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Anyone know what the black blob in the center is? It's conspicuously left out of the labeled diagram, and doesn't seem mentioned in the article either. I imagin
by jakear 3y ago
Anyone know what the black blob in the center is? It's conspicuously left out of the labeled diagram, and doesn't seem mentioned in the article either. I imagine it's the central sun in question, but isn't it odd to never mention it?
- btilly 3y agoThat's the coronagraph that blocks out the star itself so that everything else is visible. https://blogs.nasa.gov/webb/2023/03/24/how-webbs-coronagraphs-reveal-exoplanets-in-the-infrared/ https://blogs.nasa.gov/webb/2023/03/24/how-webbs-coronagraph...
- hn8305823 3y agoThere has been a lot of confusion about this but it is actually overexposed pixels deleted in software. From the lead author of the paper: https://twitter.com/AndrasGaspar/status/1655680076103716878 https://twitter.com/AndrasGaspar/status/1655680076103716878
- dylan604 3y agoBlack Hole Sun? There was a camera that "suffered" this problem, but can't remember the model to look it up.
- jmount 3y agoFilm in general used to "solarize" in some situations, which would turn some over-exposed areas black.
- dylan604 3y agoMaybe, but there was a specific video camera that would do this which earned the black hole sun moniker that I was thinking of. I want to say it was in the DV era, but I was never a connoisseur of that format so it was all just fuzzy memory from hearing/reading about it. I do remember looking at DV shooters with side-eye jealousy at their tiny camcorders while I was heaving full sized broadcast cameras on my shoulder.
- btilly 3y agoThanks. Silly me for believing NASA.
- kfarr 3y agoWhy make overexposed pixels black instead of white? Just to make it extra clear that the pixel data exceeding overexposure threshold is not mistaken for valid data?
- crazygringo 3y agoI'm baffled as well. I think it's fairly understood that any white pixel is always understood to be probably overexposed.
- friendlyasparag 3y agoAstronomy often also deals with wide ranges of pixel exposure such that it can be hard to tell the difference between overexposed and "brighter than the max on the color scale". Better to be extra clear and remove all doubt.
- eimrine 3y agoAdditional bits of information? You cannot see what shape is that area if it is surrounded with a light yellow and you will miss some info if you'll do it after JPEG conversion.
- hn8305823 3y ago> Just to make it extra clear that the pixel data exceeding overexposure threshold is not mistaken for valid data? Saturated pixels are not necessarily "invalid" the way cosmic ray bit flips and stuck pixels are, but setting them to zero does make the other bright but not saturated pixels much easier to identify.
- jakear 3y agoDoes the precise line dividing "bright but just barely not saturated" from "bright and saturated" actually matter?
- adhesive_wombat 3y ago
- asdfman123 3y agoAn mspaint.exe adjustment
- jakear 3y agoWhat's odd is even when downloading the full res image, the central colors are decidedly not all #000. There is a faint yet distinct radial gradient. It does not appear to be a compression artifact (format is png anyways).
- friendlyasparag 3y agoimages released to the press sometimes get another, um, aesthetic pass. I bet if you could get ahold of the actual image file it would have the proper sentinel sentinel value (if they're still using fits files it'd be something ridiculous like -9999.)
- sbierwagen 3y agoTo be clear, they were using the coronagraph: https://arxiv.org/pdf/2305.03789.pdf https://arxiv.org/pdf/2305.03789.pdf >The 23.0 µm coronagraph of MIRI uses a classic Lyot mask to achieve high contrast imaging near bright sources. The mask is rather large, providing an inner working angle (IWA) of ∼ 3.3λ/D, i.e., ∼ 2. Our data is the first complete reference PSF subtracted set of observations taken with JWST using this mode. There's some residual light and diffraction effects around the Lyot mask which they have manually deleted.
- hn8305823 3y agoSome images used a mask and some did not. The 25.5 micron image at the top of the article is one that did not use a mask.
- geokon 3y agoAny idea why it's not a perfect circle? Aberration in focus? And would that be pretty much equivalent to the true size of the star's corona? (seems huge..)
- cubefox 3y agoYeah. The ability of journalists to ignore the most obvious questions is baffling.
- dudeinjapan 3y agoRedacted by the CIA, because it contains evidence of extraterrestrial life.