Turns Out There Is No Actual Looking Up

Is there an up out there? New research says no. Out there in the universe, one direction is much like another. Credit: NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas; and A. Mellinger

Direction is something we humans are pretty accustomed to. Living in our friendly terrestrial environment, we are used to seeing things in term of up and down, left and right, forwards or backwards. And to us, our frame of reference is fixed and doesn’t change, unless we move or are in the process of moving. But when it comes to cosmology, things get a little more complicated.

For a long time now, cosmologists have held the belief that the universe is homogeneous and isotropic – i.e. fundamentally the same in all directions. In this sense, there is no such thing as “up” or “down” when it comes to space, only points of reference that are entirely relative. And thanks to a new study by researchers from the University College London, that view has been shown to be correct.

For the sake of their study, titled “How isotropic is the Universe?“, the research team used survey data of the Cosmic Microwave Background (CMB) – the thermal radiation left over from the Big Bang. This data was obtained by the ESA’s Planck spacecraft between 2009 and 2013.

The cosmic microwave background radiation, enhanced to show the anomalies. Credit: ESA and the Planck Collaboration
The cosmic microwave background radiation, enhanced to show the anomalies. Credit: ESA and the Planck Collaboration

The team then analyzed it using a supercomputer to determine if there were any polarization patterns that would indicate if space has a “preferred direction” of expansion. The purpose of this test was to see if one of the basic assumptions that underlies the most widely-accepted cosmological model is in fact correct.

The first of these assumptions is that the Universe was created by the Big Bang, which is based on the discovery that the Universe is in a state of expansion, and the discovery of the Cosmic Microwave Background. The second assumption is that space is homogenous and istropic, meaning that there are no major differences in the distribution of matter over large scales.

This belief, which is also known as the Cosmological Principle, is based partly on the Copernican Principle (which states that Earth has no special place in the Universe) and Einstein’s Theory of Relativity – which demonstrated that the measurement of inertia in any system is relative to the observer.

This theory has always had its limitations, as matter is clearly not evenly distributed at smaller scales (i.e. star systems, galaxies, galaxy clusters, etc.). However, cosmologists have argued around this by saying that fluctuation on the small scale are due to quantum fluctuations that occurred in the early Universe, and that the large-scale structure is one of homogeneity.

Timeline of the Big Bang and the expansion of the Universe. Credit: NASA
Timeline of the Big Bang and the expansion of the Universe. Credit: NASA

By looking for fluctuations in the oldest light in the Universe, scientists have been attempting to determine if this is in fact correct. In the past thirty years, these kinds of measurements have been performed by multiple missions, such as the Cosmic Background Explorer (COBE) mission, the Wilkinson Microwave Anisotropy Probe (WMAP), and the Planck spacecraft.

For the sake of their study, the UCL research team – led by Daniela Saadeh and Stephen Feeney – looked at things a little differently. Instead of searching for imbalances in the microwave background, they looked for signs that space could have a preferred direction of expansion, and how these might imprint themselves on the CMB.

As Daniela Saadeh – a PhD student at UCL and the lead author on the paper – told Universe Today via email:

“We analyzed the temperature and polarization of the cosmic microwave background (CMB), a relic radiation from the Big Bang, using data from the Planck mission. We compared the real CMB against our predictions for what it would look like in an anisotropic universe. After this search, we concluded that there is no evidence for these patterns and that the assumption that the Universe is isotropic on large scales is a good one.”

Basically, their results showed that there is only a 1 in 121 000 chance that the Universe is anisotropic. In other words, the evidence indicates that the Universe has been expanding in all directions uniformly, thus removing any doubts about their being any actual sense of direction on the large-scale.

Now and Then. This single all-sky image simultaneously captured two snapshots that straddle virtually the entire 13.7 billion year history of the universe. One of them is ‘now’ – our galaxy and its structures seen as they are over the most recent tens of thousands of years (the thin strip extending across the image is the edge-on plane of our galaxy – the Milky Way). The other is ‘then’ – the red afterglow of the Big Bang seen as it was just 380,000 years after the Big Bang (top and bottom of image). The time between these two snapshots therefore covers about 99.997% of the 13.7 billion year age of the universe. The image was obtained by the Planck spacecraft. Credit: ESA
A “now and then” all-sky image captured by the Planck spacecraft, simultaneously showing our galaxy and its structures seen as in recent history; and ‘then’ – the red afterglow of the Big Bang seen as it was just 380,000 years later. Credit: ESA

And in a way, this is a bit disappointing, since a Universe that is not homogenous and the same in all directions would lead to a set of solutions to Einstein’s field equations. By themselves, these equations do not impose any symmetries on space time, but the Standard Model (of which they are part) does accept homogeneity as a sort of given.

