.To the theorist, the achievement of the critical Chandrasekharmassunites the types; the supernovamechanism is either by implosion tonuclear densities and subsequent hydrodynamic ejection, or bythermonuclear runaway and explosive incineration.There is approximately one supernova explosion in the Universe

every second. In our galaxy, there is one supernova every !30–50years and one type Ia supernova every !300 years. Supernovahunters, peering deeply with only modest-aperture telescopes, cannow capture a dozen or so extragalactic supernovae per night,mostly the bright type Ias. Approximately 200 supernova remnantshells are known in theMilky Way and these are radio, optical, andX-ray echoes of only the most recent galactic supernova explosions.Within the last millennium, humans have witnessed and recordedsix supernovae in our galaxy (Table 1).

Supernovae from massive starsA star’s first thermonuclear stage is the fusion of hydrogen intohelium in its hot core. With the exhaustion of core hydrogen, moststars then proceed to shell hydrogen burning, and then to corehelium burning. The ashes of the latter are predominantly carbonand oxygen and low-mass stars do not proceed beyond this stage.However, stars withmasses from !8M! to !60–100M! (the upperlimit depending upon the heavy-element fraction at birth) proceedto carbon burning, with mostly oxygen, neon, and magnesium asashes1,2. For starsmoremassive than !9–10M!, the ashes of carbonburning achieve sufficient temperatures to ignite and they burnpredominantly to silicon, sulphur, calcium, and argon. Finally, theseproducts ignite to produce iron and its congener isotopes near thepeak of the nuclear binding energy curve. Fusion is exothermic onlyfor the assembly of lighter elements into elements up to the irongroup, not beyond. Hence, at the end of a massive star’s thermo-nuclear life, it has an ‘onion-skin’ structure in which an iron oroxygen–neon–magnesium core is nestedwithin shells comprised ofelements of progressively lower atomic weight at progressivelylower densities and temperatures. The outer zone consists ofunburned hydrogen and ‘primordial’ helium. A typical nesting isFe → Si → O → He → H. The oxygen in the ‘oxygen’ zone is themajor source of oxygen in the Universe, for little oxygen survives inthe ejecta of the rarer type Ia supernovae. These shells are not pure,

review article

728 NATURE |VOL 403 | 17 FEBRUARY 2000 |www.nature.com

FeF e O - SiOHH eH e

C ollapse of C ore(~1.5 M )

~1sec.

30,0

00- 60,000 km /s Bounce

Shock

Hot, e xtendedmantle

D E N S E

D E N S E

C O RE

C O RE

ν

ν

ν

ν

ν

ν

ν

ν

νν

M

M

M

~0.1-1sec

M

ν

ν

Prog en it or St ar

Iro n Cor e

Early Pro t o n eu t ro n S t ar

Early Su p ern ov a

Lat e P rot on eu t ro n S t a r

6x10 km8

6x10 km3

2x10 km3

2x10 km2

30 km

Figure 1 The sequence of events in the collapse of a stellar core to a nascent neutron star.It begins with a massive star with an ‘onion-skin’ structure, goes through white-dwarf coreimplosion, to core bounce and shock-wave formation, to the protoneutron-star stagebefore explosion, and finally to the cooling and isolated-neutron-star stage afterexplosion. This figure is not to scale. The wavy arrows depict escaping neutrinos and thestraight arrows depict mass motion.

Table 1 Supernovae that have exploded in our Galaxy and the LargeMagellanic Cloud within the last millennium

Supernova Year (AD) Distance (kpc) Peak visual magnitude.............................................................................................................................................................................SN1006 1006 2.0 −9.0

Crab 1054 2.2 −4.0

SN1181 1181 8.0 ?

RX J0852-4642 !1300 !0.2 ?

Tycho 1572 7.0 −4.0

Kepler 1604 10.0 −3.0

Cas A !1680 3.4 !6.0?

