Supernova SN2017 eaw

SN 2017eaw in  NGC6946 - Graphic prepared by Pip Stakkert based on images taken with the Bradford Robotic Telescope in 2015 and the Autonomous Robotic Telescope- PIRATE Telescope (Open University)  in August 2017

"Supernova are separated into two categories: those without hydrogen - Type 1 and those with - Type 11. Type 1a supernova are thermo-nuclear explosions which result when gas captured by a white dwarf in a binary pair exceeds a critical limit. All other sub-types of Supernova whether Types 1 or 2 are believed to be result of core collapse in massive stars. Whilst a star has nuclear fuel to fuse, primarily hydrogen and helium, it manages a balancing act between gravity -trying to make the star collapse and radiative pressure from the fusion process trying to make it expand. When a massive star runs out of fuel gravity overwhelms radiative pressure and the star's core collapses releasing enormous amounts of energy as a supernova.

Supernova SN2017 eaw was discovered  on 14 May 2017 by the Utah based amateur astronomer Patrick Wiggins. SN2017 is located in the intermediate spiral "Fireworks Galaxy" NGC 6946 some 22 million light years away on the border between the constellations Cepheus and Cygnus. The galaxy is no stranger to supernovae with 10 confirmed - hence the name 'Fireworks Galaxy'.

SN2017 eaw has been identified from its spectrum as a Type11P supernova which is believed to have arisen from the core collapse of a super giant star with an initial mass somewhere between 8 and 10 solar masses and a retained  hydrogen envelope.
On the 21st of August the brightness of the SN2017eaw was reported as Mag 13.5"  

I should like to take this opportunity to introduce and welcome a new member of the Jodrell Plank Observatory Team.  Ronald Clump has been appointed by the JPO Trust to be the Jodrell Plank Observatory's first CEO.  Mr. Clump joins our organisation after a successful career in business and the media.  We all wish Ronald every success in bringing his unique blend of skills and experience to bear in leading the JPO where no other Observatory has been before".

Kurt Thrust current Director of the Jodrell Plank Observatory 

Inverted image of NGC6946 showing location of SN2017eaw - (North is up) - image taken with the Autonomous Robotic Telescope (Open University)    PIRATE Telescope - 25 August 2017 (00:53:21 UTC) - Pip Stakkert

"How is it possible to see a Supernova in a Galaxy 22 million light years distant?  The simple answer to this question is because it is so very very bright.  In classical times the Greeks classified the visible (to the naked eye) stars into five groups. Group 1 stars were the brightest and Group 6 were the dimmest that could be seen. Unfortunately the human eye does not assess brightness on a linear scale and it was eventually discovered that a change from one group to the next represented a decrease in brightness by a factor of 2.512.  Today astronomers use the term 'Apparent Magnitude' to decribe the 'Groups' eg. a Mag 6 star is the dimmest star you can see with your naked eye from a dark location.  

The sun, if it were at a distance of 10 parsecs ( where one parsec = 3.26 light years)  from the earth would have a magnitude of 4.83 (this measure is known as Absolute Magnitude) As we are much closer to the sun at 93 million miles or 8.3 light minutes its apparent magnitude is much brighter at Mag -26.74

SN2017eaw was reported as Mag 13.5  - so many times dimmer than could be seen without the optical aid of a telescope.

To give some idea how intense and luminous the Supernova is we can use some mathematics to compare the supernova with our Sun. Luminosity is the rate at which an object produces radiation energy in watts and brightness or intensity (I) is given by the equation:   
  
         Intensity I = Luminosity  watts   per metre^2 
                                   4πd^2


Where d = distance from the source

If you want to compare the luminosity of a star or a supernova with the luminosity of the Sun you can write:

equation  A            Luminosity (SN2017eaw)  = (d SN)lyrs ) ^2 x Intensity (SN)
                                Luminosity (Sun)                  (d Sun )lyrs)       Intensity (Sun)


The Sun has a luminosity of approximately 3.86 x 10^26 watts


 So :       Intensity I(Sun) = 3.86 x 10^26 watts                 =  3.24 x 10^-11 w/m^2
                                           4π(3.08x 10^17) metres^2



