Astronomically Large Lenses Measure the Age and Size of the Universe (w/ Video)

Mar 01, 2010
Oftentimes it is difficult for scientists to distinguish between a very bright light far away and a dimmer source lying much closer. A gravitational lens circumvents this problem by providing multiple clues as to the distance light travels. When a large nearby object, such as a galaxy, blocks a distant object, such as another galaxy, the light can detour around the blockage. But instead of taking a single path, light can bend around the object in one of two, or four different routes, thus doubling or quadrupling the amount of information scientists receive. As the brightness of the background galaxy nucleus fluctuates, physicists can measure the ebb and flow of light from the four distinct paths, such as in the B1608+656 system imaged above. Credit: Image courtesy of Sherry Suyu (University of Bonn)

(PhysOrg.com) -- Using entire galaxies as lenses to look at other galaxies, researchers have a newly precise way to measure the size and age of the universe and how rapidly it is expanding, on a par with other techniques. The measurement determines a value for the Hubble constant, which indicates the size of the universe, and confirms the age of the universe as 13.75 billion years old, within 170 million years. The results also confirm the strength of dark energy, responsible for accelerating the expansion of the universe.

These results, by researchers at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at the US Department of Energy's SLAC National Accelerator Laboratory and Stanford University, the University of Bonn, and other institutions in the United States and Germany, will be published in The in March. The researchers used data collected by the NASA/ESA , and showed the improved precision they provide in combination with the Wilkinson Microwave Anisotropy Probe (WMAP).

The team used a technique called to measure the distances traveled from a bright, active galaxy to the earth along different paths. By understanding the time it took to travel along each path and the effective speeds involved, researchers could infer not just how far away the galaxy lies but also the overall scale of the universe and some details of its expansion.

This video is not supported by your browser at this time.
Phil Marshall (KIPAC, SLAC/Stanford) demonstrates lensing using a wine glass. Credit: Video courtesy of Brad Plummer/Julie Karceski (SLAC).

Oftentimes it is difficult for scientists to distinguish between a very bright light far away and a dimmer source lying much closer. A gravitational lens circumvents this problem by providing multiple clues as to the distance light travels. That extra information allows them to determine the size of the universe, often expressed by astrophysicists in terms of a quantity called Hubble's constant.

"We've known for a long time that lensing is capable of making a physical measurement of Hubble's constant," KIPAC's Phil Marshall said. However, gravitational lensing had never before been used in such a precise way. This measurement provides an equally precise measurement of Hubble's constant as long-established tools such as observation of supernovae and the cosmic microwave background. "Gravitational lensing has come of age as a competitive tool in the astrophysicist's toolkit," Marshall said.

When a large nearby object, such as a galaxy, blocks a distant object, such as another galaxy, the light can detour around the blockage. But instead of taking a single path, light can bend around the object in one of two, or four different routes, thus doubling or quadrupling the amount of information scientists receive. As the brightness of the background galaxy nucleus fluctuates, physicists can measure the ebb and flow of light from the four distinct paths, such as in the B1608+656 system that was the subject of this study. Lead author on the study Sherry Suyu, from the University of Bonn, said, "In our case, there were four copies of the source, which appear as a ring of light around the gravitational lens."

Though researchers do not know when light left its source, they can still compare arrival times. Marshall likens it to four cars taking four different routes between places on opposite sides of a large city, such as Stanford University to Lick Observatory, through or around San Jose. And like automobiles facing traffic snarls, light can encounter delays, too.

"The traffic density in a big city is like the mass density in a lens galaxy," Marshall said. "If you take a longer route, it need not lead to a longer delay time. Sometimes the shorter distance is actually slower."

The gravitational lens equations account for all the variables such as distance and density, and provide a better idea of when light left the background galaxy and how far it traveled.

In the past, this method of distance estimation was plagued by errors, but physicists now believe it is comparable with other measurement methods. With this technique, the researchers have come up with a more accurate lensing-based value for Hubble's constant, and a better estimation of the uncertainty in that constant. By both reducing and understanding the size of error in calculations, they can achieve better estimations on the structure of the lens and the size of the universe.

