--- Patrick Wiggins <paw@trilobyte.net> wrote:

Just shot an image of the supernova in M-51. Comparing it to last month's image it does not appear to have faded much.

The light curve at SNWeb site shows it holding steady at about mag 14.3 - http://www.astrosurf.com/snweb2/2005/05cs/05csCurv.htm http://www.rochesterastronomy.org/sn2005/sn2005cs.html Not finding any good information on the average visual duration of Type I nova and Type II supernova, in another newsgroup, I posted an inquiry and received the following replies from more experienced amateurs. The digested responses may be of interest - =================================== Original question by Canopus56 Date: 11 Jul 2005 12:30:35 -0700 Subject: Supernovae - novae - average duration ? When supernovae or novae are reported that are visible to amateur class scopes, is there a rule of thumb for how many days they will remain visible? What is the average duration of the visible light-curve? Recent examples include sn2005cs in M51, which can be still be imaged by astrophotography although its discovery date was June 26. Nova Sgr 05 #2 was discovered on July 5 and I understand is still visible. - Canopus56 -------------------------------- Reply by : Michael Richmond Date: 12 Jul 2005 08:53:29 -0700 A "typical" supernova will remain within 3 magnitudes of its peak light for one to three months. One might expect a typical supernova to remain bright for several months after discovery; however, if the event was discovered long after its maximum, it might fade to invisibility just a few weeks after it is found. Classical novae tend to evolve more quickly than supernovae: they might drop 3 magnitudes from peak in just a week or two. However, since some novae in our own Milky Way reach brighter apparent magnitudes than most supernovae -- the Nova Aql 1999 number 2, for example, reached mag 4 -- they might still be detectable in small telescopes despite dropping 5 or 6 magnitudes from their peak. Michael Richmond ------------------------------- Reply by Brian Tung Date: Wed, 13 Jul 2005 20:43:32 +0000 (UTC) Subject: Re: Supernovae - novae - average duration ? Kurt (canopus56) wrote:

Michael, I'm having problems conceptualizing why it is an SN would remain 3 magnitudes below it peak explosion brightness. For a hypothetical, wouldn't a mag 17 pre-explosion supernova just explode - there's a flash to mag 13 - and that's it? Then the star falls back to its pre-explosion magnitude. Or is there a superheated cloud of expanding stellar remnants that keeps the magnitude at a higher base-line than pre-explosion? The magnitude decreases proportionally as the size of the cloud increases?

That's partly it. What often happens is that nucleosynthesis doesn't quite finish right at iron-56. If it did, a Type Ia would be a quick flash and then the remnants would expand so quickly that they would dim very rapidly. Instead, what seems to happen is that nuclides close to iron-56 but not right at it are formed, and these decay relatively slowly over the next couple of months to supply some of the brightness. One of those apparently is cobalt-56, which decays to iron-56 with a half life of a couple of months (I think), and Type Ia supernovae do seem to have one exponential decay with a half-life of a couple of months. Brian Tung <b...@isi.edu> The Astronomy Corner at http://astro.isi.edu/ Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/ The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/ My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.txt __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com