<jabberwocky><div class="vbmenu_control"><a href="jabberwocky:;" onClick="newWindow=window.open('','usenetCode','toolbar=no,location=no,scrollbars=yes,resizable=yes,status=no,width=650,height=400'); newWindow.document.write('<HTML><HEAD><TITLE>Usenet ASCII</TITLE></HEAD><BODY topmargin=0 leftmargin=0 BGCOLOR=#F1F1F1><table border=0 width=625><td bgcolor=midnightblue><font color=#F1F1F1>This Usenet message\'s original ASCII form: </font></td></tr><tr><td width=449><br><br><font face=courier><UL><PRE>\nIn article <c45b45b3.0407171523.67f2a084@posting.google.com>, Perfectly\nInnocent <perfectlyInnocent@as-if.com> wrote:\n\n> I\'ve read that neutrinos from Supernova 1987A were observed to arrive\n> 18 hours before the photons.\n> http://www.freerepublic.com/focus/news/844807/posts\n>\n> A time lag of 18 hours seems like a long wait between the initial\n> nuclear fury and the final visible blast of stellar material being\n> ejected at millions of mph.\n> http://hubblesite.org/newscenter/newsdesk/archive/releases/1997/03/text\n>\n> Why is the detonation to explosion process so slow?\n\n\nThe neutrinos come from the core collapse, and stream out of the star\nat the speed of light. At the same time, the first bounce of the core\ncollapse sends a shock wave out from the center towards the surface of\nthe star.\n\nThe radius of the progenitor was 3e12 cm = 100 light seconds.\n(Earth-Sun distance is ~500 light seconds, the Sun is 2.3 light-seconds\nin radius). The shock wave travels much slower than the speed of\nlight, especially near the core where the density is much higher and\n(to a lesser extent) the wave is fighting upstream against the star\nfalling into the core.\n\nAlso the supernova was visible about 5 hours after the neutrinos, in a\nphoto that wasn\'t developed until after the discovery was announced.\nBut it didn\'t get really bright until it had expanded enough to give it\na lot more radiating area than it had when it was just a punk-ass blue\nsupergiant 40 times the diameter of the Sun. (Apart from the intense\nultraviolet flash at shock breakout, which wan\'t directly detected and\nput most of its flux into photons too high in energy to get through\nEarth\'s atmosphere).\n\nhttp://zebu.uoregon.edu/~soper/StarDeath/sn1987a.html\nhttp://zebu.uoregon.edu/~imamura/208/mar1/sk.html\n\n--\nDavid M. Palmer dmpalmer@email.com (formerly @clark.net, @ematic.com)\n</UL></PRE></font></td></tr></table></BODY><HTML>');"> <IMG SRC=/images/buttons/ip.gif BORDER=0 ALIGN=CENTER ALT="View this Usenet post in original ASCII form"> View this Usenet post in original ASCII form </a></div><P></jabberwocky>In article <c45b45b3.0407171523.67f2a084@posting.google.com>, Perfectly
Innocent <perfectlyInnocent@as-if.com> wrote:
> I've read that neutrinos from Supernova 1987A were observed to arrive
> 18 hours before the photons.
> http://www.freerepublic.com/focus/news/844807/posts
>
> A time lag of 18 hours seems like a long wait between the initial
> nuclear fury and the final visible blast of stellar material being
> ejected at millions of mph.
> http://hubblesite.org/newscenter/newsdesk/archive/releases/1997/03/text
>
> Why is the detonation to explosion process so slow?
The neutrinos come from the core collapse, and stream out of the star
at the speed of light. At the same time, the first bounce of the core
collapse sends a shock wave out from the center towards the surface of
the star.
The radius of the progenitor was 3e12 cm = 100 light seconds.
(Earth-Sun distance is ~500 light seconds, the Sun is 2.3 light-seconds
in radius). The shock wave travels much slower than the speed of
light, especially near the core where the density is much higher and
(to a lesser extent) the wave is fighting upstream against the star
falling into the core.
Also the supernova was visible about 5 hours after the neutrinos, in a
photo that wasn't developed until after the discovery was announced.
But it didn't get really bright until it had expanded enough to give it
a lot more radiating area than it had when it was just a punk-ass blue
supergiant 40 times the diameter of the Sun. (Apart from the intense
ultraviolet flash at shock breakout, which wan't directly detected and
put most of its flux into photons too high in energy to get through
Earth's atmosphere).
http://zebu.uoregon.edu/~soper/StarDeath/sn1987a.html
http://zebu.uoregon.edu/~imamura/208/mar1/sk.html
--
David M. Palmer dmpalmer@email.com (formerly @clark.net, @ematic.com)