Amazing Science

The black hole, located about 656 million light-years away from Earth, has a powerful jet streaming from its core. This jet, which is blasted out at light-like speeds, has “drastically” changed directions. The black hole just changed its direction in a way that is perpendicular to our line of sight, and it now faces Earth. This is a very exceptional case of jet reorientation and has led to the redefinition of the galaxy that houses this black hole.

The Peculiar Properties of PBC J2333.9-2343

PBC J2333.9-2343 is a distant galaxy that spans four million light-years. It shines strongly in radio wavelengths, making it a radio galaxy. The core of this galaxy had blasted jets in the past but had long gone quiet. In the latest research, astronomers found that the core had once again stirred the jets back to life, and one of them had changed its direction.

Given the sharp change in the jet’s orientation, astronomers have redefined the giant radio galaxy into one with a blazar at its center. Blazars are galaxies whose cores have jets aimed directly at Earth. This is the first time astronomers have observed a galaxy transform from one group to another, marking a significant milestone in our understanding of these celestial objects.

The Mystery of Jet Reorientation

While the black hole just changed its direction, the reasons behind such changes are not very well understood. Some astronomers speculate that mergers of galaxies or black holes contribute to the intermittent bursts of jet activity, and that the directions of the jets change between bursts. This erratic behavior of jets is also observed in bright but rare X-shaped galaxies.

Conclusion: A Cosmic First and Its Implications

The black hole just changed its direction, marking a cosmic first that is reshaping our understanding of black holes and their behavior. As scientists continue to study PBC J2333.9-2343 and other celestial objects, we can expect to gain more insights into the nature of black holes and their jets. These insights will not only help us understand these celestial objects better but also shed light on the mysteries of the cosmos.

Astronomers from the University of Texas and the University of Arizona have discovered a rapidly growing black hole in one of the most extreme galaxies known in the very early Universe. The discovery of the galaxy and the black hole at its centre provides new clues on the formation of the very first supermassive black holes. The new work is published in Monthly Notices of the Royal Astronomical Society.

Gravitational waves identify what could be a rare one-in-1000 event

Researchers at Cardiff University have identified a peculiar twisting motion in the orbits of two colliding black holes, an exotic phenomenon predicted by Einstein's theory of gravity. Their study, which is published in Nature and led by Professor Mark Hannam, Dr Charlie Hoy and Dr Jonathan Thompson, reports that this is the first time this effect, known as precession, has been seen in black holes, where the twisting is 10 billion times faster than in previous observations.

The binary black hole system was found through gravitational waves in early 2020 in the Advanced LIGO and Virgo detectors. One of the black holes, 40 times bigger than our Sun, is likely the fastest spinning black hole to be found through gravitational waves. And unlike all previous observations, the rapidly revolving black hole distorted space and time so much that the binary's entire orbit wobbled back and forth.

This form of precession is specific to Einstein's theory of general relativity. These results confirm its existence in the most extreme physical event we can observe, the collision of two black holes. "We've always thought that binary black holes can do this," said Professor Mark Hannam of Cardiff University's Gravity Exploration Institute. "We have been hoping to spot an example ever since the first gravitational wave detections. We had to wait for five years and over 80 separate detections, but finally we have one!"

Black holes with varying light signatures but that were thought to be the same objects being viewed from different angles are actually in different stages of the life cycle, according to a study led by Dartmouth researchers. The research on black holes known as "active galactic nuclei," or AGNs, says that it definitively shows the need to revise the widely used "unified model of AGN" that characterizes supermassive black holes as all having the same properties. The study, published in The Astrophysical Journal, provides answers to a nagging space mystery and should allow researchers to create more precise models about the evolution of the universe and how black holes develop.

"These objects have mystified researchers for over a half-century," said Tonima Tasnim Ananna, a postdoctoral research associate at Dartmouth and lead author of the paper. "Over time, we've made many assumptions about the physics of these objects. Now we know that the properties of obscured black holes are significantly different from the properties of AGNs that are not as heavily hidden." Supermassive black holes are believed to reside at the center of nearly all large galaxies, including the Milky Way. The objects devour galactic gas, dust and stars, and they can become heavier than small galaxies.

For decades, researchers have been interested in the light signatures of active galactic nuclei, a type of supermassive black hole that is "accreting," or in a rapid growth stage. Beginning in the late 1980s, astronomers realized that light signatures coming from space ranging from radio wavelengths to X-rays could be attributed to AGNs. It was assumed that the objects usually had a doughnut-shaped ring -- or "torus" -- of gas and dust around them.

The different brightness and colors associated with the objects were thought to be the result of the angle from which they were being observed and how much of the torus was obscuring the view. From this, the unified theory of AGNs became the prevalent understanding. The theory guides that if a black hole is being viewed through its torus, it should appear faint. If it is being viewed from below or above the ring, it should appear bright. According to the current study, however, the past research relied too heavily on data from the less obscured objects and skewed research results.

