Supernova Remnants
Overview
After every supernova massive amounts of material and energy are ejected throughout space, these pieces of space debris are called supernovae remnants or SNRs. They are the compounds and compressed gas produced by supernovae. Moreover, they often form a shell or bubble-like shape. SNR wavelengths are around 1000 Kelvin and are monitored to gauge the age, mass and energy produced by a supernova.
Formation of SNRs
SNRs are formed by the initial explosion and continued expansion of a supernova. As a massive star collapses, it produces a shockwave that can induce fusion reactions in the star’s outer shell. The fusion reaction then creates new nuclei that are pushed outwards by the shockwave. While the fusion process is happening the shockwave is also heating and moving the surrounding interstellar medium. The interstellar medium is then harnessed and moved in a way so that it will form a shell or blob like shape around the products of the other SNR’s. Over time the shell will weaken and spread out through space, enriching our universe with new elements.
Classification of SNR's
There are 3 main categories of type la SNRs: Shell-type, Crab-like and Composite Remnants which are all also types of planetary nebulae. Moreover, as a by-product of other types of supernovae black holes and neutron stars may be produced, this is not possible for type lA supernovae.
Role's Played by SNRs
SNR production has 2 main outcomes: Firstly, the creation of (almost) all the heavy elements throughout our galaxy, and, secondly, heating up interstellar medium surrounding the explosion, producing more energy while also distributing the SNR’s further into space. To put it simply, life would not exist without SNRs, because all elements heavier than iron were created by supernovae. So everything heavier then iron is just a by-product of a supernova this includes the cores of distant planets to the copper in our blood. The creation of these elements is possible because of the massive amounts of energy released when a supernova occurs. The energy provides the conditions necessary for fusion. During the explosion, approximately 1028 megatons of energy can be used to force small nuclei to bind together. Then this enormous amount of energy is used to propel the SNRs across the universe. Matter within the supernova is re-accelerated by this same energy. This acceleration is called the Fermi acceleration process, which makes the particles reach velocities very close to the speed of light; causing galactic cosmic rays to form from the interstellar medium. These tiny particles, that are now traveling very fast, are what form the shockwaves that push the SNR’s outwards. The Fermi reaction is a feedback loop that will only end when there is not enough materials and/or energy to sustain it. When this happens type la supernovae will end in a collapse of light, energy and mass.
Shell-type remnants:
The Cygnus Loop, an example of a shell type remnant. When a shock wave from a supernova shoots through space, any interstellar material in its path is heated and stirred up. This forms a vast shell of hot material surrounding the center. The edges of the explosion, the shell, are in a ring-like structure, hence the name. We see the SNR’s form in a ring because from our line of sight there is more hot gas than when we look directly through the middle; this phenomenon is also known as limb brightening.
Shell Remnants
Figure 7. A photo of the Cygnus Loop, a shell-type remnant Photo taken by the Hubble telescope.
Crab-like remnants:
Crab-Like Remnants
Crab nebulae, also known as plerions, Crab Nebulae are similar to shell type remnants. The major difference between the two is that Crab Nebulae contain a pulsar in the middle. A pulsar is a rotating neutron star that “pulses” out bursts of radiation every few seconds. They are filled with high-energy electrons that are ejected from the pulsar. These electrons then interact with the magnetic field in a process called synchrotron radiation. This phenomenon makes the supernova have more of a blob shape than a ring shape.
Figure 8. A photo of the Crab Nebula, a crab-like remnant. Photo taken by the Hubble telescope.
Composite remnants:
Composite Remnants
These SNRs are a mix of Shell-like and Crab-like remnants. The subtypes of composite remnants differ depending on how electromagnetic they are. There are two main kinds: thermal and plerionic. Thermal composites are more similar to crab-like remnants. However, their difference is that they have spectral lines (bright lines formed by streams of photons), which indicate the hot gas surrounding the SNR. The other main kind are plerionic composites, they are also crab-like but have more of a shell-like structure. They don't have do not have spectral lines near the center, but the shell does have spectral lines around it.
Analyzation of Supernovae Remnants
Figure 9. A photo of a composite remnant. Taken by a space telescope
We analyze SNR's due to the sheer amount of light and energy that they release as oppsed to supernovea itself as scientific instruments cannot gather a vast amount of data from its center. As such, scientists have to rely on the edges of supernovae and SNR's to learn more about its process and effects.
Kepler's SNR
This SNR was part of a type la supernova that is 20,000 light years away from Earth. In 1604 astronomers saw the explosion happen, including Johannes Kepler who the remnant is named after. This particular SNR is famous for its astounding velocity. It is currently traveling 20 million miles per hour, about 25,000 times faster than the speed of sound on Earth.
Types of Supernovae
Here are some images of different kinds of supernovae in varying stages of their life. However, because of the amount of energy released in a supernova, none of the photos below are of the moment of an explosion but rather of the result of the supernovae (i.e. supernova remnants).