These solutions are known as the Bianchi models, which were proposed by Italian mathematician Luigi Bianchi in the late 19th century. These algebraic theories, which can be applied to three-dimensional spacetime, are obtained by being less restrictive, and thus allow for a Universe that is anisotropic.

On the other hand, the study performed by Saadeh, Feeney, and their colleagues has shown that one of the main assumptions that our current cosmological models rest on is indeed correct. In so doing, they have also provided a much-needed sense of closer to a long-term debate.

“In the last ten years there has been considerable discussion around whether there were signs of large-scale anisotropy lurking in the CMB,” said Saadeh. “If the Universe were anisotropic, we would need to revise many of our calculations about its history and content. Planck high-quality data came with a golden opportunity to perform this health check on the standard model of cosmology and the good news is that it is safe.”

So the next time you find yourself looking up at the night sky, remember… that’s a luxury you have only while you’re standing on Earth. Out there, its a whole ‘nother ballgame! So enjoy this thing we call “direction” when and where  you can.

And be sure to check out this animation produced by the UCL team, which illustrates the Planck mission’s CMB data:

Further Reading: arXiv, Science

The Dutch Are Going To The Moon With The Chinese

Radio image of the night sky. Credit: Max Planck Institute for Radio Astronomy, generated by Glyn Haslam.

One of the defining characteristics of the New Space era is partnerships. Whether it is between the private and public sector, different space agencies, or different institutions across the world, collaboration has become the cornerstone to success. Consider the recent agreement between the Netherlands Space Office (NSO) and the Chinese National Space Agency (CNSA) that was announced earlier this week.

In an agreement made possible by the Memorandum of Understanding (MoU) signed in 2015 between the Netherlands and China, a Dutch-built radio antenna will travel to the Moon aboard the Chinese Chang’e 4 satellite, which is scheduled to launch in 2018. Once the lunar exploration mission reaches the Moon, it will deposit the radio antenna on the far side, where it will begin to provide scientists with fascinating new views of the Universe.

The radio antenna itself is also the result of collaboration, between scientists from Radboud University, the Netherlands Institute for Radio Astronomy (ASTRON) and the small satellite company Innovative Solutions in Space (ISIS). After years of research and development, these three organizations have produced an instrument which they hope will usher in a new era of radio astronomy.

The satellite rotates around a fixed point behind the moon – the second Lagrange, or L2, point in the Earth-moon system. This point is located 65,000 kilometres from the moon.. Credit: ru.nl
Diagram showing how the Chang’e 4 satellite will rotate around a fixed point behind the moon – the second Lagrange, or L2, point in the Earth-moon system. Credit: ru.nl

Essentially, radio astronomy involves the study of celestial objects – ranging from stars and galaxies to pulsars, quasars, masers and the Cosmic Microwave Background (CMB) – at radio frequencies. Using radio antennas, radio telescopes, and radio interferometers, this method allows for the study of objects that might otherwise be invisible or hidden in other parts of the electromagnetic spectrum.

One drawback of radio astronomy is the potential for interference. Since only certain wavelengths can pass through the Earth’s atmosphere, and local radio wave sources can throw off readings, radio antennas are usually located in remote areas of the world. A good example of this is the Very-Long Baseline Array (VLBA) located across the US, and the Square Kilometer Array (SKA) under construction in Australia and South Africa.

One other solution is to place radio antennas in space, where they will not be subject to interference or local radio sources. The antenna being produced by Radbound, ASTRON and ISIS is being delivered to the far side of the Moon for just this reason. As the latest space-based radio antenna to be deployed, it will be able to search the cosmos in ways Earth-based arrays cannot, looking for vital clues to the origins of the universe.

As Heino Falke – a professor of Astroparticle Physics and Radio Astronomy at Radboud – explained in a University press release, the deployment of this radio antenna on the far side of the Moon will be an historic achievement:

“Radio astronomers study the universe using radio waves, light coming from stars and planets, for example, which is not visible with the naked eye. We can receive almost all celestial radio wave frequencies here on Earth. We cannot detect radio waves below 30 MHz, however, as these are blocked by our atmosphere. It is these frequencies in particular that contain information about the early universe, which is why we want to measure them.”

The planned Square Kilometer Array will be the world's largest radio telescope when it begins operations in 2018  Swinburne Astronomy Productions for SKA Project Development Office
The planned Square Kilometer Array will be the world’s largest radio telescope when it begins operations in 2018. Credit: SKA Project Development Office/SAP

As it stands, very little is known about this part of the electromagnetic spectrum. As a result, the Dutch radio antenna could be the first to provide information on the development of the earliest structures in the Universe. It is also the first instrument to be sent into space as part of a Chinese space mission.

