The capacity for brightness: star nebulae

The long goodbye
The nebula NGC 6565, created as a star sheds its outer layers of gas and “dies.” Nebulae like these will last for about 10,000 years.

The appearance of a nebula around a star sometimes indicates the end of its lifetime- the transition from a red giant supernova to a white dwarf. The star sheds its outer layers of gas, leaving the core exposed. Radiation from the core illuminates the drifting gas layers, creating a nebula. What’s interesting about a study recently published by Gesicki, Zijlstra, and Bertolami on nature.com is the resolution of a decades-old mystery: why are smaller stars capable of creating bright nebulae on par with those of more massive stars? Larger stars, logically, should produce the brightest nebulae just because they have more – larger cores producing more radiation and a greater quantity of gas. However, smaller stars from older star systems have proven equally capable of creating nebulae just as bright as newer, larger stars. What scientists have discovered it that the cores of smaller stars actually heat up faster than those of larger stars, allowing more radiation to reach the outer layers of gas. This new understanding helps to demystify some of what we still don’t understand about nebulae, and has led scientists to believe that one day, our sun will form a nebula of its own.

 

(Gesicki, Zijlstra, & Bertolami, 7 May 2018, The mysterious age invariance of planetary nebula luminosity function bright cut off, natureresearch journal)

 

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