Cosmology Archives

April 16, 2008December 24, 2015 by Ian O'Neill

Galactic Ghosts Haunt Their Killers

Image of the stellar tidal stream surrounding the spiral galaxy NGC 5907 obtained with an amateur robotic telescope in the mountains of New Mexico. (R. Jay Gabany)

The title may sound dramatic, but it is very descriptive. New observations of two galaxies have shown huge streams of stars, not belonging inside those galaxies, reaching out into space. These streams are all that are left of galaxies that are now dead, eaten by their cannibal neighbour, now sitting in their place. The streams form an eerie halo around their killers, looking like ghosts of their former selves…

So what happened to these ill-fated galaxies? Galactic cannibalism is what happened. In both examples, large spiral galaxies have overrun smaller dwarf galaxies, devouring most of their stars. All that is left are the huge fossilized remains in the form of a tenuous distribution of dim, old, metal-poor stars. Judging by the lack of galactic structure in these “ghosts”, the cannibalizing spiral galaxies have been very efficient at eating their smaller dwarf cousins.

The debris surrounding NGC 5907 (approximately 40 million light-years from Earth) extends 150,000 light-years across (pictured top). NGC 5907 destroyed one of its dwarf satellite galaxies at least 4,000 million years ago, consuming the stars, star clusters and dark matter, leaving only a small number of old stars behind to form a complicated criss-cross pattern of galactic fossils.

“Our results provide a fresh insight into this spectacular phenomenon surrounding spiral galaxies and show that haloes contain fossil dwarf galaxies, thus providing us with a unique opportunity to study the final stages in the assembly of galaxies like ours.” – David MartÃnez, from the Instituto de AstrofÃsica de Canarias (IAC) leading the team that carried out these observations.

In the second spiral galaxy, NGC 4013 (50 million light-years from Earth in the constellation of Ursa Major), the ghost of another dead dwarf galaxy stretches 80,000 light-years across and is made up of old stars. Its 3D geometry is unknown, but it has similar characteristics to the Monoceros tidal stream which surrounds the Milky Way. The Monoceros tidal stream is a ring of stars, originating from a local dwarf galaxy that was eaten by our galaxy over 3,000 million years ago.

These images have a huge amount of science to offer researchers. Primarily, the detection of these galactic fossils confirms the predictions of the cold dark matter model of cosmology, which describes how the large spiral galaxies were formed from merging stellar systems.

“…fitting theoretical models to these star streams enables us to reconstruct their history and describe one of the most mysterious and controversial components of galaxies: dark matter.” – Jorge PeÃ±arrubia, theoretical astrophysicist at the University of Victoria (Canada) who is working on this project.

Source: IAC

April 14, 2008December 24, 2015 by Ian O'Neill

What was Before the Big Bang? An Identical, Reversed Universe

The Big Bounce Theory — Graphic of the Big Bounce concept (Relativity4Engineers.com)

So what did exist before the Big Bang? This question would normally belong in the realms of deep philosophical thinking; the laws of physics have no right to probe beyond the Big Bang barrier. There can be no understanding of what was there before. We have no experience, no observational capability and no way of travelling back through it (we can’t even calculate it), so how can physicists even begin to think they can answer this question? Well, a new study of Loop Quantum Gravity (LQG) is challenging this view, perhaps there is a way of looking into the pre-Big Bang “universe”. And the conclusion? The Big Bang was more of a “Big Bounce”, and the pre-bounce universe had the same physics as our universe… just backwards… Confused? I am…

LQG is a tough theory to put into words, but it basically addresses the problems associated with the incompatibilities behind quantum theory and general relativity, two crucial theories that characterize our universe. If these two theories are not compatible with each other, the search for the “Theory Of Everything” will be hindered, disallowing gravity to merge with the “Grand Unified Theory” (a.k.a. the electronuclear force). LQG quantizes gravity, thereby providing a possible explanation for gravity and a possible key to unlocking the Theory Of Everything. However, from the outset, LQG has many critics as there is little direct or indirect evidence backing up the theory.

