Questions tagged [gravitational-lensing]

Questions regarding the bending of light by mass or energy.

Filter by
Sorted by
Tagged with
4 votes
1 answer
396 views

Black hole magnification factor

Given a black hole of mass $M$ which has a distance $D_1$ to Earth and $D_2$ to a galaxy being magnified, what is the magnification factor? And a follow-up question: Does it magnify across the ...
user avatar
46 votes
1 answer
5k views

Is there a better explanation of this picture showing the very distant star "Earendel"?

"Close-up of the tiny region where Earendel happened to fall right on top of the narrow line where the magnification increases by (tens of) thousands of times. A cluster of many stars is seen ...
user avatar
  • 1,224
17 votes
4 answers
5k views

If the Sun was replaced with a sun-mass black hole, would it be visually detectable?

Assuming it had no accretion disk, could we still detect e.g. distortions of the background star field?
user avatar
  • 721
2 votes
1 answer
148 views

What is the maximum radius of an Einstein ring?

Is there an upper limit to how far out an Einstein ring can be visible? For black holes, is it a fixed multiple of their Schwarzschild radius?
user avatar
  • 721
1 vote
1 answer
37 views

In shear component $\gamma_1, \gamma_2$ of weak lensing, Why does the defining with $2\phi$ reflect "real angle"?

From the review paper Bartelmann and schneider, 1999) [Weak Gravitational Lensing], page 48. Like above, $\gamma_1 \equiv \left| \gamma \right| \cos(2\phi), \gamma_2 \equiv \left| \gamma \right|\sin(2\...
user avatar
  • 109
1 vote
1 answer
98 views

Finding the Laplacian of the deflection potential: I obtain 4𝜅(𝜃⃗ ), not 2𝜅(𝜃⃗ ). Why am I wrong?

From the review paper Bartelmann and schneider, 1999) Weak Gravitational Lensing, page 48. Like above, the Laplacian of the deflection function is convergence, $\kappa(\vec{\theta})$. I tried to ...
user avatar
  • 109
1 vote
1 answer
225 views

Is a black hole found in the centre of the low-surface-brightness and dark-matter-free galaxy AGC 114905

Per information found on Internet: AGC 114905 was discovered while observing the constellation Pisces with the VLA ground-based radio telescope. The galaxy is about 250 million light-years distant ...
user avatar
  • 571
12 votes
2 answers
2k views

How do we know that objects that appear in duplicate or triplicate, etc. due to strong gravitational lensing aren't actually multiple objects?

If we are looking at faraway objects, there is no parallax view, correct? So isn't there a chance that an object that appears multiple due to strong foreground gravitational lensing is actually ...
user avatar
  • 3,333
1 vote
0 answers
15 views

How does one think about optical depth in the context of gravitational microlensing? Is it measured or deduced from observations? Used for planning?

This excellent answer to Which studies prior to 2018 "claimed to find evidence of extragalactic planets in the Andromeda galaxy"? Which instrument was used? introduces the technique of "...
user avatar
  • 31.4k
5 votes
1 answer
353 views

How was the recently publicized Hubble image of a distant galaxy showing clearly resolved lensed in an Einstein ring produced? When was it produced?

The 24-Sep-2021 NASA Goddard video Einstein Ring Spotted by Hubble and it's Goddard Media Studio's page Einstein Ring Spotted By Hubble discuss the image, but don't really give credit to how it was ...
user avatar
  • 31.4k
4 votes
1 answer
190 views

Is quasar 2M1310-1714 outside the observable universe?

This Einstein ring Image credit: NASA / ESA / Hubble / T. Treu / Judy Schmidt shows multiple images of the quasar 2M1310-1714. Its distance is quoted at 17 billion light years and although the age ...
user avatar
3 votes
0 answers
57 views

Could we see small objects like animals on an exoplanet using Solar Gravitational Lensing (SGL) if we could use any star or a black hole for lensing?

Theoretically, if a telescope is positioned in a focal point of a supermassive black hole or a star much more massive than the Sun, would there be a limit to how far away an observable planet can be ...
user avatar
1 vote
2 answers
93 views

Can single black holes be observed by its lensing effect?

A comment on a question I asked left me confused. I asked about the possibility of observing a binary black hole by examining the lensing the binary produces. A binary has a different lensing effect ...
user avatar
2 votes
1 answer
80 views

Is there a minimum distance between two black holes in a binary system beneath which it can't be observed as a binary?

Suppose two black holes are observable by means of their lensing effect. If these holes are orbiting around each other, then is there a minimum distance from each other to be still observable as ...
user avatar
-2 votes
2 answers
104 views

Could observation of GL or other image phenomena from system of 2 merging massive dense objects and of GW caused by their merge be connected?

What is the probability to observe gravitational lensing (or any other image related phenomena) from the pair of black holes (or pair of neutron stars or black hole - neutron star) which are about to ...
user avatar
  • 571
8 votes
0 answers
109 views

How well conserved is etendue in extreme gravitational lensing scenarios?

