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Does Pluto Have Buried Oceans

December 7, 2017 by  
Filed under Around The Net

Our solar system may harbor many more potentially habitable worlds than scientists had thought.

Subsurface oceans could still slosh beneath the icy crusts of frigid, faraway worlds such as the dwarf planets Pluto and Eris, kept liquid by the heat-generating tug of orbiting moons, according to a new study. 

“These objects need to be considered as potential reservoirs of water and life,” lead author Prabal Saxena, of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said in a statement. “If our study is correct, we now may have more places in our solar system that possess some of the critical elements for extraterrestrial life.”  

Underground oceans are known, or strongly suspected, to exist on a number of icy worlds, including the Saturn satellites Titan and Enceladus and the Jovian moons Europa, Callisto and Ganymede. These oceans are kept liquid to this day by “tidal heating”: The powerful gravitational pull of these worlds’ giant parent planets stretches and flexes their interiors, generating heat via friction.

The new study suggests something similar may be going on with Pluto, Eris and other trans-Neptunian objects (TNOs).

Many of the moons around TNOs are thought to have coalesced from material blasted into space when objects slammed into their parent bodies long ago. That’s the perceived origin story for the one known satellite of Eris (called Dysnomia) and for Pluto’s five moons (as well as for Earth’s moon). 

Such impact-generated moons generally begin their lives in relatively chaotic orbits, team members of the new study said. But over time, these moons migrate to more-stable orbits, and as this happens, the satellites and the TNOs tug on each other gravitationally, producing tidal heat.

Saxena and his colleagues modeled the extent to which this heating could warm up the interiors of TNOs — and the researchers got some intriguing results.

“We found that tidal heating can be a tipping point that may have preserved oceans of liquid water beneath the surface of large TNOs like Pluto and Eris to the present day,” study co-author Wade Henning, of NASA Goddard and the University of Maryland, said in the same statement.

As the term “tipping point” implies, there’s another factor in play here as well. It’s been widely recognized that TNOs could harbor buried oceans thanks to the heat produced by the decay of the objects’ radioactive elements. But just how long such oceans could persist has been unclear. This type of heating peters out eventually, as more and more radioactive material decays into stable elements. And the smaller the object, the faster it cools down.

Tidal heating may do more than just lengthen subsurface oceans’ lives, researchers said.Next Up

“Crucially, our study also suggests that tidal heating could make deeply buried oceans more accessible to future observations by moving them closer to the surface,” said study co-author Joe Renaud, of George Mason University in Virginia. “If you have a liquid-water layer, the additional heat from tidal heating would cause the next adjacent layer of ice to melt.” 

The new study was published online last week in the journal Icarus

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Astronomers Find 72 Potential New Galaxies

December 4, 2017 by  
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Astronomers have found 72 potential galaxies hiding in plain sight inside a vast patch of the sky previously observed by the Hubble Space Telescope. The discovery not only gives astronomers new targets to study, but also will aid studies of star motion and formation and other properties of old galaxies, the researchers said.

The new study was performed by the MUSE instrument on the European Southern Observatory’s Very Large Telescope in Chile. Astronomers discovered the newfound galaxies while measuring the distances and properties of 1,600 galaxies captured by the Hubble Space Telescope during its Ultra Deep Field survey.

The 72 newfound galaxies shine in Lyman-alpha light, which is a particular wavelength of ultraviolet light. Because the galaxies are receding from us, their wavelength was stretched from ultraviolet to visible, or near-infrared.

The discoveries were made in the Hubble Ultra Deep Field, which is a tiny region of the sky in the southern constellation Fornax (the Furnace). The Hubble data were originally obtained in 2004, two years after NASA space shuttle astronauts visited the space telescope to install the Advanced Camera for Surveys (ACS) and perform other needed maintenance.

Using ACS, Hubble peered at a small region of the sky and found galaxies that had formed less than 1 billion years after the Big Bang, which kick-started the universe. (The Big Bang took place about 13.8 billion years ago, making those galaxies more than 12.8 billion years old.)

“MUSE can do something that Hubble can’t — it splits up the light from every point in the image into its component colors to create a spectrum. This allows us to measure the distance, colors and other properties of all the galaxies we can see — including some that are invisible to Hubble itself,” stated Roland Bacon, who led the survey team and is also an astrophysicist at the Center for Astrophysics Research of Lyon at the University of Lyon in France.

MUSE is a spectroscopic instrument, meaning it measures light emitted, absorbed or scattered in space. Using spectroscopy, astronomers can learn about stars, galaxies and other objects, including properties such as how fast the objects are moving and what elements they are made of. MUSE recently underwent an adaptive-optics upgrade, which could help with future studies of old galaxies, Bacon added.

The new work resulted in 10 science papers that will be published in a special issue of the journal Astronomy & Astrophysics.

“MUSE has the unique ability to extract information about some of the earliest galaxies in the universe — even in a part of the sky that is already very well-studied,” stated Jarle Brinchmann, lead author of one of the papers.

“We learn things about these galaxies that [it] is only possible [to learn] with spectroscopy, such as chemical content and internal motions — not galaxy by galaxy, but all at once for all the galaxies,” added Brinchmann, who is an astronomer at Leiden University in the Netherlands and the Institute of Astrophysics and Space Sciences at CAUP (Center for Astrophysics of the University of Porto) in Portugal. 

