Artist's impression of a quasar and a relativistic jet emanating from the center. Credit: NASA
Since the 1950s, astronomers have known of galaxies that have particularly bright centers – aka. Active Galactic Nuclei (AGNs) or quasars. This luminosity is the result of supermassive black holes (SMBHs) at their centers consuming matter and releasing electromagnetic energy. Further studies revealed that there are some quasars that appear particularly bright because their relativistic jets are directed towards Earth.
In 1978, astronomer Edward Speigel coined the term “blazar” to describe this particular class of object. Using the telescopes at the Large Binocular Telescope Observatory (LBTO) in Arizona, a research team recently observed a blazar located 13 billion light-years from Earth. This object, designated PSO J030947.49+271757.31 (or PSO J0309+27), is the most distant blazar ever observed and foretells the existence of many more!
The early universe. Credit: Tom Abel & Ralf Kaehler (KIPACSLAC)/ AMNH/NASA
Since the 1960s, astronomers have theorized that all the visible matter in the Universe (aka. baryonic or “luminous matter) constitutes just a small fraction of what’s actually there. In order for the predominant and time-tested theory of gravity to work (as defined by General Relativity), scientists have had to postulate that roughly 85% of the mass in the Universe consists of “Dark Matter”.
Despite many decades of study, scientists have yet to find any direct evidence of Dark Matter and the constituent particle and its origins remain a mystery. However, a team of physicists from the University of York in the UK has proposed a new candidate particle that was just recently discovered. Known as the d-star hexaquark, this particle could have formed the “Dark Matter” in the Universe during the Big Bang.
The building blocks of life can, and did, spontaneously assemble under the right conditions. That’s called spontaneous generation, or abiogenesis. Of course, many of the details remain hidden to us, and we just don’t know exactly how it all happened. Or how frequently it could happen.
The Murchison Widefield Array radio telescope in remote Western Australia. Brown University.
A team of scientists working with the Murchison Widefield Array (WMA) radio telescope are trying to find the signal from the Universe’s first stars. Those first stars formed after the Universe’s Dark Ages. To find their first light, the researchers are looking for the signal from neutral hydrogen, the gas that dominated the Universe after the Dark Ages.
Ever since astronomers realized that the Universe is in a constant state of expansion and that a massive explosion likely started it all 13.8 billion years ago (the Big Bang), there have been unresolved questions about when and how the first stars formed. Based on data gathered by NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) and similar missions, this is believed to have happened about 100 million years after the Big Bang.
Much of the details of how this complex process worked have remained a mystery. However, new evidence gathered by a team led by researchers from the Max Planck Institute for Astronomy indicates that the first stars must have formed rather quickly. Using data from the Magellan Telescopes at Las Campanas Observatory, the team observed a cloud of gas where star formation was taking place just 850 million years after the Big Bang.
The Orion Nebula, one of the most studied objects in the sky. It's likely that many of its protostars and their planetary disks contain water in some form. Image: NASA
The universe bathes in a sea of light, from the blue-white flickering of young stars to the deep red glow of hydrogen clouds. Beyond the colors seen by human eyes, there are flashes of x-rays and gamma rays, powerful bursts of radio, and the faint, ever-present glow of the cosmic microwave background. The cosmos is filled with colors seen and unseen, ancient and new. But of all these, there was one color that appeared before all the others, the first color of the universe.
Cosmic Microwave Background. Scientists compared this to modern galaxy distributions to track dark matter. Copyright: ESA/Planck Collaboration
Back in 2013, the European Space Agency released its first analysis of the data gathered by the Planck observatory. Between 2009 and 2013, this spacecraft observed the remnants of the radiation that filled the Universe immediately after the Big Bang – the Cosmic Microwave Background (CMB) – with the highest sensitivity of any mission to date and in multiple wavelengths.
In addition to largely confirming current theories on how the Universe evolved, Planck’s first map also revealed a number of temperature anomalies – like the CMB “Cold Spot” – that are difficult to explain. Unfortunately, with the latest analysis of the mission data, the Planck Collaboration team has found no new evidence for these anomalies, which means that astrophysicists are still short of an explanation.
This Hubble Space Telescope image represents the largest, most comprehensive "history book" of galaxies in the universe.The image, a combination of nearly 7,500 separate Hubble exposures, represents 16 years' worth of observations.The ambitious endeavor, called the Hubble Legacy Field, includes several Hubble deep-field surveys, including the eXtreme Deep Field (XDF), the deepest view of the universe. The wavelength range stretches from ultraviolet to near-infrared light, capturing all the features of galaxy assembly over time.The image mosaic presents a wide portrait of the distant universe and contains roughly 265,000 galaxies. They stretch back through 13.3 billion years of time to just 500 million years after the universe's birth in the big bang. The tiny, faint, most distant galaxies in the image are similar to the seedling villages from which today's great galaxy star-cities grew. The faintest and farthest galaxies are just one ten-billionth the brightness of what the human eye can see.The wider view contains 100 times as many galaxies as in the Hubble Ultra Deep Field, taken in 2004. The new portrait, a mosaic of multiple snapshots, covers almost the width of the full Moon. Lying in this region is the XDF, which penetrated deeper into space than this legacy field view. However, the XDF field covers less than one-tenth of the full Moon's diameter. Credits: NASA, ESA, G. Illingworth and D. Magee (University of California, Santa Cruz), K. Whitaker (University of Connecticut), R. Bouwens (Leiden University), P. Oesch (University of Geneva) and the Hubble Legacy Field team
Even after almost three decades of faithful service, the Hubble Space Telescope continues to operate and provide breathtaking images of the cosmos. As one of NASA’s Great Observatories, its observations of distant galaxies, exoplanets, and the expansion of the Universe have had a revolutionary impact on astronomy, astrophysics and cosmology.
