MPA: High Value for Hubble Constant from Two Gravitational Lenses

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bystander
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MPA: High Value for Hubble Constant from Two Gravitational Lenses

Post by bystander » Fri Sep 13, 2019 8:57 pm

High Value for Hubble Constant from Two Gravitational Lenses
Mas Planck Institute for Astrophysics | 2019 Sep 13
The expansion rate of the Universe today is described by the so-called Hubble constant and different techniques have come to inconsistent results about how fast our Universe actually does expand. An international team led by the Max Planck Institute for Astrophysics (MPA) has now used two gravitational lenses as new tools to calibrate the distances to hundreds of observed supernovae and thus measure a fairly high value for the Hubble constant. While the uncertainty is still relatively large, this is higher than that inferred from the cosmic microwave background.

Gravitational lensing describes the fact that light is deflected by large masses in the Universe, just like a glass lens will bend a light right on Earth. In recent years, cosmologists have increasingly used this effect to measure distances by exploiting the fact that, in a multiple image system, an observer will see photons arriving from different directions at different times due to the difference in optical path lengths for the various images. This measurement thus gives a physical size of the lens, and comparing it to an observed size in the sky gives a geometric distance estimate called the “angular diameter distance”. Such distance measurements in astronomy are the basis for measurements of the Hubble constant...

The team used two strong gravitational lens systems B1608+656 and RXJ1131 (see Figure 1). In each of these systems, there are four images of a background galaxy with one or two foreground galaxies acting as lenses. This relatively simple configuration allowed the scientists to produce an accurate lensing model and thus measure the angular diameter distances to a precision of 12 to 20% per lens. These distances were then applied as anchors to 740 supernovae in a public catalogue (Joint Light-curve Analysis dataset). ...

A Measurement of the Hubble Constant from Angular
Diameter Distances to Two Gravitational Lenses
~ Inh Jee et al
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Re: MPA: High Value for Hubble Constant from Two Gravitational Lenses

Post by neufer » Sat Sep 14, 2019 8:43 pm

bystander wrote:
Fri Sep 13, 2019 8:57 pm

High Value for Hubble Constant from Two Gravitational Lenses
Mas Planck Institute for Astrophysics | 2019 Sep 13
<<The value for the Hubble constant based on this new analysis is
  • 74 to 90 km/s/Mpc.
This is consistent with values derived from the distance ladder method, which uses different anchors for the supernova data, as well as with values from time-delay distances, where other gravitational lensing systems were used to determine the Hubble constant directly.

Again this new measurement confirms that there seems to be a systematic difference in values for the Hubble constant derived directly from local or intermediate sources and indirectly from the Cosmic Microwave Background,” states Eiichiro Komatsu, director at MPA, who oversaw this project. “If confirmed by further measurements, this discrepancy would call for a revision of the standard model of cosmology.
https://en.wikipedia.org/wiki/Hubble%27s_law#Determining_the_Hubble_constant wrote:

Estimated values of the Hubble constant, 2001-2019:

black represent calibrated distance ladder measurements,

red represents early universe CMB/BAO measurements
with ΛCDM parameters


while blue are independent measurements.
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Re: MPA: High Value for Hubble Constant from Two Gravitational Lenses

Post by BDanielMayfield » Sun Sep 15, 2019 2:58 pm

Since the rate of universal expansion is now known to be changing over time (accelerating) the Hubble term is demonstrably NOT CONSTANT, so why keep calling it a "constant"? If the epoch being measured is early the rate will naturally be lower than that found with methods covering later periods of universal time.

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Re: MPA: High Value for Hubble Constant from Two Gravitational Lenses

Post by Ann » Sun Sep 15, 2019 6:37 pm

BDanielMayfield wrote:
Sun Sep 15, 2019 2:58 pm
Since the rate of universal expansion is now known to be changing over time (accelerating) the Hubble term is demonstrably NOT CONSTANT, so why keep calling it a "constant"? If the epoch being measured is early the rate will naturally be lower than that found with methods covering later periods of universal time.

Bruce
I have been thinking the same thing myself, but I was told that the conditions in the early Universe ought to determine the properties of the Universe today, otherwise we need new physics.

Is that true? Hey, I'm just repeating what I think I heard.

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Re: MPA: High Value for Hubble Constant from Two Gravitational Lenses

Post by neufer » Sun Sep 15, 2019 7:56 pm

Ann wrote:
Sun Sep 15, 2019 6:37 pm
BDanielMayfield wrote:
Sun Sep 15, 2019 2:58 pm

Since the rate of universal expansion is now known to be changing over time (accelerating) the Hubble term is demonstrably NOT CONSTANT, so why keep calling it a "constant"? If the epoch being measured is early the rate will naturally be lower than that found with methods covering later periods of universal time.
I have been thinking the same thing myself, but I was told that the conditions in the early Universe ought to determine the properties of the Universe today, otherwise we need new physics.

Is that true?
The terminology: Hubble "CONSTANT" is a relic of an earlier time.

The current local expansion rate H0 is the real issue here. However, it is but one of a hand full of arbitrary parameters that go into standard Lambda-CDM model of the universe. Unfortunately no fixed set of these parameters is consistent with all the observables defined by the standard Lambda-CDM model.
https://en.wikipedia.org/wiki/Lambda-CDM_model wrote:
<<The ΛCDM (Lambda cold dark matter) or Lambda-CDM model is a parametrization of the Big Bang cosmological model in which the universe contains three major components: first, a cosmological constant denoted by Lambda (Greek Λ) and associated with dark energy; second, the postulated cold dark matter (abbreviated CDM); and third, ordinary matter. It is frequently referred to as the standard model of Big Bang cosmology because it is the simplest model that provides a reasonably good account of the following properties of the cosmos:
  • the accelerating expansion of the universe observed in the light from distant galaxies and supernovae

    the large-scale structure in the distribution of galaxies

    the existence and structure of the cosmic microwave background

    the abundances of hydrogen (including deuterium), helium, and lithium
The model assumes that general relativity is the correct theory of gravity on cosmological scales. It emerged in the late 1990s as a concordance cosmology, after a period of time when disparate observed properties of the universe appeared mutually inconsistent, and there was no consensus on the makeup of the energy density of the universe.

The ΛCDM model can be extended by adding cosmological inflation, quintessence and other elements that are current areas of speculation and research in cosmology.

Some alternative models challenge the assumptions of the ΛCDM model. Examples of these are modified Newtonian dynamics, entropic gravity, modified gravity, theories of large-scale variations in the matter density of the universe, bimetric gravity, and scale invariance of empty space.>>
Art Neuendorffer