New Clues About How Ancient Galaxies Lit Up The Universe

NASA’s Spitzer Space Telescope has revealed that some of the Universe’s earliest galaxies were brighter than expected. The excess light is a by-product of the galaxies releasing incredibly high amounts of ionising radiation. The finding offers clues to the cause of the Epoch of Reionisation, a major cosmic event that transformed the universe from being mostly opaque to the brilliant starscape seen today. The new work appears in a paper in Monthly Notices of the Royal Astronomical Society.

Researchers report on observations of some of the first galaxies to form in the universe, less than 1 billion years after the big bang (or a little more than 13 billion years ago). The data show that in a few specific wavelengths of infrared light, the galaxies are considerably brighter than scientists anticipated. The study is the first to confirm this phenomenon for a large sampling of galaxies from this period, showing that these were not special cases of excessive brightness, but that even average galaxies present at that time were much brighter in these wavelengths than galaxies we see today.

No one knows for sure when the first stars in our universe burst to life. But evidence suggests that between about 100 million and 200 million years after the Big Bang, the Universe was filled mostly with neutral hydrogen gas that had perhaps just begun to coalesce into stars, which then began to form the first galaxies. By about 1 billion years after the big bang, the Universe had become a sparkling firmament. Something else had changed, too: Electrons of the omnipresent neutral hydrogen gas had been stripped away in a process known as ionisation. The Epoch of Reionisation — the changeover from a universe full of neutral hydrogen to one filled with ionised hydrogen — is well documented.

Before this Universe-wide transformation, long-wavelength forms of light, such as radio waves and visible light, traversed the universe more or less unencumbered. But shorter wavelengths of light — including ultraviolet light, X-rays and gamma rays — were stopped short by neutral hydrogen atoms. These collisions would strip the neutral hydrogen atoms of their electrons, ionising them.

But what could have possibly produced enough ionizing radiation to affect all the hydrogen in the Universe? Was it individual stars? Giant galaxies? If either were the culprit, those early cosmic colonisers would have been different than most modern stars and galaxies, which typically don’t release high amounts of ionising radiation. Then again, perhaps something else entirely caused the event, such as quasars — galaxies with incredibly bright centres powered by huge amounts of material orbiting supermassive black holes.

“It’s one of the biggest open questions in observational cosmology,” said Stephane De Barros, lead author of the study and a postdoctoral researcher at the University of Geneva in Switzerland. “We know it happened, but what caused it? These new findings could be a big clue.”

To peer back in time to the era just before the Epoch of Reionisation ended, Spitzer stared at two regions of the sky for more than 200 hours each, allowing the space telescope to collect light that had travelled for more than 13 billion years to reach us.

As some of the longest science observations ever carried out by Spitzer, they were part of an observing campaign called GREATS, short for GOODS Re-ionization Era wide-Area Treasury from Spitzer. GOODS (itself an acronym: Great Observatories Origins Deep Survey) is another campaign that performed the first observations of some GREATS targets. The study also used archival data from the NASA / ESA Hubble Space Telescope.

Using these ultra-deep observations by Spitzer, the team of astronomers observed 135 distant galaxies and found that they were all particularly bright in two specific wavelengths of infrared light produced by ionising radiation interacting with hydrogen and oxygen gases within the galaxies. This implies that these galaxies were dominated by young, massive stars composed mostly of hydrogen and helium. They contain very small amounts of “heavy” elements (like nitrogen, carbon and oxygen) compared to stars found in average modern galaxies.

These stars were not the first stars to form in the Universe (those would have been composed of hydrogen and helium only) but were still members of a very early generation of stars. The Epoch of Reionisation wasn’t an instantaneous event, so while the new results are not enough to close the book on this cosmic event, they do provide new details about how the Universe evolved at this time and how the transition played out.

“We did not expect that Spitzer, with a mirror no larger than a Hula-Hoop, would be capable of seeing galaxies so close to the dawn of time,” said Michael Werner, Spitzer’s project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “But nature is full of surprises, and the unexpected brightness of these early galaxies, together with Spitzer’s superb performance, puts them within range of our small but powerful observatory.”

