Quote

NASA’s James Webb Space Telescope (JWST) launched into orbit around the sun in December 2021. Since then, it has been studying the history of our universe. Now, images of deep space from JWST’s Advanced Deep Extragalactic Survey (JADES) have revealed something puzzling: most galaxies rotate in the same direction.

About two-thirds of the 263 galaxies studied in a paper published February 17 in the Monthly Notices of the Royal Astronomical Society rotate clockwise, while the other one-third rotate counterclockwise.

https://www.smithsonianmag.com/smart-news/james-webb-space-telescope-reveals-that-most-galaxies-rotate-clockwise-180986224/?utm_source=smithsoniandaily&utm_medium=email&utm_campaign=editorial&lctg=92132029

5 hours ago, zapatos said:

https://www.smithsonianmag.com/smart-news/james-webb-space-telescope-reveals-that-most-galaxies-rotate-clockwise-180986224/?utm_source=smithsoniandaily&utm_medium=email&utm_campaign=editorial&lctg=92132029

Why would galaxies rotating in the opposite direction to ours seem brighter? I can see the Doppler effect would make one side red-shifted and the other blue-shifted. But I'd have thought our own motion, either towards or away from the galaxy, would simply make the galaxy look a bit more blue or red shifted overall and the rotation of the galaxy would not affect overall brightness. 

Edited March 18Mar 18 by exchemist

4 hours ago, exchemist said:

Why would galaxies rotating in the opposite direction to ours seem brighter? I can see the Doppler effect would make one side red-shifted and the other blue-shifted. But I'd have thought our own motion, either towards or away from the galaxy, would simply make the galaxy look a bit more blue or red shifted overall and the rotation of the galaxy would not affect overall brightness. 

There’s relativistic aberration (relativistic beaming) which means light is preferentially emitted in the direction of motion, but at speeds of less than 10^3 km/sec (our speed is ~230 km/s) it shouldn’t be that big

1 hour ago, swansont said:

There’s relativistic aberration (relativistic beaming) which means light is preferentially emitted in the direction of motion, but at speeds of less than 10^3 km/sec (our speed is ~230 km/s) it shouldn’t be that big

They refer to the Doppler effect, which is what has thrown me. How can that brighten anything? And how would it be affected by the direction of rotation of the observed galaxy, as opposed to relative motion of the whole thing towards or away from us?

Here's the paper: https://academic.oup.com/mnras/article/538/1/76/8019798?login=false. I've only skimmed it as yet, admittedly, but could not immediately see an explanation. 

Edited March 18Mar 18 by exchemist

2 hours ago, exchemist said:

They refer to the Doppler effect, which is what has thrown me. How can that brighten anything? And how would it be affected by the direction of rotation of the observed galaxy, as opposed to relative motion of the whole thing towards or away from us?

Here's the paper: https://academic.oup.com/mnras/article/538/1/76/8019798?login=false. I've only skimmed it as yet, admittedly, but could not immediately see an explanation. 

Relativistic beaming is from the relativistic doppler effect

https://en.m.wikipedia.org/wiki/Relativistic_beaming

“In physics, relativistic beaming (also known as Doppler beaming, Doppler boosting, or the headlight effect) is the process by which relativistic effects modify the apparent luminosity of emitting matter that is moving at speeds close to the speed of light.

…

How all of these effects modify the brightness, or apparent luminosity, of a moving object is determined by the equation describing the relativistic Doppler effect (which is why relativistic beaming is also known as Doppler beaming).”

 

edit:

Here’s one of the cited references, by the same author

https://www.degruyter.com/document/doi/10.1515/astro-2020-0001/html

They mention a Doppler shift of the bolometric flux; this means the “brightness” they are measuring is related to total energy, and blue-shifting does increase that. It’s not simply number of photons.

more:

https://en.m.wikipedia.org/wiki/Luminosity

 

edit 2:

In that reference I gave they note that observers in the southern hemisphere see rotations in the opposite direction, but I assume they accounted for this, and also for any anisotropy in the viewing field (e.g. we don’t see what’s on the other side of the galactic core)

18 hours ago, swansont said:

Relativistic beaming is from the relativistic doppler effect

https://en.m.wikipedia.org/wiki/Relativistic_beaming

“In physics, relativistic beaming (also known as Doppler beaming, Doppler boosting, or the headlight effect) is the process by which relativistic effects modify the apparent luminosity of emitting matter that is moving at speeds close to the speed of light.

