Interesting object what is this? Is this a supernova? What is this weird red dust? sorry I don't know much

https://www.legacysurvey.org//viewer/?ra=167.4101&dec=0.5766&layer=decals-dr5&zoom=16&spectra

Hi and welcome!

A red ring like that would be very strange indeed, well spotted! However, if you click on the ring and select “single exposures”, you will find that one of the exposure images has a bright white spot (2015-03-29 @ 01:57:17). On the adjacent images, you can see that the spot has been automatically masked out and the ring is what’s left.

As it’s only visible in one of the images, it’s probably an asteroid. You can click the “Look up in JPL Small Bodies database” link next to the image to check whether it’s a known asteroid, but at the moment the site looks to be timing out.

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Hi,

I did a manual search for asteroids. The red ring is identified as Main-Belt asteroid 17759 Hatta (1998 DA24)

Ine :stars::dizzy:

https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?des=17759

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I looked at single images

https://www.legacysurvey.org/viewer/exposures/?ra=167.4101&dec=0.5766&layer=decals-dr5

and it looks like there was an asteroid in one of the red filter images. It was later removed, but the software missed some of the outer part, leaving a red ring.

I tried to look up the name of the asteroid, but JPL isn’t working right now.
https://www.legacysurvey.org/viewer/jpl_lookup?ra=167.4101&dec=0.5766&date=2015-03-29%2001:57:17.985040&camera=decam

Thanks you guys! Wow more you know, so I wasn’t just crazy thinking that it was something weird; too bad it wasn’t something suuper weird :slightly_smiling_face:

So an asteroid, glitched out, specifically 17759 Hata (1998 DA24) and why are asteroids removed? Who does the removing?

The Legacy Surveys were carried out for DESI, where we are studying stars and galaxies, so asteroids are a nuisance. We try to detect and mask them out in an “outlier” detection step – which also removes cosmic rays, and airplane and satellite trails.

Okay can I ask another question while I have your attention, so when we get the spectroscopy, and it shows a :o: around the galaxy, is everything in the circle (and only what is in the circle) where the spectroscopy comes from?

(not talking about our atmosphere na absorption or anything like that, just like I am wondering more about like how the spectroscopic data is created and also specifically what the circles mean when we bring on those overlays)

For the original SDSS spectrographs, the fibers are 3 arcseconds in diameter on the sky, so very tiny. I think the circles on the sky viewer are maybe 15 arcsec in diameter? I just made them that size so they show up and you can see the object within.
With the BOSS upgrade of the spectrographs the fibers became 2 arcsec in diameter.
For DESI the fibers are 1.5 arcsec in diameter.

Those sizes are intended to collect as much galaxy light as possible, under the expected sky conditions and our ability to position the fibers, without collecting too much light from the background sky (which is one of the main things diluting the signal).

cheers,
dustin

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Oh okay cool, thanks Dustin! I am grateful for this complex education. So that’s very interesting. Most of the circles then only take 2-3 arcsecond snippets of the target galaxy, rather than the whole galaxies light, but sometimes the whole galaxy’s light if small. However that would have more noise?

I read some more based on what you said, so you punch holes in the aluminum, which transfers light to fiber optic cables in those holes, which goes to a computer? Idk for me it would be better if the arcsecond circle matched what was observed for the various surveys so that I could see what I was looking at, precisely, since if spectroscopy is only taken of part of a galaxy that like matters a lot vs the entire galaxy idk, for me, but I understand you are trying to increase visibility. Would there be any way to represent the actual size of the spectrographic snippet while also allowing for visibility, or maybe an additional setting? I get I can like kinda guess, but idk maybe its not important, idk

image

Sorry one more question for now, its probably unimportant, but I am curious as to what your thoughts are on hose two specta that are nearly the same spectra in this thread:

I think I tried making the circles the real size but it didn’t work well