AGZ00075k7
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Wisi_EU
sorry for posting on forum (while I already commented the picture), but it is important for me to know so I can train my brain to this type of interesting situation.
ra 198.29668 dec 15.74860 type STAR
Can someone tell whether this star (on DR8) is lensed by this galaxy ? It looks to me like it is.Posted
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jopipen
star http://skyserver.sdss3.org/dr8/en/tools/chart/navi.asp?ra=198.29329379&dec=15.75088346
Posted
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ElisabethB
moderator
The bright blue object, top left, is a foreground star from our galaxy. No lensing here, sorry !
Posted
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Wisi_EU
lol I'm not talking about this horrible blue thing 😃 check the coordinates I gave on DR8 and let me know what you think please.
Posted
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Wisi_EU
in response to jopipen's comment.
not the coords I gave ...
Posted
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JeanTate
in response to Wisi_EU's comment.
Here it is in DR10, zoomed in somewhat:
Can someone tell whether this star (on DR8) is lensed by this galaxy ?
It looks, to me, rather odd, almost as if there's some sort of dust lane, or plume, extending W towards and over the edge of the disk of the galaxy. But, at this level of detail, it could just be an artifact ... In terms of it being lensed: I think the galaxy is too wimpy for it create an image of a background object as far away - on the sky, in arcsecs - as this. And it's in a rather unlikely place, with respect to the galaxy's center of mass, too.
It looks to me like it is.
Could you please say a bit more about why you think that?
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Wisi_EU
thanks for your thorough answer Jean Tate.
I was just imagining something about the hypothetical ring of dark matter that could occur around galaxies, hence accounting in its "mass" and light-deviating capacity. And DR8 does say that red dot is a star ... so I assumed it was right. Maybe it isn't though.
You're right it's hard to tell whether such a situation would be possible in the first place, I've never come upon such a thing myself. A bit of extrapolation helps understanding facts sometimes.Posted
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JeanTate
in response to Wisi_EU's comment.
You're very welcome, Wisi_EU.
the hypothetical ring of dark matter that could occur around galaxies
Are you, perhaps, recalling the term 'halo'? If so, it's particularly unfortunate that the technical term astronomers use ('dark matter halo') leads to the impression that the outer parts are denser (have more mass per volume) than the inner parts ... it's exactly the opposite! 😮
I'm not good with mental pictures, but in a typical galaxy, the dark matter halo has the shape of a sphere (perhaps 'bent' a bit, so it looks like an American football), which gets denser and denser as you get closer and closer to its center. Sort of like a gas giant planet, Jupiter say, but with no relatively abrupt changes in density as you travel inward ...
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