Gravitational lensing ???

[pirate of skies (Rob)]

Hi everyone,
I was watching the HST shoot across the sky approaching from the west at around 19.11 to 19.16pm tonight. It travelled up to the zenith where it a short time after it started to fade away as it moved towards the east - further away from the suns light. At near its highest point above me, I noticed its image changed when it flew directly over one of the main stars of Scorpios tail. The image kind of warped into a circle around the star. It seemed to have been travelling in a straight path, then suddenly de-toured a little half circle around the stars point of light. Has anyone seen this effect or something similar ?

If this wasn't a Gravitational lensing effect, has anyone seen one. Is there a DSO where this effect is visible ?

[seanliddelow (Sean)]

I have noticed this effect on a much closer scale. if you close one eye and put your thumb at least 1cm from your other eye you will see a "warped" image around your thumb. Like some sort of space time effect. Surely over people have noticed this?
Einstein waited years for an eclipse when he could have done this? Or is it my wierd imagination? Try it for yourself.................

[pirate of skies (Rob)]

Thanks Sean,
I am not sure if that is the go here or not. It does seem similar to what I saw, but the image is not "on the peripheral" it was seen straight up (both figuratively and physically). Your experiment would have a lot to do with the focus length of the eye.

NOTE : My wife just caught me looking at my thumb at 1 cm from my eye. What can I say... Make sure they are in bed before you try this experiment.

Anybody else have any ideas, ?
and no, I hadn't been drinking.

[seanliddelow (Sean)]

I thought I had gone crazy.....................
Wathing TV with my thumb in front of my eyes

[seanliddelow (Sean)]

I think your case is more genuine.

[Robh (Rob)]

For gravitational lensing to occur, you need a bright distant object with a massive body (e.g. the Sun) between it and the Earth. The massive body's gravity will curve the space around it and in effect act as a lens. Thus, the distant object's light is seen to bend around the massive body on its way to the Earth. This effect was first confirmed by Arthur Eddington in a 1919 solar eclipse, when the light of distant stars was bent at the Sun's rim.
The effect you've seen is probably a combination of upper air disturbances and diffraction of the star's light as seen in the thumb experiment. The HST's mass is far to low to produce any measurable lensing effect.

Regards, Rob

[mithrandir (Andrew)]

Originally Posted by Robh

For gravitational lensing to occur, you need a bright distant object with a massive body (e.g. the Sun) between it and the Earth. The massive body's gravity will curve the space around it and in effect act as a lens. Thus, the distant object's light is seen to bend around the massive body on its way to the Earth. This effect was first confirmed by Arthur Eddington in a 1919 solar eclipse, when the light of distant stars was bent at the Sun's rim.

Hasn't that 1919 finding since been determined to be wishful thinking? The margin of error in the data is supposed to make any conclusion unsafe.

[ngcles]

Hi Mithrandir Rob & All,

Originally Posted by Robh

For gravitational lensing to occur, you need a bright distant object with a massive body (e.g. the Sun) between it and the Earth. The massive body's gravity will curve the space around it and in effect act as a lens. Thus, the distant object's light is seen to bend around the massive body on its way to the Earth. This effect was first confirmed by Arthur Eddington in a 1919 solar eclipse, when the light of distant stars was bent at the Sun's rim.
The effect you've seen is probably a combination of upper air disturbances and diffraction of the star's light as seen in the thumb experiment. The HST's mass is far to low to produce any measurable lensing effect.

Spot on. Agree completely! The observed "de-touring" was probably an optical illusion.

Originally Posted by mithrandir

Hasn't that 1919 finding since been determined to be wishful thinking? The margin of error in the data is supposed to make any conclusion unsafe.

No, not at all. That alleged discrediting of Eddington's observations is a recent invention that has little or no basis in fact. Eddington's photographs show a displacement approximately consistent with Einstein's predictions. For the same effect in the object known as "Huchra's Lens" see:

http://en.wikipedia.org/wiki/Einstein%27s_Cross

A 25-30" 'scope will show Huchra's Lens resolved though the faintest of the four images of the Quasar is said to be very, very difficult. I believe a 16" will show the lensing galaxy but not much else.


Best,

Les D

[freespace]

Originally Posted by mithrandir

Hasn't that 1919 finding since been determined to be wishful thinking? The margin of error in the data is supposed to make any conclusion unsafe.

It would appear not:

http://arxiv.org/abs/0709.0685

Einstein Cross is a very good example of gravitational lensing:

http://en.wikipedia.org/wiki/Einstein_Cross

Cheers,
Steve

[mithrandir (Andrew)]

Originally Posted by freespace

It would appear not:

http://arxiv.org/abs/0709.0685

Einstein Cross is a very good example of gravitational lensing:

http://en.wikipedia.org/wiki/Einstein_Cross

I am well aware of Einstein's Cross and wasn't suggesting lensing was bunk.

I was querying whether a final conclusion had been reached on whether Eddington's observations had sufficient reliability. It wouldn't be the first time that reviewing the margins of error in data found the conclusions unsound, but that later data proved the case.

On reading Kennefick's article I am reminded it was in Hawking's book I first saw the conjecture.

[freespace]

My bad mithrandir, I was unclear.

The Einstein cross part was in response to the GP, who asked for DSO which shows gravitational lensing. It was not meant to imply anything :-)