Supernova Sonata

What is a Supernova?

Stars which are several times more massive than our Sun end their lives in a spectacular explosion called a Supernova. The explosion occurs when the fuel for the fusion process in the core is depleted. This lack of outward pressure, which combats the inward gravitational pull, allows the star to collapse. As it shrinks, the core grows hotter and denser. New nuclear reactions begin and temporarily halt the collapse of the core. When the remaining core nuclear is basically just iron, nothing is left to fuse. Fusion in the core ends.

Very quickly, the star begins its final gravitational collapse. The core temperature rises to many billions of degrees. The iron atoms are crushed together. The force of gravity is greater than the repulsive force between the nuclei of iron. The core then recoils. The energy of the recoil produces a shock wave through the star envelope. The envelope material is heated and fuses to form new and heavier elements and radioactive isotopes. The material is exploded away from the star core and is known as a supernova remnant. Many of these are seen in the heavens. Here are examples.

Chandra X-ray Observatory

Smaller supernovae can leave behind a spinning neutron core only a few tens of miles across. Larger supernovae exert such tremendous inward shock forces that the neutron core can collapse into a black hole. It is so small and dense, that light is not fast enough to escape its gravitational pull.

Turn Up Your Volume before you watch this video. It is a musical rendition of supernovae events in a small part of the sky about as large as 16 full moons. Explanation of the process is below the video.

1. Search for Supernovae over a long time interval.

Between April 2003 and August 2006, the Canada-France-Hawaii Telescope (CFHT) monitored four regions of the sky with a large digital camera. It was watching for a type of Supernova (called Type Ia). These result from the thermonuclear detonation of white-dwarf stars.

The four fields had an area of about 16 times the area of the full Moon. That is about 1/10,000 of the entire sky. There were 241 Type Ia Supernovae seen during the three years of watching. Their positions are shown as time progresses. The animation shows a frame per day. In other words, 1 sec of video corresponds to 2 wks of real time.

2. Assign each Supernova a note to play.

Distance to each Supernova determines the volume of the note. A closer Supernova is played louder.

Supernovae also follow a similar pattern of brightening and then fading. That is seen below on the rapid rise, then slower decent of the curve. But they each also have some variations as indicated by the various colors of plots of the curves. The pitch of the notes used was determined by the Supernova’s “stretch”. How the Supernova brightens and fades is used to calculate a value for stretch. Higher notes represent higher stretch values. The pitches are from a Phrygian dominant scale for those who understand music theory.

Calán/Tololo Supernova Survey

3. Assign the instruments to be played.

Only two instruments were used. The instrument was determined by the mass of the host galaxy. Notes of Supernovae in more massive galaxies were played by upright bass. Those in less massive galaxies were played by piano.

Creators of this Work

Alex H. Parker (University of Victoria) and Melissa L. Graham (University of California Santa Barbara / LCOGT). Visit the Parker website and the Graham website.

We are stardust

If it weren’t for Supernovae, the heaviest elements would be iron. That is the top rung of the fusion process in star cores. Because of the tremendous shock waves of supernovae, fusions of  nucleii of elements heavier that iron are possible, giving us the much wider range of naturally occurring elements. Many of the elements in the rocks and minerals and our bodies came from one or more Supernovae in our vicinity of space.