There are several factors scientists still need to account for in determining distances with lenses. For example, dust in the lens can skew the results. The Hubble Space Telescope has infra-red filters useful for eliminating dust effects. The images also contain information about the number of galaxies lying around the line of vision; these contribute to the lensing effect at a level that needs to be taken into account.

Marshall says several groups are working on extending this research, both by finding new systems and further examining known lenses. Researchers are already aware of more than twenty other astronomical systems suitable for analysis with gravitational lensing.

Explore further: Monster galaxies gain weight by eating smaller neighbors

More information: Dissecting the Gravitational Lens B1608+656. II. Precision Measurements of the Hubble Constant, Spatial Curvature, and the Dark Energy Equation of State, The Astrophysical Journal, March 1, 2010. www.iop.org/EJ/abstract/0004-637X/711/1/201/

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richgibula
1.8 / 5 (5) Mar 01, 2010
So is it 13.75 billion light yrs to the center where the big bang occurred, or to the other side that expanded the other direction from us?
ShotmanMaslo
2.8 / 5 (9) Mar 01, 2010
There is no center of the big bang, the expansion is uniform, much like a surface of an inflating baloon.
Skeptic_Heretic
2 / 5 (4) Mar 01, 2010
So is it 13.75 billion light yrs to the center where the big bang occurred, or to the other side that expanded the other direction from us?

The entire Universe is where the big bang happened.

Space-time is a component of the bang bang as opposed to being the area into which the big bang expanded.

Basically the center of the big bang is the outer limit of our existence.
SincerelyTwo
2 / 5 (1) Mar 01, 2010
ShotmanMaslo, there is a center, it's just a function of space-time and not space in itself. In the analogy of the balloon, if you mark dots while it's deflated you can then observe how the dots move away from each other as the balloon inflates. The action of the balloon being inflated represents time (3D + 1D (4D?)).
Skeptic_Heretic
1 / 5 (1) Mar 01, 2010
ST,

You're making a dangerous assumption that time and causality can exist without cause. Don't go all neo-creationist on us, Hawking's biggest cop out.
Husky
3 / 5 (2) Mar 01, 2010
Still I wonder, if you had a telescope in orbit around the most distant object we have seen would you still see yet another 13 billion lightyears all around with galaxies? wich would indicate objects exist further from earth in spacetime than the supposed age of the universe

or part of this 360 view be an empty quadrant? wich would indicate some edge of the universe
frajo
1 / 5 (2) Mar 01, 2010
but physicists now believe it is comparable with other measurement methods
That's true.
They only should have mentioned that the accuracy of the other measurement methods is not exactly that famous "astronomical accuracy" which allows us to tell the positions of the planets of our local star system as they have been seen in ancient Egypt, for instance.
retrosurf
not rated yet Mar 01, 2010
So is it 13.75 billion light yrs to the center where the big bang occurred, or to the other side that expanded the other direction from us?


Neither. Sorry.
richgibula
not rated yet Mar 01, 2010
If the universe expands everywhere, where is it expanding from? In the balloon analogy, as you deflate, the dots get closer to each other. There would be a hypothetical point where the dots would meet.
Question
5 / 5 (1) Mar 01, 2010
If a Big Bang really happened and the balloon analogy correctly describes today's universe, where is the giant empty void in the center of the universe where the Big Bang originated from?
SincerelyTwo
not rated yet Mar 01, 2010
Skeptic_Heretic,

Really? It seems reasonable to assume that if things are moving apart over time, then in reverse they'd be moving closer together.

... am I missing something?

richgibula; In that balloon analogy we *are* one of the dots, and we are in space expanding everywhere. We already are inside the singularity at all times, the singularity just expanded, significantly.

Imagine deflating a balloon until even it's rubber mass is forced in to a single point. All of that balloon is inside the single point, and as it expands it is itself, the entire balloon.

We are always the singularity! Lulz... (ok not REALLY, we're only a singularity when we all occupy the same infinitely small volume?)

Better put; There is no location of the singularity, the volume of it is everything around us.

