Helix hides Comets in its Core

Helix hides Comets in its Core

169140main_piaa09178-330.jpgIt is easy in astronomy to lump different objects into specific groups. At the top-most level, there are stars, galaxies, planetary systems (including asteroids and comets), and dust-bunnies interstellar and intergalactic media (clouds and nebula). Looking a bit deeper, each of these categories can be nit-picked apart into more sub-categories. For instance, stars can be divided up by energy generation mechanism, or mass, or both. But, astronomy isn’t just the study of a bunch of discrete objects that can be junked into boxes any more than plant science is the study of how a bunch of leaves that can be classified by structure. Both sciences must consider the ecology around discrete objects. Trees grow in forests in symbiosis with other plants and animals, and are both harmed and helped through these synergistic relationships. Stars too exist in rich environments, and when we study stars and their evolution we are also studying the evolution of their planetary systems and of the galaxy they live within. Until recently, it was easy to see the average star as an isolated object on a solitary journey from molecular cloud to planetary nebulae – we simply weren’t able to see anything other than the star and what isn’t seen is easily ignored. Today, however, that is all changing.

As we peer at stars in more wavelengths and in greater detail, we are beginning to find evidence of planetary systems around more and more objects.* As we witness this co-formation of stars and planets it is becoming impossible to stick stars in discrete boxes – Stars and planetary systems must be studied as a whole. This was brought home to me by a newly released Spitzer Space Telescope image of Helix nebula (above right, credit:NASA/JPL-Caltech/K. Su (Univ. of Ariz.)). This favorite object of amateur astronomers appears as a faint swirl of light through the eyepiece of a backyard telescope in a dark location. With Spitzer, it is resolved into concentric rings marking the location of a dead star. Around that dead star are the remnants of a cometary cloud.

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