Space Warps Talk

Microlensing?

  • Mjtbarrett by Mjtbarrett

    How would microlensing appear in these images? The ?foreground star has a very bright arc...

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  • AlexandredOr by AlexandredOr

    Stars can't be lenses.. Not massive enough. Elliptical galaxies can, even galaxy clusters.

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  • Capella05 by Capella05 moderator

    I agree - in the images we are viewing microlensing would not be visible 😃

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  • Tom_Collett by Tom_Collett scientist

    The micro in microlensing means that the typical deflections are of order a microarcsecond, which is a million times below the resolution of CFHT. We've never seen multiple images with microlensing. It's detected by a change of brightness in a background star as the foreground star (or exoplanet!) crosses the line of sight.

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  • Capella05 by Capella05 moderator in response to Tom Collett's comment.

    Thanks Tom 😃

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  • JasonJason by JasonJason in response to AlexandredOr's comment.

    What was the experiment done by Eddington in 1919 all about? He used the Sun and it is a Star!

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  • anupreeta by anupreeta scientist, admin

    In principle, anything that has mass will cause deflection of light / lensing.. what matters is whether we can detect it.

    Microlensing effect has been reported in strong lenses with multiple images. Here, the stars from the lensing galaxy cause some changes in brightness of distant objects like quasars. For example, microlensing has been found in Q2237+0305 and B1600+434. But this is not the same as lensing a star by another star which is seen for stars within our own galaxy.

    @Mjtbarrett Lensing by star happens at an altogether different mass, spatial and time scales. It will not only produce very small effect (given its extremely small mass compared to a galaxy), one also needs to do observations at various epochs to be able to detect such an effect. Visual inspection of the CFHTLS images shown on the top-left can't tell you if a star is causing any lensing.

    The blue feature is most likely something called "halo" which is a reflection from the camera. For, even bigger and nearer stars, you will see bigger halos e.g. the star here - ASW0000rle

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  • Mjtbarrett by Mjtbarrett

    Thank you all for your help. Much appreciated.

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