Alongside Heino Falcke, Marc Klein Wolt – the director of the Radboud Radio Lab – is one of the scientific advisors for the project. For years, he and Falcke have been working towards the deployment of this radio antenna, and have high hopes for the project. As Professor Wolt said about the scientific package he is helping to create:

“The instrument we are developing will be a precursor to a future radio telescope in space. We will ultimately need such a facility to map the early universe and to provide information on the development of the earliest structures in it, like stars and galaxies.”

Together with engineers from ASTRON and ISIS, the Dutch team has accumulated a great deal of expertise from their years working on other radio astronomy projects, which includes experience working on the Low Frequency Array (LOFAR) and the development of the Square Kilometre Array, all of which is being put to work on this new project.

A radio antenna on the far side of the Moon will enable deep space surveys that were never before possible. Credit: NASA Goddard
A radio antenna on the far side of the Moon will enable deep space surveys that were never before possible. Credit: NASA Goddard

Other tasks that this antenna will perform include monitoring space for solar storms, which are known to have a significant impact on telecommunications here on Earth. With a radio antenna on the far side of the Moon, astronomers will be able to better predict such events and prepare for them in advance.

Another benefit will be the ability to measure strong radio pulses from gas giants like Jupiter and Saturn, which will help us to learn more about their rotational speed. Combined with the recent ESO efforts to map Jupiter at IR frequencies, and the data that is already arriving from the Juno mission, this data is likely to lead to some major breakthroughs in our understanding of this mysterious planet.

Last, but certainly not least, the Dutch team wants to create the first map of the early Universe using low-frequency radio data. This map is expected to take shape after two years, once the Moon has completed a few full rotations around the Earth and computer analysis can be completed.

It is also expected that such a map will provide scientists with additional evidence that confirms the Standard Model of Big Bang cosmology (aka. the Lambda CDM model). As with other projects currently in the works, the results are likely to be exciting and groundbreaking!

Further Reading: Radbound University

Beyond WIMPs: Exploring Alternative Theories Of Dark Matter

Image from Dark Universe, showing the distribution of dark matter in the universe. Credit: AMNH

The standard model of cosmology tells us that only 4.9% of the Universe is composed of ordinary matter (i.e. that which we can see), while the remainder consists of 26.8% dark matter and 68.3% dark energy. As the names would suggest, we cannot see them, so their existence has had to be inferred based on theoretical models, observations of the large-scale structure of the Universe, and its apparent gravitational effects on visible matter.

Since it was first proposed, there have been no shortages of suggestions as to what Dark Matter particles look like. Not long ago, many scientists proposed that Dark Matter consists of Weakly-Interacting Massive Particles (WIMPs), which are about 100 times the mass of a proton but interact like neutrinos. However, all attempts to find WIMPs using colliders experiments have come up empty. As such, scientists have been exploring the idea lately that dark matter may be composed of something else entirely. Continue reading “Beyond WIMPs: Exploring Alternative Theories Of Dark Matter”

Big Bang Theory: Evolution of Our Universe

Illustration of the Big Bang Theory
The Big Bang Theory: A history of the Universe starting from a singularity and expanding ever since. Credit: grandunificationtheory.com

How was our Universe created? How did it come to be the seemingly infinite place we know of today? And what will become of it, ages from now? These are the questions that have been puzzling philosophers and scholars since the beginning the time, and led to some pretty wild and interesting theories. Today, the consensus among scientists, astronomers and cosmologists is that the Universe as we know it was created in a massive explosion that not only created the majority of matter, but the physical laws that govern our ever-expanding cosmos. This is known as The Big Bang Theory.

For almost a century, the term has been bandied about by scholars and non-scholars alike. This should come as no surprise, seeing as how it is the most accepted theory of our origins. But what exactly does it mean? How was our Universe conceived in a massive explosion, what proof is there of this, and what does the theory say about the long-term projections for our Universe?

The basics of the Big Bang theory are fairly simple. In short, the Big Bang hypothesis states that all of the current and past matter in the Universe came into existence at the same time, roughly 13.8 billion years ago. At this time, all matter was compacted into a very small ball with infinite density and intense heat called a Singularity. Suddenly, the Singularity began expanding, and the universe as we know it began.

