Lmst

Webb telescope helps refines Hubble constant, suggesting resolution rate debate

https://phys.org/news/2025-05-webb-telescope-refines-hubble-constant.html

#HackerNews #WebbTelescope #HubbleConstant #SpaceScience #Astronomy #News #Debate

https://www.geo.fr/sciences/et-si-la-matiere-noire-evoluait-avec-le-temps-une-nouvelle-piste-de-comprehension-de-l-univers-226582
#MatièreNoire #TensionDeHubble #ÉnergieNoire #CornellUniversity #ChampsScalaires #UniversOscillant #ConstanteDeHubble #HubbleTension #DarkMatter #OscillatingDarkMatter #TimeDependentCosmology #HubbleConstant #ModifiedGravity #QuantumCosmology #DarkSector

More in the "Don't trust search results" department - This isn't even AI-generated, it seems to be just a misconception on the part of the author.

Okay - While searching for a rough estimate of the size of the observable universe at various ages, I found an excerpt from an Encyclopedia Britannica page (URL in the alt text) that sounded wrong - that the observable universe expands by one light year per year.

I plugged some rough numbers into Wolfram Alpha and got a value of 6.7 ly.
(I like Wolfram Alpha - it usually makes the right assumptions about what I'm looking for 👍🏻)

The EB article also states that as time goes by, we will be able to see *more* of the universe as light eventually reaches us from farther objects. This is exactly wrong - as the universe expands, more and more objects will recede faster than the speed of light and we will see less, not more. (Not to mention that there's a hard limit on the time during which objects that could emit light actually existed)

Am I missing something? I'm always wary of forgetting a factor of 2 or something in this kind of calculation...

#Astronomy #Cosmology #HubbleConstant

Excerpt from Encylcopedia Britanica (URL below):

However, according to Hubble's law, space has been expanding since the big bang, and thus the observable universe continues to expand as well. Calculations of this expansion show that objects that emitted light 13.8 billion years ago, from a distance of 13.8 billion light-years, are now even farther away from Earth-46 billion light-years away, approximately. This means that the
observable universe is more than 46 billion light-years in any direction from Earth and
about 93 billion light-years in diameter.

Given the constant expansion of the universe, the observable universe expands another light-
year every Earth year. At the same time, light from objects that are ever farther away
continues to reach Earth for the first time, meaning that humans are able to see more and
more of the universe with the passing of time. While humans will never be able to see the
entire universe from Earth, only the relatively small bubble of the observable universe, the
sphere of observation is ever expanding.

https://www.britannica.com/topic/observable-universe

A crude calculation for the increase in size of the observable universe per year, using 93 billion light years (converted to parsecs) for the diameter and 70 km/s/Mpc for the Hubble constant. Wolfram Alpha was used for the calculation. The answer generated is 6.7 light years.

The Complete Sample of Available SNe Ia Luminosity Calibrations from the TRGB Observed with either HST or JWST: https://arxiv.org/abs/2504.08921 (spoiler: the 'local' #HubbleConstant is really 72 to 73 km/s/Mpc) -> thread https://x.com/DScol/status/1912184923894526047

#Cosmology

Do ongoing tensions leave room for new physics?

One century after Edwin Hubble revealed his astonishing discovery of a cosmos beyond the Milky Way, the most precise measurements still can’t agree on how fast galaxies are moving.

By Wendy Freedman
https://www.nature.com/articles/d41586-025-00896-5

#HubbleTension #HubbleConstant #Physics #Astronomy #Astrophysics #Astrodon #Science #STEM

Turning the #Hubble tension into a crisis: New measurement confirms #universe is expanding too fast for current models
The universe is expanding faster than predicted by theoretical models, and faster than can be explained by our current understanding of #physics.
They arrived at a value for the #HubbleConstant of 76.5 kilometers per second per megaparsec which matches existing measurements, but not as our current understanding of physics predicts it.
https://phys.org/news/2025-01-hubble-tension-crisis-universe-fast.html

How fast is the Universe expanding? This astronomer took cosmology closer to an answer

Wendy Freedman is part of Nature’s 10, a list of people who shaped science in 2024.

https://www.nature.com/articles/d41586-024-03899-w

#Cosmology #HubbleTension #HubbleConstant #Science #Nature #astronomer #astronomi #astrophysics #STEM #WomeninSTEM #Womeninscience #Universe

Webb Researchers Discover Lensed Supernova, Confirm Hubble Tension

https://webbtelescope.org/contents/early-highlights/webb-researchers-discover-lensed-supernova-confirm-hubble-tension

#Cosmology #JWST #HubbleConstant #HubbleTension #Universe #Astrodon #science #news

On France Culture today: The Hubble Tension

... in an interview by the excellent Celine Loozen I talk about our Cosmicflows-4 measurement of the Hubble Constant, as well as the value inferred from Ho'oleilana, that are both exacerbating the tension.