See the previous Universe Today article on Loop Quantum Gravity»

Regardless, much work is being done into this area of research. The primary consequence to come from LQG is that it predicts that the Big Bang which occurred 13.7 billion years ago was actually a “Big Bounce”; our universe is therefore the product of a contracting universe before the Big Bang. The previous universe (or our universe “twin”) contracted to a single point (which could be interpreted as a “Big Crunch”) and then rebounded in a Big Bounce to produce the Big Bang as we’ve learned to accept as the birth of the universe as we know it. But until now, although the pre-bounce universe has been predicted, its characteristics could not be known. No information about the pre-bounce universe could be observed in today’s universe, the Big Bounce causes a “cosmic amnesia”, destroying all information of the previous universe.

Now, physicists Alejandro Corichi from Universidad Nacional AutÃ³noma de MÃ©xico and Parampreet Singh from the Perimeter Institute for Theoretical Physics in Ontario are working on a simplified Loop Quantum Gravity (sLQG) theory where they approximate the value of the “quantum constraint”, a key equation in the LQG theory. What happens next is a little surprising. From their calculations, it would appear that a universe, identical to our own, with identical mechanics, existed before the Big Bounce.

“…the twin universe will have the same laws of physics and, in particular, the same notion of time as in ours. The laws of physics will not change because the evolution is always unitary, which is the nicest way a quantum system can evolve. In our analogy, it will look identical to its twin when seen from afar; one could not distinguish them.” – Parampreet Singh

We are not talking about an alternate dimension; we are talking about an identical universe with the same space-time and quantum characteristics as our own. If we look at our universe now (13.7 billion years post-bounce), it would be identical to the universe 13.7 billion years before the Big Bounce. The only difference being the direction of time would be opposite; the pre-bounce universe would be reversed.

“In the universe before the bounce, all the general features will be the same. It will follow the same dynamical equations, the Einstein’s equations when the universe is large. Our model predicts that this happens when the universe becomes of the order 100 times larger than the Planck size. Further, the matter content will be the same, and it will have the same evolution. Since the pre-bounce universe is contracting, it will look as if we were looking at ours backward in time.” – Parampreet Singh

Analysing what happened before the Big Bang is only part of the story. By making this approximation of a key LQG equation, Singh and Corichi are working on models where galaxies and other physical structures leave an imprint in the pre-bounce universe to influence the post-bounce universe. Would these structures be distributed in similar ways? Will the structures in one universe be similar or identical to structures in the other universe? There may also be an opportunity to look into the future of this universe and predict whether the conditions are right for another Big Bounce (once can imagine repeated bounces, producing a cycle of universes).

For now, this research is highly theoretical and any observational evidence will remain sparse for the time being. Although this is the case, it does begin to probe the big question and may push physics a bit closer toward describing what existed before the Big Bang…

Source: Physorg.com

April 2, 2008December 24, 2015 by Ian O'Neill

Lumpy Neutron Stars can Generate Gravitational Waves

A new simulation of neutron stars suggest they may not be as smooth as predicted. The rapidly spinning exotic bodies may have significant topological features like mountains. These “lumps” on the star’s surface may cause fluctuations in space-time as the variation of the huge gravitational field varies on each spin. This fluctuation may generate gravitational waves, propagating into the cosmos, and could be detected here on Earth…

Neutron stars are the remnants of massive stars after they have exploded as supernovae. The dense core remains behind, spinning fast and composed of only neutrons. They have immense gravitational fields and thought to have as much mass as our Sun, but measuring only 20 kilometres across. As they conserve the angular momentum of their massive sun predecessor, as they are so small, they are expected to spin hundreds of times per second.

But how can these strange objects be detected? Well, for one, they may be seen as highly radiating pulsars (or, possibly, “magnetars“), flashing a beam of radiation past the Earth asÂ they spinÂ like a lighthouse, beams of high energy photons emitted from the neutron star’s poles. But what about the effect they have on space-time? Can these massive bodies create gravitational waves? (Note: A gravitational wave is a totally different creature from an atmospheric “gravity wave“.)