Astronomers have identified a rapidly growing black hole in the early universe that is considered a crucial "missing link" between young star-forming galaxies and the first supermassive black holes. They used data from NASA's Hubble Space Telescope to make this discovery. Until now, the monster, nicknamed GNz7q, had been lurking unnoticed in one of the best-studied areas of the night sky, the Great Observatories Origins Deep Survey-North (GOODS-North) field.

Archival Hubble data from Hubble's Advanced Camera for Surveys helped the team determine that GNz7q existed just 750 million years after the big bang. The team obtained evidence that GNz7q is a newly formed black hole. Hubble found a compact source of ultraviolet (UV) and infrared light. This couldn't be caused by emission from galaxies, but is consistent with the radiation expected from materials that are falling onto a black hole. Rapidly growing black holes in dusty, early star-forming galaxies are predicted by theories and computer simulations, but had not been observed until now.

"Our analysis suggests that GNz7q is the first example of a rapidly growing black hole in the dusty core of a starburst galaxy at an epoch close to the earliest supermassive black hole known in the universe," explained Seiji Fujimoto, an astronomer at the Niels Bohr Institute of the University of Copenhagen and lead author of the Nature paper describing this discovery. "The object's properties across the electromagnetic spectrum are in excellent agreement with predictions from theoretical simulations."

One of the outstanding mysteries in astronomy today is: How did supermassive black holes, weighing millions to billions of times the mass of the Sun, get to be so huge so fast? Current theories predict that supermassive black holes begin their lives in the dust-shrouded cores of vigorously star-forming "starburst" galaxies before expelling the surrounding gas and dust and emerging as extremely luminous quasars. While extremely rare, both these dusty starburst galaxies and luminous quasars have been detected in the early universe.

The team believes that GNz7q could be a missing link between these two classes of objects. GNz7q has exactly both aspects of the dusty starburst galaxy and the quasar, where the quasar light shows the dust reddened color. Also, GNz7q lacks various features that are usually observed in typical, very luminous quasars (corresponding to the emission from the accretion disk of the supermassive black hole), which is most likely explained that the central black hole in GN7q is still in a young and less massive phase. These properties perfectly match with the young, transition phase quasar that has been predicted in simulations, but never identified at similarly high-redshift universe as the very luminous quasars so far identified up to a redshift of 7.6.

"GNz7q provides a direct connection between these two rare populations and provides a new avenue toward understanding the rapid growth of supermassive black holes in the early days of the universe," continued Fujimoto. "Our discovery provides an example of precursors to the supermassive black holes we observe at later epochs."

Everything you can see, and everything you could possibly see, right now, assuming your eyes could detect all types of radiations around you -- is the observable universe. In light, the farthest we can see comes from the cosmic microwave background, a time 13.8 billion years ago when the universe was opaque like thick fog. Some neutrinos and gravitational waves that surround us come from even farther out, but humanity does not yet have the technology to detect them.

The featured image illustrates the observable universe on an increasingly compact scale, with the Earth and Sun at the center surrounded by our Solar System, nearby stars, nearby galaxies, distant galaxies, filaments of early matter, and the cosmic microwave background. Cosmologists typically assume that our observable universe is just the nearby part of a greater entity known as "the universe" where the same physics applies. However, there are several lines of popular but speculative reasoning that assert that even our universe is part of a greater multiverse where either different physical constants occur, different physical laws apply, higher dimensions operate, or slightly different-by-chance versions of our standard universe exist.

The feeding patterns of black holes offer insight into their size, researchers report. A new study revealed that the flickering in the brightness observed in actively feeding supermassive black holes is related to their mass.

Supermassive black holes are millions to billions of times more massive than the sun and usually reside at the center of massive galaxies. When dormant and not feeding on the gas and stars surrounding them, SMBHs emit very little light; the only way astronomers can detect them is through their gravitational influences on stars and gas in their vicinity. However, in the early universe, when SMBHs were rapidly growing, they were actively feeding—or accreting—materials at intensive rates and emitting an enormous amount of radiation—sometimes outshining the entire galaxy in which they reside, the researchers said.

The new study, led by the University of Illinois Urbana-Champaign astronomy graduate student Colin Burke and professor Yue Shen, uncovered a definitive relationship between the mass of actively feeding SMBHs and the characteristic timescale in the light-flickering pattern. The findings are published in the journal Science.

The observed light from an accreting SMBH is not constant. Due to physical processes that are not yet understood, it displays a ubiquitous flickering over timescales ranging from hours to decades. "There have been many studies that explored possible relations of the observed flickering and the mass of the SMBH, but the results have been inconclusive and sometimes controversial," Burke said.

