Starship Asterisk*

by **sallyseaver** » Wed Mar 22, 2017 9:09 pm

Thank you Ann, Bruce, Neufer, and Chris for all the good discussion and information about lensing, the Hubble constant and dark matter. I know that it takes time, and you may not realize the value of your contributions live on for many people...even after the day of the APOD image.

Sincerely,
Sally

by **Fred the Cat** » Sat Mar 04, 2017 4:21 pm

Ann wrote:
Fred the Cat wrote:
-- is acting like a choppy gravitational lens. A perhaps even odder thing is that by watching these background quasars flicker, you can estimate the expansion rate of the universe.
I don't suppose the universal clock is a Timex rather than a Rolex and the amount time expands depends on your state of mind.

Wait a minute - my watch says La La Land
You must have been lensed into a pocket of alternative time!

Beam me up, Scotty!

Ann

I noticed this in my Quora e-mail box today. It's difficult me to fathom a universe with different time zones but there are areas where gravity fluctuates immensely.

by **Chris Peterson** » Fri Mar 03, 2017 12:20 am

Gregrrr wrote:Is it possible that different parts of the universe expand at different rates?

Well, that's a tricky question. The Universe is four-dimensional (spacetime), which is why we essentially see back in time when we view more distant objects. And the evidence is quite strong that the part of the Universe we see far away is expanding at a different rate than what we see nearby. But in just the three spatial dimensions? There is no observational evidence to suggest that different regions are expanding at different rates (except to the extent that expansion is reduced or eliminated by gravity- the spacetime that contains galaxies, for example, isn't expanding because gravity is holding it together). And current theory doesn't suggest different regions will expand at different rates, either.

So is it possible? Yes. Does anything support the hypothesis? No.

by **Gregrrr** » Thu Mar 02, 2017 11:27 pm

Is it possible that different parts of the universe expand at different rates?

by **neufer** » Tue Feb 28, 2017 7:49 pm

rstevenson wrote:
Ann wrote:...
(And I had to go and get that darn wine glass all over again.)
And I had to empy mine again.
But the distortions in the light get easier to see the more often I empty the glass -- I think.

The things we must endure for science

by **rstevenson** » Tue Feb 28, 2017 6:50 pm

Ann wrote:...
(And I had to go and get that darn wine glass all over again.)
Ann

And I had to empy mine again. But the distortions in the light get easier to see the more often I empty the glass -- I think.

Rob

by **Ann** » Tue Feb 28, 2017 5:26 pm

neufer wrote:
Ann wrote:
Wow, Art, it worked! (Sort of) The only flashlight I've got is a pretty poor point source, since it holds seven little LED lights set in a cluster. (And a wine glass, me? Okay, I found one...)

I couldn't replicate the effect of discrete spots similar to the effects seen in the APOD, but I got a VERY uneven ring with gaps in it. Good enough! I still don't know why the Einstein Cross works the way it does, but I really believe in it now!
Having the wine glass stem cocked slightly to the side not only gets the bowl out of the way but it emulates the elliptical shape of the galactic field.

Well, with some effort and a lot of cocking, I could produce two discrete sources with the connecting ring almost all gone.

(And I had to go and get that darn wine glass all over again.)

Ann

by **Chris Peterson** » Tue Feb 28, 2017 5:04 pm

neufer wrote:Having the wine glass stem cocked slightly to the side not only gets the bowl out of the way but it emulates the elliptical shape of the galactic field.

You can also buy glass and plastic lenses that simulate gravitational lenses, or make a more effective one by simply cutting off the base of a wine glass from the stem. There's an interesting article describing some practical theory and experiments with such lenses.

by **neufer** » Tue Feb 28, 2017 4:49 pm

Click to play embedded YouTube video.

Ann wrote:
Wow, Art, it worked! (Sort of) The only flashlight I've got is a pretty poor point source, since it holds seven little LED lights set in a cluster. (And a wine glass, me? Okay, I found one...)

I couldn't replicate the effect of discrete spots similar to the effects seen in the APOD, but I got a VERY uneven ring with gaps in it. Good enough! I still don't know why the Einstein Cross works the way it does, but I really believe in it now!

Having the wine glass stem cocked slightly to the side not only gets the bowl out of the way but it emulates the elliptical shape of the galactic field.

by **Ann** » Tue Feb 28, 2017 4:37 pm

neufer wrote:
Ann wrote:
I would have liked to get a non-mathematical explanation as to how the quasar could be split into four discrete images rather than a ring.
1) Baffle down a flashlight to make a 'point source' of light at the other end of a dark room.

2) Put the base of a wine glass stem (cocked slightly to the side) between your eye and the 'point source.'

