Today's "Planet Earth Report" --Our Planet's Deep Hidden Oceans --"Where Did All the Water Come From?"
"Cosmic Messengers" --Mystery Sources Detected of Ghost Particles from the Most Extreme Environments in the Cosmos

"We are Very Perplexed" --Gaia and Hubble Space-Telescope Findings May Reveal a 'New Physics of the Universe'

 

RTEmagicC_30358_oscillation_baryonique_Chris_Blake_et_Sam_Moorfield_txdam22114_9dd4e4 (1)

The combined new data from the Gaia and Hubble Space Telescope data are in serious conflict with the Cosmic Microwave Background data," said Planck team member George Efstathiou of the Kavli Institute for Cosmology in Cambridge. The results fuel the mismatch between measurements for the expansion rate of the nearby universe, and those of the distant, primeval universe—before stars and galaxies even existed.

This so-called "tension" implies that there could be new physics underlying the foundations of the universe. Possibilities include the interaction strength of dark matter, dark energy being even more exotic than previously thought, or an unknown new particle in the tapestry of space.

 

Combining observations from NASA's Hubble Space Telescope and the European Space Agency's (ESA) Gaia space observatory (below), astronomers further refined the previous value for the Hubble constant, the rate at which the universe is expanding from the big bang 13.8 billion years ago.

 

Gaiaspacetel

But as the measurements have become more precise, the team's determination of the Hubble constant has become more and more at odds with the measurements from another space observatory, ESA's Planck mission, which is coming up with a different predicted value for the Hubble constant.

Planck mapped the primeval universe as it appeared only 360,000 years after the big bang. The entire sky is imprinted with the signature of the big bang encoded in microwaves. Planck measured the sizes of the ripples in this Cosmic Microwave Background (CMB) that were produced by slight irregularities in the big bang fireball. The fine details of these ripples encode how much dark matter and normal matter there is, the trajectory of the universe at that time, and other cosmological parameters.

 

 

 

These measurements, still being assessed, allow scientists to predict how the early universe would likely have evolved into the expansion rate we can measure today. However, those predictions don't seem to match the new measurements of our nearby contemporary universe.

"The tension seems to have grown into a full-blown incompatibility between our views of the early and late time universe," said team leader and Nobel Laureate Adam Riess of the Space Telescope Science Institute and the Johns Hopkins University in Baltimore, Maryland. "At this point, clearly it's not simply some gross error in any one measurement. It's as though you predicted how tall a child would become from a growth chart and then found the adult he or she became greatly exceeded the prediction. We are very perplexed."

In 2005, Riess and members of the SHOES (Supernova H0 for the Equation of State) team set out to measure the universe's expansion rate with unprecedented accuracy. In the following years, by refining their techniques, this team shaved down the rate measurement's uncertainty to unprecedented levels. Now, with the power of Hubble and Gaia combined, they have reduced that uncertainty to just 2.2 percent.

Because the Hubble constant is needed to estimate the age of the universe, the long-sought answer is one of the most important numbers in cosmology. It is named after astronomer Edwin Hubble, who nearly a century ago discovered that the universe was uniformly expanding in all directions—a finding that gave birth to modern cosmology.

Galaxies appear to recede from Earth proportional to their distances, meaning that the farther away they are, the faster they appear to be moving away. This is a consequence of expanding space, and not a value of true space velocity. By measuring the value of the Hubble constant over time, astronomers can construct a picture of our cosmic evolution, infer the make-up of the universe, and uncover clues concerning its ultimate fate.

The two major methods of measuring this number give incompatible results. One method is direct, building a cosmic "distance ladder" from measurements of stars in our local universe. The other method uses the CMB to measure the trajectory of the universe shortly after the big bang and then uses physics to describe the universe and extrapolate to the present expansion rate. Together, the measurements should provide an end-to-end test of our basic understanding of the so-called "Standard Model" of the universe. However, the pieces don't fit.

Using Hubble and newly released data from Gaia, Riess' team measured the present rate of expansion to be 73.5 kilometers (45.6 miles) per second per megaparsec. This means that for every 3.3 million light-years farther away a galaxy is from us, it appears to be moving 73.5 kilometers per second faster. However, the Planck results predict the universe should be expanding today at only 67.0 kilometers (41.6 miles) per second per megaparsec. As the teams' measurements have become more and more precise, the chasm between them has continued to widen, and is now about four times the size of their combined uncertainty.

Over the years, Riess' team has refined the Hubble constant value by streamlining and strengthening the "cosmic distance ladder," used to measure precise distances to nearby and far-off galaxies. They compared those distances with the expansion of space, measured by the stretching of light from nearby galaxies. Using the apparent outward velocity at each distance, they then calculated the Hubble constant.

