LinR: Star Death

If stars are small ...

When a star as big as the sun reaches the end of its life, it turns into a planetary nebula: outer 1/3 of star is blown away, leaving very hot core as a white dwarf

The classic example is M57: The Ring Nebula
  • Central star is a white dwarf (50000°)
  • Hot blue gas at centre
  • coolest red gas along the outer boundary.

Credit: H. Bond et al., Hubble Heritage Team (STScI /AURA), NASA

The star blows away its outer layers, so almost all the older ones we knew look like this.
or like this

But now we have all sorts of weird shapes.

This is the Cats-eye nebula: looks like successive explosions
Mz3: The Ant Nebula. Probably magnetic field is creating a "focussed" planetary nebula

Credit: R. Sahai (JPL) et al., Hubble Heritage Team, ESA, NASA

Planetary Nebula CRL 618: this was a red giant a few hundred years ago, but it is now expelling jets of gas

Credit: Susan R. Trammell (UNC Charlotte) et al., ESAIC, HST, ESA, NASA

NGC 2440: a very hot white dwarf which is lowing off its outer layers much faster

Credit: H. Bond (STScI), R. Ciardullo (PSU), WFPC2, HST, NASA

IC 4406: a really weird planetary nebula: probably a cylinder that we see side on. How can a round star make a square nebula? IC 4406 is most probably cylindrical, with its square appearance the result of our vantage point.

Credit: H. Bond (STScI), R. Ciardullo (PSU), WFPC2, HST, NASA

If Stars are large....

we get supernovae

Approx 1/30 yr known in Milky Way
6 visible in recorded history

  1. 1006 Type I SN 1006: History's Brightest Supernova. THis shows remnants of the expanding shockwave

    Credit: Frank Winkler (Middlebury College) et al., AURA, NOAO, NSF
  2. 1054 Type I Crab. Two superimposed pictures show how it is still expanding
  3. 1181 Type II. Now seen as radio source 3C58. THis is in X-rays

    Credit: P. Slane (Harvard-Smithsonian CfA) et al., CXC, NASA

  4. 1572 Type I Tycho Gas is still very hot, so produces X-rays,seen in blue at front of blast wave Credit: SAO, CXC, NASA
  5. 1604 Type I Kepler. Temps still in excess of 1000000°C

    Kepler's SNR from Chandra, Hubble, and Spitzer Credit: R. Sankrit and W. Blair (JHU) et al., ESA, NASA Graphic: courtesy STScI

  6. 1667 Type II Cas.A

    Credit: U. Hwang (GSFC/UMD), J.M. Lamming (NRL), et al., CXC, NASA,
    All almost in plane of galaxy.

    2 Kinds, distinguished by light curves

    TYPE I

    Decay rapidly for 30 days, exponentially afterwards
    In all galaxies

    TYPE II


    Rapid decay -> Plateau->Rapid decay

    Type I

    Type 1 have a compact object (white dwarf) with a red giant, which expands and spills material onto companion, finally triggering catastrophic collapse. All type 1a seem to be the same (very important for later on!)

    Drawing Credit: ST ScI, NASA

    Type II

    Agrees with models of core collapse of heavy (>10 M₀ ) star

    Tc > 109 °C

    Many in external galaxies:spectrum show ejected material has v - 10⁴ km s-1

    The only one we have seen recently is

    Supernova Sn 1987a

    Photographically February 23rd (unit is fraction of day!)

    1. 23rd .042 - .055, not seen.
    2. 23rd 059 - .101, not seen
    3. 23rd .39, <7m
    4. 23rd .443, m = 6.36
    5. 23rd .62, m = 6.11
    6. 24th Observed visually Sheldon
    v. fast initial rise, then increase to plateau

    3 hours before the light arrived a pulse of neutrinos hit the various detectors running at the time (Kamiokande, Mt.. Blanc) Theoretically predicted but never seen before or since.

    Star could be identified with known one in catalog Sk-69°202 in Lesser Magellanic Cloud (first time we have been able to do this!) Distance ∼ 156000 lys ∼ 50 kpc
    ⇒ Mv = -16.0

    Progenitor was blue(!) supergiant M ∼ 20M₀
    May have companion star but definitely type II. Surrounded by rings before explosion
    Can now see blast wave from explosion hitting rings of material previously ejected

    Credit: P. Challis, R. Kirshner (CfA), and B. Sugerman (STScI), NASA

    We would like to catch supernovae before they explode: here are 3 possibilities
    Eta Carinae blew off a lot of material 150 years ago: probably pre-collapse now

    Credit: J. Morse (U. Colorado), K. Davidson (U. Minnesota) et al., WFPC2, HST, NASA
    The Crescent Nebula is s shell of gas surrounding a central Wolf-Rayet star WR 136 (very hot and unstable). Should undergo a supernova explosion in next million years.

    Credit: Brian D. Moore (ASU) et al., WFPC2, HST, NASA

    NGC 3603: can see formation of stars and probably pre-collapse Sher 25 surrounded by rings

    Credit: Wolfgang Brandner (JPL/IPAC), Eva K. Grebel (U. Wash.), You-Hua Chu (UIUC), NASA

    A few even more bizarre objects...