Last week we covered multiple star systems, but what if we added thousands or even millions of stars to the mix? A star cluster. [10:21]

Today we are talking about the life-and death-of stars. Low mass stars live a long time, fusing all their hydrogen into helium over a trillion years. More massive stars like the Sun live shorter lives. They fuse hydrogen into helium, and...

Stellar mass black holes form when a very massive star dies, and its core collapses. Black holes come in different sizes, but for all of them, the escape velocity is greater than the speed of light, so nothing can escape, not matter or...

In the aftermath of an 8-20 solar mass star's demise we find a weird little object known as a neutron star. Neutrons stars are incredibly dense, spin rapidly, and have very strong magnetic fields. Neutrons stars with the strongest...

Astronomers study a lot of gorgeous things, but nebulae might be the most breathtakingly beautiful of them all. Nebulae are clouds of gas and dust in space. Some nebulae are small and dense, others can be dozens or hundreds of light...

Stellar mass black holes form when a very massive star dies, and its core collapses. Black holes come in different sizes, but for all of them, the escape velocity is greater than the speed of light, so nothing can escape, not matter or...

Massive stars fuse heavier elements in their cores than lower mass stars. This leads to the creation of heavier elements up to iron. Iron robs critical energy from the core, causing it to collapse. The shock wave, together with a huge...

Sal Khan offers a correction to his Quasar video. [1:45]

Supernova clarification based upon Sal Khan's lesson on supernovae that the explosion was observed 1,000 years ago, but the actual event was 7,500 years ago. [1:31]

Khan Academy delves into supernova (Supernovae) in this video lesson. [11:57]