Starship Asterisk*

Webb's First Deep Field

Explanation: This stunning infrared image was released one year ago as the James Webb Space Telescope began its exploration of the cosmos. The view of the early Universe toward the southern constellation Volans was achieved in 12.5 hours of exposure with Webb's NIRCam instrument. Of course the stars with six spikes are well within our own Milky Way. Their diffraction pattern is characteristic of Webb's 18 hexagonal mirror segments operating together as a single 6.5 meter diameter primary mirror. The thousands of galaxies flooding the field of view are members of the distant galaxy cluster SMACS0723-73, some 4.6 billion light-years away. Luminous arcs that seem to infest the deep field are even more distant galaxies though. Their images are distorted and magnified by the dark matter dominated mass of the galaxy cluster, an effect known as gravitational lensing. Analyzing light from two separate arcs below the bright spiky star, Webb's NIRISS instrument indicates the arcs are both images of the same background galaxy. And that galaxy's light took about 9.5 billion years to reach the James Webb Space Telescope.

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APOD Robot wrote: ↑Wed Jul 13, 2022 4:05 am Webb's First Deep Field

Wow - new record! 104 posts on July 22, 2022
viewtopic.php?t=42503

Who wants to write a summary
Which points are still unclear

I was wondering from the explanation that the Webb nearby stars have 6 spikes due to the 18 hexagonal mirror segments, although it is rarely explained, does this mean that the Hubbble stars have 4 spikes because the Hubble has 12 mirror segments? (I.e. the solution is divisible by 3.)

De58te wrote: ↑Sat Jul 15, 2023 11:15 am I was wondering from the explanation that the Webb nearby stars have 6 spikes due to the 18 hexagonal mirror segments, although it is rarely explained, does this mean that the Hubbble stars have 4 spikes because the Hubble has 12 mirror segments? (I.e. the solution is divisible by 3.)

The number of segments doesn't matter. What matters is the number of unique side angles in the aperture. Each side generates two perpendicular spikes. The JWST mirror is made up of three sets of parallel sides, which produces six spikes. The secondary supporting arm that has a unique angle produces two more.

The HST doesn't have a segmented mirror. Its round mirror produces classical Airy diffraction rings, and its four secondary supports produce four diffraction spikes.

if other 68 milli-arc sec pictures like this, were taken at any random location available to JWST, would we also see lensing like this, or is this picture unique?

C0ppert0p wrote: ↑Sat Jul 15, 2023 6:46 pm if other 68 milli-arc sec pictures like this, were taken at any random location available to JWST, would we also see lensing like this, or is this picture unique?

I think they look for the darkest parts of the sky which are gaps between the clouds of the thick disk of the Milky Way

Amazing! Really shows how insignificant we really are!