NGC 7635 is an emission nebula. The bright star at its not-quite-center throws off hot gases, known as stellar wind, that move at 4 million mph. When these hot gases slam into the cold gas and dust of interstellar space, they form an intriguingly symmetrical bubble. The star's intense ultraviolet radiation causes the gases to glow, with different elements heating to different temperatures to form distinct colors: Oxygen is hot enough to burn blue, while hydrogen and nitrogen form a cooler yellow light.
More than a quarter-century into its tenure, the Hubble is still going strong. But its successor will hit the scene soon. The James Webb Telescope, which is set to launch in 2018, will be able to look much deeper into space — and, therefore, earlier into cosmic history — than the Hubble can.