Improved Hubble yardstick gives fresh evidence for new physics in the universe

February 22, 2018 by Donna Weaver, NASA's Goddard Space Flight Center
This illustration shows 3 steps astronomers used to measure the universe's expansion rate (Hubble constant) to an unprecedented accuracy, reducing the total uncertainty to 2.3 percent. The measurements streamline and strengthen the construction of the cosmic distance ladder, which is used to measure accurate distances to galaxies near to and far from Earth. The latest Hubble study extends the number of Cepheid variable stars analyzed to distances of up to 10 times farther across our galaxy than previous Hubble results. Credit: NASA, ESA, A. Feild (STScI), and A. Riess (STScI/JHU)

Astronomers have used NASA's Hubble Space Telescope to make the most precise measurements of the expansion rate of the universe since it was first calculated nearly a century ago. Intriguingly, the results are forcing astronomers to consider that they may be seeing evidence of something unexpected at work in the universe.

That's because the latest Hubble finding confirms a nagging discrepancy showing the universe to be expanding faster now than was expected from its trajectory seen shortly after the . Researchers suggest that there may be new physics to explain the inconsistency.

"The community is really grappling with understanding the meaning of this discrepancy," said lead researcher and Nobel Laureate Adam Riess of the Space Telescope Science Institute (STScI) and Johns Hopkins University, both in Baltimore, Maryland.

Riess's team, which includes Stefano Casertano, also of STScI and Johns Hopkins, has been using Hubble over the past six years to refine the measurements of the distances to galaxies, using their stars as milepost markers. Those measurements are used to calculate how fast the universe expands with time, a value known as the Hubble constant. The team's new study extends the number of stars analyzed to distances up to 10 times farther into space than previous Hubble results.

But Riess's value reinforces the disparity with the expected value derived from observations of the early universe's expansion, 378,000 years after the big bang - the violent event that created the universe roughly 13.8 billion years ago. Those measurements were made by the European Space Agency's Planck satellite, which maps the cosmic microwave background, a relic of the big bang. The difference between the two values is about 9 percent. The new Hubble measurements help reduce the chance that the discrepancy in the values is a coincidence to 1 in 5,000.

Planck's result predicted that the Hubble constant value should now be 67 kilometers per second per megaparsec (3.3 million light-years), and could be no higher than 69 kilometers per second per megaparsec. This means that for every 3.3 million light-years farther away a galaxy is from us, it is moving 67 kilometers per second faster. But Riess's team measured a value of 73 kilometers per second per megaparsec, indicating galaxies are moving at a faster rate than implied by observations of the early universe.

The Hubble data are so precise that astronomers cannot dismiss the gap between the two results as errors in any single measurement or method. "Both results have been tested multiple ways, so barring a series of unrelated mistakes," Riess explained, "it is increasingly likely that this is not a bug but a feature of the universe."

Explaining a Vexing Discrepancy

Riess outlined a few possible explanations for the mismatch, all related to the 95 percent of the universe that is shrouded in darkness. One possibility is that dark energy, already known to be accelerating the cosmos, may be shoving galaxies away from each other with even greater - or growing - strength. This means that the acceleration itself might not have a constant value in the universe but changes over time in the universe. Riess shared a Nobel Prize for the 1998 discovery of the accelerating universe.

Another idea is that the universe contains a new subatomic particle that travels close to the speed of light. Such speedy particles are collectively called "dark radiation" and include previously known particles like neutrinos, which are created in nuclear reactions and radioactive decays. Unlike a normal neutrino, which interacts by a subatomic force, this new particle would be affected only by gravity and is dubbed a "sterile neutrino."

Yet another attractive possibility is that dark matter (an invisible form of matter not made up of protons, neutrons, and electrons) interacts more strongly with normal matter or radiation than previously assumed.

Any of these scenarios would change the contents of the , leading to inconsistencies in theoretical models. These inconsistencies would result in an incorrect value for the Hubble constant, inferred from observations of the young cosmos. This value would then be at odds with the number derived from the Hubble observations.

Riess and his colleagues don't have any answers yet to this vexing problem, but his team will continue to work on fine-tuning the universe's expansion rate. So far, Riess's team, called the Supernova H0 for the Equation of State (SH0ES), has decreased the uncertainty to 2.3 percent. Before Hubble was launched in 1990, estimates of the Hubble constant varied by a factor of two. One of Hubble's key goals was to help astronomers reduce the value of this uncertainty to within an error of only 10 percent. Since 2005, the group has been on a quest to refine the accuracy of the Hubble constant to a precision that allows for a better understanding of the universe's behavior.