3) Move the stem base around until you see 3 adjacent spots of light.

4) Wiggle the stem base to see the middle spot alternately merge with & separate from the spots to its left & right.

5) You might also be able to see a more distant fourth spot, but the wine glass stem usually gets in the way.

Wow, Art, it worked! (Sort of)

The only flashlight I've got is a pretty poor point source, since it holds seven little LED lights set in a cluster. (And a wine glass, me? Okay, I found one...)

I couldn't replicate the effect of discrete spots similar to the effects seen in the APOD, but I got a VERY uneven ring with gaps in it. Good enough! I still don't know why the Einstein Cross works the way it does, but I really believe in it now!

Ann

by **neufer** » Tue Feb 28, 2017 12:15 pm

Atabakzadeh wrote:
Why there are exactly four symmetric repeated image of this quasar around that central galaxy (acts as a gravity lens)?
If that galaxy acts as a gravity lens, then the composed pyramid image of that quasar behind it, should be something like a "Ring".
The light rays move in all directions, not only in Four directions!
Maybe this phenomena depends on the shape of central galaxy. Does it?

Both the central galaxy (i.e., the fifth central spot) and its gravitational field
have an elliptical shape which (in conjunction with the lens's off center position)
defines the 4 spots.

by **Atabakzadeh** » Tue Feb 28, 2017 6:25 am

Hello again
How you can rebut this hypothesis:
These five objects are exactly Five distinct spatial objects (stars, quasars, galaxies, etc.) visually aligned near each other, in view of an observer on Earth.

Thank you.

by **Atabakzadeh** » Tue Feb 28, 2017 6:13 am

Hello.
About this picture:
Why there are exactly four symmetric repeated image of this quasar around that central galaxy (acts as a gravity lens)?
If that galaxy acts as a gravity lens, then the composed pyramid image of that quasar behind it, should be something like a "Ring".
The light rays move in all directions, not only in Four directions!
Maybe this phenomena depends on the shape of central galaxy. Does it?

Thank you.

by **neufer** » Tue Feb 28, 2017 4:04 am

Ann wrote:
I would have liked to get a non-mathematical explanation as to how the quasar could be split into four discrete images rather than a ring.

1) Baffle down a flashlight to make a 'point source' of light at the other end of a dark room.

2) Put the base of a wine glass stem (cocked slightly to the side) between your eye and the 'point source.'

3) Move the stem base around until you see 3 adjacent spots of light.

4) Wiggle the stem base to see the middle spot alternately merge with & separate from the spots to its left & right.

5) You might also be able to see a more distant fourth spot, but the wine glass stem usually gets in the way.

by **stormin** » Tue Feb 28, 2017 3:41 am

Are we sure that some prankster astronaut didn't put a LED flashlight in the Hubble telescope at it's last servicing? I mean, look at the color temperature compared to the incandescent galaxies in the field of view.

by **Ann** » Tue Feb 28, 2017 1:51 am

On a more serious note, I would have liked to get a non-mathematical explanation as to how the quasar could be split into four discrete images rather than a ring. A video would done made wonders, because I am a visual learner.

Still, though, here goes:

Wikipedia wrote:
The foreground lens is a galaxy. When the background source is a quasar or resolved jet, the strong lensed images are usually point-like multiple images; When the background source is a galaxy or extended jet emission, the strong lensed images can be arcs or rings.

Okay. Point-like lensed sources like quasars or supernovas make point-like multiple images, but extended lensed sources like galaxies make arcs or, occasionally, rings. It sounds rather logical, although I can't picture the mechanism of how it happens in my head.

Can't say I understand what is going on in this video, but it is pretty cool, nevertheless.

Click to play embedded YouTube video.

Ann

Edit: I really did find a video showing the lensing of a discrete source, in this case a supernova. To me the video is more confusing than revealing. Watch for yourself.

by **Ann** » Tue Feb 28, 2017 12:38 am

Fred the Cat wrote:
-- is acting like a choppy gravitational lens. A perhaps even odder thing is that by watching these background quasars flicker, you can estimate the expansion rate of the universe.
I don't suppose the universal clock is a Timex rather than a Rolex and the amount time expands depends on your state of mind.

Wait a minute - my watch says La La Land

You must have been lensed into a pocket of alternative time!

Beam me up, Scotty!

Ann

by **Chris Peterson** » Mon Feb 27, 2017 11:38 pm

distefanom wrote:Ok, the images have different path length going around that galaxy from the quasar source.
But taking into account the distance we, the observers have from that galaxy and the quasar source, we can imagine an EXTREMELY ELONGATED isosceles-like triangle...

