Webb’s Fine Guidance Sensor (FGS) recently captured a view of stars and galaxies that provides a tantalizing glimpse of what the telescope’s science instruments will reveal in the coming weeks, months and years. The resulting engineering test image is among the deepest images of the universe ever taken, representing extremely faint objects, and is now the deepest image of the infrared sky. Bright stars are distinguished by their six long, sharply defined diffraction peaks. This was the result of Webb’s six-sided mirror sections. Beyond the stars – galaxies fill almost the entire background. The monochrome image is displayed in false color with white-yellow-orange-red representing the progression from brighter to dimmer. The bright star (magnitude 9.3) at the far right is 2MASS 16235798+2826079. There are only a few stars in this image – distinguished by their diffraction peaks. The remaining objects are thousands of faint galaxies, some in the nearby universe but many more in the high-redshift universe. The test image was created during a thermal stability test in mid-May. It has some raw qualities. The data was first taken to test how well the telescope could stay locked on a target. This shows the power of the telescope. In this image, the FGS image was acquired alongside NIRCam imaging of the star HD147980 over eight days in early May. This image results from a 32-hour exposure time at various overlapping points in the Guider 2 channel. Because the FGS does not use color filters when its aperture is open, unlike other science instruments, it is impossible to thoroughly examine the age of the galaxies in this image. But the FGS can still produce breathtaking images of the universe when it captures unintended images during a test.