…

How all of these effects modify the brightness, or apparent luminosity, of a moving object is determined by the equation describing the relativistic Doppler effect (which is why relativistic beaming is also known as Doppler beaming).”

 

edit:

Here’s one of the cited references, by the same author

https://www.degruyter.com/document/doi/10.1515/astro-2020-0001/html

They mention a Doppler shift of the bolometric flux; this means the “brightness” they are measuring is related to total energy, and blue-shifting does increase that. It’s not simply number of photons.

more:

https://en.m.wikipedia.org/wiki/Luminosity

 

edit 2:

In that reference I gave they note that observers in the southern hemisphere see rotations in the opposite direction, but I assume they accounted for this, and also for any anisotropy in the viewing field (e.g. we don’t see what’s on the other side of the galactic core)

OK thanks. I can see that a blue shift increases the energy of the light as received, so if they are measuring "brightness" by energy flux (which will be the case with a bolometric measurement) then a blue shifted galaxy will be "brighter" than a red shifted one of equal magnitude. Like you, I'd be tempted to discount relativistic beaming as the relative velocities of the galaxies must be <<c. 

But what I still can't follow is why the direction of rotation of the observed galaxy has an effect. I'd have though the side advancing towards us would be blue shifted and the side retreating would be red shifted, and this effect would be simply swapped round symmetrically if the direction of rotation were reversed. 

 

I'm pretty sure Brian Schmidt spoke of this at some point... could be thinking of something else though.

JWST found that about two-thirds of early galaxies rotate clockwise. This is surprising because galaxy spin directions were expected to be random. The imbalance might point to unknown features of the early universe.

2/3 of galaxies rotate in one direction, the other 1/3 rotate in the opposite direction.
Clockwise or counter-clockwise depends on which side you are looking from.

7 hours ago, MigL said:

2/3 of galaxies rotate in one direction, the other 1/3 rotate in the opposite direction.
Clockwise or counter-clockwise depends on which side you are looking from.

It has only just struck me, late in the day, that this implies there is a preferred axis of rotation for galaxies, i.e. they are not randomly orientated. That seems odd in itself, irrespective of the question of a preferred sense of rotation.

Edited June 13Jun 13 by exchemist

When galaxies were forming, they were much closer together. Given that spacetime tells matter how to move, could the global spacetime, as opposed to local, configuration in the earliest epoch of galaxy formation been biased in that proportion; preferentially leaning towards one direction of rotation?

Edited June 13Jun 13 by StringJunky

1 hour ago, StringJunky said:

When galaxies were forming, they were much closer together. Given that spacetime tells matter how to move, could the global spacetime, as opposed to local, configuration in the earliest epoch of galaxy formation been biased in that proportion; preferentially leaning towards one direction of rotation?

It suggests the universe was born with net angular momentum. Perhaps there is an inaccessible anti-universe with the opposite.😉

The statistical explanation appeals to my inner Ockham. The galaxies rotating opposite to us appear brighter, so they're their overrepresented in telescopic surveys. The BH conjecture is mind boggling - inherited angular momentum from a parent BH our verse lies inside of.

45 minutes ago, TheVat said:

The statistical explanation appeals to my inner Ockham. The galaxies rotating opposite to us appear brighter, so they're their overrepresented in telescopic surveys. The BH conjecture is mind boggling - inherited angular momentum from a parent BH our verse lies inside of.

But why brighter? I don’t understand this. The advancing side will be bluer, hence “brighter” in the sense of more energetic, in bolometric measurements, but the retreating side will be redder and “dimmer” by the same token. Why does the direction of rotation affect the overall net perceived brightness?

The James Webb Space Telescope (JWST) has observed that about two-thirds of distant galaxies in a recent study appear to rotate clockwise. This surprising result, based on data from the JADES survey, suggests a possible large-scale asymmetry in the universe - something not fully explained by current cosmological models. Scientists are now investigating whether this pattern is real or the result of observational bias.