Continue reading “Big Bang Theory: Evolution of Our Universe”

Cosmologist Thinks a Strange Signal May Be Evidence of a Parallel Universe

A simulation of galaxies during the era of deionization in the early Universe. Credit: M. Alvarez, R. Kaehler, and T. AbelCredit: M. Alvarez, R. Kaehler, and T. Abel

In the beginning, there was chaos.

Hot, dense, and packed with energetic particles, the early Universe was a turbulent, bustling place. It wasn’t until about 300,000 years after the Big Bang that the nascent cosmic soup had cooled enough for atoms to form and light to travel freely. This landmark event, known as recombination, gave rise to the famous cosmic microwave background (CMB), a signature glow that pervades the entire sky.

Now, a new analysis of this glow suggests the presence of a pronounced bruise in the background — evidence that, sometime around recombination, a parallel universe may have bumped into our own.

Although they are often the stuff of science fiction, parallel universes play a large part in our understanding of the cosmos. According to the theory of eternal inflation, bubble universes apart from our own are theorized to be constantly forming, driven by the energy inherent to space itself.

Like soap bubbles, bubble universes that grow too close to one another can and do stick together, if only for a moment. Such temporary mergers could make it possible for one universe to deposit some of its material into the other, leaving a kind of fingerprint at the point of collision.

Ranga-Ram Chary, a cosmologist at the California Institute of Technology, believes that the CMB is the perfect place to look for such a fingerprint.

This image, the best map ever of the Universe, shows the oldest light in the universe. This glow, left over from the beginning of the cosmos called the cosmic microwave background, shows tiny changes in temperature represented by color. Credit: ESA and the Planck Collaboration.
The cosmic microwave background (CMB), a pervasive glow made of light from the Universe’s infancy, as seen by the Planck satellite in 2013. Tiny deviations in average temperature are represented by color. Credit: ESA and the Planck Collaboration.

After careful analysis of the spectrum of the CMB, Chary found a signal that was about 4500x brighter than it should have been, based on the number of protons and electrons scientists believe existed in the very early Universe. Indeed, this particular signal — an emission line that arose from the formation of atoms during the era of recombination — is more consistent with a Universe whose ratio of matter particles to photons is about 65x greater than our own.

There is a 30% chance that this mysterious signal is just noise, and not really a signal at all; however, it is also possible that it is real, and exists because a parallel universe dumped some of its matter particles into our own Universe.

After all, if additional protons and electrons had been added to our Universe during recombination, more atoms would have formed. More photons would have been emitted during their formation. And the signature line that arose from all of these emissions would be greatly enhanced.

Chary himself is wisely skeptical.

“Unusual claims like evidence for alternate Universes require a very high burden of proof,” he writes.

Indeed, the signature that Chary has isolated may instead be a consequence of incoming light from distant galaxies, or even from clouds of dust surrounding our own galaxy.

SO is this just another case of BICEP2? Only time and further analysis will tell.

Chary has submitted his paper to the Astrophysical Journal. A preprint of the work is available here.

10 Interesting Facts About the Milky Way

Viewed from above, we can now see that our gaze takes across the Perseus Arm (toward the constellation Cygnus), parts of the Sagittarius and Scutum-Centaurus arms (toward the constellations Scutum, Sagittarius and Ophiuchus) and across the central bar. Interstellar dust obscures much of the center of the galaxy. Credit: NASA et. all with additions by the author.
Viewed from above, we can now see that our gaze takes across the Perseus Arm (toward the constellation Cygnus), parts of the Sagittarius and Scutum-Centaurus arms (toward the constellations Scutum, Sagittarius and Ophiuchus) and across the central bar. Interstellar dust obscures much of the center of the galaxy. Credit: NASA et. all with additions by the author.

The Milky Way Galaxy is an immense and very interesting place. Not only does it measure some 120,000–180,000 light-years in diameter, it is home to planet Earth, the birthplace of humanity. Our Solar System resides roughly 27,000 light-years away from the Galactic Center, on the inner edge of one of the spiral-shaped concentrations of gas and dust particles called the Orion Arm.

But within these facts about the Milky Way lie some additional tidbits of information, all of which are sure to impress and inspire. Here are ten such facts, listed in no particular order:

1. It’s Warped:

For starters, the Milky Way is a disk about 120,000 light years across with a central bulge that has a diameter of 12,000 light years (see the Guide to Space article for more information). The disk is far from perfectly flat though, as can be seen in the picture below. In fact, it is warped in shape, a fact which astronomers attribute to the our galaxy’s two neighbors -the Large and Small Magellanic clouds.

These two dwarf galaxies — which are part of our “Local Group” of galaxies and may be orbiting the Milky Way — are believed to have been pulling on the dark matter in our galaxy like in a game of galactic tug-of-war. The tugging creates a sort of oscillating frequency that pulls on the galaxy’s hydrogen gas, of which the Milky Way has lots of (for more information, check out How the Milky Way got its Warp).

