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Why is infrared the ideal band to detect the earliest and most-redshifted galaxies?

Large stars emit much of the there energy in the visible and near-ultraviolet wavelengths, but a galaxy at z=10 will be observed most brightly in the infra-red. Moreover, lots of the interesting ...
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21 votes
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Why use a large separate starshade instead of an occulting disk?

TL;DR: The Sun is well-resolved in small telescopes so a focal plane occulter works well. Other stars are not resolved (except in a few exciting cases using interferometry) so an internal blocking ...
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3 votes

In what measure James Webb Telescope "exceeded expectations"?

Target tracking, for one, and corresponding slew (panning) capability appear to be exceeding the design specifications. If nothing else then, JW will have a more efficient observing cycle, spending ...
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34 votes
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How does JWST position itself to see and resolve an exact target?

It's true that James Webb carries fuel, and you're right that it is not used for positioning, at least not directly (see below). Fuel is used for maintaining its orbit around L2, and was also used ...
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1 vote

How are the occurrence and nature of micrometeoroid impacts on JWST optics identified?

It has become clearer that these impacts are detected and quantified through the NIRCam wavefront analysis ('mirror selfie') that is conducted routinely. This is detailed in this July 12th report (Fig ...
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2 votes

Orientation of the optical telescope assembly in the Hubble Space Telescope

What is the orientation of the optical telescope assembly with respect to the direction of motion of the Hubble Space Telescope? It could be just about anything from parallel to perpendicular to ...
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1 vote

Orientation of the optical telescope assembly in the Hubble Space Telescope

The telescope points towards the object that Hubble is imaging. That direction could be forwards, backwards, sideways or whatever. When you talk about "direction" in space, you need to say ...
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