To picture the scene: Imagine spinning a perfectly spherical ball in a swimming pool. If the ball is perfectly stationary (not bobbing up and down and not drifting), only spinning on its axis, no ripples in the pool will be seen. Therefore, any instrument measuring ripples in the pool will not detect the presence of the spinning ball. Now spin an object not spherical (like a rugby ball, or an American football) in the pool. As this object spins, the irregularities on the surface (i.e. the pointed ends) will produce a wave on each revolution of the irregular object. The ripple instrument will detect the presence of the ball in the pool.

This is the issue facing scientists trying to detect gravitational waves from neutron stars. If they are smooth objects (perhaps spherical, or slightly flattened due to the spin), they cannot produce ripples in space-time and therefore cannot be detected. If, on the other hand, they are irregularly-shaped spinning bodies, with inhomogeneities (lumps or “mountains”) on the surface, gravitational waves may be generated. The lump will sweep out a fluctuation in space-time on each rotation. This is fine, but are neutron stars lumpy?

Well, the outlook isn’t very good. The space-time “ripple” detectors set out to observe gravitational waves have so far not detected any sign of these rapidly spinning neutron stars. This could either mean that the technology we are using is not sensitive enough to detect gravitational waves or that neutron stars are naturally smooth and cannot produce gravitational waves in the first place.

Matthias Vigelius and Andrew Melatos, researchers from University of Melbourne in Australia, think they have new hope that some types of neutron star might be detected as they are naturally lumpy. Using a new computer modelling technique, the pair believes that even a small variation in the neutron star surface will produce detectable gravitational waves. But how do these lumps form? Often, stars evolve as part of a binary system (i.e. two stars orbiting a common centre of gravity), should one die as a supernova, leaving a neutron star behind, the intense gravitational field will strip its companion star of its gases. As the gas is funnelled into the neutron star, the intense magnetic field will give structural support to the incoming gas, creating an electron-proton mix of superheated plasma sitting on top of the neutron star surface. The lumps formed at the neutron star’s magnetic poles will be a long-living feature, sweeping around the star each time it rotates. Vigelius and Melatos think that detectors such as the Laser Interferometer Gravitational-Wave Observatory (LIGO) may be able to detect this characteristic signature of an irregularly shaped neutron star…. in time.

As yet, these “lumpy” neutron stars have not been detected, but through continued observation (exposure time), it is hoped that Earth-based gravitational wave observatories may eventually receive the signal.

Source: RAS, New Scientist

April 1, 2008December 24, 2015 by Tammy Plotner

Old Galaxies Stick Together In A Young Universe

Can appearances be deceiving? According to the United Kingdom Infra-Red Telescope (UKIRT), galaxies that appear old in our Universe’s early history are positioned in huge clouds of dark matter. Using the most sensitive images ever taken, UKIRT scientists believe these galaxies will evolve into the most massive yet known.

Today University of Nottingham PhD student Will Hartley is speaking to the Royal Astronomical Society’s National Astronomy Meeting in Belfast. As the leader of the study, Hartley proposes the distant galaxies identified in the UKIRT images are considered elderly from their content of old, red stars. Because these systems are nearly 10 billion light years distant, the images are as the galaxies appeared about 4 billion years after the Big Bang. Fully evolved galaxies at that point in time are hard to explain and the answer has been puzzling astronomers who study galactic formation and evolution.

Hartley and his team used the deep UKIRT images to estimate the mass of the dark matter formed in a halo surrounding the old galaxies – a halo which collapses under its own gravity to form a even distribution of matter. By measuring their ability to form galactic clusters, astronomers can get a better sense of what causes older galaxies to stick together.

Hartley explains “Luckily, even if we don’t know what dark matter is, we can understand how gravity will affect it and make it clump together. We can see that the old, red galaxies clump together far more strongly than the young, blue galaxies, so we know that their invisible dark matter halos must be more massive.

The halos of dark matter surrounding the old galaxies in the early Universe are found to be extremely massive, containing material which is one hundred thousand billion times the mass of our Sun. In the nearby Universe, halos of this size are known to contain giant elliptical galaxies, the largest galaxies known.