SN1987A 1987 50 " 5 3.0.............................................................................................................................................................................These ‘historical’ supernovae are only a fraction of the total, because the majority were shroudedfrom view by the dust that pervades the Milky Way. Thus, it is estimated that this historical cohortrepresents only about 20% of the galactic supernovae that exploded since AD1000. Included areSN1987A, which exploded not in the Milky Way but in the Large Magellanic Cloud (one of itsnearby satellite galaxies), RX J0852-4642 (ref. 77, ref. 11), a supernova remnant whose recent(!AD1300) and very nearby birth went unrecorded, perhaps because it resides in the SouthernHemisphere (but in fact for reasons that are as yet unknown), and Cas A, a supernova remnant thatwas born in historical times, but whose fiery birth was accompanied by a muted visual display thatmay have been recorded only in the ambiguous notes of the seventeenth-century astronomer JohnFlamsteed (ref. 78). The distances and peak visual magnitudes quoted are guesses at best, exceptfor SN1987A. Astronomical magnitudes are logarithmic and are given by the formula MV ¼#2:5log10ðbrightnessÞ þ constant. Hence, every factor of ten increase in brightness represents adecrease in magnitude by 2.5. For comparison, the Moon is near −12magnitudes, Venus at peak is−4.4 magnitudes, and good eyes can see down to about +6 magnitudes.

© 2000 Macmillan Magazines Ltd

type Ia supernovae. If it were not for radioactive heating, adiabaticexpansion of the debris would cool it to near invisibility in less thanan hour. Type Ia supernovae are about ten times less prevalent thancore-collapse supernovae, but yield about ten times as much iron,are often more than ten times brighter at peak light, and arespectacular sources of nuclear g-ray lines and continuum8. It iswith these bright supernovae that observers are now obtaining thebest and, perhaps, the most provocative information about thegeometry of the Universe.

Astronomers use observational, not theoretical, criteria to typesupernovae. A type I supernova (such as a type Ia) is one with nohydrogen in its spectrum, while the spectrum of a type II supernovahas prominent hydrogen lines. The epochal supernova in the LargeMagellanic Cloud (LMC), SN1987A, was a core-collapse supernova,because it exploded as a!15–20M! blue supergiantwith a radius of!4 ! 107 km (ref. 9) and not as the canonical red supergiant with a

radius of !109 km; however, it was dimmer than a typical type IIand early relied on 56Ni to power its muted optical light curve. Yetthere is no reason to suspect that the explosion itself was not of thecommon core-collapse variety. The light curve and spectrum of asupernova reflect more its progenitor’s radius, chemical makeup,and expansion velocities than the mechanism by which it exploded.To the theorist, the achievement of the critical Chandrasekharmassunites the types; the supernovamechanism is either by implosion tonuclear densities and subsequent hydrodynamic ejection, or bythermonuclear runaway and explosive incineration.There is approximately one supernova explosion in the Universe

every second. In our galaxy, there is one supernova every !30–50years and one type Ia supernova every !300 years. Supernovahunters, peering deeply with only modest-aperture telescopes, cannow capture a dozen or so extragalactic supernovae per night,mostly the bright type Ias. Approximately 200 supernova remnantshells are known in theMilky Way and these are radio, optical, andX-ray echoes of only the most recent galactic supernova explosions.Within the last millennium, humans have witnessed and recordedsix supernovae in our galaxy (Table 1).