The Spiral Galaxy ESO 510-13 is warped similar to our own. Credit: NASA/Hubble Heritage Team (STScI / AURA), C. Conselice (U. Wisconsin / STScI/ NASA
The warp of Spiral Galaxy ESO 510-13 is similar to that of our own. Credit: NASA/Hubble

2. It Has a Halo, but You Can’t Directly See It:

Scientists believe that 90% of our galaxy’s mass consists of dark matter, which gives it a mysterious halo. That means that all of the “luminous matter” – i.e. that which we can see with the naked eye or a telescopes – makes up less than 10% of the mass of the Milky Way. Its halo is not the conventional glowing sort we tend to think of when picturing angels or observing comets.

In this case, the halo is actually invisible, but its existence has been demonstrated by running simulations of how the Milky Way would appear without this invisible mass, and how fast the stars inside our galaxy’s disk orbit the center.

The heavier the galaxy, the faster they should be orbiting. If one were to assume that the galaxy is made up only of matter that we can see, then the rotation rate would be significantly less than what we observe. Hence, the rest of that mass must be made up of an elusive, invisible mass – aka. “dark matter” – or matter that only interacts gravitationally with “normal matter”.

To see some images of the probable distribution and density of dark matter in our galaxy, check out The Via Lactea Project.

3. It has Over 200 Billion Stars:

As galaxies go, the Milky Way is a middleweight. The largest galaxy we know of, which is designated IC 1101, has over 100 trillion stars, and other large galaxies can have as many as a trillion. Dwarf galaxies such as the aforementioned Large Magellanic Cloud have about 10 billion stars. The Milky Way has between 100-400 billion stars; but when you look up into the night sky, the most you can see from any one point on the globe is about 2,500. This number is not fixed, however, because the Milky Way is constantly losing stars through supernovae, and producing new ones all the time (about seven per year).

These images taken by the Spitzer Space Telescope show the dust and gas concentrations around a supernova. Credit: NASA/JPL-Caltech
These images taken by the Spitzer Space Telescope show dust and gas concentrations around a distant supernova. Credit: NASA/JPL-Caltech

4. It’s Really Dusty and Gassy:

Though it may not look like it to the casual observer, the Milky Way is full of dust and gas. This matter makes up a whopping 10-15% of the luminous/visible matter in our galaxy, with the remainder being the stars. Our galaxy is roughly 100,000 light years across, and we can only see about 6,000 light years into the disk in the visible spectrum. Still, when light pollution is not significant, the dusty ring of the Milky Way can be discerned in the night sky.

The thickness of the dust deflects visible light (as is explained here) but infrared light can pass through the dust, which makes infrared telescopes like the Spitzer Space Telescope extremely valuable tools in mapping and studying the galaxy. Spitzer can peer through the dust to give us extraordinarily clear views of what is going on at the heart of the galaxy and in star-forming regions.

5. It was Made From Other Galaxies:

The Milky Way wasn’t always as it is today – a beautiful, warped spiral. It became its current size and shape by eating up other galaxies, and is still doing so today. In fact, the Canis Major Dwarf Galaxy is the closest galaxy to the Milky Way because its stars are currently being added to the Milky Way’s disk. And our galaxy has consumed others in its long history, such as the Sagittarius Dwarf Galaxy.

6. Every Picture You’ve Seen of the Milky Way Isn’t It:

Currently, we can’t take a picture of the Milky Way from above. This is due to the fact that we are inside the galactic disk, about 26,000 light years from the galactic center. It would be like trying to take a picture of your own house from the inside. This means that any of the beautiful pictures you’ve ever seen of a spiral galaxy that is supposedly the Milky Way is either a picture of another spiral galaxy, or the rendering of a talented artist.

Artist's concept of Sagittarius A, the supermassive black hole at the center of our galaxy. Credit: NASA/JPL
Artist’s concept of Sagittarius A, the supermassive black hole at the center of our galaxy. Credit: NASA/JPL-Caltech

Imaging the Milky Way from above is a long, long way off. However, this doesn’t mean that we can’t take breathtaking images of the Milky Way from our vantage point!

7. There is a Black Hole at the Center:

Most larger galaxies have a supermassive black hole (SMBH) at the center, and the Milky Way is no exception. The center of our galaxy is called Sagittarius A*, a massive source of radio waves that is believed to be a black hole that measures 22,5 million kilometers (14 million miles) across – about the size of Mercury’s orbit. But this is just the black hole itself.