“This provides a direct link to the present day Universe,” says Hartley, “and tell us that these distant old galaxies must evolve into the most massive but more familiar elliptical-shaped galaxies we see around us today. Understanding how these enormous elliptical galaxies formed is one of the biggest open questions in modern astronomy and this is an important step in comprehending their history.”

March 28, 2008May 8, 2017 by Fraser Cain

Why There’s More Matter Than Antimatter in the Universe

In the first few moments of the Universe, enormous amounts of both matter and antimatter were created, and then moments later combined and annihilated generating the energy that drove the expansion of the Universe. But for some reason, there was an infinitesimal amount more matter than anti matter. Everything that we see today was that tiny fraction of matter that remained.

But why? Why was there more matter than antimatter right after the Big Bang? Researchers from the University of Melbourne think they might have an insight.

Just to give you an idea of the scale of the mystery facing researchers, here’s Associate Professor Martin Sevior of the University of Melborne’s School of Physics:

“Our universe is made up almost completely of matter. While we’re entirely used to this idea, this does not agree with our ideas of how mass and energy interact. According to these theories there should not be enough mass to enable the formation of stars and hence life.”

“In our standard model of particle physics, matter and antimatter are almost identical. Accordingly as they mix in the early universe they annihilate one another leaving very little to form stars and galaxies. The model does not come close to explaining the difference between matter and antimatter we see in the nature. The imbalance is a trillion times bigger than the model predicts.”

If the model predicts that matter and antimatter should have completely annihilated one another, why is there something, and not nothing?

The researchers have been using the KEK particle accelerator in Japan to create special particles called B-mesons. And it’s these particles which might provide the answer.

Mesons are particles which are made up of one quark, and one antiquark. They’re bound together by the strong nuclear force, and orbit one another, like the Earth and the moon. Because of quantum mechanics, the quark and antiquark can only orbit each other in very specific ways depending on the mass of the particles.

A B-meson is a particularly heavy particle, with more than 5 times the mass of a proton, due almost entirely to the mass of the B-quark. And it’s these B-mesons which require the most powerful particle accelerators to generate them.

In the KEK accelerator, the researchers were able to create both regular matter B-mesons and anti-B-mesons, and watch how they decayed.

“We looked at how the B-mesons decay as opposed to how the anti-B-mesons decay. What we find is that there are small differences in these processes. While most of our measurements confirm predictions of the Standard Model of Particle Physics, this new result appears to be in disagreement.â€

In the first few moments of the Universe, the anti-B-mesons might have decayed differently than their regular matter counterparts. By the time all the annihilations were complete, there was still enough matter left over to give us all the stars, planets and galaxies we see today.

Original Source: University of Melbourne News Release

March 28, 2008December 26, 2015 by Nicholos Wethington

Galaxy Zoo Results Show that the Universe Isn’t ‘Lopsided’

In July of last year, the doors of the online galaxy classification site Galaxy Zoo opened for business. The response? Tens of thousands of people logged-in to begin classifying galaxies from the Sloan Digital Sky Survey. If you’ve been one of the users madly clicking away at galaxies on the Zoo, this is what you’ve been waiting for: the first results have been submitted for publication, and it turns out that our Universe is, in fact, not ‘lopsided’.

One of the questions the Galaxy Zoo site is trying to answer seems simple: are most of the spiral galaxies in our Universe spinning clockwise or counterclockwise? The Universe is observed to be isotropic on large scales, meaning that any direction you look, it appears the same. If this is true, the ways that galaxies spin should be the same, and we should see just as many clockwise galaxies as counterclockwise ones, in every direction.

To definitively answer whether this is true means that a large number of the galaxies in our Universe needed to be analyzed. Computers, as much as they can do for us, just aren’t so good at recognizing patterns. They have a hard time distinguishing with high accuracy whether a galaxy is spinning one way or the other. Thankfully, the human brain is masterful at recognizing patterns. We do so every day when when look at a friend’s face and know who they are. Galaxy Zoo recruited the brains of over 125,000 people to help comb through almost a million galaxies recorded by the Sloan Digital Sky Survey, a robotic telescope survey that is made available to scientists online.