We don't need to imagine anything. With this object, the source (quasar) redshift is z=1.69 and the lens (galaxy) redshift is z=0.46. So the quasar is 9.8 Gyr light travel time distant, and the lens is 4.8 Gyr light travel time distant, meaning the quasar and the galaxy are 5 Gyr light travel time apart. The maximum distance between lensed components is 2.5 arcseconds, which solves to a lens 60,000 ly across - totally believable for a galaxy.

One could say that even the non-perfect alignment of the quasar-galaxy-earth, the image appearing around the galaxy should be the same.... so we should have an Einstein ring, instead of 4 dots...

It's not just a question of alignment, but of the dark matter distribution in the lensing galaxy. It's not uniform, so the lens is lumpy.

Also the "flickering" should be essentially in sync with respect of each image... This is why I written "overlap" in my previous post....
and here the mistery arose: why we have 4 images instead of an (also maybe distorted) arc???

The flickering patterns are the same for each image, but they are time shifted with respect to each other (seen with a photometry record spanning a number of years). Over a light path that is 9.8 Gyr light travel time in length (15.6 Gly comoving distance), a mismatch at arrival of a few years represents a very, very small difference between the individual paths.

by **Fred the Cat** » Mon Feb 27, 2017 11:25 pm

-- is acting like a choppy gravitational lens. A perhaps even odder thing is that by watching these background quasars flicker, you can estimate the expansion rate of the universe.

I don't suppose the universal clock is a Timex rather than a Rolex

and the amount time expands depends on your state of mind.

Wait a minute - my watch says La La Land

by **distefanom** » Mon Feb 27, 2017 10:51 pm

I'm the same person Mario59, who posted before... sorry for the different avatar....

After viewing neufer's video (

) I've heard & recognised that all those "burps" are the very same "burp" record... (well almost most of them)
If I could have a diagram of the burp sound & it's spectrogram, I could easily see that it's the same record, not caring about the signal amplitude (which depends from the source distance) and it's spectrum (which depends from the relative velocity to the observer, ging on with the similarity...)
So there's a clear "parallel arguments" in the short cartoon movie, with the quasar's 4 images which are claimed to be the same quasar.
I'm sure that the 4 images are from the same source, but what "lock me out" is the fact that these are *FOUR* images... and couldn't clearly understand why...
Ok, the images have different path length going around that galaxy from the quasar source.
But taking into account the distance we, the observers have from that galaxy and the quasar source, we can imagine an EXTREMELY ELONGATED isosceles-like triangle, which base is the galaxy diameter (well almost) and having a vertex in the quasar source.
The two sides of this imaginary triangle are the path the light follows to get around the galaxy.
Ok, so we have, according to wikipedia, an isosceles triangle with (let's say) 100.000 ly base (average galaxy diameter) and around 8 BILLION ly in height... also a child can realize that the two long sides of the imaginary triangle are WAY BIGGER than it's base in a ratio of 1 to 80000....
Consequently it's hard to say that the quasar image follows two substantially different path lengths.
One could say that even the non-perfect alignment of the quasar-galaxy-earth, the image appearing around the galaxy should be the same.... so we should have an Einstein ring, instead of 4 dots....
Also the "flickering" should be essentially in sync with respect of each image... This is why I written "overlap" in my previous post....
and here the mistery arose: why we have 4 images instead of an (also maybe distorted) arc???

by **neufer** » Mon Feb 27, 2017 8:13 pm

Chris Peterson wrote:
Mario59 wrote:
But about the flickering? What means exactly?
Do they refer to a sudden bright luminosity change of the four images, reaches us in slightly different times?
In any case, if the surce is the very same, the brightness curve should *ALWAYS* overlap perfectly.
I'm not sure of the details of the flickering mentioned here, but there is no reason each brightness curve should align, because the total distance the light travels over each leg isn't the same. There was a recent APOD detailing a distant supernova observed via a gravitationally lensed image, with the intensity spike occurring at different times in different lensed components.

https://en.wikipedia.org/wiki/Quasar#Emission_generation wrote:
Click to play embedded YouTube video.
<<A quasar is a compact region surrounding a supermassive black hole. The region emits enormous amounts of electromagnetic energy as a result of mass from the core of a surrounding galaxy, under the influence of the black hole's gravity, falling onto the black hole's accretion disk. To create a luminosity of 10⁴⁰ watts (the typical brightness of a quasar), a super-massive black hole would have to consume the material equivalent of 10 stars per year. The brightest known quasars devour 1000 solar masses of material every year. The largest known is estimated to consume matter equivalent to 600 Earths per minute. Quasar luminosities can vary considerably over time, depending on their surroundings.>>

The four images of an Einstein Cross define the base corners of a skewed four cornered pyramid.

