CASS A Re: The youngest known galactic supernova remnant - OctAstronomy

I shot an image of it from my castro valley backyard back in 2007

the skies there were mag 3.2 at best

http://www.narrowbandimaging.com/3c461_cassA_mk1sn2_cm10_geg_cs4_s2hao3_page.htm

From: Steve Gottlieb
Sent: Sunday, August 29, 2010 2:41 PM
To: TAC mailing list
Subject: Re: [TAC] The youngest known galactic supernova remnant - OctAstronomy

By the way, my subject "the youngest known galactic supernova remnant" is misleading -- in 2008, it was discovered that the expansion rate of a small, radio supernova remnant (G1.9+0.3) implied an age of only 100 years or so. This easily makes G1.9+0.3 the youngest SNR in the Galaxy, though I'm certain it's not a visual object as it is highly obscured by dust. The discovery preprint is at http://arxiv.org/PS_cache/arxiv/pdf/0803/0803.1487v2.pdf

--Steve

On Aug 29, 2010, at 1:59 PM, Mark Johnston wrote:

  Correction: October version of Astronomy that came in mail just now, NOT
  Sept version.
  (These guys are so far ahead of the calendar)

  Mark Johnston wrote:

    The Sept 2010 Astronomy mag has Cassiopeia A being discussed with an

    extremely enhanced picture on page 49 in the context of the compact

    central neutron star it holds at it's center.

    Marko

    Steve Gottlieb wrote:

      If you're going to take a look, Marko, I realized I left off the

      position! Cas A is plotted on the U2000 atlas as a radio/x-ray

      source but there is no catalogue listing in the companion Deep Sky

      Field Guide and I couldn't find a listing within Megastar or SkyTools

      3. The center of the shell is at 23 23 24 +58 48.9 (2000) and the

      filament I described about 1.5' north of this position.

      --Steve

      On Aug 25, 2010, at 12:59 AM, Mark Johnston wrote:

        Steve throws another kool object out for a challange. Thanks, I

        have been building a list for next month mostly in Pegasus.

        Steve Gottlieb wrote:

          That would be Cas A, the strongest radio source in the sky (besides

          the sun). Based on the expansion rate of the filaments light from

          this supernova must have reached earth ~340 years ago ( roughly

          1667). Although it was not recognized as a nova at the time, it

          may have been catalogued as a 6th magnitude "star" by Astronomer

          Royal John Flamsteed in 1680, as there is no known counterpart

          today for his "star" Cassiopeia 3.

          Available images have traditionally been at radio wavelengths

          (http://images.nrao.edu/395) or x-ray

          (http://chandra.harvard.edu/photo/1999/0237/), though HST captured

          it in 2006 (http://spacetelescope.org/news/heic0609/). So, it was

          never known as a visual target and the first observation was

          probably made in the last couple of years. So, this object was

          high on my observing list earlier this month when I observed with

          Ray Cash, Mark Wagner, Richard Navarette, Ken Archuleta and Mina

          Reyes at Lassen on the peak of the Perseids. But I really didn't

          know what to expect.

          Here's the good news -- using a 21mm Ethos (108x) and an OIII

          filter, I was surprised to easily pick up the brightest filament in

          my 18-inch Starmaster. With this combination a small, elongated,

          fairly low surface brightness glow was immediately noticed,

          ~1.2'x0.4', extended ~E-W. The SNR was not seen unfiltered at 108x

          or at 175x, so it responded strongly to the OIII filter. The visual

          filament I picked up forms the northern edge of the 4' diameter

          supernova remnant. The glow is situated at the vertex of an

          isosceles triangle with a mag 11.4 star 2.5' SW and a mag 11.7 star

          2.5' NNW. The 56' field includes a number of mag 10 stars and is

          fairly rich, but there are no brighter stars. Give it a try!

          --Steve

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