25,100 light-years

Hanging in the sky like a glittering bag of diamonds, the Hercules Globular Cluster is a spherical group of hundreds of thousands of stars. The cluster was discovered by Edmund Halley (of comet fame) in 1714, and is barely visible to the naked eye. In 1974 a radio message was sent towards the cluster on behalf of humanity from the Arecibo Observatory, in the hope that such a dense collection of stars has a higher chance of one harbouring life on one of its planets.

Credit: Image made in visible light by Robert Gendler.

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