How can gravitational lensing makes a quasar appear brighter?












10












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How can gravitational lensing makes a quasar brighter than it would in the absence of a foreground galaxy?






cosmology observational-astronomy gravitational-lensing quasars







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  • 2




    $begingroup$
    How can glass lensing make sunlight appear intense enough to start fires?
    $endgroup$
    – Mason Wheeler
    Jan 25 at 15:16






  • 1




    $begingroup$
    How does a telescope lens make dim stars bright enough to see?
    $endgroup$
    – Barmar
    Jan 25 at 19:49


















10












$begingroup$


How can gravitational lensing makes a quasar brighter than it would in the absence of a foreground galaxy?






cosmology observational-astronomy gravitational-lensing quasars







share|improve this question









$endgroup$








  • 2




    $begingroup$
    How can glass lensing make sunlight appear intense enough to start fires?
    $endgroup$
    – Mason Wheeler
    Jan 25 at 15:16






  • 1




    $begingroup$
    How does a telescope lens make dim stars bright enough to see?
    $endgroup$
    – Barmar
    Jan 25 at 19:49
















10












10








10





$begingroup$


How can gravitational lensing makes a quasar brighter than it would in the absence of a foreground galaxy?






cosmology observational-astronomy gravitational-lensing quasars







share|improve this question









$endgroup$




How can gravitational lensing makes a quasar brighter than it would in the absence of a foreground galaxy?






cosmology observational-astronomy gravitational-lensing quasars




cosmology observational-astronomy gravitational-lensing quasars






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked Jan 25 at 6:48









Haris AnsariHaris Ansari

1116




1116








  • 2




    $begingroup$
    How can glass lensing make sunlight appear intense enough to start fires?
    $endgroup$
    – Mason Wheeler
    Jan 25 at 15:16






  • 1




    $begingroup$
    How does a telescope lens make dim stars bright enough to see?
    $endgroup$
    – Barmar
    Jan 25 at 19:49
















  • 2




    $begingroup$
    How can glass lensing make sunlight appear intense enough to start fires?
    $endgroup$
    – Mason Wheeler
    Jan 25 at 15:16






  • 1




    $begingroup$
    How does a telescope lens make dim stars bright enough to see?
    $endgroup$
    – Barmar
    Jan 25 at 19:49










2




2




$begingroup$
How can glass lensing make sunlight appear intense enough to start fires?
$endgroup$
– Mason Wheeler
Jan 25 at 15:16




$begingroup$
How can glass lensing make sunlight appear intense enough to start fires?
$endgroup$
– Mason Wheeler
Jan 25 at 15:16




1




1




$begingroup$
How does a telescope lens make dim stars bright enough to see?
$endgroup$
– Barmar
Jan 25 at 19:49






$begingroup$
How does a telescope lens make dim stars bright enough to see?
$endgroup$
– Barmar
Jan 25 at 19:49












1 Answer
1






active

oldest

votes


















16












$begingroup$

The quasar gives out light in all directions. The light spreads out in space. Only a very small amount of that light would be pointed exactly in the direction of your telescope.



But if a large galaxy or galaxy cluster is between the quasar and us, it bends some of the light towards us, making the quasar brighter (it would also distort the shape, but quasars are too small for their shape to be seen) This makes it brighter for us (and dimmer in other parts of space which would have got the light that is now bent towards us.)






share|improve this answer









$endgroup$









  • 8




    $begingroup$
    a tiny bit like this
    $endgroup$
    – uhoh
    Jan 25 at 7:56






  • 1




    $begingroup$
    To be clear: nothing can make the image brighter than the quasar itself is. That's that optical "entendue law". What happens is the image is made brighter than it would have been sans the lensing.
    $endgroup$
    – Carl Witthoft
    Jan 25 at 19:14











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1 Answer
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1 Answer
1






active

oldest

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active

oldest

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active

oldest

votes









16












$begingroup$

The quasar gives out light in all directions. The light spreads out in space. Only a very small amount of that light would be pointed exactly in the direction of your telescope.



