June 13, 2002: The Hubble telescope reveals a rainbow of colors in this dying star, called IC 4406. Like many other so-called planetary nebulae, IC 4406 exhibits a high degree of symmetry. The nebula's left and right halves are nearly mirror images of the other. If we could fly around IC 4406 in a spaceship, we would see that the gas and dust form a vast donut of material streaming outward from the dying star. We don't see the donut shape in this photograph because we are viewing IC 4406 from the Earth-orbiting Hubble telescope. From this vantage point, we are seeing the side of the donut. This side view allows us to see the intricate tendrils of material that have been compared to the eye's retina. In fact, IC 4406 is dubbed the "Retina Nebula."
The dark tendrils are dust lanes that were created at the boundary between the hot, colorful, glowing gas and cooler, "neutral" gas. The neutral gas does not glow and therefore cannot be seen in visible light. But this cool gas does comprise the dark dust lanes. The gas can be seen in silhouette because it is so dense. In fact, the gas in the dust lanes is 1,000 times denser than the gas in the rest of the nebula.
The lanes were formed because the boundary between the gases is unstable. This instability creates irregularities on the nebula's surface, causing the neutral gas to clump together in certain areas, much like puddles forming on a prairie after a rain. These puddles of material eventually became dense enough to be seen in silhouette. The dust lanes are like a mesh veil that has been wrapped around the bright donut.
Yes. The object has an IC (Index Catalog) number, indicating that it was first seen and recorded in the 19th century. The Hubble telescope has allowed astronomers to see IC 4406 in greater detail and to determine its three-dimensional structure.