Diagram showing the Lambda-CBR universe, from the Big Bang to the the current era. Credit: Alex Mittelmann/Coldcreation
Okay, so let’s start with the obvious. The big bang is not dead. Recent observations by the James Webb Space Telescope have not disproven the big bang, despite certain popular articles claiming otherwise. If that’s all you needed to hear, then have a great day. That said, the latest Webb observations do reveal some strange and unexpected things about the universe, and if you’d like to know more, keep reading.
Studying the universe is hard. Really hard. Like insanely, ridiculously hard. Think of the hardest thing you’ve ever done in your life, because studying the universe is quite literally exponentially way harder than whatever you came up with. Studying the universe is hard for two reasons: space and time. When we look at an object in the night sky, we’re looking back in time, as it has taken a finite amount of time for the light from that object to reach your eyes. The star Sirius is one of the brightest objects in the night sky and is located approximately 8.6 light-years from Earth. This means that when you look at it, you’re seeing what it looked like 8.6 years ago, as the speed of light is finite at 186,000 miles per second and a light year is the time it takes for light to travel in one year. Now think of something way farther away than Sirius, like the Big Bang, which supposedly took place 13.8 billion years ago. This means when scientists study the Big Bang, they’re attempting to look back in time 13.8 billion years. Even with all our advanced scientific instruments, it’s extremely hard to look back that far in time. It’s so hard that the Hubble Space Telescope has been in space since 1990 and just recently spotted the most distant single star ever detected in outer space at 12.9 billion light-years away. That’s 30 years of scanning the heavens, which is a testament to the vastness of the universe, and hence why studying the universe is hard. Because studying the universe is so hard, scientists often turn to computer simulations, or models, to help speed up the science aspect and ultimately give us a better understanding of how the universe works without waiting 30 years for the next big discovery.
The BICEP telescope in Antarctica during twilight. Credit: Steffen Richter, Harvard University
The standard model of cosmology is a remarkably powerful and accurate description of the universe, tracing its evolution from the big bang to its current state, but it is not without mysteries. One of the biggest unsolved questions of the standard model is known as early cosmic inflation.
Artist's impression of the Milky Way Galaxy. Credit: ESO
When it comes to our cosmic origins, a number of theories have been advanced throughout the course of history. Literally every culture that’s ever existed has had its own mythological tradition, which naturally included a creation story. With the birth of the scientific tradition, scientists began to understand the Universe in terms of physical laws that could be tested and proven.
With the dawn of the Space Age, scientists began testing cosmological theories in terms of observable phenomena. From all of this, a number of theories emerged by the latter half of the 20th century that attempted to explain how all matter and the physical laws governing it came to be. Of these, the Big Bang Theory remains the most widely accepted while the Steady-State Hypothesis has historically been its greatest challenger.
The Big Bang Theory: A history of the Universe starting from a singularity and expanding ever since. Credit: grandunificationtheory.com
According to the Big Bang cosmological model, our Universe began 13.8 billion years ago when all the matter and energy in the cosmos began expanding. This period of “cosmic inflation” is believed to be what accounts for the large-scale structure of the Universe and why space and the Cosmic Microwave Background (CMB) appear to be largely uniform in all directions.
However, to date, no evidence has been discovered that can definitely prove the cosmic inflation scenario or rule out alternative theories. But thanks to a new study by a team of astronomers from Harvard University and the Harvard-Smithsonian Center for Astrophysics (CfA), scientists may have a new means of testing one of the key parts of the Big Bang cosmological model.
This single all-sky image, captured by the Planck telescope, simultaneously captured two snapshots that straddle virtually the entire 13.7 billion year history of the universe. Credit: ESA
For thousands of years, human being have been contemplating the Universe and seeking to determine its true extent. And whereas ancient philosophers believed that the world consisted of a disk, a ziggurat or a cube surrounded by celestial oceans or some kind of ether, the development of modern astronomy opened their eyes to new frontiers. By the 20th century, scientists began to understand just how vast (and maybe even unending) the Universe really is.
And in the course of looking farther out into space, and deeper back in time, cosmologists have discovered some truly amazing things. For example, during the 1960s, astronomers became aware of microwave background radiation that was detectable in all directions. Known as the Cosmic Microwave Background (CMB), the existence of this radiation has helped to inform our understanding of how the Universe began. Continue reading “What is the Cosmic Microwave Background?”
