Gravitational lensing [Archive]

Nickelodeon

Oct28-09, 11:51 PM

Gravitational lensing displaces the apparent direction of a star outwards away from a gravitational source. Do you think it would be possible to see the same star at least twice simultaneously, one either side of this gravitational source?
Even more likely, if the gravitational source was great enough, I would have thought that you would see a halo.

Nick

qraal

Oct28-09, 11:59 PM

Gravitational lensing displaces the apparent direction of a star outwards away from a gravitational source. Do you think it would be possible to see the same star at least twice simultaneously, one either side of this gravitational source?
Even more likely, if the gravitational source was great enough, I would have thought that you would see a halo.

Nick

You would and such haloes have been seen when there's a nearby galaxy in front of a more distant one. The light has to come from almost immediately on the line of sight between the the intervening mass and the observer. A light source a bit to the side just appears as an arc of light.

Nickelodeon

Oct29-09, 12:30 AM

You would and such haloes have been seen when there's a nearby galaxy in front of a more distant one. The light has to come from almost immediately on the line of sight between the the intervening mass and the observer. A light source a bit to the side just appears as an arc of light.

amazing - thanks for that.

DaveC426913

Oct29-09, 12:34 AM

Gravitational lensing displaces the apparent direction of a star outwards away from a gravitational source. Do you think it would be possible to see the same star at least twice simultaneously, one either side of this gravitational source?
Even more likely, if the gravitational source was great enough, I would have thought that you would see a halo.

Nick

Yyyyyyep. Called an Einstein Ring. Google away...

seb7

Nov2-09, 05:09 AM

I've seen a TV programme demonstrating the same star seen at two (near) points in the sky at the same time.

MikeyW

Nov2-09, 05:25 AM

http://www.math.sunysb.edu/~tony/whatsnew/column/grav-lens-0299/images/HSTgravlens.jpg

Nickelodeon

Nov3-09, 03:53 AM

I've seen a TV programme demonstrating the same star seen at two (near) points in the sky at the same time.

Do you remember what the TV programme was called and when it was shown?