How does a super nova happen ? (please explain simply)

Hi Ethan,

Supernovae are the coolest!  They are actually pretty common, with about 50 stars blowing every second!

The vast majority of supernova are when a star collapses due to gravity and subsequently blows up (an implosion).  The core of all stars are layered like an onion, with the heavier elements (like iron) in the center, while the lighter elements (like hydrogen) on the outside.  Nuclear fusion, which is the process of combining lighter elements to form heavier elements and produce energy, is the fuel source of stars.  When two elements are fused, let's say two hydrogens, you form a new element, in this case helium, plus some leftover particles (junk) and energy (heat).  

As a star keeps fusing elements together, you get more heavy elements and more leftover particles (essentially junk).  However, these leftover particles are a burden, as they are not doing anything but adding extra weight, which gravity is trying to pull towards the center of the star, creating pressure in the star.  To alleviate this pressure, the star burns more fuel to actually push this material further away, like a steam valve on a tea kettle.  However, since the star is creating more heavy elements, more leftover particles are being creating, which causes even more fuel to be used (and so on).  

What you have is an epic battle between gravity and pressure.  At some point, the star can not sustain this lifestyle and gravity wins, collapsing all the material down to the core, causing it to implode (for this reason we call these core-collapse supernova).  In turn, this implosion creates a big stellar firework show!  For these supernovae, the bigger the star, the more fuel it most consume, subsequently causing the process to happen faster.  Therefore, the bigger the star, the shorter it lives.

There is also a weird second type of supernova.  These are when white dwarfs, which are the iron remnant core of a star  (something our Sun will become in billions of years), sucks gas (hydrogen and helium) off of a nearby star, kind of like a zombie star.  As the white dwarf sucks gas over time, it adds extra weight to the star, which again the star can not sustain (as above), and it also implodes.  However, the implosion ignites the extra gas it has sucked, causes this to ignite, so you get an implosion AND a thermonuclear bomb like event at the same time ,making these very bright.  We call these typa Ia supernova.

I hope this helps.



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Brad Tucker


I'm happy to answer any general questions about Astronomy, Astrophysics, and Cosmology. I'm also happy to take general, specific, and detailed questions related to supernovae, Baryonic Acoustic Oscillations, the Cosmic Microwave Background, dark matter, dark energy, and the Big Bang Theory. I'm also happy to chat about Astronomy/Astrophysics education and careers, and philosophy and science.


I am a professional research astronomer/astrophysicist/cosmologist. My research focuses on studying supernovae and using them to measure the properties of the Universe, such as how fast it is growing and what it is made of. I also frequently give talks to school groups and the public, and am a regular guest on various radio stations.

Current Research Fellow at Mt. Stromlo Observatory, the Australian National University, and in the Department of Astronomy, University of California, Berkeley.

Lots of journals, including the Astrophysical Journal, the Astronomical Journal, and Nature. I am currently in the middle of writing my first popular book.

B.A. Philosophy, University of Notre Dame, Notre Dame, IN USA B.A. Theology, University of Notre Dame, Notre Dame, IN USA B.Sc. Physics, University of Notre Dame, Notre Dame, IN USA Ph.D. Astrophysics, Mt. Stromlo Observatory, the Australian National University, Canberra, ACT, Australia

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