A computer simulation of the distribution of matter in the universe. Orange regions host galaxies; blue structures are gas and dark matter. Credit: TNG Collaboration
According to the Big Bang Theory of cosmology, the Universe began roughly 13.8 billion years ago as all matter in the Universe began to expand from a single point of infinite density. Over the next few billion years, the fundamental forces of the Universe began to separate from each other and subatomic particles and atoms formed. In time, this first stars and galaxies formed, giving rise to the large-scale structure of the Universe.
However, it was only by roughly 1 billion years after the Big Bang that the Universe began to become transparent. By about 12 billion years ago, intergalactic space was filled with gas that was much less transparent than it is now, with variations from place to place. To address why this was, a team of astronomers recently used the world’s largest telescope to search for galaxies of young stars in a huge volume of space.
The study which details their findings recently appeared in The Astrophysical Journal under the title “Evidence for Large-scale Fluctuations in the Metagalactic Ionizing Background Near Redshift Six“. The study was led by George D. Becker, a professor of astrophysics at the University of California Riverside, and included members from the University of California, Los Angeles (UCLA), and the University of California, Santa Barbara (UCSB).
This illustration shows the evolution of the Universe, from the Big Bang on the left, to modern times on the right. Credit: NASA
For the sake of their study, the team used the Subaru Telescope – the world’s largest telescope, located at the Mauna Kea Observatories in Hawaii – to examine a 500 million light-year volume of space as it existed roughly 12 billion years ago. Using this data, the team considered two possible models that could account for the variations in transparency that astronomers have been seeing during this cosmic epoch.
On the one hand, if the region contained a small number of galaxies, the team would conclude that startlight could not penetrate very far through the intergalactic gas. On the other hand, if it contained an unusually large number of galaxies, this would indicate that the region had cooled significantly over the previous several hundred million years. Prior to their observations, Beck and his team were expecting to find that it was the latter.
However, what they found was that the region contained far fewer galaxies than expected – which indicated that the opaqueness of the region was due to a lack of starlight. As Steven Furlanetto, a UCLA professor of astronomy and a co-author of the research, explained in a recent UCLA press release:
“It was a rare case in astronomy where two competing models, both of which were compelling in their own way, offered precisely opposite predictions, and we were lucky that those predictions were testable… It is not that the opacity is a cause of the lack of galaxies. Instead, it’s the other way around.”
In addition to addressing an enduring mystery in astronomy, this study also has implications for our understanding of how the Universe evolved over time. According to our current cosmological models, the period that took place roughly 380,000 t0 150 million years after the Big Bang is known as the “Dark Ages”. Most of the photons in the Universe were interacting with electrons and protons at this time, which means radiation from this period is undetectable by our current instruments.
However, by about 1 billion years after the Big Bang, the first stars and galaxies had formed. It is further believed that ultraviolet light from these first galaxies filled the Universe and is what allowed for the gas in deep space to become transparent. This would have occurred earlier in regions with more galaxies, the astronomers concluded, hence why there are variations in transparency.
In short, if more ultraviolet radiation from galaxies would lead to greater transparency in the early Universe, then the existence of fewer nearby galaxies would cause certain regions to be murkier. In the future, Becker and his team hope to further study this region of space and others like it in the hope that it will reveal clues about how the first galaxies illuminated the Universe during that early period, which remains a subject of inquiry at this point.
This research is also expected to shed more light on how the early Universe evolved, gradually giving rise to the one that are familiar with today. And as next-generation instruments are able to probe deeper into space (and hence, further back in time), we just may come to understand how existence as we know it all unfolded.
A billion years after the big bang, hydrogen atoms were mysteriously torn apart into a soup of ions. Credit: NASA/ESA/A. Felid (STScI)).
In accordance with the Big Bang model of cosmology, shortly after the Universe came into being there was a period known as the “Dark Ages”. This occurred between 380,000 and 150 million years after the Big Bang, where most of the photons in the Universe were interacting with electrons and protons. As a result, the radiation of this period is undetectable by our current instruments – hence the name.
Astrophysicists and cosmologists have therefore been pondering how the Universe could go from being in this dark, cloudy state to one where it was filled with light. According to a new study by a team of researchers from the University of Iowa and the Harvard-Smithsonian Center for Astrophysics, it may be that black holes violently ejected matter from the early Universe, thus allowing light to escape.
Their study, titled “Resolving the X-ray emission from the Lyman continuum emitting galaxy Tol 1247-232“, recently appeared in the Monthly Notices of the Royal Astronomical Society. Led by Phillip Kaaret, a professor of Physics and Astronomy at the University of Iowa – and supported by an award from the Chandra X-ray Observatory – the research team arrived at this conclusion by observing a nearby galaxy from which ultraviolet light is escaping.