When the first results started to come in, something seemed a bit odd: more counterclockwise galaxies were being reported than clockwise ones. Did this mean the Universe somehow formed more counterclockwise galaxies, or was it something funny with the way people were analyzing the data?

“You would need something pretty wacky to create the effect…Normally you talk to cosmologists and they have three responses to what’s going on. This one made their jaws drop,” said Chris Lintott, a member of the Galaxy Zoo team and a post-doctoral researcher in the Department of Physics at the University of Oxford.

News pieces on the project reported that the Universe was ‘lopsided’, and suggestions for the cause of this phenomenon ranged from the existence of a universe-wide magnetic field to a rethinking of the topology, or shape, of the Universe.

“People were very very critical when we released the data before completely analyzing the results to look for biases, but one thing we do with Galaxy Zoo is that we try to keep the process by which we’re doing the science as open as possible,” Lintott said.

After checking for biases in how users were classifying the galaxies, though, the explanation for the abundance of counterclockwise galaxies was found to exist on a smaller scale: right inside the human brain.

To test whether it was the Universe or the participants that were ‘lopsided’, the Galaxy Zoo team changed the images that people could classify. They inserted a ‘bias sample’ into the catalogue of galaxies on the site: a monochrome image, one image mirrored vertically and one mirrored diagonally for each of over 91,000 objects that were already classified.

If it was the Universe that was lopsided, the numbers in this sample should have switched around. In other words, if there were really more anticlockwise than clockwise galaxies, then there should have been more clockwise galaxies clicked on in this sample, when the image was flipped around. But the preference for anticlockwise galaxies stayed the same in the sample.

Why would people prefer to click on the “anticlockwise” button more often than the “clockwise” button? Either this is something odd about the human brain, in which given a choice between the two prefers one over the other, or there is something about the interface that is making people click on the anticlockwise button more often (i.e., people ‘like’ clicking on buttons toward the center of the screen).

Galaxy Zoo is far from finished with providing the public with an opportunity to participate in an ongoing research project. The site will enter a new phase in the coming months to better study both nature of galaxies and the workings of the human brain.

The first paper using the Galaxy Zoo data was published in the Monthly Notices of the Royal Astronomical Society. If you want to get involved in the very addictive and fun project, you can sign up at www.galaxyzoo.org.

Source: Arxiv, phone interview with Chris Lintott

March 28, 2008December 26, 2015 by Ian O'Neill

13.73 Billion Years – The Most Precise Measurement of the Age of the Universe Yet

NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) has taken the best measurement of the age of the Universe to date. According to highlyÂ precise observations of microwave radiation observed all over the cosmos, WMAP scientists now have the best estimate yet on the age of the Universe: 13.73 billion years, plus or minus 120 million years (that’s an error margin of only 0.87%… not bad really…).

The WMAP mission was sent to the Sun-Earth second Lagrangian point (L₂), located approximately 1.5 million km from the surface of the Earth on the night-side (i.e. WMAP is constantly in the shadow of the Earth) in 2001. The reason for this location is the nature of the gravitational stability in the region and the lack of electromagnetic interference from the Sun. Constantly looking out into space, WMAP scans the cosmos with its ultra sensitive microwave receiver, mapping any small variations in the background “temperature” (anisotropy) of the universe. It can detect microwave radiation in the wavelength range of 3.3-13.6 mm (with a corresponding frequency of 90-22 GHz). Warm and cool regions of space are therefore mapped, including the radiation polarity.

This microwave background radiation originates from a very early universe, just 400,000 years after the Big Bang, when the ambient temperature of the universe was about 3,000 K. At this temperature, neutral hydrogen atoms were possible, scattering photons. It is these photons WMAP observes today, only much cooler at 2.7 Kelvin (that’s only 2.7 degrees higher than absolute zero, -273.15Â°C). WMAP constantly observes this cosmic radiation, measuring tiny alterations in temperature and polarity. These measurements refine our understanding about the structure of our universe around the time of the Big Bang and also help us understand the nature of the period of “inflation”, in the very beginning of the expansion of the Universe.