To gauge the distances between nearby galaxies, his team used a special type of star as cosmic yardsticks or milepost markers. These pulsating stars, called Cephied variables, brighten and dim at rates that correspond to their intrinsic brightness. By comparing their intrinsic brightness with their apparent brightness as seen from Earth, scientists can calculate their distances.

Gaia further refined this yardstick by geometrically measuring the distance to 50 Cepheid variables in the Milky Way. These measurements were combined with precise measurements of their brightnesses from Hubble. This allowed the astronomers to more accurately calibrate the Cepheids and then use those seen outside the Milky Way as milepost markers.

"When you use Cepheids, you need both distance and brightness," explained Riess. Hubble provided the information on brightness, and Gaia provided the parallax information needed to accurately determine the distances. Parallax is the apparent change in an object's position due to a shift in the observer's point of view. Ancient Greeks first used this technique to measure the distance from Earth to the Moon.

"Hubble is really amazing as a general-purpose observatory, but Gaia is the new gold standard for calibrating distance. It is purpose-built for measuring parallax—this is what it was designed to do," Stefano Casertano of the Space Telescope Science Institute and a member of the SHOES team added. "Gaia brings a new ability to recalibrate all past distance measures, and it seems to confirm our previous work. We get the same answer for the Hubble constant if we replace all previous calibrations of the distance ladder with just the Gaia parallaxes. It's a crosscheck between two very powerful and precise observatories."

The goal of Riess' team is to work with Gaia to cross the threshold of refining the Hubble constant to a value of only one percent by the early 2020s. Meanwhile, astrophysicists will likely continue to grapple with revisiting their ideas about the physics of the early universe.

The Daily Galaxy via NASA's Goddard Space Flight Center

Most Viewed Space & Science News

Homo Naledi, Newly Discovered Species --"Maybe We've Had the Story of Human Evolution Wrong the Whole Time"

Stephen Hawking's Great Question --"Why Isn't the Milky Way Crawling With Mechanical or Biological Life?"

"Alien Minds" --'Artificial Intelligence Is Already Out There, and It's Billions of Years Old' (VIDEO)

"Point of No Return" --MIT Scientist Predicts the Event Horizon for Earth's 6th Mass Extinction 

A Neutron Star Collision in Our Milky Way Neighborhood Could Destroy Earth

 "300-Million Nuclear Bombs" --New Insights Into Global Impact of Titanic Chicxulub Mass-Extinction Event

Stephen Hawking: Wake Up, Science Deniers! --"Earth is Morphing into Venus" (WATCH Today's 'Galaxy' Stream)

"Evolutionary Leap?" AI is Mimicing the Human Brain --"But Several Orders of Magnitude Faster and More Efficiently

China Creates a Laser of Mind-Boggling Power --"Could Rip Space Asunder, Breaking the Vacuum"

"Stop Saying That Dinosaurs Went Extinct. They Didn't"

 

6a00d8341bf7f753ef022ad39da299200b-800wi

Comments

To my understanding, a contributory factor in assessing the speed of receding galaxies lies within measuring their red or blue spectral shift. Another is the parallax between a known variable star and others further away.

What is not clear, is how accurate can these measurements be, especially given intergalactic distances, when the intervening density of visible gravity mass must inevitably bend and distort light waves as observed from Earth's locality....?

We know that our sun locally distorts the light received from other stars, so this must be relativistically true for all other stars, and when one adds up their total density in lines of sight to the furthest receding galaxies....how can one have any confidence in the accuracy of such measurements....?

Since we are also struggling in the search for dark matter with the shortfall of observable mass in the universe, where the quantity of dark matter is presumed to exceed the visible mass of stars, galaxies, and gases....then the combined space-time distortions must make any observations of frequency shift or parallax over any distance very questionable.

Could not the appearance of the furthest receding galaxies moving away from us faster be just a gravity lensing effect from all the intervening matter....?

If one accepts that no light can escape a black hole, then the slowing of light in its passage past or through large concentrations of gravity masses over vast distances, and consequent frequency shifts, remains a possibility.

What about the influence of dark matter on light traveling long distances? Could it be responsible for the red shift? We don't know much about but seem to assume it's everywhere. So how could we exclude this type of effect on it?

Verify your Comment

Previewing your Comment

This is only a preview. Your comment has not yet been posted.

Working...
Your comment could not be posted. Error type:
Your comment has been posted. Post another comment

The letters and numbers you entered did not match the image. Please try again.

As a final step before posting your comment, enter the letters and numbers you see in the image below. This prevents automated programs from posting comments.

Having trouble reading this image? View an alternate.

Working...

Post a comment

Your Information

(Name is required. Email address will not be displayed with the comment.)