Webb’s 18 mirrors aligned within nanometers | Hacker News Reader

Webb’s 18 mirrors aligned within nanometers

livescience.com

22 pointsjrgd8 comments

Breaking taps has a cool video on how the alignment flexures work: https://www.youtube.com/watch?v=5MxH1sfJLBQ

Flexures are generally interesting, these flexures are amazing.

The video references the public documentation @ https://www.esmats.eu/amspapers/pastpapers/pdfs/2006/warden..... They weigh 665 grams (1.47lbs), have a range of 21mm (.826 inches) and a 7.7 nanometre (0.00000030315 inch) step. They work at temperatures down to -253C (-423.6F).

The cryocooler and these flexures have me seriously considering going back to school for a mechanical engineering/materials science degree.

In short, projects like this are an example of "let's take everything humanity has learned over the past 100,000 years and apply it to make a production scientific instrument that is deployed without any physical human intervention far from earth and operates for 20 years".

Day to day, my software work looks outright amateurish compared to that. However, the process to develop these sorts of instruments is extremely boring (mostly process following).

Perhaps a dumb question, but if it’s focused, why is the star not a point, or small blob, but rather an enormous six-armed... star shape?

These are diffraction spikes [0], caused by the support structures that carry the secondary mirror. The shape of the spikes are influenced by the arrangement of the struts. Here's a better researched answer of the same: [1]

0: https://en.wikipedia.org/wiki/Diffraction_spike 1: https://www.quora.com/What-will-the-diffraction-spikes-on-st...

I wonder if this is an artifact we’ll only see for a few specific situations or something more overall.

Right - but these are enormous. This doesn't look anything like a clean image of a star.

Is it just that it's so close / bright that the refraction spikes get so much in the way?

I am seeing multiple stackexchange answers that suggest this is due to an intentional over exposure: https://space.stackexchange.com/questions/58624/jwst-aligned...

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