The term "Eye Nebula" usually refers to the Helix Nebula, a planetary nebula located in the constellation Aquarius. While "nebula" often evokes images of gas clouds, the Helix Nebula is more specifically made up of:

* Ionized gas: This is primarily hydrogen and helium, the most abundant elements in the universe. The gas is energized by ultraviolet radiation from the central star, causing it to glow.

* Dust: The nebula also contains dust, which is made up of heavier elements like carbon, oxygen, and silicon. This dust absorbs and scatters light, contributing to the nebula's distinctive appearance.

* The central star: This is a white dwarf, the remnant of a sun-like star that has exhausted its nuclear fuel. It emits the ultraviolet radiation that ionizes the surrounding gas.

The "eye" effect is created by the central star and its surrounding ring of dust and gas, which appear to have a dark, "pupil-like" center. This center is actually a dense torus of gas and dust, creating the illusion of a black hole.

So, in summary, the Eye Nebula is a vibrant mix of ionized gas, dust, and a central white dwarf star, all working together to create its breathtaking appearance.