Highly Collimated Jet Spotted From The Red Square Nebula

Astronomers have detected a highly collimated, bipolar jet from the so-called Red Square Nebula (RSN) surrounding the B[e]-type star MWC 922. The newly discovered jet could reveal more insights into the nature of the RSN and its emission. The finding is detailed in a paper published January 24 on the arXiv pre-print repository.

Located approximately 5,500 light years away in the constellation Serpens, MWC 922 is a peculiar, infrared excess B[e] star surrounded by a square-shaped nebula. Many studies of the RSN have been carried out to date, which, for instance, revealed another nebula similar to RSN, however, little is known about the properties and evolution of RSN and MWC 922.

Now, a new study conducted by University of Colorado’s John Bally and Zen H. Chia, sheds more light on the nature of RSN and its host. Using the Double Imaging Spectrograph (DIS) on the 3.5 meter telescope at the Apache Point Observatory (APO) located near Sunspot, New Mexico, the astronomers unveiled the presence of a collimated jet orthogonal to the previously identified extended nebula associated with RSN.

“Deep, narrow-band images of the Red Square Nebula and its source star, MWC 922, reveal a highly collimated and segmented, parsec-scale jet oriented orthogonal to the previously identified emission-line nebula which can be traced towards the southwest,” the researchers wrote in the paper.

According to the study, the jet, as well as RSN, appear to be externally ionized. Describing the structure of the newfound jet, Bally and Chia revealed that it consists of a pair of segments with sizes of 0.5 light years each, on either side of the host star, separated by gaps. They noted that the most distant jet segments disappear at around 1.97 light years from the star.

The researchers calculated that the speed of the jet is around 500 km/s and that the jet’s electron density is between 50 and 100 cm-3. These parameters allowed the authors of the paper to estimate the mass loss rate of the jet segments, which was found to be at a value between 50 and 100 billionths of a solar mass per year.

Trying to explain the real nature of the newly detected jet and the extended nebula, the scientists propose two hypotheses. The first scenario suggests that the observed features might be a large excretion disk or stream of ejecta shed by MWC 922 that is preferentially illuminated and ionized from the direction of the open cluster Messier 16.

“Because of its orientation, the southwest part shadows the northeast part. Faint, 70 μm emission traces warm dust at the surface,” the paper reads.

The second theory proposed by the researchers is based on the assumption that MWC 922 may have been ejected from Messier 16. In this scenario, the jet might be a tail of ejecta left behind the star as mass lost from the star interacts with the interstellar medium through which it moves.

Explaining A Universe Composed Of Matter

The universe consists of a massive imbalance between matter and antimatter. Antimatter and matter are actually the same, but have opposite charges, but there’s hardly any antimatter in the observable universe, including the stars and other galaxies. In theory, there should be large amounts of antimatter, but the observable universe is mostly matter.

“We’re here because there’s more matter than antimatter in the universe,” says Professor Jens Oluf Andersen at the Norwegian University of Science and Technology’s (NTNU)Department of Physics. This great imbalance between matter and antimatter is all tangible matter, including life forms, exists, but scientists don’t understand why.

Physics uses a standard model to explain and understand how the world is connected. The standard model is a theory that describes all the particles scientists are familiar with. It accounts for quarks, electrons, the Higgs boson particle and how they all interact with each other. But the standard model cannot explain the fact that the world consists almost exclusively of matter. So there must be something we don’t yet understand.

When antimatter and matter meet, they annihilate, and the result is light and nothing else. Given equal amounts of matter and antimatter, nothing would remain once the reaction was completed. As long as we don’t know why more matter exists, we can’t know why the building blocks of anything else exist, either. “This is one of the biggest unsolved problems in physics,” says Andersen.

Researchers call this the “baryon asymmetry” problem. Baryons are subatomic particles, including protons and neutrons. All baryons have a corresponding antibaryon, which is mysteriously rare. The standard model of physics explains several aspects of the forces of nature. It explains how atoms become molecules, and it explains the particles that make up atoms.

