Hubble bubble may explain different measurements of expansion rate of the universe

Sep 09, 2013

The existence of the "Hubble Bubble" may explain, at least in part, the differing measurements for the expansion and therefore the age of the universe. That is the assumption of a team of physicists headed by Prof. Dr. Luca Amendola from the Institute for Theoretical Physics at Heidelberg University. In collaboration with colleagues from the Netherlands, the Heidelberg physicists developed a theoretical model that places the Milky Way inside of this type of cosmic bubble. The researchers believe the bubble can explain some of the deviations between previous measurements and the latest ones from the Planck satellite of the European Space Agency (ESA). The results of their research were published in the journal Physical Review Letters.

The has been expanding since the Big Bang. It still is, causing galaxies in our Milky Way to recede. The actual speed of this expansion is known as the Hubble constant. Due to its importance in calculating basic properties of the universe, such as its age, modern cosmology is tasked with determining the value of the constant. There are two conventional methods used, although their results are not congruent, according to Dr. Valerio Marra from Heidelberg University's Institute for Theoretical Physics. "This has been the source of intense, long-standing debate in the scientific community."

One way to determine the Hubble constant, and hence the universe's rate of expansion, is based on measuring the cosmic in space. It was released approximately 400,000 years after the Big Bang and pervades the entire universe. Several months ago the Planck satellite from the ESA delivered measurements of this ancient radiation. The Hubble constant, however, can also be derived from the movement of galaxies near the Milky Way, movement largely due to the expansion of the universe. "When you compare the results from the two methods, there is a deviation of about 9 percent", explains Dr. Marra.

In their search to explain the difference in data, the Heidelberg team thought that the reason was not some previously unrecognized error in measurement, but based on a physical effect. According to Dr. Marra, the existence of the Hubble Bubble could be the cause. The bubble describes regions of the universe where the density of matter falls below the cosmic average. "Until now knowledge of our cosmic neighbourhood has been too imprecise to determine whether or not we are in such a bubble", continues Dr. Marra. "But let's just assume for a moment that our Milky Way is located in a Hubble Bubble. Matter outside the bubble would then attract nearby galaxies so strongly that they would move more quickly than average. In this case we would measure a higher Hubble constant that would apply to our cosmic neighbourhood, but not to the universe as a whole." Dr. Marra believes that this could partly explain the conflicting measurement results. The Hubble constant measured by the Planck satellite would represent a spatial average applicable to the entire universe. The Hubble constant determined through the movement of galaxies, however, would be valid only in the vicinity of the Milky Way. "Anyone expecting the measurements from our cosmic environs to match those of the microwave radiation implicitly assumes that we live in a typical region of the cosmos. But that isn't necessarily true", continues Prof. Amendola, whose working group has been studying the for many years.

Using their research approach, the scientists have thus far been able to account for approximately one-fourth of the deviation between the two Hubble constants. Dr. Marra and his colleagues expect a detailed analysis will reduce the discrepancy even more. "Until now we have been working with a spherical Hubble Bubble. But it's far more likely that the bubble is asymmetrical, which would explain the deviating measurements even better", observes Dr. Ignacy Sawicki, also a researcher at the Institute for Theoretical Physics. "If the difference in data should manifest itself instead, this would be a major indicator that our former natural scientific view of the cosmos is still missing an ingredient", stresses Dr. Sawicki.

In addition to Valerio Marra and Ignacy Sawicki, Dr. Wessel Valkenburg from the Instituut-Lorentz of Leiden University was also member of Prof. Amendola's team. Their work was funded by the Collaborative Research Centre/Transregio "The Dark Universe".

Explore further: Magnetar discovered close to supernova remnant Kesteven 79

More information: Marra, V., Amendola, L., Sawicki, I. and Valkenburg V. Cosmic Variance and the Measurement of the Local Hubble Parameter, Physical Review Letters 110, 241305 (2013). DOI: 10.1103/PhysRevLett.110.241305

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triplehelix
3.2 / 5 (17) Sep 09, 2013
"The observable universe has been expanding since the Big Bang. It still is, causing galaxies in our Milky Way to recede."

Arrghh I cannot stand it when people muddle up solar systems, galaxies and the universe. It isn't difficult!

The milky way is a galaxy, it doesn't contain galaxies!
kelman66
3.7 / 5 (3) Sep 09, 2013
Sounds like the constant is actually an equation.
cantdrive85
1 / 5 (17) Sep 09, 2013
The "Fingers of God" may explain a lot about this discrepancy.
brt
4.7 / 5 (12) Sep 09, 2013
The "Fingers of God" may explain a lot about this discrepancy.


of course! IT'S ALL SO CLEAR NOW.
hemitite
5 / 5 (2) Sep 09, 2013
Does anyone know if the 9% lower number for the Hubble Constant from the CMB data would have any significant cosmological impact?
Torbjorn_Larsson_OM
4 / 5 (4) Sep 09, 2013
Typical. The WMAP measurements could merge CMB and astronomical Hubble measurements, but they could also reject the idea of a "Hubble bubble".