These Hubble Space Telescope images showcase 2 of the 19 galaxies analyzed in a project to improve the precision of the universe's expansion rate, a value known as the Hubble constant. The color-composite images show NGC 3972 (left) and NGC 1015 (right), located 65 million light-years and 118 million light-years, respectively, from Earth. The yellow circles in each galaxy represent the locations of pulsating stars called Cepheid variables. Credit: NASA, ESA, A. Riess (STScI/JHU)
Building a Strong Distance Ladder

The team has been successful in refining the Hubble constant value by streamlining and strengthening the construction of the cosmic distance ladder, which the astronomers use to measure accurate distances to galaxies near to and far from Earth. The researchers have compared those distances with the expansion of space as measured by the stretching of light from receding galaxies. They then have used the apparent outward velocity of galaxies at each distance to calculate the Hubble constant.

But the Hubble constant's value is only as precise as the accuracy of the measurements. Astronomers cannot use a tape measure to gauge the distances between galaxies. Instead, they have selected special classes of stars and supernovae as cosmic yardsticks or milepost markers to precisely measure galactic distances.

Among the most reliable for shorter distances are Cepheid variables, pulsating stars that brighten and dim at rates that correspond to their intrinsic brightness. Their distances, therefore, can be inferred by comparing their intrinsic brightness with their apparent brightness as seen from Earth.

Astronomer Henrietta Leavitt was the first to recognize the utility of Cepheid variables to gauge distances in 1913. But the first step is to measure the distances to Cepheids independent of their brightness, using a basic tool of geometry called parallax. Parallax is the apparent shift of an object's position due to a change in an observer's point of view. This technique was invented by the ancient Greeks who used it to measure the distance from Earth to the Moon.

The latest Hubble result is based on measurements of the parallax of eight newly analyzed Cepheids in our Milky Way galaxy. These stars are about 10 times farther away than any studied previously, residing between 6,000 light-years and 12,000 light-years from Earth, making them more challenging to measure. They pulsate at longer intervals, just like the Cepheids observed by Hubble in distant galaxies containing another reliable yardstick, exploding stars called Type Ia supernovae. This type of supernova flares with uniform brightness and is brilliant enough to be seen from relatively farther away. Previous Hubble observations studied 10 faster-blinking Cepheids located 300 light-years to 1,600 light-years from Earth.

Scanning the Stars

To measure parallax with Hubble, the team had to gauge the apparent tiny wobble of the Cepheids due to Earth's motion around the Sun. These wobbles are the size of just 1/100 of a single pixel on the telescope's camera, which is roughly the apparent size of a grain of sand seen 100 miles away.

Therefore, to ensure the accuracy of the measurements, the astronomers developed a clever method that was not envisioned when Hubble was launched. The researchers invented a scanning technique in which the telescope measured a star's position a thousand times a minute every six months for four years.

The team calibrated the true brightness of the eight slowly pulsating stars and cross-correlated them with their more distant blinking cousins to tighten the inaccuracies in their ladder. The researchers then compared the brightness of the Cepheids and supernovae in those galaxies with better confidence, so they could more accurately measure the stars' true brightness, and therefore calculate distances to hundreds of supernovae in far-flung galaxies with more precision.

Another advantage to this study is that the team used the same instrument, Hubble's Wide Field Camera 3, to calibrate the luminosities of both the nearby Cepheids and those in other galaxies, eliminating the systematic errors that are almost unavoidably introduced by comparing those measurements from different telescopes.

"Ordinarily, if every six months you try to measure the change in position of one star relative to another at these distances, you are limited by your ability to figure out exactly where the star is," Casertano explained. Using the new technique, Hubble slowly slews across a stellar target, and captures the image as a streak of light. "This method allows for repeated opportunities to measure the extremely tiny displacements due to parallax," Riess added. "You're measuring the separation between two stars, not just in one place on the camera, but over and over thousands of times, reducing the errors in measurement."

The team's goal is to further reduce the uncertainty by using data from Hubble and the European Space Agency's Gaia space observatory, which will measure the positions and distances of stars with unprecedented precision. "This precision is what it will take to diagnose the cause of this discrepancy," Casertano said.

Explore further: Hubble finds universe may be expanding faster than expected

Related Stories

Hubble view of a cosmological measuring tape

April 10, 2015

This NASA/ESA Hubble Space Telescope image shows the spiral galaxy NGC 3021 which lies about 100 million light-years away in the constellation of Leo Minor (The Little Lion).