This excellent answer to Could dark matter exist in the Universe in the form of sufficiently dense objects? includes the following image and description: Light from the background galaxy circles a ...
user avatar
  • 31.4k
5 votes
1 answer
687 views

Would the stars look different if many primordial black holes were present?

Suppose that there are many primordial black holes. These are point masses which have a small probability to collide with stars let alone themselves. They are formed in the early universe and could ...
user avatar
2 votes
1 answer
80 views

Lightest object so far to function as gravitational lense?

Many amazing discovers are based on gravitational lensing and microlensing, but as non-expert it is not obvious to me: What is the (current) lower mass limit of the lensing object(s) for which ...
user avatar
  • 5,284
9 votes
2 answers
808 views

Is it possible to observe strong gravitational lensing with amateur telescopes?

Strong gravitational lens systems like the Cosmic Horseshoe have been imaged by scientific space telescopes, but have any amateur astronomers accomplished this? Or are amateur/small ground based ...
user avatar
  • 721
4 votes
1 answer
355 views

Algorithm to fit galaxies

Do you know of any other data analysis algorithm that fits 2-D analytic functions to galaxies and point sources directly to digital images, other than GALFIT? Especially to subtract lens light from ...
user avatar
  • 43
3 votes
1 answer
114 views

Is GAIA the only game in town for looking at quadrupole gravitational deflection of light?

From Gerry Gilmore (2018) Gaia: 3-dimensional census of the Milky Way Galaxy 4.4 Fundamental physics Relativistic effects are highly significant for Gaia measurement accuracy, with tests of General ...
user avatar
  • 31.4k
4 votes
1 answer
124 views

Has GAIA learned anything about General Relativity looking near Jupiter? (Gerry Gilmore: "oblate rotating mass moving in a deeper (Solar) potential")

From Gerry Gilmore (2018) Gaia: 3-dimensional census of the Milky Way Galaxy 4.4 Fundamental physics Relativistic effects are highly significant for Gaia measurement accuracy, with tests of General ...
user avatar
  • 31.4k
3 votes
1 answer
127 views

Has a gravitational microlensing event ever been predicted? If so, has it been observed?

This answer to Are astronomers waiting to see something in an image from a gravitational lens that they've already seen in an adjacent image? describes "Deja vu all over again" (SN "...
user avatar
  • 31.4k
4 votes
0 answers
111 views

What's the largest angle that light has been "seen to bend" by gravity? (of one object by a separate object)

Gravitational lensing is everywhere! because it falls off so slowly with $r$: $$\Delta \phi \approx \frac{4GM}{c^2r_0}.$$ That's the first order term. For a nice derivation see Viktor Toth's The ...
user avatar
  • 31.4k
2 votes
0 answers
54 views

Can the lensing effect of Sagittarius A* be used to image the stars diametrically opposite to the sun?

The sun can magnify an image of a source 100 ly away nearly 100 billion times, if the ring is captured from the nearest focal point (550AU). According to Christian Ready of Launch Pad Astronomy, we ...
user avatar
3 votes
1 answer
167 views

How much solar energy concentrates at Jupiter's focal point via gravitational lensing?

How much solar energy concentrates at Jupiter's focal point via gravitational lensing?
user avatar
1 vote
1 answer
58 views

Hoag's object as an Einstein ring

What are the main arguments against Hoag's object in particular and Hoag-like objects in general to be explained as Einstein rings formed by a farther edge-on galaxy?
user avatar
  • 153
4 votes
0 answers
63 views

What exactly would the resolution of an exoplanet hypothetically imaged by using the Sun as a gravitational lens be?

This video talks about how by sending a spacecraft to around 600 AU and beyond, we would could use the Sun as a gravitational lens and take clear detailed images of exoplanets light-years away. What ...
user avatar
  • 2,222
2 votes
1 answer
100 views

Can a supernova or a close passing star create a transient sun gravity focus "habitable zone"?

This question was inspired by the previous question Would a black hole passing next to a star create a deadly focal point due to gravitational lensing?. I understand, as gravity also acts on light, ...
user avatar
  • 612
0 votes
0 answers
28 views

Does a gravitational lens around a body look 3-dimensional?

Suppose we approach a neutron star or a stellar black hole close enough, is the gravitational lens around it 3-dimensional (like a tunnel) or is it 2-dimensional? It's 3-dimensional as if you entered ...
user avatar
  • 293
6 votes
2 answers
383 views

Would a black hole passing next to a star create a deadly focal point due to gravitational lensing?

Black holes bend all kinds of radiation thanks to their giant gravity. Now imagine that a black hole passes close to some star (we know of cases when black hole devours a star). Star emits massive ...
user avatar
  • 63
1 vote
1 answer
57 views

How are all the intermediate images between the "lensed" and "unlensed" endpoints of this video generated?

Phys.org's ALMA sees most distant Milky Way look-alike describes the numerical image reconstruction of a strongly and very nicely lensed z = 4.2 galaxy by a by a foreground galaxy at z = 0.263 and ...
user avatar
  • 31.4k
0 votes
2 answers
101 views

Why is SPT0418-47 ("the most distant Milky Way look-alike") expected to evolve into an elliptical galaxy?