Supernovae from massive starsA star’s first thermonuclear stage is the fusion of hydrogen intohelium in its hot core. With the exhaustion of core hydrogen, moststars then proceed to shell hydrogen burning, and then to corehelium burning. The ashes of the latter are predominantly carbonand oxygen and low-mass stars do not proceed beyond this stage.However, stars withmasses from !8M! to !60–100M! (the upperlimit depending upon the heavy-element fraction at birth) proceedto carbon burning, with mostly oxygen, neon, and magnesium asashes1,2. For starsmoremassive than !9–10M!, the ashes of carbonburning achieve sufficient temperatures to ignite and they burnpredominantly to silicon, sulphur, calcium, and argon. Finally, theseproducts ignite to produce iron and its congener isotopes near thepeak of the nuclear binding energy curve. Fusion is exothermic onlyfor the assembly of lighter elements into elements up to the irongroup, not beyond. Hence, at the end of a massive star’s thermo-nuclear life, it has an ‘onion-skin’ structure in which an iron oroxygen–neon–magnesium core is nestedwithin shells comprised ofelements of progressively lower atomic weight at progressivelylower densities and temperatures. The outer zone consists ofunburned hydrogen and ‘primordial’ helium. A typical nesting isFe → Si → O → He → H. The oxygen in the ‘oxygen’ zone is themajor source of oxygen in the Universe, for little oxygen survives inthe ejecta of the rarer type Ia supernovae. These shells are not pure,

review article

728 NATURE |VOL 403 | 17 FEBRUARY 2000 |www.nature.com

FeF e O - SiOHH eH e

C ollapse of C ore(~1.5 M )

~1sec.

30,0

00- 60,000 km /s Bounce

Shock

Hot, e xtendedmantle

D E N S E

D E N S E

C O RE

C O RE

ν

ν

ν

ν

ν

ν

ν

ν

νν

M

M

M

~0.1-1sec

M

ν

ν

Prog en it or St ar

Iro n Cor e

Early Pro t o n eu t ro n S t ar

Early Su p ern ov a

Lat e P rot on eu t ro n S t a r

6x10 km8

6x10 km3

2x10 km3

2x10 km2

30 km

Figure 1 The sequence of events in the collapse of a stellar core to a nascent neutron star.It begins with a massive star with an ‘onion-skin’ structure, goes through white-dwarf coreimplosion, to core bounce and shock-wave formation, to the protoneutron-star stagebefore explosion, and finally to the cooling and isolated-neutron-star stage afterexplosion. This figure is not to scale. The wavy arrows depict escaping neutrinos and thestraight arrows depict mass motion.

Table 1 Supernovae that have exploded in our Galaxy and the LargeMagellanic Cloud within the last millennium

Supernova Year (AD) Distance (kpc) Peak visual magnitude.............................................................................................................................................................................SN1006 1006 2.0 −9.0

Crab 1054 2.2 −4.0

SN1181 1181 8.0 ?

RX J0852-4642 !1300 !0.2 ?

Tycho 1572 7.0 −4.0

Kepler 1604 10.0 −3.0

Cas A !1680 3.4 !6.0?

SN1987A 1987 50 " 5 3.0.............................................................................................................................................................................These ‘historical’ supernovae are only a fraction of the total, because the majority were shroudedfrom view by the dust that pervades the Milky Way. Thus, it is estimated that this historical cohortrepresents only about 20% of the galactic supernovae that exploded since AD1000. Included areSN1987A, which exploded not in the Milky Way but in the Large Magellanic Cloud (one of itsnearby satellite galaxies), RX J0852-4642 (ref. 77, ref. 11), a supernova remnant whose recent(!AD1300) and very nearby birth went unrecorded, perhaps because it resides in the SouthernHemisphere (but in fact for reasons that are as yet unknown), and Cas A, a supernova remnant thatwas born in historical times, but whose fiery birth was accompanied by a muted visual display thatmay have been recorded only in the ambiguous notes of the seventeenth-century astronomer JohnFlamsteed (ref. 78). The distances and peak visual magnitudes quoted are guesses at best, exceptfor SN1987A. Astronomical magnitudes are logarithmic and are given by the formula MV ¼#2:5log10ðbrightnessÞ þ constant. Hence, every factor of ten increase in brightness represents adecrease in magnitude by 2.5. For comparison, the Moon is near −12magnitudes, Venus at peak is−4.4 magnitudes, and good eyes can see down to about +6 magnitudes.

