An image captured by the James Webb Space Telescope portrays the galaxy LEDA 2046648 immersed in a vast group of other more or less distant galaxies. Many spiral galaxies are recognizable and this is to be expected as they’re the most common type. The NIRCam instrument captured many details of LEDA 2046648 despite being over a billion light-years away from Earth, but Webb’s performance is no longer astonishing. The observation that generated this image is among those used to calibrate the NIRISS instrument, which was out of service for a couple of weeks in the second half of January 2023 but has now resumed transmitting the collected data normally.
It took months to calibrate the James Webb Space Telescope’s instruments. Since the previews, the results have been spectacular and offered never-before-seen details of more or less distant cosmic objects. Webb was designed to probe the oldest galaxies in the universe but it already observed closer objects as well.
The observation that produced this image (ESA/Webb, NASA & CSA, A. Martel) was actually targeting the white dwarf star cataloged as WD 1657+343, a well-known star and therefore useful as a reference for interpreting the data detected by the NIRCam (Near-InfraRed Camera) and NIRISS (Near-InfraRed Imager and Slitless Spectrograph) instruments and compare them with that collected in the past by other instruments. The result was much broader, with the portrait of stars but above all many galaxies among which LEDA 2046648 stands out.
The NIRCam and NIRISS instruments can be used together or separately, depending on the type of study being conducted. NIRCam is a camera that captures even the faint infrared emissions from early galaxies. NIRISS is a spectrograph that detects the “chemical signatures” left by atoms and molecules in the light that reaches Webb allowing to obtain information on the chemical composition of the examined objects.
Recently, NASA announced that on January 15, 2023, the NIRISS instrument experienced a delay in communicating the collected data which generated a timeout in its software. It was unavailable for science observations for about two weeks while NASA and the Canadian Space Agency (CSA) worked to pinpoint the cause of the problem. There were no indications of hardware damage and the conclusion was that a cosmic ray, which is high-energy radiation from outside the solar system, probably struck the electronic systems of NIRISS. Eventually, the good old reboot fix allowed NIRISS systems to fully function again.
The abundance of galaxies shown in the image can be considered a byproduct since that wasn’t the purpose of the observation. Despite this, the galaxy LEDA 2046648 appears with many details even if it’s over a billion light-years away and the galaxy that appears below it is also clearly visible. This shows how the James Webb Space Telescope is very useful for studying the nearby universe as well and processes such as star formation.
