The expanding shell of gas and dust that surrounds the star is about five light-years wide, which equals the distance from here to the nearest star beyond the Sun, Proxima Centauri.

The huge structure was created from one or more giant eruptions about 10,000 years ago. The star's outer layers were blown into space—like a boiling teapot popping off its lid.

Crew members who took part in the Mars500 experiment showed significant changes in their gut microbiota from their 520 days in confinement, according to a new study by scientists at Université de Montreal and McGill University.

The study, published today in the Computational and Structural Biotechnology Journal and funded by the Canadian Space Agency, analyzed data from fecal samples of six crew members from Russia, Europe and China.

The crew lived in a completely sealed habitat in Moscow from June 2010 to November 2011 to simulate a manned mission to Mars, which international space agencies hope to make in the 2030s. Their confinement was the longest ever conducted with humans under controlled conditions.

The goal: to test the impact of living cut off from the world on the physiological and psychological health. In the end, all six crew members emerged with major alterations in their body mass, muscle strength and other indicators, previous studies have shown.

The discovery of microbiome alterations represents a missing link between these symptoms and deepens scientists' understanding of how well astronauts will be able to work in and recover from long-duration spaceflight, as well as how humans generally interact with their habitats.