Image Credit: ESA/Hubble & NASA; Acknowledgement: Linda Morgan-O’Connor
The Cheeseburger Nebula (NGC 7026) is a very bright bipolar planetary nebula of a little over one light-year across at its longest dimension, located about 6000 light-years away in the constellation of Cygnus (The Swan). It is approaching us at approximately 40.6 kilometers per second.
Despite their name, planetary nebulae have nothing to do with planets. The name of planetary nebulae arose because of the visual similarity between some round planetary nebulae and the planets Uranus and Neptune when viewed through early telescopes.
A planetary nebula represents the final stage in the evolution of a star similar to our Sun. Only a few thousand years ago, the star at the center of The Cheeseburger nebula was a red giant, but when it ran out its nuclear fuel, it ejected its outer layers into space to form this glowing, expanding nebula, while leaving behind its hot stellar core in the center.
Over the next several thousand years, this cloud of glowing gas and dust will gradually disperse into space, and then the star will cool and fade away for billions of years as a white dwarf. Our own Sun is expected to undergo a similar fate, but fortunately this will not occur until some 5 billion years from now.
The Cheeseburger has two big closed lobes — filled with very hot gas that emits X-rays — that are roughly butterfly-shaped, and a bright equatorial waist that contains large amounts of molecular gas and dust with the hot central white dwarf star right in the middle. Because the stellar winds that form the lobes are still plowing into the surrounding material, and because the lobes are closed, the hot gas hasn’t been able to escape.
Which could mean that eventually all that material may blow out of the lobes, popping them. When that happens – in what’s called a “blowout” – the gas will escape and it’ll probably form long, weird, filaments.
This image was produced by the Wide Field and Planetary Camera 2 aboard the Hubble Space Telescope. It shows the vivid colors that are produced by the mix of gases present in NGC 7026: starlight in green, light from glowing nitrogen gas in red, and light from oxygen in blue (in reality, this appears green, but the colour in this image has been shifted to increase the contrast).