Milestones in the history of the Universe, from the Big Bang to the present day. Credit: NAOJ/NOAO
This galaxy, known as Tol 1247-232, is a small (and possibly elliptical) galaxy located 652 million light-years away, in the direction of the southern Hydra constellation. This galaxy is one of just nine in the local Universe (and one of only three galaxies close to the Milky Way) that has been shown to emit Lyman continuum photons – a type of radiation in the ultraviolet band.
Back in May of 2016, the team spotted a single X-ray source coming from a star-forming region in this galaxy, using the Chandra X-ray observatory. Based on their observations, they determined that it was not caused by the formation of a new star. For one, new stars do not experience sudden changes in brightness, as this x-ray source did. In addition, the radiation emitted by new stars does not come in the form of a point-like source.
Instead, they determined that what they were seeing had to be the result of a very small object, which left only one likely explanation: a black hole. As Philip Kaaret, a professor in the UI Department of Physics and Astronomy and the lead author on the study, explained:
“The observations show the presence of very bright X-ray sources that are likely accreting black holes. It’s possible the black hole is creating winds that help the ionizing radiation from the stars escape. Thus, black holes may have helped make the universe transparent.”
Artist concept of matter swirling around a black hole. Credit: NASA/Dana Berry/SkyWorks Digital
However, this also raised the question of how a black hole could be emitting matter. This is something that astrophysicists have puzzled over for quite some time. Whereas all black holes have tendency to consume all that is in their path, a small number of supermassive black holes (SMBHs) have been found to have high-speed jets of charged particles streaming from their cores.
These SMBHs are what power Active Galactic Nuclei, which are compact, bright regions that has been observed at the centers of particularly massive galaxies. At present, no one is certain how these SMBHs manage to fire off jets of hot matter. But it has been theorized that they could be caused by the accelerated rotational energy of the black holes themselves.
In keeping with this, the team considered the possibility that accreting X-ray sources could explain the escape of matter from a black hole. In other words, as a black hole’s intense gravity pulls matter inward, the black hole responds by spinning faster. As the hole’s gravitational pull increases, the speed creates energy, which inevitably causes charged particles to be pushed out. As Kaaret explained:
“As matter falls into a black hole, it starts to spin and the rapid rotation pushes some fraction of the matter out. They’re producing these strong winds that could be opening an escape route for ultraviolet light. That could be what happened with the early galaxies.”
Depiction of the tidal disruption event in F01004-2237. The release of gravitational energy as the debris of the star is accreted by the black hole leads to a flare in the optical light of the galaxy. Credit and copyright: Mark Garlick
Taking this a step further, the team hypothesized that this could be what was responsible for light escaping the “Dark Ages”. Much like the jets of hot material being emitted by SMBHs today, similarly massive black holes in the early Universe could have sped up due to the accretion of matter, spewing out light from the cloudiness and allowing for the Universe to become a clear, bright place.
In the future, the UI team plans to study Tol 1247-232 in more detail and locate other nearby galaxies that are also emitting ultraviolet light. This will corroborate their theory that black holes could be responsible for the observed point source of high-energy X-rays. Combined with studies of the earliest periods of the Universe, it could also validate the theory that the “Dark Ages” ended thanks to the presence of black holes.
A Hubble image of the galaxy cluster Abell 1689, which acts as a lens to focus the light from much more distant galaxies, including some very dusty star-forming galaxies in the early universe (seen as the nearly point-like blue smudges in this image). Credit: NASA-Hubble
In their pursuit of learning how our Universe came to be, scientists have probed very deep into space (and hence, very far back in time). Ultimately, their goal is to determine when the first galaxies in our Universe formed and what effect they had on cosmic evolution. Recent efforts to locate these earliest formations have probed to distances of up to 13 billion light-years from Earth – i.e. about 1 billion years after the Big Bang.
From this, scientist are now able to study how early galaxies affected matter around them – in particular, the reionization of neutral atoms. Unfortunately, most early galaxies are very faint, which makes studying their interiors difficult. But thanks to a recent survey conducted by an international team of astronomers, a more luminous, massive galaxy was spotted that could provide a clear look at how early galaxies led to reionization.
Illustration of the depth by which Hubble imaged galaxies in prior Deep Field initiatives, in units of the Age of the Universe. Credit: NASA and A. Feild (STScI)
In accordance with Big Bang model of cosmology, reionization refers to the process that took place after the period known as the “Dark Ages”. This occurred between 380,000 and 150 million years after the Big Bang, where most of the photons in the Universe were interacting with electrons and protons. As a result, the radiation of this period is undetectable by our current instruments – hence the name.