The NASA / CSA / ESA James Webb Space Telescope, set to launch in 2021, will study the Universe in many of the same wavelengths observed by Spitzer. But where Spitzer’s primary mirror is only 85 centimetres in diameter, Webb’s is 6.5 metres — about 7.5 times larger — enabling Webb to study these galaxies in far greater detail. In fact, Webb will try to detect light from the first stars and galaxies in the Universe. The new study shows that due to their brightness in those infrared wavelengths, the galaxies observed by Spitzer will be easier for Webb to study than previously thought.

“These results by Spitzer are certainly another step in solving the mystery of cosmic reionisation,” said Pascal Oesch, an assistant professor at the University of Geneva and a co-author on the study. “We now know that the physical conditions in these early galaxies were very different than in typical galaxies today. It will be the job of the James Webb Space Telescope to work out the detailed reasons why.”

Spinning Black Hole Sprays Light-Speed Plasma Clouds Into Space

Astronomers have discovered rapidly swinging jets coming from a black hole almost 8000 light-years from Earth.

Published today in the journal Nature, the research shows jets from V404 Cygni’s black hole behaving in a way never seen before on such short timescales.

The jets appear to be rapidly rotating with high-speed clouds of plasma — potentially just minutes apart — shooting out of the black hole in different directions.

Lead author Associate Professor James Miller-Jones, from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR), said black holes are some of the most extreme objects in the Universe.

“This is one of the most extraordinary black hole systems I’ve ever come across,” Associate Professor Miller-Jones said.

“Like many black holes, it’s feeding on a nearby star, pulling gas away from the star and forming a disk of material that encircles the black hole and spirals towards it under gravity.

“What’s different in V404 Cygni is that we think the disk of material and the black hole are misaligned. “This appears to be causing the inner part of the disk to wobble like a spinning top and fire jets out in different directions as it changes orientation.”

V404 Cygni was first identified as a black hole in 1989 when it released a big outburst of jets and radiation.

Astronomers looking at archival photographic plates then found previous outbursts in observations from 1938 and 1956.

Associate Professor Miller-Jones said that when V404 Cygni experienced another very bright outburst in 2015, lasting for two weeks, telescopes around the world tuned in to study what was going on.

“Everybody jumped on the outburst with whatever telescopes they could throw at it,” he said.

“So we have this amazing observational coverage.”

When Associate Professor Miller-Jones and his team studied the black hole, they saw its jets behaving in a way never seen before.

Where jets are usually thought to shoot straight out from the poles of black holes, these jets were shooting out in different directions at different times.

And they were changing direction very quickly — over no more than a couple of hours.

Associate Professor Miller-Jones said the change in the movement of the jets was because of the accretion disk — the rotating disk of matter around a black hole.

He said V404 Cygni’s accretion disk is 10 million kilometres wide, and the inner few thousand kilometres was puffed up and wobbling during the bright outburst.

“The inner part of the accretion disk was precessing and effectively pulling the jets around with it,” Associate Professor Miller-Jones said.

“You can think of it like the wobble of a spinning top as it slows down — only in this case, the wobble is caused by Einstein’s theory of general relativity.”

The research used observations from the Very Long Baseline Array, a continent-sized radio telescope made up of 10 dishes across the United States, from the Virgin Islands in the Caribbean to Hawaii.

Co-author Alex Tetarenko — a recent PhD graduate from the University of Alberta and currently an East Asian Observatory Fellow working in Hawaii — said the speed the jets were changing direction meant the scientists had to use a very different approach to most radio observations.

“Typically, radio telescopes produce a single image from several hours of observation,” she said.

“But these jets were changing so fast that in a four-hour image we just saw a blur.

“It was like trying to take a picture of a waterfall with a one-second shutter speed.” Instead, the researchers produced 103 individual images, each about 70 seconds long, and joined them together into a movie.

“It was only by doing this that we were able to see these changes over a very short time period,” Dr Tetarenko said.

Study co-author Dr Gemma Anderson, who is also based at ICRAR’s Curtin University node, said the wobble of the inner accretion disk could happen in other extreme events in the Universe too.