The team compiled a large data set of actively feeding SMBHs to study the variability pattern of flickering. They identified a characteristic timescale, over which the pattern changes, that tightly correlates with the mass of the SMBH. The researchers then compared the results with accreting white dwarfs, the remnants of stars like our sun, and found that the same timescale-mass relation holds, even though white dwarfs are millions to billions times less massive than SMBHs.

The light flickers are random fluctuations in a black hole's feeding process, the researchers said. Astronomers can quantify this flickering pattern by measuring the power of the variability as a function of timescales. For accreting SMBHs, the variability pattern changes from short timescales to long timescales. This transition of variability pattern happens at a characteristic timescale that is longer for more massive black holes.

The team compared black hole feeding to our eating or drinking activity by equating this transition to a human belch. Babies frequently burp while drinking milk, while adults can hold in the burp for a more extended amount of time. Black holes kind of do the same thing while feeding, they said. "These results suggest that the processes driving the flickering during accretion are universal, whether the central object is a supermassive black hole or a much more lightweight white dwarf," Shen said.

The search for life beyond Earth is really just getting started, but science has an encouraging early answer: there are plenty of planets in the galaxy, many with similarities to our own. But what we don’t know fills volumes.

Observations from the ground and from space have confirmed thousands of planets beyond our solar system. Our galaxy likely holds trillions. But so far, we have no evidence of life beyond Earth. Is life in the cosmos easily begun, and commonplace? Or is it incredibly rare?

More questions than answers

In the thousands of years humanity has been contemplating the cosmos, we are the first people to know one thing for sure: The stars beyond our Sun are teeming with planets. They come in many varieties, and a good chunk of them are around the size of Earth. Like most scientific questions, though, getting an answer to this one just breeds more questions: Which, if any, of these exoplanets harbors some form of life? How quickly does life get its start? And how long does it last? 

Where is everybody?

The universe's eerie silence has its own name – the "Fermi paradox." Physicist Enrico Fermi famously posed the question: "Where is everybody?" Even at slow travel speeds, the universe's billions of years of existence allow plenty of time for intelligent, technological lifeforms to traverse the galaxy. Why, then, is the cosmos so quiet?

Meanwhile, exoplanet discoveries over the past two decades have filled in a few of the terms in the much-debated Drake Equation – a chain of numbers that might one day tell us how many intelligent civilizations we can expect to find. Most of its terms remain blank – the fraction of planets with life, with intelligent life, with detectable technology – but the equation itself suggests we might one day arrive at an answer. It feels at least a little more hopeful than Fermi's silence.

Is Earth an Oddball? We stand at a crossroads in the search for life. We've found thousands of planets in our Milky Way galaxy, a large fraction of them in Earth's size range and orbiting in their stars' "habitable zones" – the distance from the star at which liquid water could exist on the surface. We know the galaxy likely holds trillions of planets. Our telescopes in space and on the ground, and our remote-sensing technology, grow ever more powerful. Yet so far, the only life we know of is right here at home. For the moment, we're staring into the void, hoping someone is staring back.

No matter if you enjoy taking or just watching images of space, NASA has a treat for you. They have made their entire collection of images, sounds, and video available and publicly searchable online. It’s 140,000 photos and other resources available for you to see, or even download and use it any way you like.

You can type in the term you want to search for and browse through the database of stunning images of outer space. Additionally, there are also images of astronauts, rocket launches, events at NASA and other interesting stuff. What’s also interesting is that almost every image comes with the EXIF data, which could be useful for astrophotography enthusiasts.

NASA recently launched a GIPHY account full of awesome animated gifs. It’s also great that photography is an important part of their missions, and so it was even before “pics or it didn’t happen” became the rule. The vast media library they have now published is available to everyone, free of charge and free of copyright. Therefore, you can take a peek at the fascinating mysteries of space, check out what it’s like inside NASA’s premises, or download the images to make something awesome from them. Either way, you will enjoy it!

The word “Universe” comes from the Latin “Universum”, which was used by Roman authors to refer to the cosmos as they knew them. This consisted of the Earth and all life as well as the Moon, the Sun, the planets that they knew about (Mercury, Venus, Mars, Jupiter, Saturn) and the stars.

The term “cosmos”, on the other hand, is derived from the Greek word kosmos, which means "order" or “the world”. Other words commonly used to define all of known-existence include “Nature” (from the Germanic word natur) and the English word “everything” (self-explanatory).

Today, the word Universe is used by scientists to refer to all existing matter and space. This includes the Solar System, the Milky Way, all known galaxies, and superstructures. In terms of modern science and astrophysics, it also includes all time, space, matter, energy, and the fundamental forces that bind them.

Cosmology, on the other hand, is used to describe the study of the Universe (or cosmos) and the forces that bind it. Thanks to thousands of years of scholarship, what we know about the physical Universe has grown by leaps and bounds. And yet, there is still so much that we don't understand.

Astronomers have detected a stealthy black hole from its effects on an interstellar gas cloud. This intermediate mass black hole is one of over 100 million quiet black holes expected to be lurking in our Galaxy. These results provide a new method to search for other hidden black holes and help us understand the growth and evolution of black holes.

Black holes are objects with such strong gravity that everything, including light, is sucked in and cannot escape. Because black holes do not emit light, astronomers must infer their existence from the effects their gravity produces in other objects. Black holes range in mass from about 5 times the mass of the Sun to supermassive black holes millions of times the mass of the Sun. Astronomers think that small black holes merge and gradually grow into large ones, but no one had ever found an intermediate mass black hole, hundreds or thousands of times the mass of the Sun.

A research team led by Shunya Takekawa at the National Astronomical Observatory of Japan noticed HCN-0.009-0.044, a gas cloud moving strangely near the center of the Galaxy 25,000 light-years away from Earth in the constellation Sagittarius. They used ALMA (Atacama Large Millimeter/submillimeter Array) to perform high resolution observations of the cloud and found that it is swirling around an invisible massive object.

Takekawa explains, "Detailed kinematic analyses revealed that an enormous mass, 30,000 times that of the Sun, was concentrated in a region much smaller than our Solar System. This and the lack of any observed object at that location strongly suggests an intermediate-mass black hole. By analyzing other anomalous clouds, we hope to expose other quiet black holes."

A multitude of discoveries are on the horizon after this much awaited release, which is based on 22 months of charting the sky. The new data includes positions, distance indicators and motions of more than one billion stars, along with high-precision measurements of asteroids within our Solar System and stars beyond our own Milky Way Galaxy.

"The observations collected by Gaia are redefining the foundations of astronomy," says Günther Hasinger, ESA Director of Science.Preliminary analysis of this phenomenal data reveals fine details about the make-up of the Milky Way's stellar population and about how stars move, essential information for investigating the formation and evolution of our home Galaxy.

"Gaia is an ambitious mission that relies on a huge human collaboration to make sense of a large volume of highly complex data. It demonstrates the need for long-term projects to guarantee progress in space science and technology and to implement even more daring scientific missions of the coming decades."

Gaia was launched in December 2013 and started science operations the following year. The first data release, based on just over one year of observations, was published in 2016; it contained distances and motions of two million stars.

The new data release, which covers the period between 25 July 2014 and 23 May 2016, pins down the positions of nearly 1.7 billion stars, and with a much greater precision. For some of the brightest stars in the survey, the level of precision equates to Earth-bound observers being able to spot a Euro coin lying on the surface of the Moon.

The universe is expanding, with every galaxy beyond the Local Group speeding away from us. Today, most of the universe's galaxies are already receding faster than the speed of light. All galaxies currently beyond 18 billion light-years are forever unreachable by us, no matter how much time passes.

Our universe is full of stars and galaxies everywhere and in all directions. From our vantage point, we observe up to 46.1 billion light years away. Our visible universe contains an estimated ~ 2 trillion galaxies. However, most of them are already permanently unavailable for us.

So bright that it pushes the energy limits of physics.

Billions of light years away, there is a giant ball of hot gas that is brighter than hundreds of billions of suns. It is hard to imagine something so bright. So what is it? Astronomers are not really sure, but they have a couple theories. They think it may be a very rare type of supernova — called a magnetar — but one so powerful that it pushes the energy limits of physics, or in other words, the most powerful supernova ever seen as of today. This object is so luminous that astronomers are having a really difficult time finding a way to describe it.

“If it really is a magnetar, it's as if nature took everything we know about magnetars and turned it up to 11,” said Krzysztof Stanek, professor of astronomy at Ohio State University and the team's co-principal investigator, comedically implying it is off the charts on a scale of 1 to 10.The object was first spotted by the All Sky Automated Survey of Supernovae (ASAS-SN or “assassin”), which is a small network of telescopes used to detect bright objects in the universe. Although this object is ridiculously bright, it still can’t be seen by the naked eye because it is 3.8 billion light years away.

ASAS-SN, since it began in 2014, has discovered nearly 250 supernovae, however this discovery, ASASSN-15lh, stands out because of its sheer magnitude. It is 200 times more powerful than the average supernova, 570 billion times brighter than the sun, and 20 times brighter than all the stars in the Milky Way Galaxy combined. “We have to ask, how is that even possible?” said Stanek. “It takes a lot of energy to shine that bright, and that energy has to come from somewhere.”

Todd Thompson, professor of astronomy at Ohio State, has one possible explanation. The supernova could have generated an extremely rare type of star called a millisecond magnetar — a rapidly spinning and very dense star with a crazy strong magnetic field. This is how crazy magnetars are: to shine as bright as it does, this magnetar would have to spin at least 1,000 times a second, and convert all of that rotational energy to light with pretty much 100 percent efficiency — making it the most extreme example of a magnetar that is physically possible.

Given those constraints,” Thompson said, “will we ever see anything more luminous than this? If it truly is a magnetar, then the answer is basically no.” Over the coming months, the Hubble Space Telescope will try to solve this mystery by giving astronomers time to see the host galaxy surrounding this object. The team may find that this bright object lies in the very center of a large galaxy — meaning the object is not a magnetar at all — and the gas around it is actually evidence of a supermassive black hole.

If that is the case, then the bright light could be explained by a new kind of event, said study co-author Christopher Kochanek, professor of astronomy at Ohio State. It would be something that has never, ever been seen before at the center of a galaxy.

Whether it is a magnetar, a supermassive black hole, or something else entirely (like a white hole), the results are probably going to lead to new thinking about how objects form in the universe.

Cosmologists are getting closer to understanding what the future and ultimate fate of the universe will be.

Late last century, one of the most pressing issues in modern cosmology was to measure the deceleration rate of the universe. Given the amount of mass observed in the cosmos it was thought that it might be enough to cause an eventual contraction of the expansion. Remarkably, two independent teams of scientists found the exact opposite. The universe was not slowing down in its expansion, it was accelerating. This profound discovery lead to the Nobel prize in physics in 2011. However, understanding the implications of it remains challenging.

One way to think about the accelerating universe is that there must be some kind of material (or field) that permeates the universe that exerts a negative pressure (or a repulsive gravity). We call this dark energy. This may sound a bit far-fetched, but independent experiments have been conducted to corroborate the acceleration of the universe and the existence of dark energy. From 2006, I was involved in the WiggleZ Dark Energy Survey – a scientific experiment to independently confirm the acceleration. Not only did we find that the acceleration is happening, but we provided compelling evidence that the cause of this was dark energy. We observed that dark energy was retarding the growth of massive superclusters of galaxies. The growth rate of superclusters like Virgo is providing strong evidence for the existence of dark energy.
We therefore think that dark energy is real. If the concept of dark energy and its repulsive gravitation force is too weird, then an alternative to consider is that perhaps our theory of gravitation needs to be modified. This might be achieved in in a similar way that relativity advanced Newtonian gravitation. Either way, we need new physics to explain it.

The future

Before turning to the very distant future, I will mention another relevant survey: GAMA. Using that survey, we found that the universe is slowing "dying". Put another way: the peak era of star formation is well behind us, and the universe is already fading.

The more "immediate" future can be predicted with some certainty. Five billion years from now, the sun will enter its red giant phase. Depressingly, no more than two more billion years after that, it will consume Earth.

After that, the relative strength of dark energy and how it might vary over time becomes important. The stronger and faster the repulsive force of dark energy is, the more likely it is that the universe will experience a Big Rip. Put bluntly: the Big Rip is what happens when the repulsive force of dark energy is able to overcome gravitation (and everything else). Bodies that are gravitationally bound (such as our local supercluster, our own Milky Way galaxy, our solar system, and eventually ourselves) become ripped apart and all that is left is (probably) lonesome patches of vacuum. The data from the WiggleZ survey and other experiments do not rule out the Big Rip, but push it in to the exceptionally far future (if at all).

Somewhat more pressing is the heat death of the universe. As the universe carries on expanding, we will no longer be able to observe galaxies outside our local group (100 million years from now). Star formation will then cease in about 1-100 trillion years as the supply of gas needed will be exhausted. While there will be some stars around, these will run out of fuel in some 120 trillion years. All that is left at that point is stellar remnants: black holes, neutron stars, & white dwarfs being the prime examples. One hundred quintillion (10<sup>20) years from now, most of these objects will be swallowed up by the supermassive black holes at the heart of galaxies.

Scientists have known for almost a century that the universe is expanding, meaning the distance between galaxies across the universe is becoming ever more vast every second. But exactly how fast space is stretching, a value known as the Hubble constant, has remained stubbornly elusive.

Now, University of Chicago professor Wendy Freedman and colleagues have a new measurement for the rate of expansion in the modern universe, suggesting the space between galaxies is stretching faster than scientists would expect. Freedman's is one of several recent studies that point to a nagging discrepancy between modern expansion measurements and predictions based on the universe as it was more than 13 billion years ago, as measured by the European Space Agency's Planck satellite.

As more research points to a discrepancy between predictions and observations, scientists are considering whether they may need to come up with a new model for the underlying physics of the universe in order to explain it.

"The Hubble constant is the cosmological parameter that sets the absolute scale, size and age of the universe; it is one of the most direct ways we have of quantifying how the universe evolves," said Freedman. "The discrepancy that we saw before has not gone away, but this new evidence suggests that the jury is still out on whether there is an immediate and compelling reason to believe that there is something fundamentally flawed in our current model of the universe.”

