What is Nova?

About Nova

• Nova is any of a class of exploding stars whose luminosity temporarily increases from several thousand to as much as 100,000 times its normal level. 
• A nova reaches maximum luminosity within hours after its outburst and may shine intensely for several days or occasionally for a few weeks, after which it slowly returns to its former level of luminosity.
• Stars that become novas are nearly always too faint before eruption to be seen with the unaided eye. 
• Their sudden increase in luminosity, however, is sometimes great enough to make them readily visible in the nighttime sky.
• To observers, such objects may appear to be new stars; hence the name nova, from the Latin word for “new.”
• Studying novae is crucial to advancing our knowledge about fundamental astrophysical processes, including stellar evolution.
• How do Novas occur?
  • Commonly, novas start as white dwarf stars that are part of a binary star system.
  • Binary stars are two stars that are close together in the distance and revolve around each other. 
  • The white dwarf is small and dense, and it is essentially the insides of a star that lost its outer layers. These are older stars that have lost their shine and fuel.
  • The white dwarf is most likely paired with a red giant. 
  • The white dwarf begins to pull on its companion, the red giant, with gravitational forces.
  • The white dwarf takes fuel and matter, especially hydrogen, from its companion and pulls it towards itself. The matter is quickly hurled towards the surface of the white dwarf.
  • Layers of material from the red giant gather on the surface of the white dwarf. As the layers are created, the material begins to grow hotter.
  • When the layers become compressed and hot enough, the material begins to combust and explodes through thermonuclear reactions. 
  • The hydrogen material begins to react specifically with helium. The explosion of the materials causes the white dwarf to suddenly become bright as it throws off some of the material.

Q1) What is a Red Giant?

Red giants are stars going through their death stages. It has slowly swollen up to many times its original size. Once a star becomes a red giant, it might stay that way for up to a billion years. Then the star will slowly contract and cool to become a white dwarf. The opposite of red giants, white dwarfs are Earth-sized, ultra-dense corpses of stars radiating a tiny fraction of their original energy. Eventually, after billions of years, these stars will become totally cold and radiate no energy. They’ll end their lives as a so-called black dwarf: a tiny, burned-out, virtually-invisible cinder.

Source: Recently discovered nova investigated by astronomers