Subscribe to our free daily newsletters
. 24/7 Space News .




Subscribe to our free daily newsletters



TIME AND SPACE
Measurement of Hubble constant questioned by Nobel laureate Riess' team
by Staff Writers
Beijing, China (SPX) Nov 13, 2015


Comparison of different measurements of Hubble constant. Image courtesy Science China Press. For a larger version of this image please go here.

In 1920's Edwin Hubble, an American astronomer, showed that the recessional velocity of a galaxy increases with its distance from the earth, known as Hubble's law. Hubble's law is taken as the first observational basis for the expansion of the Universe, and provides strong evidence for the Big Bang model.

The value of the expansion rate is called the Hubble constant. Hubble constant is a critical parameter in cosmology and the measurement of Hubble constant is a key task for the astrophysicists and cosmologists. Recently a Chinese team leaded by Prof. Qing-Guo Huang from the institute of theoretical physics at Chinese Academy of Sciences proposed to utilize the Baryon Acoustic Oscillation (BAO) datasets to accurately determine the Hubble constant.

Their work, entitled "An accurate determination of the Hubble constant from baryon acoustic oscillation datasets", was published in Sci China-Phys Mech Astron 2015, Vol. 58 No. 9.

The Universe is expanding. One may immediately ask what is the expansion rate of the Universe, i.e. the value of the Hubble constant. Under the framework of general relativity proposed by Albert Einstein one hundred years ago, the total energy density of our Universe can be also determined by the Hubble constant because our Universe is spatially flat.

Usually, according to the Hubble's law, the value of the Hubble constant is estimated by measuring the redshifts of distant galaxies and determining the distances to the same galaxies. For most of the second half of the 20th century, the Hubble constant was estimated to be between 50 and 100 km/s/Mpc. Until Hubble Space Telescope and its Key project released their results, the Hubble constant was measured accurately at the first time. This result was significantly improved by Nobel laureate Adam Riess and his collaborators in 2011.

BAO is considered as a standard ruler in the Universe and is used to explore the expansion history of the Universe. However, usually ones thought that BAO data alone could not be used to determine the Hubble constant. It is true for the low-redshift BAO datasets alone because of the degeneracy. But, "The combination of the low and high-redshift BAO data can be used to precisely determine the Hubble constant", said the authors.

In addition, they found that the low-redshift anisotropic BAO alone could be used to precisely determine the Hubble constant as well. Combining both the isotropic and anisotropic BAO datasets, they achieved a determination of the Hubble constant with around 1.3% precision! However, their result is relatively low compared to that obtained by Riess et al..

On the other hand, the Hubble constant can be also determined by the anisotropies of Cosmic Microwave Background, for example the data from Planck satellite, indirectly. In the cosmological constant and cold dark matter model, the data released by Planck satellite in 2013 imply that the Hubble constant is also lower than that obtained by Riess et al., but consistent with that obtained by this Chinese team. The comparison of different Hubble constant measurements shows up in Figure 1.

Now the result obtained by Riess et al. is questioned. For example, G. Efstathiou reanalyzed the Riess et al. Cepheid data. Based on the revised geometric maser distance to NGC 4258, he found that the Hubble constant was consistent with both Planck satellite and BAO datasets.

It is recognized that an accurate measurement of the Hubble constant has potential to reveal exotic new physics, for example, a time-varying dark energy, additional relativisitic particles, or neutrino mass. The Chinese team leaded by Prof. Qing-Guo Huang made an important contribution to the measurement of the Hubble constant.

C. Cheng, Q.-G. Huang, "An accurate determination of the Hubble constant from baryon acoustic oscillation datasets", Science China Physics, Mechanics and Astronomy (2015)58(9):599801.doi:10.1007/s11433-015-5684-5


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only

.


Related Links
Science China Press
Understanding Time and Space






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

Previous Report
TIME AND SPACE
Have scientists found evidence of a parallel universe?
Pasadena, Calif. (UPI) Nov 4, 2015
Caltech cosmologist Ranga-Ram Chary thinks he may have found evidence of a parallel universe. In a new study, published in the Astrophysical Journal, Chary suggests cosmic bruising - one universe bumping up against another universe - could explain an anomaly he found in the map of the cosmic microwave background. The cosmic microwave background is the light leftover from the me ... read more


TIME AND SPACE
Gaia's sensors scan a lunar transit

SwRI scientists explain why moon rocks contain fewer volatiles than Earth's

All-female Russian crew starts Moon mission test

Russian moon mission would need 4 Angara-A5V launches

TIME AND SPACE
Dust devils detected by seismometer could guide Mars mission

Amnesia Event Slows Down Opportunity Robotic Arm Work

Swiss Camera Leaves for Mars

NASA mission reveals speed of solar wind stripping Martian atmosphere

TIME AND SPACE
Orion's European module ready for testing

General Dynamics demos SGSS Command and Control Infrastructure for NASA

Orion Service Module Stacking Assembly Secured For Flight

Global partnerships in orbit support economic growth on and off the Earth

TIME AND SPACE
New rocket readies for liftoff in 2016

China's self-developed Mars probe to be on show

Could Sino-U.S. cooperation bring the Martian home?

China's scientific satellites to enter uncharted territory

TIME AND SPACE
Cygnus Starts Final Round of Processing for Station Cargo Delivery

US astronauts dodge ammonia on risky spacewalk

UK astronaut dreams of heavenly Christmas pudding

NASA drops Boeing from race for $3.5 billion cargo contract

TIME AND SPACE
LISA Pathfinder topped off for Vega launch that will test Relativity

Ariane 5 lofts dual birds

Rocket launch from Hawaii carrying UH payload experiences anomaly

Commercial Spaceflight Gets A Boost With Latest Congressional Moves

TIME AND SPACE
New Results from GPI Exoplanet Survey

Newfound Earth-size exoplanet may be an important milestone in search for alien life

UCLA professor proposes simpler way to define what makes a planet

Distant world's weather is mixed bag of hot dust and molten rain

TIME AND SPACE
Electron microscopy method sculpts 3-D structures at atomic level

BU Satellite Team Gets Big Boost from NASA

System helps novices design 3-D-printable robotic creatures

Queen's University professor to unveil self-levitating displays




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News






The content herein, unless otherwise known to be public domain, are Copyright 1995-2017 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement