Starship Asterisk*

Ann wrote: ↑Fri Nov 13, 2020 6:15 am

Tarantula_HOO_final_2_1024[1].jpg

The Tarantula Nebula with the remnant of SN 1987A.
Photo: Ignacio Diaz Bobillo.

Supernova 1987A (center) at the time of explosion. Photo: ESO - https://www.eso.org/public/images/eso0708a/

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So where is the supernova remnant in today's APOD? Can you spot it?

Ann

APOD Robot wrote: ↑Fri Nov 13, 2020 5:06 am The Tarantula Zone

Explanation: The rich field of view spans about 2 degrees or 4 full moons, in the southern constellation Dorado.

neufer wrote: ↑Fri Nov 13, 2020 5:23 pm

APOD Robot wrote: ↑Fri Nov 13, 2020 5:06 am The Tarantula Zone

Explanation: The rich field of view spans about 2 degrees or 4 full moons, in the southern constellation Dorado.

The statement that this "view spans about 2 degrees or 4 full moons" seems rather fishy to me.

ignacio_db wrote: ↑Fri Nov 13, 2020 5:21 pm I registered both images against each other, and cropped the SN area with the same geometry. Could it be the red star at the center, sided by two white stars?

Ignacio

ignacio_db wrote: ↑Fri Nov 13, 2020 5:40 pm

neufer wrote: ↑Fri Nov 13, 2020 5:23 pm

APOD Robot wrote: ↑Fri Nov 13, 2020 5:06 am The Tarantula Zone

Explanation: The rich field of view spans about 2 degrees or 4 full moons, in the southern constellation Dorado.

The statement that this "view spans about 2 degrees or 4 full moons" seems rather fishy to me.

The precise FOV is 1d 3' 47.8" x 1d 18' 46.0".

Ignacio

rkennaway wrote: ↑Fri Nov 13, 2020 3:32 pm "Formless protoplasm able to mock and reflect all forms and organs and processes — viscous agglutinations of bubbling cells — rubbery fifteen-foot spheroids infinitely plastic and ductile — slaves of suggestion, builders of cities — more and more sullen, more and more intelligent, more and more amphibious, more and more imitative! Great God! What madness made even those blasphemous Old Ones willing to use and carve such things?"

johnnydeep wrote: ↑Fri Nov 13, 2020 7:38 pm

ignacio_db wrote: ↑Fri Nov 13, 2020 5:40 pm

neufer wrote: ↑Fri Nov 13, 2020 5:23 pm
The statement that this "view spans about 2 degrees or 4 full moons" seems rather fishy to me.

The precise FOV is 1d 3' 47.8" x 1d 18' 46.0".

Ignacio

So, this is roughly 1 degree x 1 degree, and not 2 degrees wide per the text? How did you determine the exact field of view?

were the Tarantula Nebula closer, say 1,500 light-years distant like the local star forming Orion Nebula, it would take up half the sky

Tarantulas are very nice wrote: ↑Fri Nov 13, 2020 10:31 pm

were the Tarantula Nebula closer, say 1,500 light-years distant like the local star forming Orion Nebula, it would take up half the sky

Imagine getting out of the cabin at night and seeing that across half the sky. Our view of nature would perhaps be rather less arrogant, and astronomy would be taken seriously indeed.

(We'd have H-alpha eyes, the right atmosphere, and a high tolerance for being blasted by supernovae, OK?)

Chris Peterson wrote: ↑Fri Nov 13, 2020 11:32 pm

Tarantulas are very nice wrote: ↑Fri Nov 13, 2020 10:31 pm

were the Tarantula Nebula closer, say 1,500 light-years distant like the local star forming Orion Nebula, it would take up half the sky

Imagine getting out of the cabin at night and seeing that across half the sky. Our view of nature would perhaps be rather less arrogant, and astronomy would be taken seriously indeed.

(We'd have H-alpha eyes, the right atmosphere, and a high tolerance for being blasted by supernovae, OK?)

The problem is that even with 100% efficient eyes, you'd still need to stare at one spot in the sky for many minutes, and somehow integrate the photons your eyes were collecting, to see anything remotely like this.

In reality, if we were close enough to this to see it covering half the sky, it would look like a barely discernible gray haze, dimmer than the Milky Way.

Ann wrote: ↑Sat Nov 14, 2020 4:51 am

Chris Peterson wrote: ↑Fri Nov 13, 2020 11:32 pm

Tarantulas are very nice wrote: ↑Fri Nov 13, 2020 10:31 pm

Imagine getting out of the cabin at night and seeing that across half the sky. Our view of nature would perhaps be rather less arrogant, and astronomy would be taken seriously indeed.

(We'd have H-alpha eyes, the right atmosphere, and a high tolerance for being blasted by supernovae, OK?)

The problem is that even with 100% efficient eyes, you'd still need to stare at one spot in the sky for many minutes, and somehow integrate the photons your eyes were collecting, to see anything remotely like this.

In reality, if we were close enough to this to see it covering half the sky, it would look like a barely discernible gray haze, dimmer than the Milky Way.

Okay, but this part of the Tarantula Nebula would surely be ablaze at a distance of only 1500 light-years, right?