Hubble rules out one alternative to dark energy

March 14, 2011

( -- Astronomers using NASA's Hubble Space Telescope have ruled out an alternate theory on the nature of dark energy after recalculating the expansion rate of the universe to unprecedented accuracy.

Recommended for you

See a passing comet this Sunday

December 14, 2018

On Sunday, Dec. 16, the comet known as 46P/Wirtanen will make one of the 10 closest comet flybys of Earth in 70 years, and you may even be able to see it without a telescope.

Mars InSight lander seen in first images from space

December 14, 2018

On Nov. 26, NASA's InSight mission knew the spacecraft touched down within an 81-mile-long (130-kilometer-long) landing ellipse on Mars. Now, the team has pinpointed InSight's exact location using images from HiRISE, a powerful ...

Video: Enjoying the Geminids from above and below

December 14, 2018

On the night of December 13, into the morning of December 14, 2018, tune into the night sky for a dazzling display of fireballs. Thanks to the International Space Station, this sky show – the Geminids meteor shower—will ...


Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (6) Feb 22, 2018
Take the center of the birth of the universe and go radially outward in your mind's eye which always is Newtonian and not Einsteinian. The universe's Hubble Constant is now least a partial differential function of time and distance from the radial center and increasing such that so far as we know, the third derivative of the equation of distance from CofU/t exists and is non-zero. Therefore at some point the velocity of stars at the outer edge will have a velocity of 'c' with respect to the universe's center and will no longer accellerate cuz' they, according to Einstein, KNOW that the kosmik-kops are gonna get em' if they dare speed faster.. This will become the universe's shell, the spot where all galaxies then pile up. This will make an enormouse dyson sphere at the 'edge of the universe'. Soon this Dyson sphere becomes an enoumous black hole and the universe impodes a finite time trom now.....maybe....sooooon! Same way it inflated and implodes in instant of time...ENDO!
1 / 5 (3) Feb 22, 2018
Sorry, double mouse click event that 'the moving finger writ. cannot erase! At least in PhysOrg space. More of this and I will click/tweet faster than Donald Duck with a grade 'f'
1 / 5 (5) Feb 22, 2018
The original prediction was that expansion started out extremely fast and slowed. The evidence was expected to be found in the slowing rate but instead it is speeding up. Researchers stuck to the old formula and ignored the evidence, assuming instead that some magical God-like force must be causing the universe to behave differently to their prediction and so out pops Dark Energy.

Perhaps a new model needs to be formulated rather than ever more exotic patches to the old model? Even Dark Radiation (dark light) has been hypothesized, along with variable light speed and other exotic solutions.

In the old days scientists tabled the data and formulated a model based on that and that alone. These days a model is formulated and the data 'adjusted' to fit it. Looks like religion won after all, well, its methodology has been adopted by 'science'...
1 / 5 (3) Feb 22, 2018
Water to ice is a unique phase change. It expands rather than shrinks. Expanding space is movement to a phase where time becomes irrelevant. Do the thought experiment.
1 / 5 (1) Feb 22, 2018
Have we determined that the expansion rate is equal in all directions yet?
1 / 5 (2) Feb 22, 2018
If there are multiverse's that affect our universe, than maybe the gravity from adjacent universes change the red shifting by a small but gradually decreasing amount. For example if the gravity from our universe approaches zero at the center of our universe in a linear fashion and the gravity from adjacent universes decreases by the square of the inverse distance from its center then we have the following equation. would be 2-y=1/y^2 which one of the results is the golden ratio where the fraction is the fraction of the distance from the next universe is equal to the golden ratio. This would be in addition to the other causes of redshifting of light. Michael John Sarnowski
1 / 5 (1) Feb 22, 2018
It could be that there exists particles that repel other particles. They would not be visible close to us because they have been pushed away, but they result in the universe expanding.
1 / 5 (1) Feb 23, 2018
Thats there model assuming the universe started at a single point and this being the first universe, but if the universe doesnt come from a big bang, and galaxy clusters tracking each other out into deep space over 200 billion years from an older universe and they are the seeds of creating a new universe by the destruction of there central core masses over time spreading out those seeds of mini galaxies that were anchored by those CCMs over a giant arch of space by galaxy clusters multiple points of construction space would not be expanding but matter is expanding in an already expanded,space thats trillions of years old its just as possible that galaxies are the seeds not big bangs
1 / 5 (3) Feb 23, 2018
Already solved. Check out the Primer Fields series on my Youtube channel Benoît Mussche. The universe is largely magnetic in nature, and LaPoint proves it with experiments.
1 / 5 (2) Feb 23, 2018
If we are a holographic projection of the information on the event horizon of a black hole, could dark energy and it's change be something to do with the black holes' continuing evaporation?
1.3 / 5 (4) Feb 23, 2018
We try to do too much with very limited data. We have only been observing the universe for at most a few hundred years, not even a nanosecond in the overall age of the universe. What we see in this ultra limited view is not enough to extrapolate the entire history of the universe. We have not observed more than 90% of the universe and we don't even know what composes 95% of the mass in the universe. To make such confident and all encompassing conclusions is not warranted. We must constantly remind ourselves of how much we don't know rather than thinking we know much more than we do.
1 / 5 (2) Feb 23, 2018
Could this be the first hint towards the mysterious dark matter/energy story?
4 / 5 (4) Feb 23, 2018
at some point the velocity of stars at the outer edge will have a velocity of 'c' with respect to the universe's center and will no longer accellerate cuz' they, according to Einstein,
Osiris1 you don't understand Einstein (but don' worry, just try hard and you will). First thing there is no "center of the universe". Secondly, Einstein theory does not say that you can not move faster than c in respect another object. What it says is that you can not "accelerate" to a faster speed in respect to it. But if space itself is expanding you are not accelerating. In this way you are moving faster than c in respect to the far away galaxies, although once they move at c you will not see them anymore .
1 / 5 (2) Feb 23, 2018
The gravitational pull from the edge surrounding our universe gets stronger and stronger the closer we get this surrounding edge. Soon our "time" is up and our galaxy swallowed by what's beyond this edge:-)
1.6 / 5 (7) Feb 23, 2018
Home Astronomy & Space Astronomy February 22, 2018
Improved Hubble yardstick gives fresh evidence for new physics in the universe