© 2000 Macmillan Magazines Ltd

core collapse supernovae

sn 1987a

type Ia supernovae. If it were not for radioactive heating, adiabaticexpansion of the debris would cool it to near invisibility in less thanan hour. Type Ia supernovae are about ten times less prevalent thancore-collapse supernovae, but yield about ten times as much iron,are often more than ten times brighter at peak light, and arespectacular sources of nuclear g-ray lines and continuum8. It iswith these bright supernovae that observers are now obtaining thebest and, perhaps, the most provocative information about thegeometry of the Universe.

Astronomers use observational, not theoretical, criteria to typesupernovae. A type I supernova (such as a type Ia) is one with nohydrogen in its spectrum, while the spectrum of a type II supernovahas prominent hydrogen lines. The epochal supernova in the LargeMagellanic Cloud (LMC), SN1987A, was a core-collapse supernova,because it exploded as a!15–20M! blue supergiantwith a radius of!4 ! 107 km (ref. 9) and not as the canonical red supergiant with a

radius of !109 km; however, it was dimmer than a typical type IIand early relied on 56Ni to power its muted optical light curve. Yetthere is no reason to suspect that the explosion itself was not of thecommon core-collapse variety. The light curve and spectrum of asupernova reflect more its progenitor’s radius, chemical makeup,and expansion velocities than the mechanism by which it exploded.To the theorist, the achievement of the critical Chandrasekharmassunites the types; the supernovamechanism is either by implosion tonuclear densities and subsequent hydrodynamic ejection, or bythermonuclear runaway and explosive incineration.There is approximately one supernova explosion in the Universe

every second. In our galaxy, there is one supernova every !30–50years and one type Ia supernova every !300 years. Supernovahunters, peering deeply with only modest-aperture telescopes, cannow capture a dozen or so extragalactic supernovae per night,mostly the bright type Ias. Approximately 200 supernova remnantshells are known in theMilky Way and these are radio, optical, andX-ray echoes of only the most recent galactic supernova explosions.Within the last millennium, humans have witnessed and recordedsix supernovae in our galaxy (Table 1).

Supernovae from massive starsA star’s first thermonuclear stage is the fusion of hydrogen intohelium in its hot core. With the exhaustion of core hydrogen, moststars then proceed to shell hydrogen burning, and then to corehelium burning. The ashes of the latter are predominantly carbonand oxygen and low-mass stars do not proceed beyond this stage.However, stars withmasses from !8M! to !60–100M! (the upperlimit depending upon the heavy-element fraction at birth) proceedto carbon burning, with mostly oxygen, neon, and magnesium asashes1,2. For starsmoremassive than !9–10M!, the ashes of carbonburning achieve sufficient temperatures to ignite and they burnpredominantly to silicon, sulphur, calcium, and argon. Finally, theseproducts ignite to produce iron and its congener isotopes near thepeak of the nuclear binding energy curve. Fusion is exothermic onlyfor the assembly of lighter elements into elements up to the irongroup, not beyond. Hence, at the end of a massive star’s thermo-nuclear life, it has an ‘onion-skin’ structure in which an iron oroxygen–neon–magnesium core is nestedwithin shells comprised ofelements of progressively lower atomic weight at progressivelylower densities and temperatures. The outer zone consists ofunburned hydrogen and ‘primordial’ helium. A typical nesting isFe → Si → O → He → H. The oxygen in the ‘oxygen’ zone is themajor source of oxygen in the Universe, for little oxygen survives inthe ejecta of the rarer type Ia supernovae. These shells are not pure,

review article

728 NATURE |VOL 403 | 17 FEBRUARY 2000 |www.nature.com

FeF e O - SiOHH eH e

C ollapse of C ore(~1.5 M )

~1sec.

