Author Topic: Tuesday, 22 April, 2014: Star? Galaxy? Both!  (Read 3718 times)

JeanTate

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Tuesday, 22 April, 2014: Star? Galaxy? Both!
« on: April 22, 2014, 12:38:30 am »


"Sometimes I find beautiful pictures with astonishing conjunctions galaxy and star. It's just for esthetic reasons that I propose to collect them here..."

So begins the first post, by AlexandredOr, in a very long thread, Conjunctions galaxy/star.

These galaxy-star conjunctions are of many different kinds; for example:







Sometimes such a conjunction causes confusion, not only for zooites, but even for the SDSS imaging software pipeline; like this:



And sometimes even a spectrum doesn't really help clear up the confusion!  ;D



Fortunately, there are two spectra for of this conjunction: 725253573776009216, which is a "starforming galaxy"; and 725251924911220736, an "M3 star". Now imagine there was just one; how would it have helped?




Do you have favorite star-galaxy conjunction?


While many objects were posted as DR7, AHZ, DR8, etc images, all in this post are DR9. From top to bottom they are:

* might be more visually striking in the original, AHZ5000eme:


** in the DR8/AGS original image the star is much less obvious, AGS00000hm:

AlexandredOr

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Re: Tuesday, 22 April, 2014: Star? Galaxy? Both!
« Reply #1 on: April 22, 2014, 10:03:42 am »
 :D :D :D
Thx Jean  :D
One of my favorite :

Baby star opening its eyes on the Universe.

zutopian

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Re: Tuesday, 22 April, 2014: Star? Galaxy? Both!
« Reply #2 on: April 22, 2014, 01:30:34 pm »
Related "Object of the Day":

Aug 2 2012 Star overlapping galaxy?:
http://www.galaxyzooforum.org/index.php?topic=280316.0

zutopian

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« Last Edit: April 22, 2014, 03:44:31 pm by zutopian »


zutopian

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Re: Tuesday, 22 April, 2014: Star? Galaxy? Both!
« Reply #5 on: April 22, 2014, 03:25:39 pm »
And following one is also my favorite.:


http://cas.sdss.org/astro/en/tools/explore/obj.asp?id=587731886269202658
Lower arm tip: QSO
Upper arm tip: Star
« Last Edit: April 22, 2014, 03:45:16 pm by zutopian »

JeanTate

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Re: Tuesday, 22 April, 2014: Star? Galaxy? Both!
« Reply #6 on: April 28, 2014, 02:30:44 pm »
Thanks AlexandredOr and zutopian!  :)

Color contrasts, positioning, angles, unusual patterns, ... and no doubt several other features all contribute to making a galaxy/star conjunction visually appealing.

From a scientific perspective there's also considerable appeal too. Take SDSS J170348.21+244228.7 (DR7 ObjId 587733432461754555, a.k.a. AGS00001dn) for example (Quench project image, then DR9 one):



Here's its spectrum:


Doesn't look much like it's a composite (star+galaxy), does it? There are a couple of strange, unmarked absorption lines though ...

Zooite mlpeck produced this remarkable plot, which shows how the light from each of the star and galaxy contributes to the overall spectrum*:



Diffraction spikes - the four 'compass points' which are nearly always seen with bright stars in SDSS images - are features which make many star/galaxy conjunctions visually appealing. And they are often what seems to make an image of a star - whether SDSS or Hubble - worthy of being posted in The best Stars! thread (there's no separate thread, here in the GZ forum, on diffraction spikes  ::)). I'm thinking of writing an OotD on diffspikes (as I call them); good idea?

* for details, see his post, on page 2 of the Potentially Problematic Sources in 'Subset 2 -- 1149 Source Sample' thread in Quench Talk (I can't give you a direct link, because Talk doesn't allow you to easily get links to posts ...  :()

zutopian

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Re: Tuesday, 22 April, 2014: Star? Galaxy? Both!
« Reply #7 on: April 28, 2014, 04:07:45 pm »
You are welcome!
The case in above post is actually related to the scientific "Object of the Day", which I had mentioned in my post on April 22, 2014, 01:30:34 pm.:

Aug 2 2012 Star overlapping galaxy?:
http://www.galaxyzooforum.org/index.php?topic=280316.0

planetaryscience

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Re: Tuesday, 22 April, 2014: Star? Galaxy? Both!
« Reply #8 on: May 04, 2014, 06:45:49 pm »
just found this one:


1237666227511232340
I like to find asteroids and galaxy mergers- but all galaxies are still fine to me.

JeanTate

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Re: Tuesday, 22 April, 2014: Star? Galaxy? Both!
« Reply #9 on: May 05, 2014, 06:17:17 pm »
Cool!  8)

Pity there's no spectrum ...  :(

planetaryscience

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Re: Tuesday, 22 April, 2014: Star? Galaxy? Both!
« Reply #10 on: May 12, 2014, 02:21:08 pm »
I like to find asteroids and galaxy mergers- but all galaxies are still fine to me.