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The icy blue wings of a bipolar planetary nebula

Planetary nebulae such as Hen 2-437 form when an ageing low-mass star — such as the Sun — reaches the final stages of life. The star swells to become a red giant, before casting off its gaseous outer layers into space. Hen 2-437 is a bipolar nebula — the material ejected by the dying star has streamed out into space to create the two icy blue lobes pictured here.

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ASTRO-H satellite poised to enhance views of X-ray sky

A new science satellite, the ASTRO-H X-ray Observatory, will blast into Earth orbit this month. The project, led by the Japan Aerospace Exploration Agency (JAXA), aims to collect a wealth of new data on everything from the formation of galaxy clusters to the warping of space and time around black holes. ASTRO-H boasts a sensitivity level that is orders of magnitude better than previous technology.

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Tim Peake’s Principia spacewalk

European Space Agency astronaut Tim Peake pictured during his 4 hour 43 minute spacewalk to replace a failed power regulator and install cabling on the International Space Station. Tim commented on this image: “Today’s exhilarating spacewalk will be etched in my memory forever — quite an incredible feeling!”

Top Stories 2015

No. 9 Rosetta rides with its comet

While 2014 was the year the Rosetta spacecraft celebrated making it into orbit around a comet, 2015 was the year it got down to some serious hard work. Its comet, with the tongue-twisting name 67P/Churyumov–Gerasimenko, made its closest approach (186 million kilometres) to the Sun, a period known as perihelion when the comet would be expected to be at its most active. Rosetta was there to witness this.

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Hubble sees two galaxies become one

This image, taken with the Wide Field Planetary Camera 2 on board the NASA/ESA Hubble Space Telescope, shows the galaxy NGC 6052, located around 230 million light-years away in the constellation of Hercules. It is a “new” galaxy in the process of forming, the result of a merger between two separate galaxies that were gradually drawn together by gravity.

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Terzan 1: a home for old stars

This image, taken with the Wide Field Planetary Camera 2 on board the NASA/ESA Hubble Space Telescope, shows the globular cluster Terzan 1. Lying around 20,000 light-years from us in the constellation of Scorpius, it is one of about 150 globular clusters belonging to our galaxy, the Milky Way.

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Finding new worlds with a play of light and shadow

One method to discover planets beyond the solar system by far is transit photometry, which measures changes in a star’s brightness when a planet crosses in front of its star along our line of sight. NASA’s Kepler Space Telescope has used this technique to become the most successful planet-hunting spacecraft to date, with more than a thousand established discoveries. Satellites carrying improved technology for all-sky surveys are now planned, missions that will tell us a great deal about alien planetary systems similar to our own.

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Philae’s descent to comet 67P

Recently released images compiled into a movie show the descent of the European Space Agency’s Philae lander to its first touchdown site, Agilkia, on Comet 67P/Churyumov–Gerasimenko on 12 November 2014. The image sequence starts just over two miles from the comet, and the final image is from just 9 metres above the landing site.

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OSIRIS discovers balancing rock on comet 67P

Scientists from Rosetta’s OSIRIS team have discovered an extraordinary formation in the Aker region on the larger lobe of comet 67P/Churyumov-Gerasimenko. The largest of a group of three boulders with a diameter of approximately 30 metres appears to perch on the rim of a small depression. There seems to be only a very small contact area with the nucleus.

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Delta Cephei’s secret companion and intriguing past

Delta (δ) Cephei, prototype of Cepheids, which has given its name to all similar variable stars, was discovered 230 years ago by the English astronomer John Goodricke. The Cepheids role as distance calibrators for more than a century means δ Cephei is one of the most studied stars, but astronomers were shocked to discover that they lacked an essential piece of information…