But if a large galaxy or galaxy cluster is between the quasar and us, it bends some of the light towards us, making the quasar brighter (it would also distort the shape, but quasars are too small for their shape to be seen) This makes it brighter for us (and dimmer in other parts of space which would have got the light that is now bent towards us.)






share|improve this answer









$endgroup$









  • 8




    $begingroup$
    a tiny bit like this
    $endgroup$
    – uhoh
    Jan 25 at 7:56






  • 1




    $begingroup$
    To be clear: nothing can make the image brighter than the quasar itself is. That's that optical "entendue law". What happens is the image is made brighter than it would have been sans the lensing.
    $endgroup$
    – Carl Witthoft
    Jan 25 at 19:14
















16












$begingroup$

The quasar gives out light in all directions. The light spreads out in space. Only a very small amount of that light would be pointed exactly in the direction of your telescope.



But if a large galaxy or galaxy cluster is between the quasar and us, it bends some of the light towards us, making the quasar brighter (it would also distort the shape, but quasars are too small for their shape to be seen) This makes it brighter for us (and dimmer in other parts of space which would have got the light that is now bent towards us.)






share|improve this answer









$endgroup$









  • 8




    $begingroup$
    a tiny bit like this
    $endgroup$
    – uhoh
    Jan 25 at 7:56






  • 1




    $begingroup$
    To be clear: nothing can make the image brighter than the quasar itself is. That's that optical "entendue law". What happens is the image is made brighter than it would have been sans the lensing.
    $endgroup$
    – Carl Witthoft
    Jan 25 at 19:14














16












16








16





$begingroup$

The quasar gives out light in all directions. The light spreads out in space. Only a very small amount of that light would be pointed exactly in the direction of your telescope.



But if a large galaxy or galaxy cluster is between the quasar and us, it bends some of the light towards us, making the quasar brighter (it would also distort the shape, but quasars are too small for their shape to be seen) This makes it brighter for us (and dimmer in other parts of space which would have got the light that is now bent towards us.)






share|improve this answer









$endgroup$



The quasar gives out light in all directions. The light spreads out in space. Only a very small amount of that light would be pointed exactly in the direction of your telescope.



But if a large galaxy or galaxy cluster is between the quasar and us, it bends some of the light towards us, making the quasar brighter (it would also distort the shape, but quasars are too small for their shape to be seen) This makes it brighter for us (and dimmer in other parts of space which would have got the light that is now bent towards us.)







share|improve this answer












share|improve this answer



share|improve this answer










answered Jan 25 at 7:33









James KJames K

34.7k256118




34.7k256118








  • 8




    $begingroup$
    a tiny bit like this
    $endgroup$
    – uhoh
    Jan 25 at 7:56






  • 1




    $begingroup$
    To be clear: nothing can make the image brighter than the quasar itself is. That's that optical "entendue law". What happens is the image is made brighter than it would have been sans the lensing.
    $endgroup$
    – Carl Witthoft
    Jan 25 at 19:14














  • 8




    $begingroup$
    a tiny bit like this
    $endgroup$
    – uhoh
    Jan 25 at 7:56






  • 1




    $begingroup$
    To be clear: nothing can make the image brighter than the quasar itself is. That's that optical "entendue law". What happens is the image is made brighter than it would have been sans the lensing.
    $endgroup$
    – Carl Witthoft
    Jan 25 at 19:14








8




8




$begingroup$
a tiny bit like this
$endgroup$
– uhoh
Jan 25 at 7:56




$begingroup$
a tiny bit like this
$endgroup$
– uhoh
Jan 25 at 7:56




1




1




$begingroup$
To be clear: nothing can make the image brighter than the quasar itself is. That's that optical "entendue law". What happens is the image is made brighter than it would have been sans the lensing.
$endgroup$
– Carl Witthoft
Jan 25 at 19:14




$begingroup$
To be clear: nothing can make the image brighter than the quasar itself is. That's that optical "entendue law". What happens is the image is made brighter than it would have been sans the lensing.
$endgroup$
– Carl Witthoft
Jan 25 at 19:14


















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