▶ at t=33:30 https://www.radiofrance.fr/franceculture/podcasts/la-science-cqfd/constante-de-hubble-la-tension-monte-7710009

#Cosmology #Hubble #HubbleConstant #HubbleTension #Hooleilana #science #Astrodon

in the #arXiv

DESI Peculiar Velocity Survey – Fundamental Plane

by Khaled Said and co-authors
https://arxiv.org/abs/2408.13842

#Cosmology #galaxies #cosmicflows #astronomy #astrophysics #astrodon #science #STEM #DESI #FundamentalPlane #HubbleConstant #TullyFisher

There, it only took 9 days: https://arxiv.org/abs/2408.11770
#HubbleConstant #H0

Huh, Freedman et al. find H0 = 68 with the JAGB method and H0 = 70 with TRGB (https://arxiv.org/abs/2408.06153) with JWST. OK, the error bars are still large...
How long before Riess et al. find 73 again using the same data?
#HubbleConstant #H0

Difference ways of measuring the Hubble Constant still don't agree with each other, yet.

"A long-awaited study of the cosmic expansion rate suggests that when it comes to the Hubble tension, cosmologists are still missing something."

https://www.quantamagazine.org/the-webb-telescope-further-deepens-the-biggest-controversy-in-cosmology-20240813/

#Cosmology #HubbleConstant #Space #Measurements

Back in April I posted about a meeting at the Royal Society in London called Challenging the Standard Cosmological Model, some of which I attended virtually. In that post I mentioned that Wendy Freedman gave a talk related to the ongoing issue of the Hubble Tension, i.e. the discrepancy between different types of measurement of the Hubble Constant, usually characterized as local measurements (using stellar distance indicators) and larger-scale measurements (chiefly Planck). There are quite a few posts about this issue on this blog. Anyway, Wendy Freedman mention in her talk that her latest work on stellar distances suggested a value of 69.1 ± km s-1 Mpc-1, which reduces the tension with Planck significantly. At the time, however, there was no paper explaining how this number was derived.

Yesterday there appeared on arXiv a preprint by Freedman et al. which summarizes the recent results. The abstract is here:

We present the latest results from the Chicago Carnegie Hubble Program ( CCHP) to measure the Hubble constant using data from the James Webb Space Telescope (JWST). This program is based upon three independent methods: (1) Tip of the Red Giant Branch (TRGB) stars, (2) JAGB (J-Region Asymptotic Giant Branch) stars, and (3) Cepheids. Our program includes 10 nearby galaxies, each hosting Type Ia supernovae (SNe Ia), suitable for measuring the Hubble constant (H0). It also includes NGC 4258, which has a geometric distance, setting the zero point for all three methods. The JWST observations have significantly higher signal-to-noise and finer angular resolution than previous observations with the Hubble Space Telescope (HST). We find three independent values of H0 = 69.85 ± 1.75 (stat) ± 1.54 (sys) for the TRGB, H0 = 67.96 ± 1.85 (stat) ± 1.90 (sys) km s-1 Mpc-1 for the JAGB, and H0 = 72.05 ± 1.86 (stat) ± 3.10 (sys) for Cepheids. Tying into SNe Ia, and combining these methods adopting a flat prior, yields our current estimate of H0 = 69.96 ± 1.05 (stat) ± 1.12 (sys) km s-1 Mpc-1. The distances measured using the TRGB and the JAGB method agree at the 1% level, but differ from the Cepheid distances at the 2.5-4% level. The value of H0 based on these two methods with JWST data alone is H0 = 69.03 ± 1.75 (total error) km s-1 Mpc-1. These numbers are consistent with the current standard ΛCDM model, without the need for the inclusion of additional new physics. Future JWST data will be required to increase the precision and accuracy of the local distance scale.

You can read the full paper on arXiv here. A summary of the summary is that of the three methods they use, two give lower values of the Hubble constant and one (Cepheids) gives a higher value but with larger errors. The number quoted in the Royal Society talk was presumably preliminary as it doesn’t match any of the numbers in the abstract, but the point remains.

You can see the reduction in scatter in the new JWST measurements in this Figure (old on the left and new on the right).

On the face of it, these results suggest that the Hubble tension is greatly reduced. I am sure, however, that advocates of a higher value will have been preparing their ripostes and it’s just a matter of time before they arrive on the arXiv too!

https://telescoper.blog/2024/08/14/hubble-tension-reduced/

#arXiv240806153 #HubbleConstant #HubbleTension #JWST #WendyFreedman