Just prior to this period, the “Recombination” occurred, where hydrogen and helium atoms began to form. Initially ionized (with no electrons bound to their nuclei) these molecules gradually captured ions as the Universe cooled, becoming neutral. During the period that followed – i.e. between 150 million to 1 billion years after the Big Bang – the large-scale structure of the Universe began to form.
Intrinsic to this was the process of reionization, where the first stars and quasars formed and their radiation reionized the surrounding Universe. It is therefore clear why astronomers want to probe this era of the Universe. By observing the first stars and galaxies, and what effect they had on the cosmos, astronomers will get a clearer picture of how this early period led to the Universe as we know it today.
Luckily for the research team, the massive, star-forming galaxies of this period are known to contain a great deal of dust. While very faint in the optical band, these galaxies emit strong radiation at submillimeter wavelengths, which makes them detectable using today’s advanced telescopes – including the South Pole Telescope (SPT), the Atacama Pathfinder Experiment (APEX), and Atacama Large Millimeter Array (ALMA).
NASA’s Spitzer Space Telescope captured this stunning infrared image of the center of the Milky Way Galaxy, where the black hole Sagitarrius A resides. Image: NASA/JPL-Caltech
For the sake of their study, Strandet and Weiss relied on data from the SPT to detect a series of dusty galaxies from the early Universe. As Maria Strandet and Axel Weiss of the Max Planck Institute for Radio Astronomy (and the lead author and co-authors on the study, respectively) told Universe Today via email:
“We have used light of about 1 mm wavelength, which can be observed by mm telescopes like SPT, APEX or ALMA. At this wavelength the photons are produced by the thermal radiation of dust. The beauty of using this long wavelength is, that for a large redshift range (look back time), the dimming of galaxies [caused] by increasing distance is compensated by the redshift – so the observed intensity is independent of the redshift. This is because, for higher redshift galaxies, one is looking at intrinsically shorter wavelengths (by (1+z)) where the radiation is stronger for a thermal spectrum like the dust spectrum.”
This was followed by data from ALMA, which the team used to determine the distance of the galaxies by looking at the redshifted wavelength of carbon monoxide molecules in their interstellar mediums (ISM). From all the data they collected, they were able to constrain the properties of one of these galaxies – SPT0311-58 – by observing its spectral lines. In so doing, they determined that this galaxy existed just 760 million years after the Big Bang.
“Since the signal strength at 1mm is independent of the redshift (look back time), we do not have an a priori clue if an object is relatively near (in the cosmological sense) or at the epoch of reionization,” they said. “That is why we undertook a large survey to determine the redshifts via the emission of molecular lines using ALMA. SPT0311-58 turns out to be the highest redshift object discovered in this survey and in fact the most distant massive dusty star-forming galaxy so far discovered.”
The Hubble Ultra Deep Field seen in ultraviolet, visible, and infrared light. Image Credit: NASA, ESA, H. Teplitz and M. Rafelski (IPAC/Caltech), A. Koekemoer (STScI), R. Windhorst (Arizona State University), and Z. Levay (STScI)
From their observations, they also determined that SPT0311-58 has a mass of about 330 billion Solar-masses, which is about 66 times as much as the Milky Way Galaxy (which has about 5 billion Solar-masses). They also estimated that it is forming new stars at a rate of several thousand per year, which could as be the case for neighboring galaxies that are dated to this period.
This rare and distant object is one of the best candidates yet for studying what the early Universe looked like and how it has evolved since. This in turn will allow astronomers and cosmologists to test the theoretical basis for the Big Bang Theory. As Strandet and Weiss told Universe Today about their discovery:
“These objects are important to understanding the evolution of galaxies as a whole since the large amounts of dust already present in this source, only 760 million years after the Big Bang, means that it is an extremely massive object. The mere fact that such massive galaxies already existed when the Universe was still so young puts strong constraints on our understanding of galaxy mass buildup. Furthermore the dust needs to form in a very short time, which gives additional insights on the dust production from the first stellar population.”
The ability to look deeper into space, and farther back in time, has led to many surprising discoveries of late. And these have in turn challenged some of our assumptions about what happened in the Universe, and when. And in the end, they are helping scientists to create a more detailed and complete account of cosmic evolution. Someday soon, we might even be able to probe the earliest moments in the Universe, and watch creation in action!
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.
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. 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
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!