Hubble’s latest contribution comes in the form of a deep-sky mosaic image that was constructed using 16 years’ worth of observations. Known as the “Hubble Legacy Field“, this mosaic is being described as the largest and most comprehensive “history book” of galaxies. All told, it contains roughly 265,000 galaxies that date back to just 500 million years after the Big Bang.
Image of planetary nebula NGC 7027 with illustration of helium hydride molecules. In this planetary nebula, SOFIA detected helium hydride, a combination of helium (red) and hydrogen (blue), which was the first type of molecule to ever form in the early universe. This is the first time helium hydride has been found in the modern universe.
Credits: NASA/ESA/Hubble Processing: Judy Schmidt
It takes a rich and diverse set of complex molecules for things like stars, galaxies, planets and lifeforms like us to exist. But before humans and all the complex molecules we’re made of could exist, there had to be that first primordial molecule that started a long chain of chemical events that led to everything you see around you today.
Though it’s been long theorized to exist, the lack of observational evidence for that molecule was problematic for scientists. Now they’ve found it and those scientists can rest easy. Their predictive theory wins!
Artist impression of 14 galaxies detected by ALMA as they appear in the very early, very distant universe. These galaxies are in the process of merging and will eventually form the core of a massive galaxy cluster. Credit: NRAO/AUI/NSF; S. Dagnello
Looking deep into the observable Universe – and hence, back to the earliest periods of time – is an immensely fascinating thing. In so doing, astronomers are able to see the earliest galaxies in the Universe and learn more about how they evolved over time. From this, they are not only able to see how large-scale structures (like galaxies and galaxy clusters) formed, but also the role played by dark matter.
Most recently, an international team of scientists used the Atacama Large Millimeter-submillimeter Array (ALMA) to observe the Universe when it was just 1.4 billion years old. What they observed was a “protocluster”, a series of 14 galaxies located 12.4 billion light-years away that were about to merge. This would result in the formation of a massive galaxy cluster, one of the largest objects in the known Universe.
ALMA image of 14 galaxies forming a protocluster known as SPT2349-56. These galaxies are in the process of merging and will eventually form the core of a truly massive galaxy cluster. Credit: ALMA (ESO/NAOJ/NRAO); B. Saxton (NRAO/AUI/NSF)
As they indicate in their study, this protocluster (designated SPT2349-56) was first observed by the National Science Foundation’s South Pole Telescope. Using the Atacama Pathfinder Experiment (APEX), the team conducted follow-up observations that confirmed that it was an extremely distant galactic source, which was then observed with ALMA. Using ALMA’s superior resolution and sensitivity, they were able to distinguish the individual galaxies.
What they found was that these galaxies were forming stars at rate 1,000 times faster than our galaxy, and were crammed inside a region of space that was about three times the size of the Milky Way. Using the ALMA data, the team was also able to create sophisticated computer simulations that demonstrated how this current collection of galaxies will likely grow and evolve over billion of years.
These simulations indicated that once these galaxies merge, the resulting galaxy cluster will rival some of the most massive clusters we see in the Universe today. As Scott Chapman, and astrophysicist at Dalhousie University and a co-author on the study, explained:
“Having caught a massive galaxy cluster in throes of formation is spectacular in and of itself. But, the fact that this is happening so early in the history of the universe poses a formidable challenge to our present-day understanding of the way structures form in the universe.”
Zooming in to the galaxies discovered by ALMA that are evolving into a galaxy cluster. Credit: ALMA (ESO/NAOJ/NRAO), T. Miller & S. Chapman et al.; Herschel; South Pole Telescope; (NRAO/AUI/NSF) B. Saxton
The current scientific consensus among astrophysicists states that a few million years after the Big Bang, normal matter and dark matter began to form larger concentrations, eventually giving rise to galaxy clusters. These objects are the largest structures in the Universe, containing trillions of stars, thousands of galaxies, immense amounts of dark matter and massive black holes.
However, current theories and computer models have suggested that protoclusters – like the one observed by ALMA – should have taken much longer to evolve. Finding one that dates to just 1.4 billion years after the Big Bang was therefore quite the surprise. As Tim Miller, who is currently a doctoral candidate at Yale University, indicated:
“How this assembly of galaxies got so big so fast is a bit of a mystery, it wasn’t built up gradually over billions of years, as astronomers might expect. This discovery provides an incredible opportunity to study how galaxy clusters and their massive galaxies came together in these extreme environments.”
Looking to the future, Chapman and his colleagues hope to conduct further studies of SPT2349-56 to see how this protoclusters eventually became a galaxy cluster. “ALMA gave us, for the first time, a clear starting point to predict the evolution of a galaxy cluster,” he said. “Over time, the 14 galaxies we observed will stop forming stars and will collide and coalesce into a single gigantic galaxy.”
The study of this and other protoclusters will be made possible thanks to instruments like ALMA, but also next-generation observatories like the Square Kilometer Array (SKA). Equipped with more sensitive arrays and more advanced computer models, astronomers may be able to create a truly accurate timeline of how our Universe became what it is today.