All of the mass trying to get into the black hole – called the accretion disk – forms a disk that has 4.6 million times the mass of our Sun and would fit inside the orbit of the Earth. Though like other black holes, Sgr A* tries to consume anything that happens to be nearby, star formation has been detected near this behemoth astronomical phenomenon.

8. It’s Almost as Old as the Universe Itself:

The most recent estimates place the age of the Universe at about 13.7 billion years. Our Milky Way has been around for about 13.6 billion of those years, give or take another 800 million. The oldest stars in our the Milky Way are found in globular clusters, and the age of our galaxy is determined by measuring the age of these stars, and then extrapolating the age of what preceded them.

Though some of the constituents of the Milky Way have been around for a long time, the disk and bulge themselves didn’t form until about 10-12 billion years ago. And that bulge may have formed earlier than the rest of the galaxy.

9. It’s Part of the Virgo Supercluster:

As big as it is, the Milky Way is part of an even larger galactic structures. Our closest neighbors include the Large and Small Magellanic Clouds, and the Andromeda Galaxy – the closest spiral galaxy to the Milky Way. Along with some 50 other galaxies, the Milky Way and its immediate surroundings make up a cluster known as the Local Group.

A mosaic of telescopic images showing the galaxies of the Virgo Supercluster. Credit: NASA/Rogelio Bernal Andreo
A mosaic of telescopic images showing the galaxies of the Virgo Supercluster. Credit: NASA/Rogelio Bernal Andreo

And yet, this is still just a small fraction of our stellar neighborhood. Farther out, we find that the Milky Way is part of an even larger grouping of galaxies known as the Virgo Supercluster. Superclusters are groupings of galaxies on very large scales that measure in the hundreds of millions of light years in diameter. In between these superclusters are large stretches of open space where intrepid explorers or space probes would encounter very little in the way of galaxies or matter.

In the case of the Virgo Supercluster, at least 100 galaxy groups and clusters are located within it massive 33 megaparsec (110 million light-year) diameter. And a 2014 study indicates that the Virgo Supercluster is only a lobe of a greater supercluster, Laniakea, which is centered on the Great Attractor.

10. It’s on the move:

The Milky Way, along with everything else in the Universe, is moving through space. The Earth moves around the Sun, the Sun around the Milky Way, and the Milky Way as part of the Local Group, which is moving relative to the Cosmic Microwave Background (CMB) radiation – the radiation left over from the Big Bang.

The CMB is a convenient reference point to use when determining the velocity of things in the universe. Relative to the CMB, the Local Group is calculated to be moving at a speed of about 600 km/s, which works out to about 2.2 million km/h. Such speeds stagger the mind and squash any notions of moving fast within our humble, terrestrial frame of reference!

We have written many interesting articles about the Milky Way for Universe Today. Here’s 10 Interesting Facts about the Milky Way, How Big is the Milky Way?, What is the Closest Galaxy to the Milky Way?, and How Many Stars Are There in the Milky Way?

For many more facts about the Milky Way, visit the Guide to Space, listen to the Astronomy Cast episode on the Milky Way, or visit the Students for the Exploration and Development of Space at seds.org.

How Massive Is A Neutrino? Cosmology Experiment Gives A Clue

Artist's conception of Planck, a space observatory operated by the European Space Agency, and the cosmic microwave background. Credit: ESA and the Planck Collaboration - D. Ducros

There have been a lot of attempts over the years to figure out the mass of a neutrino (a type of elementary particle). A new analysis not only comes up with a number, but also combines that with a new understanding of the universe’s evolution.

The research team investigated the mass further after observing galaxy clusters with the Planck observatory, a space telescope with the European Space Agency. As the researchers examined the cosmic microwave background (the afterglow of the Big Bang), they saw a difference between their observations and other predictions.

“We observe fewer galaxy clusters than we would expect from the Planck results and there is a weaker signal from gravitational lensing of galaxies than the CMB would suggest. A possible way of resolving this discrepancy is for neutrinos to have mass. The effect of these massive neutrinos would be to suppress the growth of dense structures that lead to the formation of clusters of galaxies,” the researchers stated.

The HST WFPC2 image of gravitational lensing in the galaxy cluster Abell 2218, indicating the presence of large amount of dark matter (credit Andrew Fruchter at STScI).
The HST WFPC2 image of gravitational lensing in the galaxy cluster Abell 2218, indicating the presence of large amount of dark matter (credit Andrew Fruchter at STScI).

Neutrinos are a tiny piece of matter (along with other particles such as quarks and electrons). The challenge is, they’re hard to observe because they don’t react very easily to matter. Originally believed to be massless, newer particle physics experiments have shown that they do indeed have mass, but how much was not known.

