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What is this in Capricorn?

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#1 Edward E

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Posted 07 December 2012 - 11:29 AM

I was using Wikisky to look at the area around Neptune when a small object grabbed my attention. At first I thought it was a comet because of what looked like a trail caused by the object moving during the exposure but a look @ Aladin showed the object from earlier pictures of the area so its not a comet. WIKISKY nor Aladin did not give a NGC, IC, PGC, UGC, Pal, Ter or any other designations to the object. Looking over detailed charts (MegaStar, Skychart 3x or TriAtlas C) showing objects to 15 mag does not show the object either. Anyone here have a clue to it's nature? Maybe a dwarf galaxy?

Here is a screen shot of the area with the object pointed to by the green arrow with the objects RA & Dec.

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#2 Edward E

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Posted 07 December 2012 - 11:51 AM

Here is a zoomed in image of the object of interest from WIKISKY.

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#3 Tom Polakis

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Posted 07 December 2012 - 12:04 PM

Nice catch! It looks like a comet that was present when they shot that POSS2 image through the red filter. The trailing during the exposure is apparent, as I'm sure you noticed.

If you go to the STScI's Digitized Sky Survey image retrieval site, you can retrieve from "POSS2/UKSTU Red." Then, enter the 2000 coordinates you have in WikiSky, select 60'x60' height and width, and retrieve as a GIF. You will see the same object that you found in WikiSky, which must be using the POSS2 as its source. Now, go back to the form, and select POSS2 blue or any of the other surveys, and the comet is not there.

Somewhere, the people responsible for POSS2 documented the date/time of all of the survey images, so it would be possible to back out the comet that was imaged on this plate.

Tom

#4 Edward E

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Posted 07 December 2012 - 12:59 PM

Your right Tom, it's a comet. I checked with google "sky" which has images from 2 to 3 years ago and there is no object at that position. It would be very constructive for the date and time of the posed images to easily accessible. Now what comet is it? A new mystery to solve.

Here is a screen clip from google sky:

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#5 Edward E

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Posted 07 December 2012 - 01:14 PM

To answer my own question about date and time, with the DSS images the info is in the FITS file header. You just need an application that can open and read the header. Google, well we are out of luck there and WIKISKY does seem to use POSS2 survey image.

#6 Tom Polakis

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Posted 07 December 2012 - 01:22 PM

Now what comet is it? A new mystery to solve.


I went into the Aladin Sky Atlas to see if it might give the data for the POSS2 plate that shows the object. After flailing around a bit, I found that you can overlay the DSS image, and there it is again on the red image. Right clicking on the layer title and going to Properties brought up a way to get at the FITS header. Here you can find the exposure time (85 minutes), and the date and time: October 9, 1988 at 10:19 UT.

It seems like the comet's ID could be backed out of planetarium software like SkySafari that shows "all" comets. Just point it in that part of Capricornus, set the time and date, and have it plot the comets.

Tom

#7 IVM

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Posted 07 December 2012 - 05:07 PM

And a nice-looking one, especially in red ;)

#8 Tom Polakis

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Posted 07 December 2012 - 09:14 PM

Just plotted the comets in SkySafari. The nearest comet on that date of the image is 29P/Schwassmann-Wachmann, but it's about a degree to the west-southwest of the position in the image. The direction and amount of motion is right on, though. The software shows it very near the position on September 19, 1988, several weeks earlier.

The most likely problem is the orbital elements, which are for the current epoch, and not for 1988. If it really is 29P/Schwassmann-Wachmann, the object you found on the POSS2 image turned out to be a pretty interesting comet!

Tom

#9 J Lowrey

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Posted 08 December 2012 - 01:01 PM

This is very interesting, you might send the coordinates to the IAU Minor planet center. I bet they could find out if it was a known comet or not.

#10 David Knisely

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Posted 08 December 2012 - 02:04 PM

It might also be a plate defect or a reflected image of one of the bright stars at the far right edge of the field. I have seen this sort of thing quite a few times with the POSS images, so I have to keep my guard up for them. Clear skies to you.

#11 Tom Polakis

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Posted 09 December 2012 - 11:00 AM

I wrote to Brian Skiff at Lowell, and he confirmed that it's Comet 29P/Schwassmann-Wachmann.

Enter 29P/Schwassmann-Wachmann into JPL Horizons ephemeris generator, and a time range of 1988-Oct-09 to 1988-Oct-10 with a one-hour interval, and you get this position at 10h UT.

1988-Oct-09 10:00 21 52 15.70 -08 39 20.3

That's right on top of the position of the comet on the POSS2 red image.

Tom

#12 J Lowrey

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Posted 09 December 2012 - 04:46 PM

Tom good detective work!

#13 mrfritz44

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Posted 09 December 2012 - 09:37 PM

This post drove me to compare the WIKISKY image with Stellarium and I found nothing in Stellarium. Not that it matters, but the post piqued my interest.

Now for a hypothetical question. What are the chances that high definition images could be uploaded to public sources and still contain surprises like new comets, supernovae, or NEO's?

My hunch is that the data is scoured by a computer so that any prospective discovery would already have been made, but then again with projects like GalaxyZoo could the human eye still be the best way to analyze high definition images such as these?

Fred

#14 Man in a Tub

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Posted 09 December 2012 - 10:38 PM

This has been a very interesting thread which I have added as a favorite. I use the ESO and STScI DSS browsers frequently.

:grin:

#15 Edward E

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Posted 10 December 2012 - 12:44 PM

Thank you Tom for confirming the nature of the object in question. Comet 29P/Schwassmann-Wachmann is a "Centaur" body, a group of recently recognized objects that orbit between Jupiter and Neptune and are though to have be pulled from the Kuiper Belt. This "comet" undergoes an increase in brightness from its normal 16 V mag up to 10 V mag ~ every 13 years. The last outburst was observed between 2008 & 2010 but was very week.

Though this is not a new discovery, it was a personal discovery for me in that I learned where WIKISKY was acquiring their images, the subtle changes in orbital positions over time and new resources to use when working with comets and the fun of finding transient objects in these posted images.

Thank you to everyone who for their suggestions and ideas and again a big thank you to Tom for his detective work.






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