The Pillars of Creation—that sounds like James Cameron’s latest 3-D epic. But it is in fact a massive cosmic structure that is a cauldron of star creation. Located in the Eagle nebula 6500 light years away, the Pillars are as much as four light years in length.
In the Realm of the Eagle
The Eagle nebula is listed in the Messier catalog as M16. It has long fascinated astronomers because of a massive cosmic structure that towers four light years (lys) into interstellar space from it. These columns have come to be known as the Pillars of Creation. The name was earned because these massive structures of dust and hydrogen gas are creating new stars on a continuing basis. Visually, they form the talons of the Eagle.
It has been the Hubble telescope that has given astronomers an understanding of what is happening in these soaring cosmic towers.
The ‘Pillars’ are incredibly dense for such celestial gas clouds. Because they are so dense, they collapse under their own weight, and as this happens, the collapsing gas forms proto stars. As the stars form, they accrete more material from the cloud and grow into full fledged stars.
But in doing so, they prophesy the end of their own growth. In the first image below, the Pillars are near the bottom of the eagle.
A Nest of EGGS
As they accrete material, they give off torrents of ultraviolent light. The pressure of this light ‘boils’ away the gas surrounding them in a process called photoevaporation. You can see signs of this in the Hubble image below. The ghostly streamers of gas are the material being blown away by photoevaporation. When most of the gas around the stars is gone, what is left is much denser than the surrounding material and forms compact pockets around the young star. These are called evaporating gaseous globules, or EGGs.
Hubble has imaged EGGs in various guises. Some appear as bumps on the Pillars. Others, apparently cleared of more material, look like fingers protruding from the Pillar. Some EGGs apparently have even separated completely from the Pillar, and are floating alone in space. Below are Hubble images of some of these various EGG types .
As the stars continue to use up the gas in the EGGs, they eventually reach a point at which there is no more hydrogen to fuel their growth. At that point their growth as stars stops, and the EGGs disappear. They are now just new stars in the firmament.
Because these new stars have cleared all the material from their vicinity, astronomers feel it is unlikely that there is enough material around them to form planets. This is a far different way of star formation as seen in other star nurseries such as the Orion nebula, where stars form and continue to grow and acquire an accretion disk that may someday form planets.
But it may hold the clue to a puzzle that has plagued astronomy for decades. Why do Main Sequence stars exhibit such a wide range of sizes, from red dwarfs to blue giants? The Pillar’s stars, because they form relatively quickly and use up their formative material, are smaller stars. Other stars continue to grow as they pull in more mass from their accretion disk. Could this explain the range of the Main Sequence?
The Pillars of Creation may hold as many answers as it does questions.
Sources and Credits
Source: NASA Hubble Site http://hubblesite.org/newscenter/archive/releases/1995/44/image/a/
Eagle nebula: Wikipedia http://en.wikipedia.org/wiki/File:Eagle_Nebula_from_ESO.jpg
All Pillar Images: NASA Hubble Site