Explore further: Astronomers measure universe expansion, get hints of 'new physics' (Update)Posted on 01/22/2019 2:38:36 PM PST by ETL
The question of how quickly the universe is expanding has been bugging astronomers for almost a century. Different studies keep coming up with different answers—which has some researchers wondering if they've overlooked a key mechanism in the machinery that drives the cosmos.
Now, by pioneering a new way to measure how quickly the cosmos is expanding, a team led by UCLA astronomers has taken a step toward resolving the debate. The group's research is published today in Monthly Notices of the Royal Astronomical Society.
At the heart of the dispute is the Hubble constant, a number that relates distances to the redshifts of galaxies—the amount that light is stretched as it travels to Earth through the expanding universe. Estimates for the Hubble constant range from about 67 to 73 kilometers per second per megaparsec, meaning that two points in space 1 megaparsec apart (the equivalent of 3.26 million light-years) are racing away from each other at a speed between 67 and 73 kilometers per second.
"The Hubble constant anchors the physical scale of the universe," said Simon Birrer, a UCLA postdoctoral scholar and lead author of the study. Without a precise value for the Hubble constant, astronomers can't accurately determine the sizes of remote galaxies, the age of the universe or the expansion history of the cosmos.
Most methods for deriving the Hubble constant have two ingredients: a distance to some source of light and that light source's redshift. Looking for a light source that had not been used in other scientists' calculations, Birrer and colleagues turned to quasars, fountains of radiation that are powered by gargantuan black holes. And for their research, the scientists chose one specific subset of quasars—those whose light has been bent by the gravity of an intervening galaxy, which produces two side-by-side images of the quasar on the sky.
Light from the two images takes different routes to Earth. When the quasar's brightness fluctuates, the two images flicker one after another, rather than at the same time. The delay in time between those two flickers, along with information about the meddling galaxy's gravitational field, can be used to trace the light's journey and deduce the distances from Earth to both the quasar and the foreground galaxy. Knowing the redshifts of the quasar and galaxy enabled the scientists to estimate how quickly the universe is expanding.
The UCLA team, as part of the international H0liCOW collaboration, had previously applied the technique to study quadruply imaged quasars, in which four images of a quasar appear around a foreground galaxy. But quadruple images are not nearly as common—double-image quasars are thought to be about five times as abundant as the quadruple ones.
To demonstrate the technique, the UCLA-led team studied a doubly imaged quasar known as SDSS J1206+4332; they relied on data from the Hubble Space Telescope, the Gemini and W.M. Keck observatories, and from the Cosmological Monitoring of Gravitational Lenses, or COSMOGRAIL, network—a program managed by Switzerland's Ecole Polytechnique Federale de Lausanne that is aimed at determining the Hubble constant.
Tommaso Treu, a UCLA professor of physics and astronomy and the paper's senior author, said the researchers took images of the quasar every day for several years to precisely measure the time delay between the images. Then, to get the best estimate possible of the Hubble constant, they combined the data gathered on that quasar with data that had previously been gathered by their H0liCOW collaboration on three quadruply imaged quasars.
"The beauty of this measurement is that it's highly complementary to and independent of others," Treu said.
The UCLA-led team came up with an estimate for the Hubble constant of about 72.5 kilometers per second per megaparsec, a figure in line with what other scientists had determined in research that used distances to supernovas—exploding stars in remote galaxies—as the key measurement. However, both estimates are about 8 percent higher than one that relies on a faint glow from all over the sky called the cosmic microwave background, a relic from 380,000 years after the Big Bang, when light traveled freely through space for the first time.
"If there is an actual difference between those values, it means the universe is a little more complicated," Treu said.
On the other hand, Treu said, it could also be that one measurement—or all three—are wrong.
The researchers are now looking for more quasars to improve the precision of their Hubble constant measurement. Treu said one of the most important lessons of the new paper is that doubly imaged quasars give scientists many more useful light sources for their Hubble constant calculations. For now, though, the UCLA-led team is focusing its research on 40 quadruply imaged quasars, because of their potential to provide even more useful information than doubly imaged ones.
Explore further: Astronomers measure universe expansion, get hints of 'new physics' (Update)
More information: S Birrer et al. H0LiCOW - IX. Cosmographic analysis of the doubly imaged quasar SDSS 1206+4332 and a new measurement of the Hubble constant, Monthly Notices of the Royal Astronomical Society (2019). DOI: 10.1093/mnras/stz200
Journal reference: Monthly Notices of the Royal Astronomical Society 
The Hubble Constant is the unit of measurement used to describe the expansion [rate] of the universe. The cosmos has been getting bigger since the Big Bang kick-started the growth about 13.82 billion years ago. [I]n fact, it's getting faster in its acceleration as it gets bigger.
What's interesting about the expansion is not only the rate, but also the implications, according to NASA. If the expansion begins to slow down, that implies that there is something in the universe that is making the growth slow down — perhaps dark matter, which can't be sensed with conventional instruments. If the growth gets faster, though, it's possible that dark energy is pushing the expansion faster.
As of January 2018, measurements from multiple telescopes showed that the rate of expansion of the universe is different depending on where you look.
The nearby universe (measured by the Hubble Space Telescope and Gaia space telescope) has a rate of expansion of 45.6 miles per second per megaparsec, while the more distant background universe (measured by the Planck telescope) is a bit slower, expanding at 41.6 miles per second per megaparsec. A megaparsec is a million parsecs, or about 3.3 million light-years, so this is almost unimaginably fast.
Discovery by Hubble
The constant was first proposed by Edwin Hubble (the namesake for the Hubble Space Telescope). Hubble was an American astronomer who studied galaxies, particularly those that are far away from us.
