Since the start of scientific operations of the James Webb Space Telescope in July of last year, we have been treated to many images showing targets in space from the nebula to the deep fields. This month, Webb researchers shared a new image captured by the telescope’s NIRCam instrument that shows a beautiful field of galaxies and an important astronomical phenomenon called gravitational lensing.
The image shows a large galaxy cluster called RX J2129, located 3.2 billion light-years away, which acts as a magnifying glass and bends light from more distant galaxies. behind it. That is the reason for the stretched shape of some galaxies towards the upper right of the image.
One of the lensed galaxies is particularly remarkable because it has something special. In the upper right, the same galaxy is imaged three times, due to the lensing effect. Within this triple-lensed galaxy is an unusually bright event, a Type Ia supernova. This happens when a small but dense star called a white dwarf is part of a binary system with another star and pulls material from its companion. This continues until the white dwarf has too much mass and it collapses, then it explodes in an even brighter flash of light.
The light from these Type Ia supernovae is important for two reasons: first, it is so bright that it can be seen even from another galaxy, and second, it is (usually) of a constant brightness. That means astronomers can look at a very distant Type Ia supernova and know exactly how far away it is, making it useful for measuring cosmological distances. These items are called “standard candles.”
This image captures an extremely distant Type Ia supernova, and that is useful in telling researchers how strong the gravitational lensing effect is. To confirm their results, the researchers also collected data using Webb’s other instruments, its NIRSpec spectrogram, to measure the composition of the supernova.
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