“Anytime you get a misalignment between the spin of a black hole and the material falling in, you would expect to see this when a black hole starts feeding very rapidly,” Dr Anderson said.

“That could include a whole bunch of other bright, explosive events in the Universe, such as supermassive black holes feeding very quickly or tidal disruption events, when a black hole shreds a star.”

Unusual Galaxies Defy Dark Matter Theory

After drawing both praise and skepticism, the team of astronomers who discovered NGC 1052-DF2 – the very first known galaxy to contain little to no dark matter – are back with stronger evidence about its bizarre nature.

Dark matter is a mysterious, invisible substance that typically dominates the makeup of galaxies; finding an object that’s missing dark matter is unprecedented, and came as a complete surprise.

“If there’s one object, you always have a little voice in the back of your mind saying, ‘but what if you’re wrong?’ Even though we did all the checks we could think of, we were worried that nature had thrown us for a loop and had conspired to make something look really special whereas it was really something more mundane,” said team leader Pieter van Dokkum, Sol Goldman Family Professor of Astronomy at Yale University.

Now, van Dokkum’s team has not one, but two, new studies supporting their initial observations, demonstrating that dark matter is in fact separable from galaxies.

Team members include Roberto Abraham, Professor of Astronomy and Astrophysics at the University of Toronto, Aaron Romanowsky, Associate Professor of Physics and Astronomy at San Jose State University, Charlie Conroy, Professor of Astronomy at Harvard University, and Shany Danieli, a graduate student at Yale University.

“The fact that we’re seeing something that’s just completely new is what’s so fascinating,” said Danieli, who first spotted the galaxy about two years ago. “No one knew that such galaxies existed, and the best thing in the world for an astronomy student is to discover an object, whether it’s a planet, a star, or a galaxy, that no one knew about or even thought about.”

What Happened Before the Big Bang?

A team of scientists has proposed a powerful new test for inflation, the theory that the universe dramatically expanded in size in a fleeting fraction of a second right after the Big Bang. Their goal is to give insight into a long-standing question: what was the universe like before the Big Bang?

Although cosmic inflation is well known for resolving some important mysteries about the structure and evolution of the universe, other very different theories can also explain these mysteries. In some of these theories, the state of the universe preceding the Big Bang – the so-called primordial universe – was contracting instead of expanding, and the Big Bang was thus a part of a Big Bounce.

To help decide between inflation and these other ideas, the issue of falsifiability – that is, whether a theory can be tested to potentially show it is false – has inevitably arisen. Some researchers, including Avi Loeb of the Center for Astrophysics | Harvard & Smithsonian (CfA) in Cambridge, Mass., have raised concerns about inflation, suggesting that its seemingly endless adaptability makes it all but impossible to properly test.

“Falsifiability should be a hallmark of any scientific theory. The current situation for inflation is that it’s such a flexible idea, it cannot be falsified experimentally,” Loeb said. “No matter what value people measure for some observable attribute, there are always some models of inflation that can explain it.”

Now, a team of scientists led by the CfA’s Xingang Chen, along with Loeb, and Zhong-Zhi Xianyu of the Physics Department of Harvard University, have applied an idea they call a “primordial standard clock” to the non-inflationary theories, and laid out a method that may be used to falsify inflation experimentally. The study will appear in Physical Review Letters as an Editors’ Suggestion.

In an effort to find some characteristic that can separate inflation from other theories, the team began by identifying the defining property of the various theories – the evolution of the size of the primordial universe.

“For example, during inflation, the size of the universe grows exponentially,” Xianyu said. “In some alternative theories, the size of the universe contracts. Some do it very slowly, while others do it very fast.

“The attributes people have proposed so far to measure usually have trouble distinguishing between the different theories because they are not directly related to the evolution of the size of the primordial universe,” he continued. “So, we wanted to find what the observable attributes are that can be directly linked to that defining property.”

The signals generated by the primordial standard clock can serve such a purpose. That clock is any type of heavy elementary particle in the primordial universe. Such particles should exist in any theory and their positions should oscillate at some regular frequency, much like the ticking of a clock’s pendulum.

