JWST images

[wimvb]

54 minutes ago, StuartT said:

Usually the problem is how to get rid of them in post-processing!

Better to get to the cause of the problem: get a Mak-Newt 😁

(that’s what I did)

[markse68]

13 hours ago, IB20 said:

Some nice images of Messier 74 yesterday from JWST.

Credits: @gbrammer and Judy Schmidt.

Incredible! the central eye looks so peaceful and the structure around it so fluid

[StuartT]

14 hours ago, wimvb said:

Better to get to the cause of the problem: get a Mak-Newt 😁

(that’s what I did)

or a SCT like me

[IB20]

Anyone fancy having a go at GLASS-z13? 

 

[robin_astro]

On 19/07/2022 at 08:00, IB20 said:

Some nice images of Messier 74 yesterday from JWST

They have spotted in that image what is left of SN 2013ej , a supernova which reached a bright mag 12 back in August 2013

https://www.wis-tns.org/astronotes/astronote/2022-147

Robin

 

Edited July 20, 2022 by robin_astro

[StuartT]

3 hours ago, robin_astro said:

a supernova which reached a bright mag 12 back in August 2013

...although probably a bit earlier back in time than that, in all fairness.. 😉

[Paul M]

The Universe seems to be getting "smaller" with each new JWST revelation.

And they're only just getting going!

 

[robin_astro]

3 hours ago, StuartT said:

...although probably a bit earlier back in time than that, in all fairness.. 😉

In  who's reference frame ? not the photons 😉

 

 

[robin_astro]

26 minutes ago, robin_astro said:

In  who's reference frame ? not the photons 😉

 

 

....and any case, since the  (apparent) magnitude is a measurement of the photon flux at the earth, the brightness did peak at ~mag 12 in August 2013 😉 

[andrew s]

6 hours ago, robin_astro said:

In  who's reference frame ? not the photons 😉

 

 

Photons don't have a reference frame. If they did they would be a rest in it? 😊

Regards Andrew 

[robin_astro]

3 hours ago, andrew s said:

photons don't have a reference frame. If they did they would be a rest in it? 😊

Very true. They have no concept of time, a bit like me these days 😀

[robin_astro]

10 minutes ago, robin_astro said:

Very true. They have no concept of time, a bit like me these days 😀

In which case substitute neutrino for photon in the above 🙂

[StuartT]

19 hours ago, robin_astro said:

....and any case, since the  (apparent) magnitude is a measurement of the photon flux at the earth, the brightness did peak at ~mag 12 in August 2013 😉 

touché my friend.

[markse68]

On 20/07/2022 at 18:16, IB20 said:

Anyone fancy having a go at GLASS-z13? 

 

They say this about Glass-Z13: "Both of the galaxies are much smaller than Earth’s Milly Way Galaxy, which is 100,000 light-years across. GLASS-z13 is estimated to be about 1,600 light-years across" which seems pretty tiny, but how on earth do they make an estimate like that? Is it using the visible size and an estimate for how much the universe has expanded since the light left it (magnifying its image)? Or is it based on theory for how big early galaxies should be? Do they take into account gravitational lensing effects? They don't really have much to compare it with.

Mark

[gilesco]

10 hours ago, markse68 said:

They say this about Glass-Z13: "Both of the galaxies are much smaller than Earth’s Milly Way Galaxy, which is 100,000 light-years across. GLASS-z13 is estimated to be about 1,600 light-years across" which seems pretty tiny, but how on earth do they make an estimate like that? Is it using the visible size and an estimate for how much the universe has expanded since the light left it (magnifying its image)? Or is it based on theory for how big early galaxies should be? Do they take into account gravitational lensing effects? They don't really have much to compare it with.

Mark

 

[andrew s]

14 hours ago, markse68 said:

They say this about Glass-Z13: "Both of the galaxies are much smaller than Earth’s Milly Way Galaxy, which is 100,000 light-years across. GLASS-z13 is estimated to be about 1,600 light-years across" which seems pretty tiny, but how on earth do they make an estimate like that? Is it using the visible size and an estimate for how much the universe has expanded since the light left it (magnifying its image)? Or is it based on theory for how big early galaxies should be? Do they take into account gravitational lensing effects? They don't really have much to compare it with.

Mark

I think you'll find it is calculated based on the measured angular dimensions and red shift  using models of the gravitational lensing and the LCMD cosmology .

Regards Andrew 

[DaveS]

https://m.youtube.com/shorts/RJe0s1iDYLc

 

 

 

 

 

Edited July 22, 2022 by DaveS

[globular]

39 minutes ago, andrew s said:

I think you'll find it is calculated based on the measured angular dimensions and red shift  using models of the gravitational lensing and the LCMD cosmology .

Regards Andrew 

Each measurement and model will have error bounds. I assume 1,600 will be the 50th percentile result when bringing it all together.  I wonder what the 10th and 90th percentile results are? Feels to me that the error bounds must me quite large given all the unknowns. They should be published too really (maybe they are somewhere?)

[Gfamily]

Published paper here

 

https://arxiv.org/abs/2207.09434

[andrew s]

33 minutes ago, globular said:

Each measurement and model will have error bounds. I assume 1,600 will be the 50th percentile result when bringing it all together.  I wonder what the 10th and 90th percentile results are? Feels to me that the error bounds must me quite large given all the unknowns. They should be published too really (maybe they are somewhere?)

You will need to find the relevant peer reviewed paper. It will have the relevant error bars. However,  it s very difficult to calculate systematic errors and all "cosmological " distances rely on what cosmological model you accept.  One advantage of the LCDM cosmology is the it is easiest to apply.

Regards Andrew 

See @Gfamily's post above.

Edited July 22, 2022 by andrew s

[Zermelo]

This is quite cool:

Zoom Into the Southern Ring Nebula Captured by NASA James Webb Space Telescope

 

[robin_astro]

On 22/07/2022 at 09:13, gilesco said:

"Cows, small or far away?"

Bizarrely in our universe this is only true out to about 1.5 redshift. Beyond that all cows look about the same size or even larger 🙂

https://arxiv.org/abs/astro-ph/9905116v4

Section 6 "Angular Diameter Distance"

[markse68]

if these early galaxies really are measured as predicted to be much smaller than the galaxies we see in our time frame, would there not be many more of them given the universe was much smaller and denser back then? Why do we only see the odd one or two of them? Are the others just way too small and dim to see? Or are the distances between them so stretched in the intervening expansion that they look very far apart?

[markse68]

4 hours ago, robin_astro said:

Bizarrely in our universe this is only true out to about 1.5 redshift. Beyond that all cows look about the same size or even larger 🙂

https://arxiv.org/abs/astro-ph/9905116v4

Section 6 "Angular Diameter Distance"

which is really convenient when trying to observe very distant and possibly relatively small early galaxies!

[globular]

9 minutes ago, markse68 said:

if these early galaxies really are measured as predicted to be much smaller than the galaxies we see in our time frame, would there not be many more of them given the universe was much smaller and denser back then? Why do we only see the odd one or two of them? Are the others just way too small and dim to see? Or are the distances between them so stretched in the intervening expansion that they look very far apart?

Lots of guesswork and approximations in this early, yet to be peer reviewed, paper.  But they seem to take an opposite view to you....
"we wouldn't expect these early galaxies to be as common as they appear to be. We estimate that if galaxies were visible at the rates we'd expect, we'd have had to search through an area 10 times larger to come up with them"

Isn't the relatively limited time frame in which the universe was in the state necessary to form these "small" galaxies (a few hundred million years) part of the answer as to why there are a lot less of them compared to the billions of years in which the more familiar ones were forming?