Astronomers discover new way to measure Universe

September 27, 2011, Niels Bohr Institute
Every galaxy has a supermassive black hole at its heart, millions to billions of times the mass of the Sun. When these dark hearts of galaxies actively accrete matter they become incredibly bright. These are quasars, and they outshine everything else in the universe.

( -- Astronomers at Copenhagen's Niels Bohr Institute have found a new way to measure distances. This may not sound like much, but working out how far away something is, is one of the toughest fundamental problems in astrophysics and is central to cosmology as it allows scientists to work out the age of the Universe and what it’s fundamental properties are. Because their new method uses quasars, some of the brightest objects known, scientists say they will be able to determine distances much further than achieved to date, paving the way to a better understanding of dark energy.

Finding new ways to measure cosmic distances has a strong pedigree in . In the 1990s a way was discovered to use supernovae, the explosions of massive stars, to measure distances. From that finding stemmed the discovery of the acceleration of the in 1998, which showed that 70% of the Universe was made up of .

Now, Dr. Darach Watson and colleagues have discovered a way to find accurate distances using quasars. Quasars are powered by the supermassive black holes at the hearts of galaxies, and are so luminous that they can vastly outshine all the stars in their host galaxy combined. Due to their extreme luminosity, scientists have been searching for ways to use them to measure distances since they were discovered in the 1960s. After more than four decades, those attempts have finally been successful.

“It was a discovery waiting to happen,” says Dr. Kelly Denney, a member of the team. It has been known for some time that the size of the gas cloud falling into the supermassive black hole is related to the luminosity of the quasar. Watson and colleagues realised that new data on the sizes of gas clouds that were being measured for other reasons were now accurate enough to allow them to predict the luminosities of the quasars. Knowing how bright the quasars appeared from earth, they could easily determine how far away they were.

Quasars can be detected to very large distances, much farther than supernovae, which are currently the best measure of distance. “That’s what makes quasars so exciting,” says Watson, “seeing farther away means seeing farther back in time, and knowing how the universe expanded with time is the key to understanding dark energy.” Being able to measure the universe accurately at great distances will have profound implications for scientists’ future understanding of dark energy and the ultimate fate of the cosmos.

Explore further: Discovery that quasars don't show time dilation mystifies astronomers

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2.3 / 5 (14) Sep 27, 2011
Ok, so how do they measure the sizes of the gas clouds at such huge distances?

Yeah, yet another circular logic measuring tool.

You can't very well know the absolute size of something unless you already know it's distance very well to begin with, else you could be mislead by illusions in depth perception or other properties of the surrounding environment.

The quality of these articles just seems to get worse and worse:

"We improved technology A," but no citation of data on how much.

"We improved this measurement or made a new measurement technique," but no real information on how those assumptions are made in the first place, nor how anyone would verify the assumptions are correct...

This isn't really even a scientific endeavor, since you can't manually test the method, and at best you have circumstancial, circular reasoning to agree with itself.

It's more a guesstimate than science, particularly since galaxy size and age varies from one to the next anyway.
1 / 5 (17) Sep 27, 2011
Every galaxy has a supermassive black hole at its heart, millions to billions of times the mass of the Sun. When these dark hearts of galaxies actively accrete matter they become incredibly bright. These are quasars, and they outshine everything else in the universe.

1. Fragmentation of these central, compact objects powers the universe as it expands [Neutron Repulsion].

2. Reformation of a central, compact object is the result when the universe collapses [Gravitational Attraction].

Competition between Neutron Repulsion and Gravitational Attraction sustains our infinite and dynamic universe - the Great Reality (God, Cosmos, etc) that surrounds us and supports life.

"Is the Universe Expanding?" The Journal of Cosmology 13, 4187-4190 (2011)

With kind regards,
Oliver K. Manuel
Research career (1961-2011)

5 / 5 (20) Sep 27, 2011
The size of the infalling gas cloud is measured using a technique called reverberation mapping. In a nutshell, they're using light echoes to "see" the size of the cloud.

They observe the nuclear continuum (in X-rays), which tells them about the inner part of the accretion disk. This probes very close to the central supermassive black hole. They notice some variation in brightness. Let's say there is a flare-up for some reason here.

After some time, in infalling gas cloud will show the exact same variation, just delayed in time. It takes time for the light near the black hole to travel out to this gas cloud. The cloud then absorbs and re-emits the light or simply reflects the light towards us. Since it is these simple processes that give off the light from the gas cloud, the brightness near the black hole directly affects the brightness we see from the gas cloud.

The time delay is the light travel time between the central black hole and the gas cloud. Distance is c*(time delay).
5 / 5 (16) Sep 27, 2011
Of course, at cosmological distances, things are naturally complicated a bit. So we need an approximate handle on the distance already. We get that simply from the cosmological redshift (z). This is gotten from various atomic emission lines, which are very plentiful in the spectra of galaxies.

Due to the expansion of the universe, times are dilated by a factor (1 z). But uncertainty in the value of "z" contributes only proportionally to the uncertainty in the absolute distance, and we can measure emission/absorption lines to about the angstrom level (10^{-10} m).

So this is an exciting piece of news. The authors hope to accurately measure the distances to galaxies around 10 billion light years distant.
1.7 / 5 (9) Sep 27, 2011

How do you account for effects like gravitational time dilations and length contraction effects inside the galaxy unless you already know the mass of the galaxy AND the distribution of said mass within the galaxy?

Galaxies are so big that it takes around 100,000 years for light to cross it's diameter just one time, and how would you know the exact amount of time for light to cross among clouds of gases if you don't know the correct values PRECISELY for effects such as time dilation?

You're still left needing to guess or just make an assumption at some point.
5 / 5 (18) Sep 27, 2011
Well, fortunately, the light only has to travel some light days or light months, as opposed to 100,000 ly. And even the emission from the inner part of the accretion disk is fairly far from the center of the black hole.

These supermassive black holes are enormous. The size of a black hole with the mass of the sun is about 3 km and black holes scale directly with the mass. These black holes can up to 10^{10} times the mass of the sun. And all the mass is concentrated at the very center. So even the inner accretion disk is perhaps billions of km from the singularity.

At these distances, gravity is quite weak, and we can very easily justify using simple Newtonian formulas. This means that there is basically no gravitational time dilation between the inner accretion disk and the gas clouds we are measuring.

And we are concerned with perhaps a light month, which is a tiny fraction of the galaxy. Other relativistic effects do not manifest because we are of what we are measuring.
5 / 5 (2) Sep 27, 2011
It would be interesting to correlate distance measurements obtained with this method with the current standard using supernovae, to see to what extent they're in agreement.
not rated yet Sep 28, 2011
before measuring the size of universe first decide .."what exactly universe is" ! ..just group of few galaxies doesn't mean the universe ..
4 / 5 (4) Sep 28, 2011
before measuring the size of universe first decide .."what exactly universe is" ! ..just group of few galaxies doesn't mean the universe ..

The universe is what we can see and what we can infer from what we see.
1.7 / 5 (3) Sep 28, 2011
A problem of the new method

It has been observed recently, at the case of more distant galaxies their black holes are relatively larger than at the case of the more close ones. This effect is easy to explain with dense aether theory - but it could bring a bias into measurements at very distant scope with the above method.
not rated yet Sep 28, 2011
"It has been observed recently, at the case of more distant galaxies their black holes are relatively larger than at the case of the more close ones."

Where? Not in those links.

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