The primordial universe was not entirely uniform. There were tiny irregularities in density on minuscule scales that became the seeds of the large-scale structure observed in today’s universe. This is the primary source of information physicists rely on to learn about what happened before the Big Bang. The ticks of the standard clock generated signals that were imprinted into the structure of those irregularities. Standard clocks in different theories of the primordial universe predict different patterns of signals, because the evolutionary histories of the universe are different.

“If we imagine all of the information we learned so far about what happened before the Big Bang is in a roll of film frames, then the standard clock tells us how these frames should be played,” Chen explained. “Without any clock information, we don’t know if the film should be played forward or backward, fast or slow, just like we are not sure if the primordial universe was inflating or contracting, and how fast it did so. This is where the problem lies. The standard clock put time stamps on each of these frames when the film was shot before the Big Bang, and tells us how to play the film.”

The team calculated how these standard clock signals should look in non-inflationary theories, and suggested how they should be searched for in astrophysical observations. “If a pattern of signals representing a contracting universe were found, it would falsify the entire inflationary theory,” Xianyu said.

The success of this idea lies with experimentation. “These signals will be very subtle to detect,” Chen said, “and so we may have to search in many different places. The cosmic microwave background radiation is one such place, and the distribution of galaxies is another. We have already started to search for these signals and there are some interesting candidates already, but we need more data.”

Many future galaxy surveys, such as US-lead LSST, European’s Euclid and the newly approved project by NASA, SphereX, are expected to provide high quality data that can be used toward the goal.

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First Accurate 3D Map Of The Milky Way Reveals A Warped Galaxy

Our Milky Way galaxy’s disk of stars is anything but stable and flat. Instead, it becomes increasingly ‘warped’ and twisted far away from the Milky Way’s centre, according to astronomers from Macquarie University and the Chinese Academy of Sciences, who have built the first accurate 3D map of Earth’s home galaxy and unveiled it today in a paper published in Nature Astronomy.

o;s centre, according to astronomers from Macquarie University and the Chinese Academy of Sciences, who have built the first accurate 3D map of Earth’s home galaxy and unveiled it today in a paper published in Nature Astronomy.
From a great distance, our galaxy would look like a thin disk of stars that orbit once every few hundred million years around its central region, where hundreds of billions of stars provide the gravitational ‘glue’ to hold it all together.

But the pull of gravity becomes weaker far away from the Milky Way’s inner regions. In the galaxy’s far outer disk, the hydrogen atoms making up most of the Milky Way’s gas disk are no longer confined to a thin plane, but they give the disk an S-like, warped appearance.

“It is notoriously difficult to determine distances from the sun to parts of the Milky Way’s outer gas disk without having a clear idea of what that disk actually looks like,” says Xiaodian Chen, a researcher at the Chinese Academy of Sciences in Beijing and lead author of the article in Nature Astronomy.

“However, we recently published a new catalogue of well-behaved variable stars known as classical Cepheids, for which distances as accurate as 3 to 5 per cent can be determined.” That database allowed the team to develop the first accurate three-dimensional picture of our Milky Way out to its far outer regions.

Classical Cepheids are young stars that are some four to 20 times as massive as our Sun and up to 100,000 times as bright. Such high stellar masses imply that they live fast and die young, burning through their nuclear fuel very quickly, sometimes in only a few million years.

They show day- to month-long pulsations, which are observed as changes in their brightness. Combined with a Cepheid’s observed brightness, its pulsation period can be used to obtain a highly reliable distance.

“Somewhat to our surprise, we found that in 3D our collection of 1339 Cepheid stars and the Milky Way’s gas disk follow each other closely. This offers new insights into the formation of our home galaxy,” says Macquarie University’s Professor Richard de Grijs, astronomer and senior co-author on the paper.

“Perhaps more important, in the Milky Way’s outer regions, we found that the S-like stellar disk is warped in a progressively twisted spiral pattern.”

This reminded the team of earlier observations of a dozen other galaxies which also showed such progressively twisted spiral patterns.

