At the Edge of the Helix Nebula
			
		
		
			Credit:  R. O'Dell and K. Handron 
(Rice University), 
NASA
		
		
			While exploring the inner edge of the 
Helix Nebula with the 
Hubble Space Telescope's 
Wide Field Planetary Camera 2, 
astronomers were able to produce 
this striking image - rich in details of an exotic environment. 
This planetary nebula, created near the final phase of a sun-like 
star's life, is composed of 
tenuous shells of gas ejected by the
hot central star. 
The atoms of gas, stripped of 
electrons by 
ultraviolet radiation from the central star, 
radiate light at characteristic energies allowing specific 
chemical elements to be identified. 
In this image, emission from 
nitrogen is represented as red, 
hydrogen emission as green, and 
oxygen as blue. 
The inner edge of the 
Helix Nebula, also known as NGC 7293, is in the direction toward 
the central star, which is toward the upper right. 
Clearly visible near the inner edge are finger shaped 
cometary knots.