“The standard model of physics includes all the particles we know about. The newest particle, the Higgs boson, was discovered in 2012 at CERN, says Andersen. With this discovery, an important piece fell into place. But not the final one. The standard model works perfectly to explain large parts of the universe, so researchers are intrigued when something doesn’t fit. Baryon asymmetry belongs in this category.

Physicists do have their theories as to why there is more matter, and thus why we undeniably exist. “One theory is that it’s been this way since the Big Bang,” says Andersen. In other words, the imbalance between matter and antimatter is a basic precondition that has existed more or less from the beginning.

Quarks are among nature’s smallest building blocks. An early surplus of quarks relative to antiquarks was propagated as larger units formed. But Andersen doesn’t care for this explanation. “We’re still not happy with that idea, because it doesn’t tell us much,” he says.

So why was this imbalance present from the beginning? Why did quarks initially outnumber antiquarks? “In principle, it’s possible to generate asymmetry within the standard model of physics—that is, the difference between the amount of matter and antimatter. But we run into two problems,” says Andersen.

First of all, scientists have to go way back in time, to just after the Big Bang when everything started—we’re talking about 10 picoseconds, or 10-11 seconds after the Big Bang.

The second problem is that temperatures have to be around 1 trillion degrees Kelvin, or 1015 degrees. That’s scorching—consider that the sun’s surface is only about 5700 degrees. Regardless, it is not sufficient to explain baryonic matter. “It can’t work. In the standard model, we don’t have enough matter,” Andersen says. “The problem is that the jump in the expectation value of the Higgs field is too small,” he adds for the benefit those with only a minimum grasp of physics.

“It’s probably not just our imagination that’s imposing limits, but lots of possibilities exist,” says Andersen. These possibilities therefore need to work together with the standard model. “What we’re really looking for is an extension of the standard model. Something that fits into it.”

Neither he nor other physicists doubt that the standard model is right. The model is continuously tested at CERN and other particle accelerators. It’s just that the model isn’t yet complete. Andersen and his colleagues are investigating various possibilities for the model to fit with the imbalance between matter and antimatter. The latest results were recently published in Physical Review Letters.

“Actually, we’re talking about phase transitions,” says Andersen. His group is considering processes of change in matter, like water turning into steam or ice under changing conditions. They’re also considering whether matter came about as a result of an electroweak phase transition (EWPT) and formed a surplus of baryons just after the Big Bang. The electroweak phase transition occurs by the formation of bubbles. The new phase expands, a bit like water bubbles, and takes over the entire universe.

Andersen and his colleagues tested the so-called “two Higgs doublet” model (2HDM), one of the simplest extensions of the standard model. They searched for possible areas where the right conditions are present to create matter. “Several scenarios exist for how the baryon asymmetry was created. We studied the electroweak phase transition using the 2HDM model. This phase transition takes place in the early stage of our universe,” says Andersen.

The process is comparable to boiling water. When water reaches 100 degrees Celsius, gas bubbles form and rise up. These gas bubbles contain water vapour which is the gas phase. Water is a liquid. When it transitions from the gas phase to the liquid phase in the early universe during a process in which the universe expands and is cooled, a surplus of quarks is produced compared to antiquarks, generating the baryon asymmetry.

Last but not least, the researchers are also doing mathematics. In order for the models to work in sync, parameters or numerical values have to fit so that both models are right at the same time. So the work is about finding these parameters. In the most recent article in Physical Review Letters, Andersen and his colleagues narrowed down the mathematical area in which matter can be created and at the same time correspond to both models. They have now narrowed the possibilities.

“For the new model (2HDM) to match what we already know from CERN, for example, the parameters in the model can’t be just anything. On the other hand, to be able to produce enough baryon asymmetry, the parameters also have to be within a certain range. So that’s why we’re trying to narrow the parameter range. But that’s still a long way off,” says Andersen. In any case, the researchers have made a bit of headway on the road to understanding why we and everything else are here.

The Milky Way is Warped

The 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 center, according to astronomers from National Astronomical Observatories of Chinese Academy of Sciences (NAOC).