 As: 
              I(SN2017aew) = I(Sun)x(2.512)^(MagSun - MagSN2017aew)

Then     I (SN2017aew) = (3.24 x 10^-11 w/m^2)(2.512)^(4.823 - 13.5)

 or         Intensity (SN) =(3.24 x 10^ -11)  = 1.095 x 10^ -14
                                        (2.512)^ 8.677

And from the intensity it is possible to calculate the Luminosity using equation A above

              L(SN2017aew) = L(Sun) x    (distance to SN lyrs)^2    x I (SN)
                                                                    (32.6 lyrs )                  I (Sun)
So
              L (SN2017 eaw) = (3.86 x 10^26) x (22 x 10^6)^2  x  1.095 x 10^ -14
                                                                            (32.6)             3.24 x 10^-11

or       Approximately    Luminosity (SN2017 eaw)  =    5.94 x 10^34 Watts

or       Approximately  the Supernova was, at the time that its magnitude was determined, 150 million times more luminous  than our Sun. - Thats why at the vast distance of 22million light years this 'enormous bang' could be seen from Earth with relatively small telescopes. The other mind boggling fact is that this Supernova actually occured some 22 million years ago towards the end of the geological Oligocene epoch. At that time our ancestral apes were still in Africa. The photons of light we captured from SN 2017 eaw have been travelling for all that time to reach us.

Clearly, if you were anywhere near this cataclysmic event, Rayburns and Factor 40 Sunscreen would not do the business."

Archie Mendes  - visiting Astrophysicist and Mathematician at the Jodrell Plank Observatory.
                                                        
 Please note the calculations are only approximate and account for visible light only.

A Wolf-Rayet Star

NGC 6888 The crescent Nebula in the Constellation Cygnus - Autonomous Robotic Telescope - PIRATE Telescope - telescope.org - Open University - 1x3minute exposure -Sulphur, Hydrogen Alpha and Oxygen filters.

" A very disappointing 2017 Perseid Meteor shower here at the Jodrell  Plank Observatory in Lowestoft. The whole team turned out for two nights and early mornings but only managed to spot eleven meteors in total. We took over 600 x 15 second exposures at ISO 3200 using our automated Canon Cameras but failed to secure one image of a 2017 Perseid.  Hopefully, the LVST will have registered and recorded a  plethora of radar reflections from Perseid plasma trails in the upper atmosphere over the South of France. 

At about 2.30 am. on the 13th of August, just as we were about to pack up the equipment, our neighbour Mr Shrodinger, came around  saying that all our noise and comings and goings had spooked his cat. He neither knew where it was or whether it was dead or alive!  The poor man was in a right old quantum state". 

Kurt Thrust current Director of the Jodrell Plank Observatory.

Enlargement of the above widefield image of The Crescent Nebula with annotation identifying the Wolf-Rayet star HD192163 or WR136
- PIRATE Telescope - telescope.org - Open University

The Crescent Nebula is located not far from the star Sadr in the constellation Cygnus the Swan. The Nebula is being driven by the Wolf-Rayet Star HD192163 or WR136. Only stars some 30 times the mass of our Sun become Wolf-Rayet stars towards the end of their time on the main sequence and after they have gone through the 'red giant' phase of expansion.

Starmap showing the location of the Crescent Nebula - Credit SkyMap Pro and Pip Stakkert

'The Crescent Nebula (also known as NGC 6888, Caldwell 27, Sharpless 105) is an emission nebula in the constellation Cygnus, about 5000 light-years away from Earth. It was discovered by Friedrich Wilhelm Herschel in 1792. It is formed by the fast stellar wind from the Wolf-Rayet star WR 136 (HD 192163) colliding with and energizing the slower moving wind ejected by the star when it became a red giant around 250,000 to 400,000 years ago. The result of the collision is a shell and two shock waves, one moving outward and one moving inward. The inward moving shock wave heats the stellar wind to X-ray-emitting temperatures'. Credit Wikipedia

"The Wolf-Rayet star HD192163 is very very hot - having a surface temperature of 70,000 degrees K, in comparison the surface temperature of the Sun is a  mere 5,778 degrees K.  It is estimated that the star is 250,000 times brighter than the Sun. Its hot surface is emitting high energy ultra violet light which is causing the previously shed shells of gas to glow. There is evidence that the star is binary, having a low mass spectral class M or K companion star which revolves around a common centre of gravity every 5 days or so.  " Archie Mendes - visiting Astrophysicist and Mathematician.