In a new paper accepted for publication in The Astrophysical Journal, Freedman and her team announced a new measurement of the Hubble constant using a kind of star known as a red giant. Their new observations, made using Hubble, indicate that the expansion rate for the nearby universe is just under 70 kilometers per second per megaparsec (km/sec/Mpc). One parsec is equivalent to 3.26 light-years distance. This measurement is slightly smaller than the value of 74 km/sec/Mpc recently reported by the Hubble SH0ES (Supernovae H0 for the Equation of State) team using Cepheid variables, which are stars that pulse at regular intervals that correspond to their peak brightness. This team, led by Adam Riess of the Johns Hopkins University and Space Telescope Science Institute, Baltimore, Maryland, recently reported refining their observations to the highest precision to date for their Cepheid distance measurement technique.

According to current understanding, the Hubble constant should be about 67.5 kilometers per second per Mpc, plus/minus 0.5. Any discrepancy shows that the evolution and expansion of the universe are more complicated than previously thought. There is still more to understand about how the universe is changing.

The new James Webb Space Telescope is likely to help clarifying the situation. Then, scientists should be able to view new mileposts that are even further away and in higher resolution as a result of this.

Using data from ESA's Gaia mission, astronomers have shown that a part of the Milky Way known as the 'thick disc' began forming 13 billion years ago, around 2 billion years earlier than expected, and just 0.8 billion years after the Big Bang.

This surprising result comes from an analysis performed by Maosheng Xiang and Hans-Walter Rix, from the Max-Planck Institute for Astronomy, Heidelberg, Germany. They took brightness and positional data from Gaia's Early Data Release 3 (EDR3) dataset and combined it with measurements of the stars' chemical compositions, as given by data from China's Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) for roughly 250 000 stars to derive their ages.

They chose to look at sub giant stars. In these stars, energy has stopped being generated in the star's core and has moved into a shell around the core. The star itself is transforming into a red giant star. Because the sub giant phase is a relatively brief evolutionary phase in a star's life, it permits its age to be determined with great accuracy, but it's still a tricky calculation.

How old are the stars?

The age of a star is one of the most difficult parameters to determine. It cannot be measured directly but must be inferred by comparing a star's characteristics with computer models of stellar evolution. The compositional data helps with this. The Universe was born with almost exclusively hydrogen and helium. The other chemical elements, known collectively as metals to astronomers, are made inside stars, and exploded back into space at the end of a star's life, where they can be incorporated into the next generation of stars. So, older stars have fewer metals and are said to have lower metallicity.

The LAMOST data gives the metallicity. Together, the brightness and metallicity allow astronomers to extract the star's age from the computer models. Before Gaia, astronomers were routinely working with uncertainties of 20-40 percent, which could result in the determined ages being imprecise by a billion years or more.

Gaia's EDR3 data release changes this. "With Gaia's brightness data, we are able to determine the age of a sub giant star to a few percent," says Maosheng. Armed with precise ages for a quarter of a million sub giant stars spread throughout the galaxy, Maosheng and Hans-Walter began the analysis.

Deep learning has helped advance the state-of-the-art in multiple fields over the last decade, with scientific research as no exception.

The Kepler instrument is a space-based telescope designed to study and planets outside our solar system, aka exoplanets. The first exoplanet orbiting a star like our own was described by Didier Queloz and Michel Mayor in 1995, landing the pair the 2019 Nobel Prize in Physics. More than a decade later when Kepler was launched in 2009, the total number of known exoplanets was less than 400. The now-dormant telescope began operation in 2009, discovering more than 1,000 new exoplanets before a reaction wheel, a component used for precision pointing, failed in 2013.

This brought the primary phase of the mission to an end.

Some clever engineering changes allowed the telescope to begin a second period of data acquisition, termed K2. The data from K2 were noisier and limited to 80 days of continuous observation or less. These limitations pose challenges in identifying promising planetary candidates among the thousands of putative planetary signals, a task that had been previously handled nicely by a convolutional neural network (AstroNet) working with the data from Kepler’s primary data collection phase. Researchers at the University of Texas, Austin decided to try the same approach and derived AstroNet-K2 from the architecture of AstroNet to sort K2 planetary signals.

After training, AstroNet-K2 had a 98% accuracy rate in identifying confirmed exoplanets in the test set, with low false positives. The authors deemed this performance to be sufficient for use as an analysis tool rather than full automation, requiring human follow-up.

From the paper:

While the performance of our network is not quite at the level
required to generate fully automatic and uniform
planet candidate catalogs, it serves as a proof of
concept. — (Dattilo et al. 2019)

AstroNet-K2 receives this blog post’s coveted “Best Value” award for achieving a significant scientific bang-for-your-buck. Unlike the other two projects on this list that are more conceptual demonstrations, this project resulted in actual scientific progress, adding two new confirmed entries to the catalog of known exoplanets: EPIC 246151543 b and EPIC 246078672 b.

