Difference Between Nova and Supernova

Main Difference – Nova vs Supernova

Nova and Supernova are two types of cosmological events that occur in the universe. Novae are much less powerful explosions compared to supernovae. A nova is a result of a runaway nuclear reaction where Hydrogen nuclei fuse into Helium. A supernova, on the other hand, is a cataclysmic explosion where elements heavier than Iron and Nickel are produced. After a nova explosion, the white dwarf returns to its original stage gradually. But after a supernova explosion, the remnant becomes a black hole or a neutron star. This is the main difference between nova and supernova.

What is a Nova

The simple meaning of the Latin word “nova” is “new”. In science, however, novae are not new stars though they look like stars for a short period of time.

A nova is a sudden increase in the brightness of a white dwarf. Normally, a nova occurs on the surface a white dwarf which is a part of a binary system. Typically, the other members of such binary system is a normal star or a small white dwarf. If the white dwarf has an enough amount of matter, its gravitational force can draw Hydrogen from its companion star while they are orbiting around each other. The drawn Hydrogen gas is compressed under the rigorous gravity of the white dwarf. If the pressure and temperature are sufficient enough to fuse Hydrogen into Helium, a sudden thermonuclear explosion called a nova explosion occurs on the surface of the white dwarf as a result of the rapid fusion. During the explosion, a vast amount of energy is released, brightening the white dwarf suddenly. A typical nova explosion can produce several thousand of solar luminosities. After the explosion, its brightness declines over time.

In a typical nova explosion, only a small percentage of drawn Hydrogen is fused into Helium.

There is another type of novae called Helium novae. As scientist believe, a Helium nova is an explosion of the Helium shell of a white dwarf. A Helium nova isn’t a nova caused by Hydrogen fusion reaction.

What is a Supernova

Supernovae are supreme astronomical events that take place in the universe. Simply, they are spacious heavy element factories. There are mainly two types of supernovae (type I and type II).

Type I supernova are somewhat similar to novae. They (white dwarfs) draw matter from their companion objects. As a result, they collapse very rapidly under their own fiery gravity and explode. Depending on their spectra, type I supernovae are classified into three sub-categories namely, type Ia, Ib, and Ic.

Type II supernova occurs when a massive star use up its fuel.  At the beginning of a star, its Hydrogen nuclei fuse into Helium. If the Star’s temperature and material density are sufficient enough after its primary fuel or Hydrogen is used up, its Helium nuclei begin to fuse into Carbon and Oxygen at the center. These thermonuclear processes gradually spread out from the star’s center towards the surface layer by layer and continues until heavy nuclei such as iron and Nickel are produced. Once, the mass of the star’s core exceeds the Chandrasekhar’s limit, the star’s core suddenly collapses inward (implodes) causing to increase its temperature and density dramatically. Eventually, the star reaches its final stage forming a supernova explosion. Supernovae are the most powerful explosions in the universe. They release a huge amount of energy into space. Also, they eject a vast amount of matter including heavy nuclei. As physicist believe, supernovae are the primary source of heavy nuclei such as Uranium. 

Difference Between Nova and Supernova

Plural Form:

Nova: Novae or novas.

Supernova: Supernovae or supernovas.

Subcategorization:

Nova: Nova can be categorized based on their light curves.

Supernova: Supernova can be categorized based on their spectra.

Luminosity of the Explosion:

Nova: Nova has several thousand solar luminosities.

Supernova: Supernova can outshine an entire galaxy.

Thermonuclear Synthesis:

Nova: Hydrogen nuclei fuse into Helium nuclei.

Supernova: Supernovae are the primary sources of heavy nuclei such as Uranium and Silver.

Nature of the Explosion:

Nova: Nova is much less powerful compared to supernovae.

Supernova: Supernova is the largest explosions that take place in the universe.

After the Explosion:

Nova: Nova returns to its original stage over time. (Brightness declines over time).

Supernova: A neutron star, pulsar or a black hole is formed depending on the amount of mass of the remnant.

Image Courtesy:

” GK Persei: Nova of 1901 Nova” by X-ray: NASA/CXC/RIKEN/D.Takei et al; Optical: NASA/STScI; Radio: NRAO/VLA – , (Public Domain) via Commons Wikimedia 

“SN 1994D, a type Ia supernova in the NGC 4526 galaxy” by NASA/ESA (CC BY 3.0) via Commons Wikimedia 

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