Wednesday, May 23, 2012

Observing Alert - Supernova 2012cg Discovered In Virgo Galaxy NGC 4424

It's official. According to AAVSO Special Notice #283 compiled by Elizabeth O. Waagen, there's a brand new, shiny supernova out there... at an observable magnitude! According to data taken with LOSS and reported by M. Kandrashoff, S. B. Cenko, W. Li, and A. V. Filippenko, spectra indicates a Type 1a supernova event began on approximately May 17, 2012 and has continued to brighten.

Cataloged as Supernova 2012cg, the event is visible in barred spiral galaxy, NGC 4424 located in the constellation of Virgo. Coordinates are RA 12 27 12.83 - Dec. +09 25 13.2. The supernova began erupting at an unfiltered magnitude of 16.9 and has now reached magnitude 12.9.

Spectra indicating the object to be a Type Ia supernova discovered about two weeks before maximum were obtained by: L. Pei, M. Nguyen, D. Carson, and A. J. Barth (University of California, Irvine) with the Kast double spectrograph on the Shane 3-m telescope at Lick Observatory on 2012 May 18 UT and reported by S. B. Cenko, A. V. Filippenko, and J. M. Silverman (University of California, Berkeley), and A. Gal-Yam (Weizmann Institute of Science); and J. Irwin with the F. L. Whipple Observatory 1.5-m telescope (+ FAST) on 2012 May 18 UT and reported by G. H. Marion, R. P. Kirshner, and R. J. Foley (Harvard-Smithsonian Center for Astrophysics, CfA), and P. Challis (Australian National University) on behalf of the CfA Supernova Group.

Originally discovered on February 27, 1865, by Heinrich d'Arrest, NGC 4424 is a 12th magnitude barred spiral whose recessional velocity of 435 km/sec isn't aggressive enough to obtain an accurate distance measurements.Current consensus places the distance to be approximately 50 million light years, making its apparent size of 3.6 by 1.8 arc minutes to measure out to about 50,000 light years in diameter. According to a study done by R. Winnick and J. Kenney, NGC 4424 is " believed to be one of the clearest cases for a significant merger in the Virgo cluster. The R and B-band images reveal banana-shaped isophotes, which are thought to have resulted from a significant and recent merger. New spectra from the DensePak fiber array reveal double-peaked stellar absorption lines within the galaxy. These double-peaked features indicate the existence of co-spatial, counter-rotating stellar components within NGC 4424, further strengthening the merger theory."

Catch a supernova in a most unusual galaxy!

Submitted by Tammy Plotner. Image Credit: Dr. Joe Brimacombe, Coral Towers Observatory, Cairns, AU

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