The ESA’s Gaia space telescope is a powerhouse of technical wizardry. This system is used to systematically observe a large volume of our galaxy to measure both star brightnesses and positions. Since the same camera settings don’t work for stars of different brightnesses, and different cameras are good at seeing different colors, Gaia uses a suite of different detectors to gather information on everything that enters its field of view.
It is easy to calibrate position measurements between cameras because you can literally just line up the different images. Sorting any offsets that might exist in how brightness is measured from camera to camera is harder, however, and isn’t something Gaia can do without a little help from its friends. This is where the Chinese LAMOST telescope comes into play.
LAMOST is designed to observe stars of highly varying brightnesses across all their different colors simultaneously using a sensitive spectrograph. By looking at more than 800,000 stars with both LAMOST and Gaia, it became possible to calibrate Gaia’s brightness measurements to an unprecedented degree. According to team member Niu Zexi: Our work could be beneficial to studies where a high-precision color-color diagram is required, including the estimation of Gaia photometric metallicities, detection of peculiar objects, discrimination between binaries and single stars, and so on.
This is the kind of science that isn’t all that exciting. They literally used over 800,000 stars to calibrate their digital brightness measuring sticks, but this tedious work means all the more exciting research is possible.
CAS press release
“Correction to the Photometric Colors of the Gaia Data Release 2 with the Stellar Color Regression Method,” Zexi Niu, Haibo Yuan, and Jifeng Liu, 2021 March 4, The Astrophysical Journal