There are three different flavors or types of neutrinos, and previous analysis suggested the sum was somewhere above 0.06 eV (less than a billionth of a proton’s mass.) The new result suggests it is closer to 0.320 +/- 0.081 eV, but that still has to be confirmed by further study. The researchers arrived at that by using the Planck data with “gravitational lensing observations in which images of galaxies are warped by the curvature of space-time,” they stated.

“If this result is borne out by further analysis, it not only adds significantly to our understanding of the sub-atomic world studied by particle physicists, but it would also be an important extension to the standard model of cosmology which has been developed over the last decade,” the researchers stated.

The research was done by the University of Manchester’s Richard Battye and the University of Nottingham’s Adam Moss. A paper on the work is published in Physical Review Letters and is also available in preprint version on Arxiv.

What Is The Evidence For The Big Bang?

What Is The Evidence For The Big Bang?

Almost all astronomers agree on the theory of the Big Bang, that the entire Universe is spreading apart, with distant galaxies speeding away from us in all directions. Run the clock backwards to 13.8 billion years ago, and everything in the Cosmos started out as a single point in space. In an instant, everything expanded outward from that location, forming the energy, atoms and eventually the stars and galaxies we see today. But to call this concept merely a theory is to misjudge the overwhelming amount of evidence.

There are separate lines of evidence, each of which independently points towards this as the origin story for our Universe. The first came with the amazing discovery that almost all galaxies are moving away from us.

In 1912, Vesto Slipher calculated the speed and direction of “spiral nebulae” by measuring the change in the wavelengths of light coming from them. He realized that most of them were moving away from us. We now know these objects are galaxies, but a century ago astronomers thought these vast collections of stars might actually be within the Milky Way.

In 1924, Edwin Hubble figured out that these galaxies are actually outside the Milky Way. He observed a special type of variable star that has a direct relationship between its energy output and the time it takes to pulse in brightness. By finding these variable stars in other galaxies, he was able to calculate how far away they were. Hubble discovered that all these galaxies are outside our own Milky Way, millions of light-years away.

So, if these galaxies are far, far away, and moving quickly away from us, this suggests that the entire Universe must have been located in a single point billions of years ago. The second line of evidence came from the abundance of elements we see around us.

In the earliest moments after the Big Bang, there was nothing more than hydrogen compressed into a tiny volume, with crazy high heat and pressure. The entire Universe was acting like the core of a star, fusing hydrogen into helium and other elements.

This is known as Big Bang Nucleosynthesis. As astronomers look out into the Universe and measure the ratios of hydrogen, helium and other trace elements, they exactly match what you would expect to find if the entire Universe was once a really big star.

Line of evidence number 3: cosmic microwave background radiation. In the 1960s, Arno Penzias and Robert Wilson were experimenting with a 6-meter radio telescope, and discovered a background radio emission that was coming from every direction in the sky – day or night. From what they could tell, the entire sky measured a few degrees above absolute zero.

WMAP data of the Cosmic Microwave Background. Credit: NASA
WMAP data of the Cosmic Microwave Background. Credit: NASA

Theories predicted that after a Big Bang, there would have been a tremendous release of radiation. And now, billions of years later, this radiation would be moving so fast away from us that the wavelength of this radiation would have been shifted from visible light to the microwave background radiation we see today.

The final line of evidence is the formation of galaxies and the large scale structure of the cosmos. About 10,000 years after the Big Bang, the Universe cooled to the point that the gravitational attraction of matter was the dominant form of energy density in the Universe. This mass was able to collect together into the first stars, galaxies and eventually the large scale structures we see across the Universe today.

These are known as the 4 pillars of the Big Bang Theory. Four independent lines of evidence that build up one of the most influential and well-supported theories in all of cosmology. But there are more lines of evidence. There are fluctuations in the cosmic microwave background radiation, we don’t see any stars older than 13.8 billion years, the discoveries of dark matter and dark energy, along with how the light curves from distant supernovae.

So, even though it’s a theory, we should regard it the same way that we regard gravity, evolution and general relativity. We have a pretty good idea of what’s going on, and we’ve come up with a good way to understand and explain it. As time progresses we’ll come up with more inventive experiments to throw at. We’ll refine our understanding and the theory that goes along with it.

Most importantly, we can have confidence when talking about what we know about the early stages of our magnificent Universe and why we understand it to be true.

Astronomers Map Dark Matter Throughout the Entire Universe

Full sky map of the cosmic microwave background. The color red indicates a cool spot while the color blue indicates a hot spot. Image credit: NASA.

