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I was going through the zoomable image of Milky way and after zooming to this particular location, we can see a reddish area on the left side of a probably large star. Here is a screenshot I took after zooming to that particular area: image

So is this gas cloud or some weird lens effect ?

Edit: Location ( center of the blue rectangle )

enter image description here

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  • $\begingroup$ Can you give the location... ? $\endgroup$ – Rob Jeffries Jul 25 '17 at 11:46
  • $\begingroup$ @RobJeffries, I have edited and added an image. The particular object is at the top right. Thanks. $\endgroup$ – astre Jul 25 '17 at 11:54
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    $\begingroup$ The coordinates ! $\endgroup$ – Rob Jeffries Jul 25 '17 at 12:44
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    $\begingroup$ Given that this is a mosaic of multiple images, I'd be inclined to say that particular part of the image simply has classic lens flare. $\endgroup$ – StephenG Jul 26 '17 at 7:23
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    $\begingroup$ Looks like J. J. Abrams took this picture $\endgroup$ – Beta Decay Jul 27 '17 at 18:57
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This particular object I tracked down by comparing the visual with the infrared image of the sky. It was a little tricky because no very bright star appears at that location. But after making comparisons, the star in the original image is HD 155161, also known as V* AH Sco, indicating that it is a variable.

In fact, Simbad lists it as a red supergiant at coordinates [17 11 17.02114, -32 19 30.7132], and visual magnitude of about 7.5 Red supergiants are often unstable and are semi-regular varible stars.

That explains why it is much brighter in the VISTA infrared image than in the optical. Red supergiants have cool outer layers that give off much of their radiation as infrared, not as visible light.

Looking at the star on Aladin Lite, even in the infrared, there is not a hint of nebulosity around the star. The conclusion is that this is an optical effect, lens flare or similar.

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As the comments have said, this is simply a camera effect known as a lens flare

If you look around at the various bright stars, you can see this in multiple places, e.g.:

and also:

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  • $\begingroup$ Do you know if lens flare can account for the reddish region to the left of the star? $\endgroup$ – HDE 226868♦ Jul 28 '17 at 12:02
  • $\begingroup$ @HDE226868 I think so. You can a reddish colour on the edge of the flare of the bottom image. $\endgroup$ – Beta Decay Jul 28 '17 at 12:22

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