The relative timing delays of the four images define the relative diagonal lengths to
the apex (i.e., us) from which one can determine the distance to the gravitational lens.

https://en.wikipedia.org/wiki/Einstein_Cross wrote:
[b][color=#0000FF][size=200]Huchra's Lens in Pegasus[/size][/color][/b]
<<The Einstein Cross (Q2237+030 or QSO 2237+0305) is a gravitational lensed quasar that sits directly behind ZW 2237+030, Huchra's Lens. Four images of the same distant quasar (plus one in the centre, too dim to see) appear around a foreground galaxy due to strong gravitational lensing. While gravitationally lensed light sources are often shaped into an Einstein ring, due to elongated shape of the lensing galaxy and the quasar being off-centre, the images form a peculiar cross-shape instead.

The quasar's redshift indicates that it is located about 8 billion light years from Earth, while the lensing galaxy is at a distance of 400 million light years. The apparent dimensions of the entire foreground galaxy are 0.87 × 0.34 arcminutes, while the apparent dimension of the cross in its centre accounts for only 1.6x1.6 arcseconds. The individual images are labelled A through D (i.e. QSO 2237+0305 A), the lensing galaxy is sometimes referred to as QSO 2237+0305 G.>>

by **Chris Peterson** » Mon Feb 27, 2017 6:42 pm

Mario59 wrote:This is EXACTLY what I was thinking.
It's rather difficult to explain the 4 SINGLE images instead of a ring, if no spectrogram of each of them is known to me.

Actually, it's very easy to explain. Rings are much rarer than split images, because rings only occur given near perfect alignment and very uniform lenses. We seldom have either.

But about the flickering? What means exactly?
Do they refer to a sudden bright luminosity change of the four images, reaches us in slightly different times?
In any case, if the surce is the very same, the brightness curve should *ALWAYS* overlap perfectly.

I'm not sure of the details of the flickering mentioned here, but there is no reason each brightness curve should align, because the total distance the light travels over each leg isn't the same. There was a recent APOD detailing a distant supernova observed via a gravitationally lensed image, with the intensity spike occurring at different times in different lensed components.

by **Mario59** » Mon Feb 27, 2017 6:37 pm

This is EXACTLY what I was thinking.
It's rather difficult to explain the 4 SINGLE images instead of a ring, if no spectrogram of each of them is known to me.
Since I don't know the exact spectrogram, I need to faith them, of course. But about the flickering? What means exactly?
Do they refer to a sudden bright luminosity change of the four images, reaches us in slightly different times?
In any case, if the surce is the very same, the brightness curve should *ALWAYS* overlap perfectly.
Is this what happens, and so one can say that the 4 images are of the very same source????
please someone can clarify me.
thanks
Mario

by **Ann** » Mon Feb 27, 2017 3:16 pm

tomatoherd wrote:Why is it an Einstein cross instead of an Einstein RING?

Wikipedia wrote:

The Einstein Cross (Q2237+030 or QSO 2237+0305) is a gravitational lensed quasar that sits directly behind ZW 2237+030, Huchra's Lens. Four images of the same distant quasar (plus one in the centre, too dim to see) appear around a foreground galaxy due to strong gravitational lensing.[1][2]

While gravitationally lensed light sources are often shaped into an Einstein ring, due to elongated shape of the lensing galaxy and the quasar being off-centre, the images form a peculiar cross-shape instead.

: Click to view full size image

[c]Elliptical (and elongated?) galaxy M59. Source:
https://mcdonaldobservatory.org/news/re ... /0202.html.
(But it looks like an SDSS image to me.)[/c]

So if I got this correctly, the elliptical galaxy doing the lensing of the quasar is itself elongated, and the quasar is also slightly off-center. In other words, the Earth, the lensing galaxy and the quasar don't form a perfectly straight line. If the lensing galaxy had been perfectly spherical, and the lineup of the quasar, the lensing galaxy and ourselves had been perfect, we would have seen an Einstein ring instead of an Einstein cross.

At least I think so!

Ann

by **Chris Peterson** » Mon Feb 27, 2017 3:13 pm

BDanielMayfield wrote:In it's article on Dark Matter,
Wikipedia wrote:The first robust indications that the mass to light ratio was anything other than unity came from measurements of galaxy rotation curves.
Now it seems that this early reason for suspecting the existence of Dark Matter may have been completely explained away.

What is interesting, however, is that the dark matter explanation for galaxy rotation curves could be completely eliminated and it would have almost no impact on the need for, and evidence of, dark matter. Galaxy rotation curves are what first got people's attention, but since then so many other lines of evidence have developed that have nothing to do with that.

Starship Asterisk*

APOD: Four Quasar Images Surround a Galaxy... (2017 Feb 27)

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