What is the difference between a Type IIb supernova and a Type IIn supernova?

A supernova is a powerful explosion that occurs when a star runs out of fuel and its core collapses. There are many types of supernovae, but two of the most interesting are Type IIb and Type IIn.

Type IIb supernovae occur when a massive star loses most of its outer envelope and explodes. These supernovae show evidence of both hydrogen and helium in their spectra, but the hydrogen is weaker than in normal Type II supernovae. They are also associated with the collapse of the star's core.

Type IIn supernovae, on the other hand, occur when a massive star has already shed most of its outer envelope and is surrounded by a dense, circumstellar material. This dense material is ionized by the supernova shockwave, producing strong emission lines in the spectra. Type IIn supernovae are also characterized by a slow rise to maximum brightness and a long plateau phase.

So, the main difference between Type IIb and Type IIn supernovae is the amount of hydrogen in their spectra and the presence of a circumstellar material around the latter. Type IIb supernovae have weaker hydrogen lines than Type II supernovae, while Type IIn supernovae have strong emission lines due to the interaction with the dense material.

Type IIb and Type IIn supernovae are both core-collapse supernovae, which means that they are caused by the collapse of the core of a massive star. However, there are some key differences between the two types of supernovae.

• Hydrogen lines: Type IIb supernovae do not show hydrogen lines in their spectra, while Type IIn supernovae do. This is because Type IIb supernovae have lost their outer hydrogen envelopes, while Type IIn supernovae have not.
• Light curves: Type IIb supernovae have light curves that decline rapidly after the initial explosion, while Type IIn supernovae have light curves that plateau for a period of time before declining. This is thought to be due to the interaction of the supernova ejecta with a dense circumstellar medium (CSM) in the case of Type IIn supernovae.
• Progenitor stars: Type IIb supernovae are thought to be the explosions of Wolf-Rayet stars, which are massive stars that have lost their outer hydrogen envelopes. Type IIn supernovae are thought to be the explosions of Luminous Blue Variables (LBVs), which are also massive stars that have lost their outer hydrogen envelopes, but which have a dense CSM.

In summary, the main differences between Type IIb and Type IIn supernovae are:

• Hydrogen lines: Type IIb supernovae do not show hydrogen lines in their spectra, while Type IIn supernovae do.
• Light curves: Type IIb supernovae have light curves that decline rapidly after the initial explosion, while Type IIn supernovae have light curves that plateau for a period of time before declining.
• Progenitor stars: Type IIb supernovae are thought to be the explosions of Wolf-Rayet stars, while Type IIn supernovae are thought to be the explosions of Luminous Blue Variables.