Combining their new results with those other observations, the researchers concluded that the Milky Way’s warped spiral pattern is most likely caused by ‘torques’ – or rotational forcing – by the massive inner disk.

“This new morphology provides a crucial updated map for studies of our galaxy’s stellar motions and the origins of the Milky Way’s disk,” according to Licai Deng, senior researcher at the Chinese Academy of Sciences and co-author on the paper.

Active Galaxies Point To New Physics Of Cosmic Expansion

Investigating the history of our cosmos with a large sample of distant ‘active’ galaxies observed by ESA’s XMM-Newton, a team of astronomers found there might be more to the early expansion of the universe than predicted by the standard model of cosmology.

According to the leading scenario, our universe contains only a few percent of ordinary matter. One quarter of the cosmos is made of the elusive dark matter, which we can feel gravitationally but not observe, and the rest consists of the even more mysterious dark energy that is driving the current acceleration of the universe’s expansion.

This model is based on a multitude of data collected over the last couple of decades, from the cosmic microwave background, or CMB – the first light in the history of the cosmos, released only 380,000 years after the big bang and observed in unprecedented detail by ESA’s Planck mission – to more ‘local’ observations. The latter include supernova explosions, galaxy clusters and the gravitational distortion imprinted by dark matter on distant galaxies, and can be used to trace cosmic expansion in recent epochs of cosmic history – across the past nine billion years.

A new study, led by Guido Risaliti of Università di Firenze, Italy, and Elisabeta Lusso of Durham University, UK, points to another type of cosmic tracer – quasars – that would fill part of the gap between these observations, measuring the expansion of the universe up to 12 billion years ago.

Quasars are the cores of galaxies where an active supermassive black hole is pulling in matter from its surroundings at very intense rates, shining brightly across the electromagnetic spectrum. As material falls onto the black hole, it forms a swirling disc that radiates in visible and ultraviolet light; this light, in turn, heats up nearby electrons, generating X-rays.

Three years ago, Guido and Elisabeta realised that a well-known relation between the ultraviolet and X-ray brightness of quasars could be used to estimate the distance to these sources – something that is notoriously tricky in astronomy – and, ultimately, to probe the expansion history of the universe.

Astronomical sources whose properties allow us to gauge their distances are referred to as ‘standard candles’.

The most notable class, known as ‘type-Ia’ supernova, consists of the spectacular demise of white dwarf stars after they have over-filled on material from a companion star, generating explosions of predictable brightness that allows astronomers to pinpoint the distance. Observations of these supernovas in the late 1990s revealed the universe’s accelerated expansion over the last few billion years.

“Using quasars as standard candles has great potential, since we can observe them out to much greater distances from us than type-Ia supernovas, and so use them to probe much earlier epochs in the history of the cosmos,” explains Elisabeta.
With a sizeable sample of quasars at hand, the astronomers have now put their method into practice, and the results are intriguing.

Digging into the XMM-Newton archive, they collected X-ray data for over 7000 quasars, combining them with ultraviolet observations from the ground-based Sloan Digital Sky Survey. They also used a new set of data, specially obtained with XMM-Newton in 2017 to look at very distant quasars, observing them as they were when the universe was only about two billion years old. Finally, they complemented the data with a small number of even more distant quasars and with some relatively nearby ones, observed with NASA’s Chandra and Swift X-ray observatories, respectively.

“Such a large sample enabled us to scrutinise the relation between X-ray and ultraviolet emission of quasars in painstaking detail, which greatly refined our technique to estimate their distance,” says Guido.

The new XMM-Newton observations of distant quasars are so good that the team even identified two different groups: 70 percent of the sources shine brightly in low-energy X-rays, while the remaining 30 percent emit lower amounts of X-rays that are characterised by higher energies. For the further analysis, they only kept the earlier group of sources, in which the relation between X-ray and ultraviolet emission appears clearer.

“It is quite remarkable that we can discern such level of detail in sources so distant from us that their light has been travelling for more than ten billion years before reaching us,” says Norbert Schartel, XMM-Newton project scientist at ESA.

