🌌 NASA Astronomy Picture of the Day
The Blue Snowball Planetary Nebula Credit:
Date: 1996-11-21

Explanation:
Will the Sun one day look like - a blue snowball?
Maybe! The Blue Snowball is a planetary nebula
- and in 5 billion years the Sun
will throw off its outer layers and go through a planetary nebula
phase. A star can appear "normal" only so long as there
are sufficient nuclear reactions in its core. Soon thereafter,
gravity will win out and compress the stellar core to higher temperatures.
Eventually the core becomes a white dwarf.
These high temperatures somehow cause the expulsion of star's
outer layers, creating a planetary nebula
such as the Blue Snowball
pictured above. Although the Blue Snowball, also known as NGC
7662, does appear blue, the above picture's colors
are not real and were chosen to highlight the emission of certain
ions in the nebula. Many things are still not known about planetary nebula,
including details of the physical mechanism that creates the nebula,
and the reason for fast knots of gas in the outer regions known
as fliers.







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