In 1929 — based on a realization from astronomer Harlow Shapley that galaxies appear to be moving away from the Milky Way — Hubble found that the farther these galaxies are from Earth, the faster they appear to be moving, according to NASA.
While scientists then understood the phenomenon to be galaxies moving away from each other, today astronomers know that what is actually being observed is the expansion of the universe. No matter where you are located in the cosmos, you would see the same phenomenon happening at the same speed.
Hubble's initial calculations have been refined over the years, as more and more sensitive telescopes have been used to make the measurements, including Hubble and Gaia (which examined a kind of variable star called Cepheid variables) and other telescopes that extrapolated the constant based on measurements of the cosmic microwave background — a constant background temperature in the universe that is sometimes called the "afterglow" of the Big Bang. ..."
Big Bang Bing, i mean, Big Bang Ping!
As I sit in my recliner pondering the speed of the earth around the sun which in turn is in rotation through the galaxy which in turn is speeding through the universe, I figure added all up I’m going about a million miles per hour which explains why I feel so tired at my age.
That speed is ~66,000 miles per hour (18 miles per second).
So if anyone nags you about sitting in your chair all day, "not going anywhere", show them this.
There are 3,600 seconds in an hour.
That's 18 x 3,600 MILES you've traveled every hour you were sitting on your butt!
wonder if the Comma of Pythagoras fits into this theory?
H0LiCOW == H0 [abbreviation for Hubble constant] Lenses in COSMOGRAIL’s Wellspring
Phil Rizzuto could not be reached for comment…
From the Universe’s perspective, I understand we are all traveling 1.3 million mph, give or take...
Light from the two images takes different routes to Earth. When the quasar’s brightness fluctuates, the two images flicker one after another, rather than at the same time. The delay in time between those two flickers, along with information about the meddling galaxy’s gravitational field, can be used to trace the light’s journey and deduce the distances from Earth to both the quasar and the foreground galaxy. Knowing the redshifts of the quasar and galaxy enabled the scientists to estimate how quickly the universe is expanding.
...
Clever. I wish I would have thought of it.
They say that there is no one, universal reference frame by which to calculate "absolute" velocity, or position. However, the Colby Cosmic Microwave Background *may* be such a reference frame. Within it we can see the movement of our Milky Way galaxy.
I think you are asking if the Cosmic Microwave Background (CMB) can be used as an absolute frame of reference for the objects in the universe.
Over a period of observational years we can get an idea on the density of the CMB to create an image like this:
However, this is an accumulation of samples that have reached us during the few decades we have known the CMB was there and recorded it. If you are looking at a GRB 5 billion light years away or a type II super nova 300 million light years away you are getting a high resolution image of a specific local event that happened 5 B or 300 M years ago. But the CMB is everywhere in the observable universe and faint at about 2.73 K.
We can make some assumptions based on CMB we can see now, but between expansion, gravitation effects, and time we can not rely on the CMB as being a absolute reference frame, as what we can see now does not necessarily indicate what changes the CMB is going through the farther away it is.
So the CMB is A frame of reference, but not THE frame of reference. As shown by Special Relativity, every frame of reference is equally valid. So if you are observing from different relativistic reference positions the CMB is going to appear to have very different wavelength, directions, etc. The following is a image showing red shifting and blue shifting of CMB reaching our detectors…its obvious the CMB is not simply spreading symmetrically from a “central point”.
CMB red and blue shifting, density, rotation are going to tell us more about relatively local areas of space, ie. the rotation of our galaxy or Andromeda and the Milky Way moving towards each other at a closing speed of ~ 110 km/s, but the farther away an object is the less information the CMB can tell us about that object’s relative motion to it.
Bottom line: CMB is a useful frame of reference but not an absolute frame of reference that would allow us to pretend that it is THE resting position of the universe. Areas of the CMB are in motion relative to other areas of the CMB, even after accounting the fact each part of it is moving at c.
https://www.quora.com/Why-cant-the-CMB-be-a-universal-reference-frame
From the CMB data it is seen that the earth appears to be moving at 368±2 km/s relative to the reference frame of the CMB (also called the CMB rest frame, or the frame of reference in which there is no motion through the CMB).[84]
The Local Group (the galaxy group that includes the Milky Way galaxy) appears to be moving at 627±22 km/s in the direction of galactic longitude l = 276°±3°, b = 30°±3°.[85][86]
This motion results in an anisotropy of the data (CMB appearing slightly warmer in the direction of movement than in the opposite direction).[87]
From a theoretical point of view, the existence of a CMB rest frame breaks Lorentz invariance even in empty space far away from any galaxy.[88]
The standard interpretation of this temperature variation is a simple velocity red shift and blue shift due to motion relative to the CMB, but alternative cosmological models can explain some fraction of the observed dipole temperature distribution in the CMB.[89]
https://en.wikipedia.org/wiki/Cosmic_microwave_background#CMBR_dipole_anisotropy
Thanks ETL.
Interesting, but will take time to digest that!
I think my 1.3 mil is from a vsauce episode :-)
Good info, thanks. God must be amused and pleased at the efforts to understand His Creation. He certainly has a great sense of humor.
their H0liCOW collaboration
Not only that, but the absolute direction and speed of the planet’s motion is measured by the Doppler shift of the cosmic background radiation.
Lensing galaxies are a relatively new discovery. The newspapers reported astronomers finding McDonald’s arches in the galaxy, and couldn’t figure it out for a while.
Thanks ETL, bfl.
Thanks ETL.
Woo Hoo! I can eat that pizza now!
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.