After skimming through the data and bringing the sample down to about 1600 quasars, the astronomers were left with the very best observations, leading to robust estimates of the distance to these sources that they could use to investigate the universe’s expansion.

“When we combine the quasar sample, which spans almost 12 billion years of cosmic history, with the more local sample of type-Ia supernovas, covering only the past eight billion years or so, we find similar results in the overlapping epochs,” says Elisabeta.

“However, in the earlier phases that we can only probe with quasars, we find a discrepancy between the observed evolution of the universe and what we would predict based on the standard cosmological model.”
Looking into this previously poorly explored period of cosmic history with the help of quasars, the astronomers have revealed a possible tension in the standard model of cosmology, which might require the addition of extra parameters to reconcile the data with theory.

“One of the possible solutions would be to invoke an evolving dark energy, with a density that increases as time goes by,” says Guido.

Incidentally, this particular model would also alleviate another tension that has kept cosmologists busy lately, concerning the Hubble constant – the current rate of cosmic expansion. This discrepancy was found between estimates of the Hubble constant in the local universe, based on supernova data – and, independently, on galaxy clusters – and those based on Planck’s observations of the cosmic microwave background in the early universe.

“This model is quite interesting because it might solve two puzzles at once, but the jury is definitely not out yet and we’ll have to look at many more models in great detail before we can solve this cosmic conundrum,” adds Guido.

The team is looking forward to observing even more quasars in the future to further refine their results. Additional clues will also come from ESA’s Euclid mission, scheduled for a 2022 launch to explore the past ten billion years of cosmic expansion and investigate the nature of dark energy.

“These are interesting times to investigate the history of our universe, and it’s exciting that XMM-Newton can contribute by looking at a cosmic epoch that had remained largely unexplored so far,” concludes Norbert.

Star Material Could Be Building Block Of Life

An organic molecule detected in the material from which a star forms could shed light on how life emerged on Earth, according to new research led by Queen Mary University of London.

The researchers report the first ever detection of glycolonitrile (HOCH2CN), a pre-biotic molecule which existed before the emergence of life, in a solar-type protostar known as IRAS16293-2422 B.

This warm and dense region contains young stars at the earliest stage of their evolution surrounded by a cocoon of dust and gas — similar conditions to those when our Solar System formed.

Detecting pre-biotic molecules in solar-type protostars enhances our understanding of how the solar system formed as it indicates that planets created around the star could begin their existence with a supply of the chemical ingredients needed to make some form of life.

This finding, published in the journal Monthly Notices of the Royal Astronomical Society: Letters, is a significant step forward for pre-biotic astrochemistry since glycolonitrile is recognised as a key precursor towards the formation of adenine, one of the nucleobases that form both DNA and RNA in living organisms.

IRAS16293-2422 B is a well-studied protostar in the constellation of Ophiuchus, in a region of star formation known as rho Ophiuchi, about 450 light-years from Earth.

The research was also carried out with the Centro de Astrobiología in Spain, INAF-Osservatorio Astrofisico di Arcetri in Italy, the European Southern Observatory, and the Harvard-Smithsonian Center for Astrophysics in the USA.

Lead author Shaoshan Zeng, from Queen Mary University of London, said: “We have shown that this important pre-biotic molecule can be formed in the material from which stars and planets emerge, taking us a step closer to identifying the processes that may have led to the origin of life on Earth.”

The researchers used data from the Atacama Large Millimeter/submillimetre Array (ALMA) telescope in Chile to uncover evidence for the presence of glycolonitrile in the material from which the star is forming — known as the interstellar medium.

With the ALMA data, they were able to identify the chemical signatures of glycolonitrile and determine the conditions in which the molecule was found. They also followed this up by using chemical modelling to reproduce the observed data which allowed them to investigate the chemical processes that could help to understand the origin of this molecule.

This follows the earlier detection of methyl isocyanate in the same object by researchers from Queen Mary. Methyl isocyanate is what is known as an isomer of glycolonitrile — it is made up of the same atoms but in a slightly different arrangement, meaning it has different chemical properties.

The research was partially funded by Queen Mary University of London and the UK Science and Technology Facilities Council.