From a great distance, the 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, together with a huge mass of dark matter, 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 Dr. Chen Xiaodian, a researcher at NAOC and lead author of the article published in Nature Astronomy on Feb. 4.

“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 percent can be determined.” That database allowed the team to develop the first accurate three-dimensional picture of the Milky Way out to its far outer regions.

Classical Cepheids are young stars that are some four to 20 times as massive as the 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 3-D, 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 Prof. Richard de Grijs from Macquarie University in Sydney, Australia, and senior co-author of the paper. “Perhaps more importantly, 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 our results with those other observations, we concluded that the Milky Way’s warped spiral pattern is most likely caused by torques—or rotational forcing—by the massive inner disk,” says Dr. LIU Chao, senior researcher and co-author of the paper.

“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,” says Dr. DENG Licai, senior researcher at NAOC and co-author of the paper.

The ‘Stuff’ of the Universe Keeps Changing

The composition of the universe – the elements that are the building blocks for every bit of matter – is ever-changing and ever-evolving, thanks to the lives and deaths of stars.

An outline of how those elements form as stars grow and explode and fade and merge is detailed in a review article published Jan. 31 is the journal Science.

“The universe went through some very interesting changes, where all of a sudden the periodic table – the total number of elements in the universe – changed a lot,” said Jennifer Johnson, a professor of astronomy at The Ohio State University and the article’s author.

“For 100 million years after the Big Bang, there was nothing but hydrogen, helium and lithium. And then we started to get carbon and oxygen and really important things. And now, we’re kind of in the glory days of populating the periodic table.”

The periodic table has helped humans understand the elements of the universe since the 1860s, when a Russian chemist, Dmitri Mendeleev, recognized that certain elements behaved the same way chemically, and organized them into a chart – the periodic table.

It is chemistry’s way of organizing elements, helping scientists from elementary school to the world’s best laboratories understand how materials around the universe come together.

But, as scientists have long known, the periodic table is just made of stardust: Most elements on the periodic table, from the lightest hydrogen to heavier elements like lawrencium, started in stars.
The table has grown as new elements have been discovered – or in cases of synthetic elements, have been created in laboratories around the world – but the basics of Mendeleev’s understanding of atomic weight and the building blocks of the universe have held true.

Nucleosynthesis – the process of creating a new element – began with the Big Bang, about 13.7 billion years ago. The lightest elements in the universe, hydrogen and helium, were also the first, results of the Big Bang. But heavier elements – just about every other element on the periodic table – are largely the products of the lives and deaths of stars.

Johnson said that high-mass stars, including some in the constellation Orion, about 1,300 light years from Earth, fuse elements much faster than low-mass stars. These grandiose stars fuse hydrogen and helium into carbon, and turn carbon into magnesium, sodium and neon. High-mass stars die by exploding into supernovae, releasing elements – from oxygen to silicon to selenium – into space around them.

Smaller, low-mass stars – stars about the size of our own Sun – fuse hydrogen and helium together in their cores. That helium then fuses into carbon. When the small star dies, it leaves behind a white dwarf star. White dwarfs synthesize other elements when they merge and explode. An exploding white dwarf might send calcium or iron into the abyss surrounding it. Merging neutron stars might create rhodium or xenon. And because, like humans, stars live and die on different time scales – and because different elements are produced as a star goes through its life and death – the composition of elements in the universe also changes over time.

“One of the things I like most about this is how it takes several different processes for stars to make elements and these processes are interestingly distributed across the periodic table,” Johnson said. “When we think of all the elements in the universe, it is interesting to think about how many stars gave their lives – and not just high-mass stars blowing up into supernovae. It’s also some stars like our Sun, and older stars. It takes a nice little range of stars to give us elements.”

Ancient Asteroid Impacts Played A Role In Creation Of Earth’s Future Continents

The heavy bombardment of terrestrial planets by asteroids from space has contributed to the formation of the early evolved crust on Earth that later gave rise to continents — home to human civilisation.