For information regarding the spectrum of HD192163 follow the link:
 http://adsabs.harvard.edu/full/1975A%26A....40..459C

One clear night in July 2017

Widefield image of the Western Veil

Enlarged detail of NGC 6970 Western Veil Nebula 'The Witches Broom' Detail

" After many poor weather nights at the Jodrell Plank Observatory, we have finally benefitted from some clear night skies. On the night of the 31st of July and the morning of the 1st of August we managed to have the 127mm. Meade Apo-Refractor operational for four hours - taking images of NGC6970, Messier15 and Messier 27. Today my old chum Pip Stakkert has been busy with the imaging team preparing these deep sky images" - Kurt Thrust - current Director of the Jodrell Plank Observatory.

"Ten thousand years ago or more, our ancestors looking up into the constellation Cygnus the Swan will have seen a bright light as a star exploded in a supernova. The veil nebula  is the shock wave from that explosion which is ploughing through the instellar medium. Ionised hydrogen and oxygen can be seen glowing in different colours. The 'Witches Broom'spans about 35 light years and is approximately 1400 light years away. The bright star is 52 Cygni and although it appears linked to the nebula has nothing to do with the original supernova". - Pip Stakkert - Imaging Team Leader

The Eastern Veil imaged from the Jodrell Plank Observatory back in 2015

Messier 15 in the constellation Pegasus

 

Messier 15 Globular Star cluster

"M15 is about 33,600 light-years from Earth, and 175 light years in diameter. It has an absolute magnitude of -9.2, which translates to a total luminosity of 360,000 times that of the Sun. Messier 15 is one of the most densely packed globulars known in the Milky Way galaxy. Its core has undergone a contraction known as 'core collapse' and it has a central density cusp with an enormous number of stars surrounding what may be a central black hole.
Home to over 100,000 stars, the cluster is notable for containing a large number of variable stars (112) and pulsars (8), including one double neutron star system, M15 C. M15 also contains Pease 1, the first planetary nebula discovered within a globular cluster in 1928. Just three others have been found in globular clusters since then". Credit: Wikipedia

Widefield image of the Dumbell Nebular M27 in the constellation Vulpecula 'The Fox'

Planetary Nebula Messier 27

Final enlargement and colour adjustments to bring out the central 'knots' and the 'white dwarf' star more or less in the centre of the nebula

"A planetary nebula, often abbreviated as PN or plural PNe, is a kind of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from old red giant stars late in their lives. The word "nebula" is Latin for mist or cloud, and the term "planetary nebula" is a misnomer that originated in the 1780s with astronomer William Herschel because when viewed through his telescope, these objects resemble the rounded shapes of planets. Herschel's name for these objects was popularly adopted and has not been changed  They are a relatively short-lived phenomenon, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years.
A mechanism for formation of most planetary nebulae is thought to be the following: at the end of the star's life, during the red-giant phase, the outer layers of the star are expelled by strong stellar winds. After most of the red giant's atmosphere is dissipated, the ultraviolet radiation of the hot luminous core, called a planetary nebula nucleus (PNN), ionizes the outer layers earlier ejected from the star. Absorbed ultraviolet light energises the shell of nebulous gas around the central star, causing it to appear as a brightly coloured planetary nebula.

The Dumbbell Nebula (also known as Apple Core Nebula, Messier 27, M 27, or NGC 6853) is a planetary nebula in the constellation Vulpecula, at a distance of about 1,360 light-years.
This object was the first planetary nebula to be discovered; by Charles Messier in 1764. At its brightness of visual magnitude 7.5 and its diameter of about 8 arcminutes, it is easily visible in binoculars." Credit: Wikipedia