![]() ![]() “We went out to get coffee, saw the pictures and we knew that the game had changed,” Balick says.Īstronomers had assumed that red giants were spherically symmetrical, and a round star should produce a round planetary nebula. Then he and his colleague Adam Frank, of the University of Rochester in New York, were at a conference in Austria and saw Hubble’s first photos of planetary nebulae. Until the Hubble Space Telescope launched in 1990, “we were pretty sure we were on the right track” toward understanding the process, says Bruce Balick, an astronomer at the University of Washington. The whole process is very fast by astronomical standards but slow by human standards, typically taking centuries to millennia. ![]() This star, which is hotter and brighter than the red giant it came from, illuminates and warms the escaped gas, until the gas starts glowing by itself - and we see a planetary nebula. It cannot be any gentle zephyr, this wind it needs to have the strength of a rocket blast.Īfter the star’s outer layer has escaped, the much smaller inner layer collapses into a white dwarf. Yet it takes a great deal of energy to expel this material completely without having it fall back into the star. Astronomers theorized that these pulsations produce shock waves that blast gas and dust into space, creating what’s called a stellar wind. It also churns like a boiling pot of water underneath the surface, causing the outer layers to pulse in and out. With only a weak gravitational hold on its outer layers, it sheds mass very rapidly near the end of its life, losing as much as 1 percent per century. The dominant theory of planetary nebula formation previously involved only a single star - the red giant itself. All of the gas and dust in the nebula was expelled by the red star. On the right, a mid-infrared image easily distinguishes the dying star at the nebula’s center (red) from its companion star (blue). On the left, a near-infrared image shows spectacular concentric shells of gas, which chronicle the history of the dying star’s outbursts. NASA’s new James Webb Space Telescope has revealed extraordinary details in the Southern Ring Nebula, a planetary nebula that lies around 2,500 light-years away in the constellation Vela. This second star shapes the transformation into a planetary nebula, much as a potter shapes a vessel on a potter’s wheel. ![]() Observations and computer models are now pointing to an explanation that would have seemed outlandish 30 years ago: Most red giants have a much smaller companion star hiding in their gravitational embrace. How does a cosmic butterfly emerge from the seemingly featureless, round cocoon of a red giant star? But as beautiful as they are, they have also been a riddle to astronomers. (More massive stars have a much more violent end, an explosion called a supernova.) Planetary nebulae come in a stunning variety of shapes, as suggested by names like the Southern Crab, the Cat’s Eye and the Butterfly. They are the normal end stage for stars that range from half the Sun’s mass up to eight times its mass. The galaxy is studded with thousands of these jewel-like memorials, known as planetary nebulae. In a glorious denouement, it will eject these layers into space to form a beautiful veil of light, which will glow like a neon sign for thousands of years before fading. After swallowing Mercury, Venus and Earth with hardly a burp, it will grow so large that it can no longer hold onto its outermost layers of gas and dust. Billions of years from now, as our Sun approaches the end of its life and helium nuclei begin to fuse in its core, it will bloat dramatically and turn into what’s known as a red giant star. ![]()
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