End In Fire

The supernova in the Large Magellanic Cloud

Paul Murdin, Cambridge University Press, 1990

About SN1987A, a.k.a. Sk-69 202 in the Large Magellanic Cloud, which University of Toronto astronomer Ian Shelton first observed 1987 February 27 with the 24 inch telescope at the Las Campanas Observatory in Chile. Sanduleak = Sk-69202 .

page 68 - Type II vary a lot.

page 71: Timeline for SN1987A (need observed aftermath)

Observed time


status of star

20 million years ago


star formed, burned hydrogen for some 15 million years

3 million years ago

end of Pliocene

began burning helium (in core)

20 thousand years ago


began burning carbon (in core)


began burning neon and oxygen (in core)

1987 Feb 20

began burning silicon, producing an iron core

1987 Feb 23 7:35 UT


page 79: The outer surface expanded at speeds up to 0.1c . Expanded 5x in first hour, 1 AU in 10 hours. Increase in surface area greater than cooling so luminosity increases.

page 164: fig 55: X ray to 450 days: 5 to 10 counts/sec 6 to 16 keV, 1 to 2 counts/sec 16-28 keC. WHAT SENSOR AREA?

page 165: fig 56: Ginga xray spectrum, september 1987: 6 counts/m2 at 5 keV, rolling down to 1 /m2 at 1keV, flat to 35 keV. Not sure this can be turned into all-spectrum counts or energy.

page 167: fig 58: Photons/keV-cm2

Type II supernovae (SnII) are the explosion of stars between 8 and 40 M⊙ (solar masses) at the end of an 10 million year lifetime for a 25 M⊙ star. Estimated 0.02 SnII per year in our galaxy - most not visible. If the galaxy has 200 billion stars, the rate is 1 in 1e13 SnII per year. If there are an average of 200 stars within 20 light years (6.14 parsecs), then within radius R (in parsecs) there are 0.864 R³ stars, or 8.64e-14 R³ SnII per year. The average time between SnII versus distance, rounded to an order of magnitude, is :

1 pc

10 Ty

2 pc

1 Ty

5 pc

100 Gy

10 pc

10 Gy

20 pc

1 Gy

50 pc

100 My

100 pc

10 My

So, over the next 5 billion years, our solar system might see 5 SnII within 20 parsecs distance, and 50 SnII within 50 pc. The brightest star in the sky, Sirius, is close but only 2 M⊙. Canopus is 9 M⊙ and a possible SnII candidate, but 100 pc away. In 10 My, with a radial velocity of 20 km/s (assumed positive), it will be more than 200 pc further away.

EndInFire (last edited 2015-12-10 20:54:16 by KeithLofstrom)