Hiding in plain sight – star cluster Gaia 1
The prominent star in this image, obtained with the Wide-Field Infrared Survey Explorer (WISE), is Sirius, the brightest star in the night sky.
To the left of Sirius, and centred in this image, lies Gaia 1, a massive star cluster that was discovered by astronomers mining the first data released from the Gaia mission. Gaia 1 was discovered as a stellar over-density – a region where the density of stars was higher than expected.
Gaia 1 could have been discovered more than a century and a half ago, when astronomers William and Caroline Herschel were mapping stars to estimate the shape of the Milky Way, had it not been so close to Sirius.
(For additional images of this field see the WISE legacy survey.)