Of course they are happy to invent new physics and faerie dust and such, but will never, ever reconsider the original hypotheses.
1 / 5 (6) Feb 23, 2018
Too many flaws to cover; so, briefly...

1) Wrong/naive Model/Assumptions leading to GIGO. As recently highlighted in PO news item/study:

2) Circuitous arguments/logics lead to self-determined GIGO 'confirmatory' backup checks for original wrong/naive 'measurement'. As in above article, using redshift data to check results of 'distance measurement' which assumed redshift was correct in the first instance.

3) Cepheid and Type Ia 'standard candle' supernovae NOT STATIONARY or SAME (local conditions/contents vary). So, fast-moving Cepheids and Supernovae 'features' can be RED- or BLUE-shifted, depending on PROPER MOTION (ie, radial velocity peculiar to EACH case); not to mention known variability in local dust/dynamical effects on light brightness/shifting locally/along line-of-sight path from there to here.

4) CMB created NOW all over! BH EH region EMIT EXTREME REDSHIFTED MWs.

It's all GIGO.

RE-DO properly.
1.2 / 5 (6) Feb 23, 2018
PS to above.

That link showed how peculiar velocities MAY NOT MATCH the 'host galaxy' determined 'distance/velocity; hence individual cepheids and supernovae may have different red/blue shifting than host galaxy.

Oh, almost forgot; here is a link highlighting/explaining how what can go drastically wrong when wrong models are chosen to set-up initial parameters/assumptions/expectations for 'observational exercises' using such UNRELIABLE interpretational/analytical constructs/techniques...

So, the message is: STOP; and think what naive/simplistic/circuitous/wrong assumptions and models are doing to so-called 'scientific' observations/conclusions.

GIGO is REAL; and it has infested the literature/methodologies/conclusions from supposedly 'competent objective' astrophysicists/theorists/experimenters.

Time to 'purge' that GIGO; and RE-DO, RE-THINK, from reliable facts/principles.

Cheers. :)
Uncle Ira
3.8 / 5 (5) Feb 23, 2018
@ Really-Skippy. How you are Cher? I am good and getting better, thanks for asking.

Too many flaws to cover;
You been saying that thing for years.

It's all GIGO.
That is a new one to me. Is that one of the theories from the Earthman Playclub? GIGO, it has a nice ring to it, GIGO with Volumetrifications.
1 / 5 (1) Feb 25, 2018
Thisis an old claim of Reiss, and - unless I am mistaken - the peer review published paper makes none of the claims about discrepancies. It does make some other cosmological claims apart from the calibration based on very sparse data.