Then Planck showed inconsistencies between CMB and astronomical Hubble measurements, and was in turn inconsistent with WMAP when it had to choose the best parameter set.

And now these geezers claim that they have found a gap for a new and local "Hubble Bubble". From 1/4th of the necessary bridging.

Um, NO. That is a possibility, not a testable prediction.
Torbjorn_Larsson_OM
4 / 5 (4) Sep 09, 2013
@kelman66: Yeah, in modern inflationary standard cosmology it is, it is only historical reasons that makes people say "Hubble's constant" as he thought it was. Look through Susskind's cosmological lectures on utoobe, he calls it "the Hubble thingie" or "the Hubble function" - it is derivable. Only during exponential growth of an early inflation era or a late dark energy dominated era universe is the Hubble function approaching a constant value. It isn't actually constant as of yet, we are still in the late part of the switch over from the matter dominated era.

@hemitite: People are looking at that now, google and read the web Planck archives. AFAIK many data sets are suddenly inconsistent, whereas during WMAP they could be merged. The vagaries of increased precision.

The smart money is on the astronomical set being wrong (less well constrained - more constraints, longer constrain chains, more data mergers, less precision). Which means no Hubble Bubble gumming up the works.
Fleetfoot
5 / 5 (4) Sep 10, 2013
And now these geezers claim that they have found a gap for a new and local "Hubble Bubble". From 1/4th of the necessary bridging.

Um, NO. That is a possibility, not a testable prediction.


In order to get a testable prediction actually tested, you have to announce it to get others intrested in doing the test. It's the first step towards getting the testing funded.
Fleetfoot
5 / 5 (5) Sep 10, 2013
it is only historical reasons that makes people say "Hubble's constant" as he thought it was.


I think it was intended as a "constant of proportionality" in which case the use of the term remains valid, even though the value varies with time.
Captain Stumpy
1 / 5 (7) Sep 13, 2013
would the existence and amount variability of dark matter affect this in any meaningful fashion?

seems to me that the dark matter in our local group (is that what they meant and instead said "galaxies in the milky way"?) would effect the speed at which other galaxies approach or retreat from us in a measurable way... or am I off base here?
Fleetfoot
4 / 5 (4) Sep 14, 2013
would the existence and amount variability of dark matter affect this in any meaningful fashion?

seems to me that the dark matter in our local group (is that what they meant and instead said "galaxies in the milky way"?) would effect the speed at which other galaxies approach or retreat from us in a measurable way... or am I off base here?


You are right that it has an effect and in fact it affects motion on much larger scales, there is a very good (17 minute) video on the local flow here:

http://irfu.cea.fr/cosmography

The Hubble Constant is defined based on the background expansion over larger scales and there is obviously a question on what ranges are "large enough" to average out the more local effects. Note also there aren't separate processes at work, curvature reflects the combination of local and global influences so the large scale average of DM is a contributor to the constant.
Captain Stumpy
1.6 / 5 (7) Sep 14, 2013
@Fleetfoot
thanks for that video link... quite astonishing to view! had a time with the heavy French accent in a couple of places, but a GREAT video!

fascinating...
Fleetfoot
5 / 5 (3) Sep 15, 2013
Sorry, the link is here: http://www.scienc...x-85942. IMO it's impossible to design working model of Universe expansion without having the dense aether model on mind as there are no other alternatives. ..


As the article says, it's only a problem if you attempt to describe it with an aether theory:

"For substance-models, the expansion-paradox is a strict contradiction: Substance cannot by some magic globally appear without being locally supplied somewhere"

The mention of SR is spurious, it is a simplification which omits gravitational effects. The whole article seems to have been written by someone who doesn't really understand modern cosmology.
Fleetfoot
5 / 5 (2) Sep 15, 2013
@Fleetfoot
thanks for that video link... quite astonishing to view! had a time with the heavy French accent in a couple of places, but a GREAT video!

fascinating...


Yes, the accent is very difficult but the video really puts our place in the universe into perspective.
Captain Stumpy
1 / 5 (6) Sep 15, 2013
Yes, the accent is very difficult but the video really puts our place in the universe into perspective.


very much so! I think this is the best "perspective" video that I have seen... really drums home the size of the universe!

is there a review process before phsy.org publishes on-line? there are links to submit to phys.org, but what is the criterion for publication here?
Fleetfoot
5 / 5 (1) Sep 16, 2013
The video was published on phys.org in June:

http://phys.org/n...rse.html
Captain Stumpy
1 / 5 (6) Sep 16, 2013
@Fleetfoot

not for the video... some of the articles...

just wondering...

still an awesome video! THANKS!