Bluegrass Amateur Astronomy Club (Lexington, KY)


Type II-P supernova recently found in Messier 66
Date: June 11, 2016

A Type II-P supernova (SN2016cok) was recently found in Messier 66 (NGC 3627), an intermediate spiral galaxy in the constellation Leo. This supernova was identified by telescopes located in Hawaii and Chile that are part of the All Sky Automated Survey for SuperNovae.

Even though M66 is located approximately 36 million light years from Earth it is easily visible with even modest sized amateur telescopes and is one of three galaxies commonly referred to as the Leo triplet, the other two being M65 (NGC 3623) and NGC 3628. The accompanying image of M66 with the indicated location of the supernova was taken by Rick Schrantz on May 30, 2016. Rick captured the image with an 8-inch Ritchey-Chretien optical tube and a ST10XME camera unfiltered.

m66 supernova

A supernova is a large and violent explosion that is literally the death of a star. Most stars that undergo such explosions are extremely massive, about 8 to 50 times the mass of our sun. Smaller stars such as our Sun undergo nuclear fusion to create helium. This reaction releases energy. With massive stars that become Type II supernovas the temperature and pressure is so great that fusion produces elements heavier than helium until the core of these stars is composed of iron and nickel which do not as easily undergo fusion. When they do the reaction is endothermic. The energy output in the core over time becomes greatly reduced and the core is compressed by the star’s mass eventually causing the core to rapidly implode or collapse, resulting in a violent explosion or shockwave. The shockwave encounters the collapsing outer layers which are blown apart producing the supernova. Type II-P supernova have hydrogen in their visual emission spectrum and their luminosity decays very slowly and thus appears bright for an extended period of time. The core of many Type II-P stars can evolve into a Neutron Star. These stars are very small, with a radius of only about 12 miles, but they are about twice as dense as the sun.

Type Ia supernova differ from Type II in several ways. The formation of Type Ia supernova are the result of an interaction between binary stars where at least one of the stars has evolved into a white dwarf while the other has evolved into a red giant. Here, the white dwarf accretes mass from the red giant. Eventually the mass of the white dwarf is so great that the core temperature increases and ignites carbon fusion. This “runaway” fusion results in a supernova. Because white dwarfs are devoid of hydrogen these supernova lack spectra hydrogen lines. Type I supernova also differ from Type II in that their luminosity decays at a faster rate.

-Written by Lawerence Brewer (with help from Rick Schrantz and Tim Knauer)

References:



Lexington Clear Sky Chart
Raven Run Clear Sky Chart