So nothing tangible here; maybe this will affect consensus, maybe not. Meanwhile the interesting first gravity wave distance measurement put the expansion value right in the middle of the purported discrepancy between the concatenated data (Planck) and the isolated supernova results (Reiss et al). But of course that data is even sparser as of yet.
3.7 / 5 (6) Feb 25, 2018
@bhj: "Have we determined that the expansion rate is equal in all directions yet?"

Interestingly, yes. The models are based on isotropy and that works. Even better, the cosmic background radiation reaches us from volumes that have been causally isolated by inflation, and they show the same background temperature to 10^-5 parts. (Mackita mistakenly describes the remaining fluctuations.)

@Osiris1, grandpa, ursiny, stein-age: "Take the center", " at the center", " started at a single point", "the edge".

Amazingly that so many do not understand the geometry of the universe [ https://en.wikipe...ceptions ]. The Hot Big Bang is a point in time, not in space, when inflation stopped and its potential energy was converted to hot matter.
3.7 / 5 (6) Feb 25, 2018
@RKS: "The original prediction was that expansion started out extremely fast and slowed. ... Researchers stuck to the old formula".

And so the expansion does, whereafter its rate goes up again. Even the pre-inflationary big bang models were good approximations for the first phase. The reason why we have inflationary big bang models is - obviously - because scientists did not stick to the old formula, albeit dark energy - the cosmological constant - *was* kept.
3.7 / 5 (6) Feb 25, 2018
@mackita:"It can be explained by dark matter surrounded by massive objects."

Obviously no; which is why you do not present a peer reviewed paper on that subject.

And that would not hold up against dark matter observations anyway, which include *all* dark matter and also exclude the baryonic content to a few percent at most.

"This is result of occupational driven attitude".

Of course it is, as it is meant to be. Did you think science, which gives us so much, was free? These things are often said; amazingly that so many do not understand the economics of science.

@BPF: " The universe is largely magnetic".

[Looks around the room:] Obviously no; which is why you do not present a peer reviewed paper on that subject.
not rated yet Feb 25, 2018
I wonder is there are large clusters out there that we cannot see due to the bending of light? They could be there but invisible because the light and radiation has been bent enough to miss our orbit.
not rated yet Feb 26, 2018
The trouble is you are setting constants with our frame of reference of time. whereas the time flow at any event further from the earth is not the same as on earth
5 / 5 (1) Feb 26, 2018
good article nonetheless
5 / 5 (4) Feb 26, 2018
The trouble is you are setting constants with our frame of reference of time. whereas the time flow at any event further from the earth is not the same as on earth

Time is not independent of space. Physicists talk about spacetime for a reason (and not "space and time"). If time were independent and flowed differently elsewhere this would be very obvious. At the very latest such a discrepancy was laid to rest with the latest neutrino merger data from LIGO (because the gravitational wave arrived exactly with the flash of radiation - as predicted by GR where spacetime behaves the same everywhere. If it didn't then there would have been a lag between the two)
5 / 5 (1) Feb 26, 2018
neutrino merger data

...that should be "neutron star merger", of course. Sorry.
3 / 5 (2) Feb 26, 2018
I have to agree with reality check. GIGO is garbage in garbage out. The only reliable form of distance calculation is parallax because it does not depend on red shift nor brightness. Unfortunately, it can only be used for objects within a few thousand light years.

The biggest assumption scientists make is that the universe is expanding. There is no question that everything is moving away from each other, but no reason this couldn't be from proper velocities rather than expanding space.
3 / 5 (2) Feb 27, 2018
The trouble is you are setting constants with our frame of reference of time. whereas the time flow at any event further from the earth is not the same as on earth

Time is not independent of space. Physicists talk about spacetime for a reason (and not "space and time"). If time were independent and flowed differently elsewhere this would be very obvious. At the very latest such a discrepancy was laid to rest with the latest neutrino merger data from LIGO (because the gravitational wave arrived exactly with the flash of radiation - as predicted by GR where spacetime behaves the same everywhere. If it didn't then there would have been a lag between the two)

so GW travelled at the speed of light? what bollocks. GR is all a load of sheites
not rated yet Apr 03, 2018

Hi, There is now a very simple way to calculate Hubble's Constant, by inputting to an equation, the numerical value of Pi and the speed of light (C) from Maxwell's equations. NO space probe measurements (with their inevitable small measuring / interpretation errors) are now required. Hubble's Constant is 'fixed' at 70.98047 PRECISELY. This maths method removes the errors / tolerances that is always a part of attempting to measuring something as 'elusive' as Hubble's Constant.
The equation to perform this can be found in 'The Principle of Astrogeometry' on Amazon Kindle Books, David.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.