Changes

==Properties and Structure==

==Properties and Structure==

The nebula is thought to lie some 5,000 [[light year]]s from Earth.<ref name=nasa/> With an apparent size of 1.445&nbsp;×&nbsp;0.724, its physical size corresponds to 0.33&nbsp;×&nbsp;0.17 light years. Intervening dust causes the nebula to appear to be [[hourglass]] shaped though its structure is more complicated than this. It consists of large, rapidly expanding gas cloud as well as a small [[torus|toriodal]] (doughnut-shaped) cloud that is much [[density|denser]] and surrounds the central [[star]]. This smaller region of gas block light traveling outwards from the stars equator (i.e. perpendicular to the axis of the lobes) meaning only the lobes are illuminated by the star's light and visible. These is also appears to be a hollow cylindrical structure surrounding the star itself, thought to have been formed jets of [[hydrogen]] and [[helium]] gas emitted from the star's polar regions.

The nebula is thought to lie some 5,000 [[light year]]s from Earth.<ref name=nasa/> With an apparent size of 1.445&nbsp;×&nbsp;0.724, its physical size corresponds to 0.33&nbsp;×&nbsp;0.17 light years. Intervening dust causes the nebula to appear to be [[hourglass]] shaped though its structure is more complicated than this. It consists of large, rapidly expanding gas cloud as well as a small [[torus|toroidal]] (doughnut-shaped) cloud that is much [[density|denser]] and surrounds the central [[star]]. This smaller region of gas block light traveling outwards from the stars equator (i.e. perpendicular to the axis of the lobes) meaning only the lobes are illuminated by the star's light and visible. These is also appears to be a hollow cylindrical structure surrounding the star itself, thought to have been formed jets of [[hydrogen]] and [[helium]] gas emitted from the star's polar regions.

This complicated structure is believed to be the result of the ejection of [[gas]] and [[dust]] by the nebula's central [[star]], a [[red giant]]. The gas in the nebula is expanding rapidly, at some 164&nbsp;km/s.<ref name=constellation-guide/> It is this rapid expansion is thought to have cooled to the nebula to only 1&nbsp;kelvin.<ref name=NRAO/>

This complicated structure is believed to be the result of the ejection of [[gas]] and [[dust]] by the nebula's central [[star]], a [[red giant]]. The gas in the nebula is expanding rapidly, at some 164&nbsp;km/s.<ref name=constellation-guide/> It is this rapid expansion is thought to have cooled to the nebula to only 1&nbsp;kelvin.<ref name=NRAO/>