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From NASA - New Webb Image captures clearest view of Neptune's rings in decades: enter image description here

Does anyone know what the bright blue on the left top corner of the picture is? It is a reflection of sorts or is it a star? If so what star?

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That is Triton, Neptune's moon. The colours are false, since the JWST is an infrared telescope. Triton is an unusual object and probably didn't form with Neptune. Instead, it is likely a captured Kuiper belt object. It has a similar appearance to Pluto.

Also, the caption of the image states it clearly:

What do we see in Webb's latest image of the ice giant Neptune? Webb captured seven of Neptune’s 14 known moons: Galatea, Naiad, Thalassa, Despina, Proteus, Larissa, and Triton. Neptune’s large and unusual moon, Triton, dominates this Webb portrait of Neptune as a very bright point of light sporting the signature diffraction spikes seen in many of Webb’s images.

Triton looks much brighter than Neptune because the methane that Neptune is made of strongly absorbs infrared light. The mid-IR albedo of gassy Neptune is only circa 1% (ie, Neptune is as black as coal in the infrared) From The emissivity of volatile ices on Triton and Pluto it seems like icy Tridon's mid-IR albedo is probably like 50% (ie as grey as new concrete).

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  • $\begingroup$ Oh wait shoot I didn't drag the green line all the way. whoops! Should this question be deleted then since it's obvious? Thanks for the answer though! $\endgroup$
    – DialFrost
    Sep 24, 2022 at 14:31
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    $\begingroup$ I would say leave it. The image is getting quite a lot of visibility in the media so I think you are far from being the only person wondering what the "funny object" is; especially since JWST's point spread function for very bright objects looks so different from "normal" diffraction spikes due to the mirror segments and the three supports for the secondary mirrors $\endgroup$ Sep 24, 2022 at 16:08
  • $\begingroup$ Do you know why it looks so much brighter than Neptune itself? $\endgroup$
    – seldon
    Sep 25, 2022 at 10:49
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    $\begingroup$ Neptune is made of lots of Methane, which is very dark in infrared, and so reflects very little of the sun's light. This makes the high clouds on Neptune stand out. Neptune looks dark because it is dark, at these wavelengths. $\endgroup$
    – James K
    Sep 25, 2022 at 10:56
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    $\begingroup$ @JamesK holy granola! The mid-IR albedo of gassy Neptune is only circa 1% From The emissivity of volatile ices on Triton and Pluto it seems like icy Tridon's mid-IR albedo is probably like 50%! $\endgroup$
    – uhoh
    Sep 25, 2022 at 11:05

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