In addition to the intrinsic challenges of the K2 data, the signals for the planets were further confounded by Mars transiting the observiation window and by 5 days of missing data associated with a safe mode event. This is a pretty good example of effective machine learning in action: the authors took an existing conv-net with a proven track record and modified it to perform well on the given data, adding a couple new discoveries from a difficult observation run without re-inventing the wheel.

Worth noting is that the study’s lead author, Anne Dattilo, was an undergraduate at the time the work was completed. That’s a pretty good outcome for an undergraduate research project. The use of open-source software and building on previously developed architectures underlines the fact that deep learning is in a advanced readiness phase. The technology is not fully mature to the point of ubiquity, but the tools are all there on the shelf ready to be applied.

The Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) is home to many interdisciplinary projects which benefit from the synergy of a wide range of expertise available at the institute. One such project is the study of black holes that could have formed in the early universe, before stars and galaxies were born.

Such primordial black holes (PBHs) could account for all or part of dark matter, be responsible for some of the observed gravitational waves signals, and seed supermassive black holes found in the center of our Galaxy and other galaxies. They could also play a role in the synthesis of heavy elements when they collide with neutron stars and destroy them, releasing neutron-rich material. In particular, there is an exciting possibility that the mysterious dark matter, which accounts for most of the matter in the universe, is composed of primordial black holes. The 2020 Nobel Prize in physics was awarded to a theorist, Roger Penrose, and two astronomers, Reinhard Genzel and Andrea Ghez, for their discoveries that confirmed the existence of black holes. Since black holes are known to exist in nature, they make a very appealing candidate for dark matter.

The recent progress in fundamental theory, astrophysics, and astronomical observations in search of PBHs has been made by an international team of particle physicists, cosmologists and astronomers, including Kavli IPMU members Alexander Kusenko, Misao Sasaki, Sunao Sugiyama, Masahiro Takada and Volodymyr Takhistov. To learn more about primordial black holes, the research team looked at the early universe for clues. The early universe was so dense that any positive density fluctuation of more than 50 percent would create a black hole. However, cosmological perturbations that seeded galaxies are known to be much smaller. Nevertheless, a number of processes in the early universe could have created the right conditions for the black holes to form.  

One exciting possibility is that primordial black holes could form from the “baby universes” created during inflation, a period of rapid expansion that is believed to be responsible for seeding the structures we observe today, such as galaxies and clusters of galaxies. During inflation, baby universes can branch off of our universe. A small baby (or “daughter”) universe would eventually collapse, but the large amount of energy released in the small volume causes a black hole to form.

An even more peculiar fate awaits a bigger baby universe. If it is bigger than some critical size, Einstein's theory of gravity allows the baby universe to exist in a state that appears different to an observer on the inside and the outside. An internal observer sees it as an expanding universe, while an outside observer (such as us) sees it as a black hole. In either case, the big and the small baby universes are seen by us as primordial black holes, which conceal the underlying structure of multiple universes behind their “event horizons.” The event horizon is a boundary below which everything, even light, is trapped and cannot escape the black hole. 

Gravitational wave detectors have opened a new window to the universe by measuring the ripples in spacetime produced by colliding black holes and neutron stars, but they are ultimately limited by quantum fluctuations induced by light reflecting off of mirrors. LSU Ph.D. physics alumnus Jonathan Cripe and his team of LSU researchers have conducted a new experiment with scientists from Caltech and Thorlabs to explore a way to cancel this quantum backaction and improve detector sensitivity.

In a new paper inPhysical Review X, the investigators present a method for removing quantum backaction in a simplified system using a mirror the size of a human hair and show the motion of the mirror is reduced in agreement with theoretical predictions. The research was supported by the National Science Foundation.

Despite using 40-kilogram mirrors for detecting passing gravitational waves, quantum fluctuations of light disturb the position of the mirrors when the light is reflected. As gravitational wave detectors continue to grow more sensitive with incremental upgrades, this quantum backaction will become a fundamental limit to the detectors' sensitivity, hampering their ability to extract astrophysical information from gravitational waves.

"We present an experimental testbed for studying and eliminating quantum backaction," Cripe said. "We perform two measurements of the position of a macroscopic object whose motion is dominated by quantum backaction and show that by making a simple change in the measurement scheme, we can remove the quantum effects from the displacement measurement. By exploiting correlations between the phase and intensity of an optical field, quantum backaction is eliminated."

Garrett Cole, technology manager at Thorlabs Crystalline Solutions (Crystalline Mirror Solutions was acquired by Thorlabs Inc. last year), and his team constructed the micromechanical mirrors from an epitaxial multilayer consisting of alternating GaAs and AlGaAs. An outside foundry, IQE North Carolina, grew the crystal structure while Cole and his team, including process engineers Paula Heu and David Follman, manufactured the devices at the University of California Santa Barbara nanofabrication facility.

