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Gorn
2019-Jul-29, 02:07 AM
Hello. I am now a 'believer' in G. Microlensing.

Instead of a 'planet' blocking light from a star while it transits said object..the G. field of a planet can lense or redirect light waves
that would simply miss your telescope on Earth and cause a star to 'brighten' when viewed from Earth.

Question: The Sun has a G. focal point that is far from Earth. Hundreds of au. away. Can someone tell me how far away the G. focal point of
Jupiter would be in our solar system? And how powerful would a telescope be that is put there?

Thanks for any and all responses
Bye
Gorn

ronin
2019-Jul-29, 11:04 AM
According to this page https://www.centauri-dreams.org/2016/04/26/gravitational-lensing-with-planets/ 6100AU.

holmes4
2019-Jul-29, 12:12 PM
"The Sun has a G. focal point"

Totally untrue

Mark

holmes4
2019-Jul-29, 12:12 PM
"The Sun has a G. focal point"

Totally untrue

Mark

Hornblower
2019-Jul-29, 08:48 PM
Hello. I am now a 'believer' in G. Microlensing.

Instead of a 'planet' blocking light from a star while it transits said object..the G. field of a planet can lense or redirect light waves
that would simply miss your telescope on Earth and cause a star to 'brighten' when viewed from Earth.

Question: The Sun has a G. focal point that is far from Earth. Hundreds of au. away. Can someone tell me how far away the G. focal point of
Jupiter would be in our solar system? And how powerful would a telescope be that is put there?

Thanks for any and all responses
Bye
Gorn

There is more to the science of gravitational lensing than merely believing in it. We must do the quantitative ray tracing and analyze the results.

Suppose we watch Jupiter transit the Sun from afar. The spot on the Sun that is geometrically blocked subtends about 36 arcseconds as seen from Jupiter. The linked information on microlensing shows that a ray grazing Jupiter is deflected about 1/60 arcsecond. Thus only a sliver at the edge of the occulted spot will have any light deflected into our line of sight. That means a vanishingly slight reduction of the amount of dimming of the Sun. It certainly will not brighten the Sun the way it would brighten a background star a vast distance beyond the planet's gravitational focal length.

Gorn
2019-Aug-16, 10:19 AM
Sorry about the huge time delay. I was saying or thinking as an example. Suppose as seen from our solar system we view a planet as big as Jupiter that surrounds a star..will say like Alpha Centauri. This star has a certain small size and brightness as seen from Earth. The planet then transits that star. If seen from the right angle..and logic tells you it does not matter the situation..photons are re-directed by gravitational fields..a larger number of photons could enter a telescope on Earth. That means an increase in brightness.

I have seen it as well

Thanks
G

Strange
2019-Aug-16, 12:57 PM
Sorry about the huge time delay. I was saying or thinking as an example. Suppose as seen from our solar system we view a planet as big as Jupiter that surrounds a star..will say like Alpha Centauri. This star has a certain small size and brightness as seen from Earth. The planet then transits that star. If seen from the right angle..and logic tells you it does not matter the situation..photons are re-directed by gravitational fields..a larger number of photons could enter a telescope on Earth. That means an increase in brightness.

I have seen it as well

Thanks
G

I don't know, but I suspect that the gravitational lensing by a planet would be too small to make up for the light lost by the transit.

It seems that gravitational lensing used to detect exoplanets uses the fact that the planet will add to the gravitational lensing of its star (of another star behind it). More information here:

https://en.wikipedia.org/wiki/Gravitational_microlensing#Detection_of_extrasolar _planets
https://en.wikipedia.org/wiki/Methods_of_detecting_exoplanets#Gravitational_micr olensing

ngc3314
2019-Aug-16, 01:24 PM
In the exoplanet community, this situation goes by the designation of self-lensing. It has been detected for binary stars (https://www.cfa.harvard.edu/~avanderb/saganworkshop2018/275.full.pdf), with an amplitude of only 0.1% for a white dwarf in front of a Sunlike star. For gravitational lensing in general, the effect is strongest when the lensing object is midway along the line of sight, so having the lens orbiting the background star is much less favorable.