Eye On The Sky: the top astro images of 2017

The top astro images released in 2017, as picked by BBC Sky at Night Magazine.

Although it looks like the pattern of a shell on the beach, this intriguing spiral is in fact astronomical in nature. The Atacama Large Millimeter/submillimeter Array (ALMA) captured this remarkable image of a binary star system, where two stars — LL Pegasi and its companion — are locked in a stellar waltz, orbiting around their common centre of gravity. The old star LL Pegasi is continuously losing gaseous material as it evolves into a planetary nebula, and the distinct spiral shape is the imprint made by the stars orbiting in this gas. The spiral spans light-years and winds around with extraordinary regularity. Based on the expansion rate of the spiralling gas, astronomers estimate that a new “layer” appears every 800 years — approximately the same time it takes for the two stars to complete one orbit around each other. LL Pegasi was first highlighted about 10 years ago when the NASA/ESA Hubble Space Telescope obtained a picture of the almost-perfect spiral structure. This was the first time a spiral pattern had been found in material surrounding an old star. Now, ALMA’s observations, of which this image only shows one “cross-section”, have added an extra dimension to reveal the exquisitely-ordered 3D geometry of the spiral pattern. A full view of the 3D video can be seen in this video. An additional image shows a composition of the ALMA and Hubble data. Links:  ALMA and Hubble observe LL Pegasi 3D view of LL Pegasi

Each month in BBC Sky at Night Magazine we present our favourite images captured by the world’s biggest and most hardworking telescopes for our Eye On The Sky image gallery.

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Here we present a month-by-month selection of the most amazing astrophotos that made our monthly galleries in 2017.

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