GLIMPSE-17775 in Abell S1063 (NIRCam image annotated)

The little red dot that would come to be known as GLIMPSE-17775 was fortunately included in the NASA/ESA/CSA James Webb Space Telescope’s field of view as it was observing galaxy cluster Abell S1063 for a different scientific purpose. GLIMPSE-17775 is located behind the galaxy cluster and has a cosmological redshift of 3.5, meaning it existed about 1.8 billion years after the Big Bang.

Since galaxy clusters like Abell S1063 are some of the most massive objects in the Universe, light emitted by objects farther away can become distorted as it reaches the telescope. This effect is known as gravitational lensing. The combination of Webb’s 30 hours of observing time and gravitational lensing enabled scientists to obtain the deepest spectrum to date of a little red dot. The result: the strongest evidence to date of a hot, dense gas cocoon known as a “black hole star.”

[Image description: A field of galaxies against the black background of space. In the centre is a bright-white elliptical galaxy that is the core of the Abell S1063 galaxy cluster. Around the core are short, curved red lines, which are distant background galaxies magnified and warped by gravitational lensing. A couple of foreground stars appear large and bright with Webb’s signature eight-point diffraction spike pattern. Toward the very bottom, slightly off center toward the right, is a small red dot that is highlighted by an orange square outline. A larger orange square in the top right corner shows the object in more detail. The object, labeled “GLIMPSE-17775” looks like a fuzzy red dot with a yellow core.]