Hubble reveals Ring Nebula's intriguing details

NASA`s Hubble Space Telescope bring us new, detailed look at the very popular Ring Nebula. Observations by Hubble of the glowing gas shroud around an old, dying, sun-like star reveal some very intriguing details. New images display a more complex structure than astronomers previously thought and gave them the opportunity to construct the most accurate 3-D model of the Ring Nebula.

C. Robert O`Dell of Vanderbilt University in Nashville, US compares nebula with a jelly doughnut, because it`s filled with material in the middle. He is the leader of a research team that with the help of Hubble and several ground-based telescopes acquired the best view to date of this amazing nebula. O`Dell explained that with Hubble's detail, we can see a completely different shape than what's been thought about historically for this classic nebula. He also added that the new Hubble observations show the nebula in much clearer detail, and we see things are not as simple as we previously thought.

The Ring Nebula is located in the constellation Lyra, roughly 2,000 light-years from Earth and measures around 1 light-year across.

In this composite image, visible-light observations by NASA’s Hubble Space Telescope are combined with infrared data from the ground-based Large Binocular Telescope in Arizona to assemble a dramatic view of the well-known Ring Nebula. (Credit: NASA, ESA, C.R. Robert O’Dell (Vanderbilt University), G.J. Ferland (University of Kentucky), W.J. Henney and M. Peimbert (National Autonomous University of Mexico) Credit for Large Binocular Telescope data: David Thompson (University of Arizona)

Earlier observations by several telescopes had discovered the gaseous material in the center of the ring. Hubble's sharp-eyed Wide Field Camera 3 shows the nebula's structure in more detail. The ring appears to wrap around a blue, football-shaped structure. Each end of the structure protrudes out of opposite sides of the ring.

Because the nebula is tilted toward Earth astronomers can view the ring face-on. In the picture acquired by Hubble, the blue structure is actually the glow of helium. Radiation unleashed by the white dwarf star, which looks like a white dot in the center of the ring, is stirring the helium to glow. The white dwarf is what remained of a sun-like star that has depleted its hydrogen fuel and has casted off its outer layers of gas to gravitationally collapse to a compact object.

O`Dell and his team were amazed by the detailed Hubble views of the dark, irregular knots of dense gas embedded along the inner rim of the ring. These gaseous tentacles, which resemble spokes in a wheel, formed when expanding hot gas moved into cool gas ejected previously by the doomed star. These knots are more resilient to erosion by the wave of ultraviolet light coming from the star. The Hubble photos have enabled the team to pair the knots with the spikes of light around the bright, main ring, which are the result a shadow effect. Astronomers have discovered comparable knots in other planetary nebulae.

These large amounts of gas was discharged by the central star about 4,000 years ago. The original star was several times larger than our sun. After repeating the process of converting hydrogen to helium in it`s core for billions of years, the star began to run out of fuel. It then became a red giant. Throughout this phase, the star casted off its outer gaseous layers into space and began to collapse as fusion reactions began to shut down. Ultraviolet light from the dying star activated the gas, making it glow.

This planetary nebula's simple, graceful appearance is thought to be due to perspective: our view from Earth looking straight into what is actually a barrel-shaped cloud of gas shrugged off by a dying central star. Hot blue gas near the energizing central star gives way to progressively cooler green and yellow gas at greater distances with the coolest red gas along the outer boundary. (Credit: NASA/Hubble Heritage Team)

The Ring Nebula will carry on expanding for the next 10,000 years, and will become fainter and fainter until it finally merges with the interstellar medium. Studying the nebula`s fate will give us insight into the sun's ending in another 6 billion years. Because our sun is smaller than the Ring Nebula's progenitor star, it will not have such an extravagant demise.

According to O`Dell, when the sun becomes a white dwarf, it will heat more slowly after it ejects its outer gaseous layers. The material will be farther away once it becomes hot enough to illuminate the gas, and so this larger distance means the sun's nebula will be fainter because it is more extended, he concluded.

Source: NASA

Featured image credit: NASA/Hubble Heritage Team

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