More than 3.8 billion years ago, in a time period called the Hadean eon, our planet Earth was constantly bombarded by asteroids, which caused the large-scale melting of its surface rocks. Most of these surface rocks were basalts, and the asteroid impacts produced large pools of superheated impact melt of such composition. These basaltic pools were tens of kilometres thick, and thousands of kilometres in diameter.

“If you want to get an idea of what the surface of Earth looked like at that time, you can just look at the surface of the Moon which is covered by a vast amount of large impact craters,” says Professor Rais Latypov from the School of Geosciences of the University of the Witwatersrand in South Africa.

The subsequent fate of these ancient, giant melt sheet remains, however, highly debatable. It has been argued that, on cooling, they may have crystallized back into magmatic bodies of the same, broadly basaltic composition. In this scenario, asteroid impacts are supposed to play no role in the formation of the Earth’s early evolved crust.

An alternative model suggests that these sheets may undergo large-scale chemical change to produce layered magmatic intrusions, such as the Bushveld Complex in South Africa. In this scenario, asteroid impacts may have played an important role in producing various igneous rocks in the early Earth’s crust and therefore they may have contributed to its chemical evolution.

There is no direct way to rigorously test these two competing scenarios because the ancient Hadean impact melts have been later obliterated by plate tectonics. However, by studying the younger impact melt sheet of the Sudbury Igneous Complex (SIC) in Canada, Latypov and his research team have inferred that ancient asteroid impacts were capable of producing various rock types from the earlier Earth’s basaltic crust. Most importantly, these impacts may have made the crust compositionally more evolved, i.e. silica-rich in composition. Their research has been published in a paper in Nature Communications.

The SIC is the largest, best exposed and accessible asteroid impact melt sheet on Earth, which has resulted from a large asteroid impact 1.85 billion years ago. This impact produced a superheated melt sheet of up to 5 km thick. The SIC now shows a remarkable magmatic stratigraphy, with various layers of igneous rocks.

“Our field and geochemical observations — especially the discovery of large discrete bodies of melanorites throughout the entire stratigraphy of the SIC — allowed us to reassess current models for the formation of the SIC and firmly conclude that its conspicuous magmatic stratigraphy is the result of large-scale fractional crystallization,” says Latypov.

“An important implication is that more ancient and primitive Hadean impact melt sheets on the early Earth and other terrestrial planets would also have undergone near-surface, large-volume differentiation to produce compositionally stratified bodies. The detachment of dense primitive layers from these bodies and their sinking into the mantle would leave behind substantial volumes of evolved rocks (buoyant crustal blocks) in the Hadean crust. This would make the crust compositionally layered and increasingly more evolved from its base towards the Earth’s surface.”

“These impacts made the crust compositionally more evolved — in other words, silica-rich in composition,” says Latypov. “Traditionally, researchers believe that such silica-rich evolved rocks — which are essentially building buoyant blocks of our continents — can only be generated deep in the Earth, but we now argue that such blocks can be produced at new-surface conditions within impact melt pools.”

World’s Largest Digital Sky Survey Issues Biggest Astronomical Data Release Ever

The Space Telescope Science Institute (STScI) in Baltimore, Maryland, in conjunction with the University of Hawai’i Institute for Astronomy (IfA), is releasing the second edition of data from Pan-STARRS—the Panoramic Survey Telescope & Rapid Response System—the world’s largest digital sky survey. This second release contains over 1.6 petabytes of data (a petabyte is 1015 bytes or one million gigabytes), making it the largest volume of astronomical information ever released. The amount of imaging data is equivalent to two billion selfies, or 30,000 times the total text content of Wikipedia. The catalog data is 15 times the volume of the Library of Congress.

The Pan-STARRS observatory consists of a 1.8-meter telescope equipped with a 1.4-billion-pixel digital camera, located at the summit of Haleakalā, on Maui. Conceived and developed by the IfA, it embarked on a digital survey of the sky in visible and near-infrared light in May 2010. Pan-STARRS was the first survey to observe the entire sky visible from Hawai’i multiple times in many colors of light. One of the survey’s goals was to identify moving, transient, and variable objects, including asteroids that could potentially threaten the Earth. The survey took approximately four years to complete, scanning the sky 12 times in five filters. This second data release provides, for the first time, access to all of the individual exposures at each epoch of time. This will allow astronomers and public users of the archive to search the full survey for high-energy explosive events in the cosmos, discover moving objects in our own solar system, and explore the time domain of the universe.