Phys.org's ALMA sees most distant Milky Way look-alike describes the image reconstruction of a strongly and very nicely lensed z = 4.2 galaxy by a by a foreground galaxy at z = 0.263 and says: "...
user avatar
  • 31.4k
0 votes
1 answer
100 views

First Confirmed Visual Observation of Gravitational Lensing

Is it possible to identify the first direct observation of the gravitational lensing? What object was lensed, and where did the energy detected fall on the electromagnetic spectrum?
user avatar
  • 117
24 votes
3 answers
3k views

Is it possible to detect gravitational lensing behind the Moon?

Eddington waited for an eclipse to happen to be able to observe gravitational lensing of the stars behind the Sun. And nowadays, amateurs can do the same thing. Of course, the Moon is much lighter ...
user avatar
  • 16.7k
3 votes
4 answers
135 views

Is it plausible to use other stars for the proposed FOCAL mission instead of the Sun?

For some time, the far-reaching and speculative idea of using the Sun as a gravitational lens has been floating around. See this and this. This would require sending a spacecraft about ~550 AU of a ...
user avatar
0 votes
1 answer
109 views

At what gravity does a body's gravitational lensing become observable?

I wonder whether we know at how much gravitation a gravitational lensing around a celestial body becomes observable (visible in the sense of that we see stars on the wrong places, stars behind the ...
user avatar
  • 1,166
18 votes
1 answer
2k views

Was the Sun's gravitational lensing observed in other solar eclipses than the one in 1919?

In 1919 the gravitational lensing by the Sun has been observed during a total solar eclipse. Did someone observe the lensing in any other total eclipses? Last year there was a total eclipse in Chile ...
user avatar
  • 1,166
10 votes
1 answer
121 views

Is it possible to see stars that are gravitationally lensed by the sun from the ground?

Roughly 100 years ago, Eddington confirmed Einstein’s general relativity theory by photographing stars behind the obscured Sun during a total eclipse. A coronograph is a device that mimics what ...
user avatar
  • 16.7k
5 votes
0 answers
159 views

Can primordial black holes be found orbiting other stars?

A recent study suggests a that a primordial black hole may be orbiting the sun at and that they can be common near other star systems. What measurements and equipment can perhaps find BH's near ...
user avatar
8 votes
1 answer
264 views

What is the gravitational lensing focal distance of a white dwarf star?

I tried looking this up, but I couldn't find any formula on gravitational lensing distance. I know that our Sun's is about 550 AU, though further distances work too, as it's not a single focus due ...
user avatar
  • 22.9k
3 votes
1 answer
160 views

Gravitational lensing

I was reading about gravitational lensing. I was just curious to know if there are any formulae or methods to find the angle at which the light deflects due to strong gravitational lensing? And how ...
user avatar
2 votes
1 answer
78 views

How are microlensing events used to constrain the size of innermost stable circular orbits around spinning black holes?

The third paragraph of the introduction to the ArXiv preprint Constraining Quasar Relativistic Reflection Regions and Spins with Microlensing says: Quasar microlensing has significantly improved our ...
user avatar
  • 31.4k
3 votes
1 answer
372 views

Why is this Einstein ring pink?

I'm having a hard time understanding this image in the CNN News item This glowing ring of light is from a distant galaxy. The caption (from this version of the article) says: This image shows ...
user avatar
  • 31.4k
5 votes
2 answers
300 views

What is the actual visual characteristics of a black hole?

Is there a safe distance in which a black hole can be observed with the human eye? What is a safe distance? I have seen many computer simulated and artist renditions, and I am not sure if they ...
user avatar
  • 1
1 vote
1 answer
233 views

Why don't we see the gas behind the black hole?

In computer simulations of what a black hole might look like and many artist renderings of black holes, they all seem to show the brightly glowing gas BEHIND the black hole due to gravitational ...
user avatar
  • 111
12 votes
1 answer
2k views

Are astronomers waiting to see something in an image from a gravitational lens that they've already seen in an adjacent image?

@RobJeffries' answer to the question Does gravitational lensing provide time evolution information? points out that there can be a substantial different in arrival times of light from a given source ...
user avatar
  • 31.4k
2 votes
0 answers
57 views

Within a given image of a multiple-image producing gravitational lens, does Fermat's principle apply?

The question Does gravitational lensing provide time evolution information? is excellent! When we see multiple images of the same object because of the phenomenon of gravitational lensing, do all the ...
user avatar
  • 31.4k
6 votes
1 answer
140 views

Does gravitational lensing provide time evolution information?

When we see multiple images of the same object because of the phenomenon of gravitational lensing, do all the images show the lensed object at the same point in time? Does it take the same amount of ...
user avatar
  • 446
7 votes
3 answers
380 views

Is gravitational lensing a good way to search for negative mass?

Is it possible to verify negative mass with gravitational lensing? The following video proposes an idea that galaxies are surrounded by negative mass: https://youtu.be/MZtS7cBMIc4 Could this be ...
user avatar
  • 3,919