"By performing this measurement on a mirror visible to the naked eye—at room temperature and at frequencies audible to the human ear—we bring the subtle effects of quantum mechanics closer to the realm of human experience," said LSU Ph.D. candidate Torrey Cullen. "By quieting the quantum whisper, we can now listen to the more subtle notes of the cosmic symphony."

There are a few fundamental facts about the Universe — its origin, its history, and what it is today — that are awfully hard to wrap your head around.

There are a few fundamental facts about the Universe — its origin, its history, and what it is today — that are awfully hard to wrap your head around. One of them is the Big Bang, or the idea that the Universe began a certain time ago: 13.8 billion years ago to be precise. That’s the first moment we can describe the Universe as we know it to be today: full of matter and radiation, and the ingredients that would eventually grow into stars, galaxies, planets and human beings. So how far away can we see? You might think, in a Universe limited by the speed of light, that would be 13.8 billion light years: the age of the Universe multiplied by the speed of light. But 13.8 billion light years is far too small to be the right answer. In actuality, we can see for 46 billion light years in all directions, for a total diameter of 92 billion light years.

Mathematical model suggests dark matter may have been produced before the big bang during cosmic inflation, when space was expanding rapidly

Researchers believe dark matter makes up about 80% of the universe's mass, but its origins and composition remain among the most elusive mysteries in modern physics. A new Johns Hopkins University study suggests dark matter may have existed before the big bang. The study, published in Physical Review Letters, presents a new idea of how dark matter was created and how it might be identified during astronomical observations.

"The study revealed a new connection between particle physics and astronomy," says Tommi Tenkanen, a postdoctoral fellow in JHU'sDepartment of Physics and Astronomy and the study's author. "If dark matter consists of new particles that were born before the big bang, they affect the way galaxies are distributed in the sky in a unique way. This connection may be used to reveal their identity and make conclusions about the times before the big bang, too."

While not much is known about its origins, astronomers have shown that dark matter plays a crucial role in the formation of galaxies and galaxy clusters. Though not directly observable, scientists know dark matter exists by its gravitation effects on how visible matter moves and is distributed in space.

For a long time, researchers believed that dark matter must be a byproduct of the big bang. Scientists have long sought this kind of dark matter, but so far all experimental searches have been unsuccessful. "If dark matter were truly a remnant of the big bang, then in many cases researchers should have seen a direct signal of dark matter in different particle physics experiments already," Tenkanen says.

Using a new, simple mathematical framework, the study shows that dark matter may have been produced before the big bang during an era known as the cosmic inflation when space was expanding very rapidly. The rapid expansion is believed to lead to copious production of certain types of particles called scalars. So far, only one scalar particle has been discovered, the famous Higgs boson.

"We do not know what dark matter is, but if it has anything to do with any scalar particles, it may be older than the big bang," Tenkanen explains. "With the proposed mathematical scenario, we don't have to assume new types of interactions between visible and dark matter beyond gravity, which we already know is there."

A new theory tries to explain the mysterious phenomena that exists at the center of black holes.

Black holes are among the most mysterious places in the universe; locations where the very fabric of space and time are warped so badly that not even light can escape from them. According to Einstein's theory of general relativity, at their center lies a singularity, a place where the mass of many stars is crushed into a volume with exactly zero size. However, two recent physics papers, published on Dec.10 in the journals Physical Review Letters and Physical Review D, respectively, may make scientists reconsider what we think we know about black holes. Black holes might not last forever, and it's possible that we've completely misunderstood their nature and what they look like at the center, according to the papers. [read: Stephen Hawking's Most Far-Out Ideas About Black Holes]

Astronomers and physicists have long held that the idea of a singularity simply must be wrong. If an object with mass has no size, then it has infinite density. And, as much as researchers throw around the word "infinity," infinities of that kind don't exist in nature. Instead, when you encounter an infinity in a real, physical, science situation, what it really means is that you've pushed your mathematics beyond the realm where they apply. You need new math.

It's easy to give a familiar example of this. Newton's law of gravity says that the strength of the gravitational attraction changes as one over the distance squared between two objects. So if you took a ball located far from Earth, it would experience a certain weight. Then, as you brought it closer to Earth, the weight would increase. Taking that equation to the extreme, as you brought the object near to the center of Earth, it would experience an infinite force. But it doesn't. Instead, as you bring the object close to the surface of Earth, Newton's simple law of gravity no longer applies. You have to take into account the actual distribution of Earth’s mass, and this means that you need to use different and more complex equations that predict different behavior. Similarly, while Einstein's theory of general relativity predicts that a singularity of infinite density exists at the center of black holes, this can't be true. At very small sizes, a new theory of gravity must come into play. This theory is called quantum gravity.