Dr. Heather Flewelling, a researcher at the Institute for Astronomy in Hawai’i, and a key designer of the PS1 database, stated that “Pan-STARRS DR2 represents a vast quantity of astronomical data, with many great discoveries already unveiled. These discoveries just barely scratch the surface of what is possible, however, and the astronomy community will now be able to dig deep, mine the data, and find the astronomical treasures within that we have not even begun to imagine.”

“We put the universe in a box and everyone can take a peek,” said database engineer Conrad Holmberg.

The four years of data comprise 3 billion separate sources, including stars, galaxies, and various other objects. This research program was undertaken by the PS1 Science Consortium—a collaboration among 10 research institutions in four countries, with support from NASA and the National Science Foundation (NSF). Consortium observations for the sky survey were completed in April 2014. The initial Pan-STARRS public data release occurred in December 2016, but included only the combined data and not the individual exposures at each epoch of time.

“The Pan-STARRS1 Survey allows anyone access to millions of images and catalogs containing precision measurements of billions of stars, galaxies, and moving objects,” said Dr. Ken Chambers, Director of the Pan-STARRS Observatories. “While searching for Near Earth Objects, Pan-STARRS has made many discoveries from ‘Oumuamua passing through our solar system to lonely planets between the stars; it has mapped the dust in three dimensions in our galaxy and found new streams of stars; and it has found new kinds of exploding stars and distant quasars in the early universe. We hope people will discover all kinds of things we missed in this incredibly large and rich dataset.”

The Space Telescope Science Institute hosts the storage hardware, the computers that handle the database queries, and the user-friendly interfaces to access the data. The survey data resides in the Mikulski Archive for Space Telescopes (MAST), which serves as NASA’s repository for all of its optical and ultraviolet-light observations, some of which date to the early 1970s. It includes all of the observational data from such space astrophysics missions as Hubble, Kepler, GALEX, and a wide variety of other telescopes, as well as several all-sky surveys. Pan-STARRS marks the nineteenth mission to be archived in MAST.

Ancient Crystals Offer Evidence Of The Start of Earth’s Core Solidifying

A quartet of researchers from the University of Rochester and the University of California has found evidence of the starting period for the solidification of Earth’s core. In their paper published in the journal Nature Geoscience, Richard Bono, John Tarduno, Francis Nimmo and Rory Cottrell describe their analysis of ancient crystals found in eastern Canada, what they found, and why they believe their results offer clues about the formation of Earth’s inner core. Peter Driscoll, with the Carnegie Institution for Science, has written a News and Views piece on the study in the same journal issue.

Planetary scientists have found strong evidence that suggests the Earth has an inner and an outer core. The inner core is believed to be solid, while the outer core is made up of molten material. Prior evidence has also indicated that the entire core was once liquid, but as the interior cooled, the innermost part began to crystallize. It is at this point that scientists disagree—some suggest the start of solidification began as far back as 2.5 billion years ago. Others believe it was much more recent—perhaps as recent as just 500 million years ago. In this new effort, the researchers have found evidence that supports the latter theory.

The work by the researchers involved carefully analyzing plagioclase and clinopyroxene crystals, which have been dated to approximately 565 million years ago. The crystals are important because they contain bits of metal called inclusions. The inclusions are very small and needle-shaped and aligned themselves with the Earth’s magnetic field as they became embedded in the crystal. Since the Earth’s magnetic field is generated by activity in the inner core, the inclusions are a means of determining the state of the core during the time when the crystals formed. The researchers report that their analysis showed that the magnetic field was significantly weaker than it is today, suggesting that solidification of the core must have occurred soon thereafter or the magnetic field would have collapsed altogether. The reason it did not, theory suggests, is because as the inner core solidified, he magnetic field became stronger.