A Gaia test image of the young star cluster NGC 1818 in the Large Magellanic Cloud, taken as part of calibration and testing before the science phase of the mission begins. The field-of-view is 212 x 212 arcseconds and the image is approximately oriented with north up and east left. The integration time of the image was 2.85 seconds and the image covers an area less than 1% of the full Gaia field of view.
Gaia’s overall design is optimized for making precise position measurements and the primary mirrors of its twin telescopes are rectangular rather than round. To best match the images delivered by the telescopes, the pixels in Gaia’s focal plane detectors are then also rectangular. In order to produce this image of NGC 1818, the image has been resampled onto square pixels. Furthermore, to maximize its sensitivity to very faint stars, Gaia’s main camera does not use filters and provides wide-band intensity data, not true-color images. The false-color scheme used here relates to intensity only. The real colors and spectral properties of the stars are measured by other Gaia instruments.
Photo credit: ESA/DPAC/Airbus DS
Note: For more information, see Gaia Comes Into Focus.