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March 21, 2014

The Spire, a dust pillar in the Eagle Nebula

The Spire, a dust pillar in the Eagle Nebul

Image Credit: NASA, ESA, and The Hubble Heritage Team STScI/AURA)

The Spire is a pillar of cold gas and dust – looking like a winged fairy-tale creature poised on a pedestal – of about 9.5 light-years high within the Eagle Nebula (Messier 16), located some 7,000 light-years away from Earth in the northern constellation of Serpens Cauda (Serpent’s Tail).

The Eagle Nebula contains several evaporating dust sculptures, such as this “Spire” and the “Pillars of Creation”. In fact, the Eagle Nebula is a giant evaporating shell of gas and dust inside of which is a growing cavity filled with a spectacular stellar nursery currently forming an open cluster of stars.

Stars in the Eagle Nebula are born in clouds of cold hydrogen gas that reside in chaotic neighborhoods, where energy from young stars sculpts fantasy-like landscapes in the gas. This tower may be a giant incubator for those newborn stars. A torrent of ultraviolet light from a band of massive, hot, young stars (off the top of the image) is eroding the pillar.

The starlight also is responsible for illuminating the tower’s rough surface. Streamers of gas can be seen boiling off this surface, creating the haze around the structure and highlighting its three-dimensional shape. The pillar is silhouetted against the background glow of more distant gas.

The edge of the dark hydrogen cloud at the top of the tower is resisting erosion; thick clouds of hydrogen gas and dust have survived longer than their surroundings in the face of a blast of ultraviolet light from the hot, young stars.

Inside the gaseous tower, stars may be forming. Some of those stars may have been created by dense gas collapsing under gravity. Other stars may be forming due to pressure from gas that has been heated by the neighboring hot stars.

The first wave of stars may have started forming before the massive star cluster began venting its scorching light. The star birth may have begun when denser regions of cold gas within the tower started collapsing under their own weight to make stars.

The bumps and fingers of material in the center of the tower are examples of these star-forming areas. These regions may look small but they are roughly the size of our Solar System. The fledgling stars continued to grow as they fed off the surrounding gas cloud. They abruptly stopped growing when light from the star cluster uncovered their gaseous cradles, separating them from their gas supply.

Ironically, the young cluster’s intense starlight may be inducing star formation in some regions of the tower. Examples can be seen in the large, glowing clumps and finger-shaped protrusions at the top of the structure. The stars may be heating the gas at the top of the tower and creating a shock front, as seen by the bright rim of material tracing the edge of the nebula at top, left. As the heated gas expands, it acts like a battering ram, pushing against the darker cold gas. The intense pressure compresses the gas, making it easier for stars to form. This scenario may continue as the shock front moves slowly down the tower.

This image was taken in November 2004 with the Advanced Camera for Surveys aboard the NASA/ESA Hubble Space Telescope, and was in scientifically re-assigned colors released in 2005 as part of the fifteenth anniversary celebration of the launch of the Hubble Space Telescope. The dominant colors in the image were produced by gas energized by the star cluster’s powerful ultraviolet light. The blue color at the top is from glowing oxygen. The red colon in the lower region is from glowing hydrogen. (The text is partly acquired from Spacetelescope.org.)

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