It is a matter of exposure for the WMAP mission, the longer it observes the better refined the measurements. After seven years of results-taking, the WMAP mission has tightened the estimate on the age of the Universe down to an error margin of only 120 million years, that’s 0.87% of the 13.73 billion years since the Big Bang.

“Everything is tightening up and giving us better and better precision all the time […] It’s actually significantly better than previous results. There is all kinds of richness in the data.” – Charles L. Bennett, Professor of Physics and Astronomy at Johns Hopkins University.

This will be exciting news to cosmologists as theories on the very beginning of the Universe are developed even further.

Source: New York Times

March 10, 2008December 26, 2015 by Fraser Cain

Cosmic Neutrinos, the End of the Dark Ages, and Inflation: 5 Years of WMAP Data

We now know the Universe is around 13.7 billion years old. But just a few years ago, cosmologists had no idea, putting the range around 10-20 billion years old – some even thought it could be 100 billion years old. We can thank NASA’s Wilkinson Microwave Anisotropy Probe for giving us the concrete answer. And now, NASA released 5 years of data collection, telling astronomers more about the earliest moments in the Universe, the background sea of cosmic neutrinos and the end of the Dark Ages.

WMAP looks at the Universe with microwave eyes. It may sound like a strange wavelength to use when witnessing the highest energy event ever – the aftermath of the Big Bang. But there’s a trick, over the billions of years of time, the Universe has been expanding. Radiation has had its wavelengths stretched out across the billions of light-years of distance and expansion. The visible light after the Big Bang has become a diffuse glow of microwaves in all directions.

Astronomers use WMAP to study the subtle temperature variations in this microwave background radiation to understand what the Universe looked like at the very beginning.

This 5th anniversary release of data is the icing on the cake, with some significant new findings.

First up, WMAP found evidence for a background sea of cosmic neutrinos that permeate the background of the Universe. These almost weightless sub-atomic particles zip around at nearly the speed of light. In fact, there are millions passing through your body right now, blasted out from the Sun. They don’t interact with anything, so they don’t cause any harm. In fact, a neutrino could probably make it through several light years of solid lead without being stopped.

So, in addition to the solar neutrinos there seem to be a sea of background neutrinos, generated during the Universe’s early development.

The second big discovery is clear evidence that the first generation of stars took more than a half-billion years to create a cosmic fog.

“We now have evidence that the creation of this fog was a drawn-out process, starting when the universe was about 400 million years old and lasting for half a billion years,” said WMAP team member Joanna Dunkley of the University of Oxford in the U.K. and Princeton University in Princeton, N.J. “These measurements are currently possible only with WMAP.”

Finally, WMAP put in tight constraints on the concept of “inflation”. This was an incredible burst of growth in the first trillionth of a second of the Universe. This period of inflation left ripples in the fabric of space, detectable in the cosmic microwave background radiation.

All in all, it’s been a good 5 years for WMAP.

Original Source: NASA News Release

March 10, 2008December 26, 2015 by Fraser Cain

Podcast: How Big is the Universe?

Weâ€™re ready to complete our trilogy of discovery about the universe. Weâ€™ve learned that it has no center; rather everywhere is its center and nowhere. We discovered that the universe seems to be flat. It’s not open, it’s not closed, it’s flat. If that doesnâ€™t make any sense, you need to listen to the previous show because thereâ€™s no way I could give that an explanation.

So now we want to know: â€œHow big is it?â€ Does it go on forever or is it finite in scale? How much of it can we see?

Click here to download the episode

How Big is the Universe? – Show notes and transcript

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.

March 5, 2008December 26, 2015 by Fraser Cain

Podcast: What is the Shape of the Universe?

Some of the biggest questions in the universe depend on its shape. Is it curved? Is it flat? Is it open? Those may not make that much sense to you, but in fact itâ€™s very important for astronomers. So which is it? How do we know? How did we figure it out? Why does it matter?

Click here to download the episode

What is the shape of the Universe? – Show notes and transcript

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.