Chris Peterson wrote: ↑Sat Nov 14, 2020 1:13 pm

Ann wrote: ↑Sat Nov 14, 2020 4:51 am

Chris Peterson wrote: ↑Fri Nov 13, 2020 11:32 pm

The problem is that even with 100% efficient eyes, you'd still need to stare at one spot in the sky for many minutes, and somehow integrate the photons your eyes were collecting, to see anything remotely like this.

In reality, if we were close enough to this to see it covering half the sky, it would look like a barely discernible gray haze, dimmer than the Milky Way.

Okay, but this part of the Tarantula Nebula would surely be ablaze at a distance of only 1500 light-years, right?

You'd see a cluster of bright stars. The nebulosity wouldn't be anything other than a faint glow. If fact, the bright stars might make it harder to see than in some other parts.

Ann wrote: ↑Sat Nov 14, 2020 1:55 pm

Chris Peterson wrote: ↑Sat Nov 14, 2020 1:13 pm

Ann wrote: ↑Sat Nov 14, 2020 4:51 am

Okay, but this part of the Tarantula Nebula would surely be ablaze at a distance of only 1500 light-years, right?

You'd see a cluster of bright stars. The nebulosity wouldn't be anything other than a faint glow. If fact, the bright stars might make it harder to see than in some other parts.

I get it, Chris, but you know me... I often prefer the bright (blue) stars over the nebulosity anyway.

Surely R136 would look like a mighty impressive cluster from a distance of 1,500 light-years?

Ann

ignacio_db wrote: ↑Fri Nov 13, 2020 7:58 pm

johnnydeep wrote: ↑Fri Nov 13, 2020 7:38 pm

ignacio_db wrote: ↑Fri Nov 13, 2020 5:40 pm

The precise FOV is 1d 3' 47.8" x 1d 18' 46.0".

Ignacio

So, this is roughly 1 degree x 1 degree, and not 2 degrees wide per the text? How did you determine the exact field of view?

By plate-solving the image.

Ignacio

Plate-solving is a image analysis that detects the stars and then tries to identify them using catalogs of know stars. If the analysis is successful it is possible to calculate the Right Accession (RA) and Declination (Dec) of the image center which tells where exactly is pointing the telescope, image orientation, resolution and etc. Plate-solving is the engine of many scientific studies for example comet, asteroid hunting and orbit analysis.

Nowadays we are lucky to have access to many advanced techniques and devices that in the past were available only for the biggest professional observatories. Plate-solving is one these techniques that makes imaging much productive, accurate and pleasant. There are two types of solving - Near and Blind. The first one needs to know approximately where "you are" and solving will tell you exactly where "you are", it is very fast because you already know context . For the second one you don't need know where "you are" and solving will find the position without knowing the starting position, it is slower because there is need to match star patterns from all over the sky.

johnnydeep wrote: ↑Sat Nov 14, 2020 7:30 pm

ignacio_db wrote: ↑Fri Nov 13, 2020 7:58 pm

johnnydeep wrote: ↑Fri Nov 13, 2020 7:38 pm

So, this is roughly 1 degree x 1 degree, and not 2 degrees wide per the text? How did you determine the exact field of view?

By plate-solving the image.

Ignacio

Ok. I had to look up "plate-solving". Did you do this with software or manually? And, again, assuming your FOV is correct, the APOD is wrong to say it is 2 degrees wide, right?

Chris Peterson wrote: ↑Sat Nov 14, 2020 7:51 pm

johnnydeep wrote: ↑Sat Nov 14, 2020 7:30 pm

ignacio_db wrote: ↑Fri Nov 13, 2020 7:58 pm

By plate-solving the image.

Ignacio

Ok. I had to look up "plate-solving". Did you do this with software or manually? And, again, assuming your FOV is correct, the APOD is wrong to say it is 2 degrees wide, right?

It can be done inside some image processing programs (this image was processed with PixInsight, which has a plate solving tool). It can also be done by uploading an image to Astrometry.net, which can solve almost anything. This image has almost all the stars processed out, by virtue of so much signal coming from a very narrow H-alpha and OIII channels. But there were probably enough stars in the unprocessed frames to get a solution. It's also easy enough to just solve a clean star field, which will give you the pixel scale for a given imaging train, and just use that value, multiplied by the number of pixels on an axis.

johnnydeep wrote: ↑Sat Nov 14, 2020 10:21 pm

Chris Peterson wrote: ↑Sat Nov 14, 2020 7:51 pm

johnnydeep wrote: ↑Sat Nov 14, 2020 7:30 pm

Ok. I had to look up "plate-solving". Did you do this with software or manually? And, again, assuming your FOV is correct, the APOD is wrong to say it is 2 degrees wide, right?

It can be done inside some image processing programs (this image was processed with PixInsight, which has a plate solving tool). It can also be done by uploading an image to Astrometry.net, which can solve almost anything. This image has almost all the stars processed out, by virtue of so much signal coming from a very narrow H-alpha and OIII channels. But there were probably enough stars in the unprocessed frames to get a solution. It's also easy enough to just solve a clean star field, which will give you the pixel scale for a given imaging train, and just use that value, multiplied by the number of pixels on an axis.

Neat!