There is no 'position' where the singularity started, the balloon analogy fails in that aspect.
nevermark
1 / 5 (1) Mar 02, 2010
@richgibula, @Question,

Space expanding is different from anything else expanding. It does not have to expand "from" somewhere. For instance, in the game Asteroids objects going off one side smoothly show up on the other. This is an unbounded yet finite space, like our own. There are no "edges" for the asteroids and spaceship. (The screen edges we see are artifacts of how we are viewing the little universe, not the universe itself.)

Now imagine the size of the screen grows. For the inhabitants of the Asteroid universe, space is getting larger, yet it is not growing from any one place.

Also note that there is no empty void. The growing balloon analogy is a good illustration but like all analogies breaks down.

Our universe is similar, except instead of 2 dimension increasing according to the time dimension, we have 3 dimensions growing. And the topology of our universe is "bumpy" compared to the flat Asteroids universe, by all the masses in it warping space and time.
Temple
3 / 5 (2) Mar 02, 2010
Still I wonder, if you had a telescope in orbit around the most distant object we have seen would you still see yet another 13 billion lightyears all around with galaxies?


The universe is larger than 13.75 billion light-years in every direction away from us. Current calculations show that the furthest objects we've seen are 13.75 billion years old, but since space has been constantly expanding behind the photons over that time, these objects are now over 45 billion light-years away.

So, we see ourselves in the centre of a sphere which is over 90 billion light-years in diameter, and since we don't assume we're in the 'centre' of the universe, we assume the universe is (much!) bigger. When we look just to the side of the oldest object, we only see the light from the Big Bang itself, because the further we look, the further back in time we see.

That light from the Big Bang is incredibly redshifted and faint due to the universe's expansion, it's the Cosmic Background Radiation.
nevermark
2.3 / 5 (3) Mar 02, 2010
It is mind boggling how big the actual universe might be. According to the theory of cosmic inflation (which explains how the universe got to be so flat despite quantum fluctuations that would have misshaped the universe when it was very small) the actual universe is now 10^23 to 10^26 times as large as the observable universe, which would mean roughly 10^34 to 10^37 light years in circumference.

There simply isn't any way to imagine something that large or how many galaxies, stars or varieties of lifeforms that could exist in it.

And there is the distinct possibility that the big bang was an offshoot of some greater reality. Our current physics isn't good enough at this point to do more than suggest many possibilities, none of which may match the strangeness of the truth!
Skeptic_Heretic
1 / 5 (1) Mar 02, 2010
Skeptic_Heretic,

Really? It seems reasonable to assume that if things are moving apart over time, then in reverse they'd be moving closer together.

... am I missing something?

Yes, evidence for the intial state in existence prior to time.

You're assuming time can be decoupled from our existence rather than time being a byproduct of our existence. Neither your stance nor mine on the issue can be determined to be correct and so stating generally that the expansion of the universe itself represents time is false.
richgibula
not rated yet Mar 02, 2010
So, what is the approximate shape of the visible universe? Is there a overall model somewhere to look at?
nevermark
3.7 / 5 (3) Mar 02, 2010
The universe appears "flat" within 2% as far as we can see. Aside from local warping due to galaxies, space is almost Newtonian, like space in our every day lives.

The global shape of the universe beyond what we can see is unknown. It may also be flat. If so it can be imagined like an expanding 3D sphere, where opposite edges are "connected" and not really edges at all. So leaving one side of the sphere would take you to the other without any perception of crossing an "edge" since there really isn't one. (The edge is just in our visualization.)

Space is growing faster than the speed of light, so there are points moving away faster than light even if you move towards them at (or nearly) the speed of light. So for any inhabitant, there is a sphere of observability, and within that a sphere or reachability.

The observable boundary is how far we look before seeing the universe's beginning in all directions. The reachability boundary does not look special and has to be calculated.
yyz
5 / 5 (2) Mar 03, 2010
A fascinating (free) paper on this spectacular system is available here: http://www.astro....08H0.pdf (w-annotated illustrations).

Just an incredible astrophysical object :)
yyz
5 / 5 (1) Mar 05, 2010
Speaking of strong lensing, the first strongly-lensing quasar has been found! Details at: http://arxiv.org/...2.4991v1 . The authors state that this is just the beginning in the search for strong lensing QSOs.