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This image, captured by our Hubble Space Telescope (@NASAHubble), shows the vivid blue and red hues of a planetary nebula that is located about 11,000 light-years from Earth. When a star ages and the red giant phase of its life comes to an end, it starts to eject layers of gas from its surface leaving behind a hot and compact white dwarf. Sometimes this ejection results in elegantly symmetric patterns of glowing gas, but this planetary nebula is much less structured. Planetary nebulae are one of the main ways in which elements heavier than hydrogen and helium are dispersed into space after their creation in the hearts of stars. Eventually some of this out-flung material may form new stars and planets. In this iamge, the vivid blue and red hues come from material including ionized oxygen and hydrogen glowing under the action of the fierce ultraviolet radiation from the still hot central star. Credit: ESA/Hubble & NASA
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Rhea is a heavily-cratered, airless world, while Titan’s nitrogen-rich atmosphere is even thicker than Earth’s. This natural color image was taken in visible light by the Cassini spacecraft on Nov. 19, 2009, at a distance of approximately 713,300 miles (1,148,000 kilometers) from Rhea. After a nearly 20-year mission that overflowed with discoveries, the Cassini spacecraft ended its mission on Sept. 15, 2017. Credit: NASA/JPL-Caltech/Space Science Institute