Warped visions of the cosmic microwave background – the earliest detectable light – allow astronomers to map the total amount of visible and invisible matter throughout the universe.

Roughly 85 percent of all matter in the universe is dark matter, invisible to even the most powerful telescopes, but detectable by its gravitational pull.

In order to find dark matter, astronomers look for an effect called gravitational lensing: when the gravitational pull of dark matter bends and amplifies light from a more distant object. In its most eccentric form it results in multiple arc-shaped images of distant cosmic objects.

The Hubble Space Telescope shows the effect of gravitational lensing as background galaxies are warped by the galaxy cluster MACS J1206. Image Credit: NASA
The Hubble Space Telescope shows the effect of gravitational lensing as background galaxies are warped by the galaxy cluster MACS J1206. Image Credit: NASA

But there’s one caveat here: in order to detect dark matter there must be an object directly behind it. The ‘stars’ have to be aligned.

In a recent study led by Dr. James Geach of the University of Hertfordshire in the United Kingdom, astronomers have set their eyes on the cosmic microwave background (CMB) instead.

“The CMB is the most distant/oldest light we can see,” Dr. Geach told Universe Today. “It can be thought of as a surface, backlighting the entire universe.”

The photons from the CMB have been hurling toward the Earth since the universe was only 380,000 years old. A single photon has had the chance to run into plenty of matter, having effectively probed all the matter in the universe along its line of sight.

“So our view of the CMB is a bit distorted from what it intrinsically looks like – a bit like looking at the pattern on the bottom of a swimming pool,” Dr. Geach said.

By noting the small distortions in the CMB, we can probe all of the dark matter throughout the entire universe. But doing just this is extremely challenging.

The team observed the southern sky with the South Pole Telescope, a 10 meter telescope designed for observations in the microwave. This large, groundbreaking survey produced a CMB map of the southern sky, which was consistent with previous CMB data from the Planck satellite.

The characteristic signatures of gravitational lensing by intervening matter can not be extracted by eye. Astronomers relied on the use of a well-developed mathematical procedure. We wont go into the nasty details.

This produced a “map of the total projected mass density between us and the CMB. That’s quite incredible if you think about it – it’s an observational technique to map all of the mass in the universe, right back to the CMB,” Dr. Geach explained.

But the team didn’t finish their analysis there. Instead, they continued to measure the CMB lensing at the positions of quasars – powerful supermassive black holes in the centers of the earliest galaxies.

“We found that regions of the sky with a large density of quasars have a clearly stronger CMB lensing signal, implying that quasars are indeed located in large-scale matter structures,” Dr. Ryan Hickox of Dartmouth College – second author on the study – told Universe Today.

Finally, the CMB map was used to determine the mass of these dark matter halos. These results matched those determined in older studies, which looked at how the quasars clustered together in space, with no reference to the CMB at all.

Consistent results between two independent measurements is a powerful scientific tool. According to Dr. Hickox, it shows that “we have a strong understanding of how supermassive black holes reside in large-scale structures, and that (once again) Einstein was right.”

The paper has been accepted for publication in the Astrophysical Journal Letters and is available for download here.

This Very Old Cosmic Light Has A Bend To It

Artist's impression of how huge cosmic structures deflect photons in the cosmic microwave background (CMB). Credit: ESA and the Planck Collaboration

Leftover radiation from the Big Bang — that expansion that kick-started the universe — can be bent by huge cosmic structures, just like other light that we see in the universe. While the finding seems esoteric at first glance, scientists say the discovery could pave the way for finding a similar kind of signal that indicate the presence of gravitational waves in the moments after the universe was born.

That light is called the cosmic microwave background and is the radiation that was visible when the universe became transparent to radiation, 380,000 years after the Big Bang. A tiny bit of the CMB is polarized. There are two types of polarized light in the CMB: E-modes (first detected in 2002) and B-modes (which were just detected using a telescope in Antarctica and ESA’s Herschel space observatory.

“[B-modes] can arise in two ways,” the European Space Agency wrote in a press release.

“The first involves adding a twist to the light as it crosses the Universe and is deflected by galaxies and dark matter – a phenomenon known as gravitational lensing. The second has its roots buried deep in the mechanics of a very rapid phase of enormous expansion of the Universe, which cosmologists believe happened just a tiny fraction of a second after the Big Bang – ‘inflation’.”

More results are on the way from ESA’s Planck telescope in 2014, at which point scientists hope to see this B-mode of the second type. For now, check out the full study in Physical Review Letters. There is also a preprint version available on Arxiv.

Sources: ESA and ESA Herschel