30,0

00- 60,000 km /s Bounce

Shock

Hot, e xtendedmantle

D E N S E

D E N S E

C O RE

C O RE

ν

ν

ν

ν

ν

ν

ν

ν

νν

M

M

M

~0.1-1sec

M

ν

ν

Prog en it or St ar

Iro n Cor e

Early Pro t o n eu t ro n S t ar

Early Su p ern ov a

Lat e P rot on eu t ro n S t a r

6x10 km8

6x10 km3

2x10 km3

2x10 km2

30 km

Figure 1 The sequence of events in the collapse of a stellar core to a nascent neutron star.It begins with a massive star with an ‘onion-skin’ structure, goes through white-dwarf coreimplosion, to core bounce and shock-wave formation, to the protoneutron-star stagebefore explosion, and finally to the cooling and isolated-neutron-star stage afterexplosion. This figure is not to scale. The wavy arrows depict escaping neutrinos and thestraight arrows depict mass motion.

Table 1 Supernovae that have exploded in our Galaxy and the LargeMagellanic Cloud within the last millennium

Supernova Year (AD) Distance (kpc) Peak visual magnitude.............................................................................................................................................................................SN1006 1006 2.0 −9.0

Crab 1054 2.2 −4.0

SN1181 1181 8.0 ?

RX J0852-4642 !1300 !0.2 ?

Tycho 1572 7.0 −4.0

Kepler 1604 10.0 −3.0

Cas A !1680 3.4 !6.0?

SN1987A 1987 50 " 5 3.0.............................................................................................................................................................................These ‘historical’ supernovae are only a fraction of the total, because the majority were shroudedfrom view by the dust that pervades the Milky Way. Thus, it is estimated that this historical cohortrepresents only about 20% of the galactic supernovae that exploded since AD1000. Included areSN1987A, which exploded not in the Milky Way but in the Large Magellanic Cloud (one of itsnearby satellite galaxies), RX J0852-4642 (ref. 77, ref. 11), a supernova remnant whose recent(!AD1300) and very nearby birth went unrecorded, perhaps because it resides in the SouthernHemisphere (but in fact for reasons that are as yet unknown), and Cas A, a supernova remnant thatwas born in historical times, but whose fiery birth was accompanied by a muted visual display thatmay have been recorded only in the ambiguous notes of the seventeenth-century astronomer JohnFlamsteed (ref. 78). The distances and peak visual magnitudes quoted are guesses at best, exceptfor SN1987A. Astronomical magnitudes are logarithmic and are given by the formula MV ¼#2:5log10ðbrightnessÞ þ constant. Hence, every factor of ten increase in brightness represents adecrease in magnitude by 2.5. For comparison, the Moon is near −12magnitudes, Venus at peak is−4.4 magnitudes, and good eyes can see down to about +6 magnitudes.

© 2000 Macmillan Magazines Ltd

sn 1987a: neutinos

stellar corpses: neutron stars

The energy of formation of a neutron star is largely determined by the change in the gravitational binding caused by core-collapse. Just before collapse we have a core with mass comparable to the sun and radius of about 1000km. After the collapse we have a neutron star with a similar mass but with a radius of about 10 km:

Dead Stars and Black Holes

a.k.a. Astronomy 15 Winter Quarter 2008

Gravity Triumphant: Key Concepts

ET = EK + Ug (1)

Ug ⇤ �GM2

R= 3⇥ 1046

�MNS

M�

⇥2 �10 km

RNS

⇥J (2)

B = �3

5G (3)

EK =AM5/3

R2(4)

MOV = 1.5� 2.5M� (5)

MOV = 4MC (6)

RNS

R�= 0.00001

�MNS

M�

⇥1/3

(7)

1

2mv2

esc +�GMm

r= 0 + 0 (8)

vesc = c =

⇤2GM

RS(9)

neutron star kicks!

core collapse supernovae

supernova remnants

supernova remnants

As it propagates, a SNR causes a strong shock to occur since the ejecta is moving highly supersonically compared to the surrounding mass

supernova remnants

Detection of 1keV photons from SNRs suggest:

10 pcHow much energy does it take to ionize this much gas?

where does the energy comes from?

but the sound speed

supernova remnants