Astronomers also found hydrogen halos in old galaxies, which could provide more information about how material leaves and enters galaxies formed early in the universe’s history. Future research directions could include looking at star formation, galactic winds, galaxy mergers or even a phenomenon known as cosmic reionization. 

That phenomenon explains how light returned to a dark universe hundreds of millions of years ago. “First light” in the universe was roughly 380,000 years after the Big Bang, when the cosmos cooled down and fundamental particles were able to combine into atoms. However, once these combinations ceased, the universe entered a dark age, because there was no other light available — the first stars weren’t shining yet. Reionization occurred between 150 million years and 650 million years after the Big Bang, when the first stars and galaxies were formed from collapsing groups of gas, producing light in the universe again.

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Astronomers Find Intense Illumination In Early Universe

December 1, 2017 by  
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Imagine what the iconic pillars of the Eagle Nebula would look like if a powerful force caused the stellar nursery to create stars at a thousand times its current rate.

New observations confirm that a bright point of light in the constellation Dorado is in fact an intense, extraordinarily bright region of star birth. It was formed by the repetitive collision of two spiral galaxies so far away that their light comes from the early universe. 

Dominik Riechers, an astronomer at Cornell University in Ithaca, New York, and lead author on the new study, observed the colliding starburst galaxies with his team using the Atacama Large Millimeter/submillimeter Array (ALMA) in northern Chile. The galaxies are similar in structure to Earth’s home, the Milky Way galaxy, which also hosts the star-forming Eagle Nebula..

The new findings suggest that the brightness of the two starburst galaxies isn’t merely a result of their collision. The two spiral structures located 12.7 billion light-years away from Earth, known collectively as the ADFS-27 system, also have more star-making material to work with than Earth’s home galaxy does. In fact, ADFS-27 has “50 times the amount of star-forming gas as the Milky Way,” researchers said in a statement from ALMA.

Starburst galaxies are relatively rare, and the research team said they were astounded to find two of the massive galaxies near each other. These observations are also a dramatic look into the past: Because the starburst galaxies are so far away, astronomers are actually observing them as they appeared when the universe was only 1 billion years old. At that time, the universe was just becoming transparent, as the process of reionization finished.

“Considering their extreme distance from Earth and the frenetic star-forming activity inside each, it’s possible we may be witnessing the most intense galaxy merger known to date,” Riechers said in the statement. Their predicted course is to ultimately merge into one large elliptical galaxy. And because distance creates a long lag time between when events in those galaxies occur and when we can observe them here, that massive merger may have already occurred.

Courtesy-Space

Does Space Dust Transport Life Around The Galaxy

November 29, 2017 by  
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It may not take an asteroid strike to transport life from one planet to another.

Fast-moving dust could theoretically knock microbes floating high up in a world’s atmosphere out into space, potentially sending the bugs on a trip to another planet — perhaps even one orbiting a different star, according to a new study.

“The proposition that space-dust collisions could propel organisms over enormous distances between planets raises some exciting prospects of how life and the atmospheres of planets originated,” study author Arjun Berera, a professor in the School of Physics and Astronomy at the University of Edinburgh in Scotland, said in a statement.  

“The streaming of fast space dust is found throughout planetary systems and could be a common factor in proliferating life,” Berera added.

Berera isn’t the first person to propose that organisms could hop from world to world throughout the cosmos. That basic idea, known as panspermia, has been around for thousands of years. It has received renewed interest recently, however, as scientists have demonstrated that some organisms — such as certain bacteria, and micro-animals known as tardigrades — can survive for extended periods in space.

But researchers have generally regarded comet or asteroid impacts as the only viable way to get simple life-forms off a planet and into space, whence they could perhaps blunder their way to a different habitable world. (We won’t consider here the “directed panspermia” idea, which posits that intelligent aliens have seeded the galaxy with life or its building blocks.)

Comet or asteroid impacts do indeed blast rocks from planet to planet. Scientists have found numerous meteorites here on Earth that were once part of Mars — including one known as ALH84001, which some scientists think may preserve signs of ancient Red Planet life.

In the new study, Berera examined what likely happens when bits of interplanetary dust hit molecules and particles in Earth’s atmosphere. This space stuff rains down on us every day, hitting the planet at speeds of between 22,400 mph and 157,000 mph (36,000 to 253,000 km/h).

He calculated that small particles floating at least 93 miles (150 kilometers) above Earth’s surface could theoretically get knocked into space by this wandering dust. It’s unclear if microbes could survive such violent collisions; that’s an area ripe for future research, Berera wrote in the new paper, which has been accepted for publication in the journal Astrobiology. (You can read the study for free at the online preprint site arXiv.org.)

And even if these micro-impacts are invariably fatal, they could still help life get a foothold on other worlds by sending its building blocks — the complex molecules that make up a microbe corpse, for example — out into space, he added.

Courtesy-Space

Astronomers Get New Telescope To Find Exploding Stars

November 22, 2017 by  
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A powerful new camera that will help scientists search for exploding stars and fast-moving objects in Earth’s solar system has captured its first image of the night sky.

The Zwicky Transient Facility (ZTF) is officially up and running at the California Institute of Technology’s Palomar Observatoryin the mountains northeast of San Diego. Its primary piece of hardware is a wide-field camera, attached to a 48-inch (122 centimeters) telescope, that can image the entire visible plane of the Milky Way galaxy twice per night and the entire night sky every three nights, according to a statement from Caltech.

The first image from ZTF shows a region of the sky in the constellation Orion that includes the Horsehead Nebula, a star-forming region imaged in glorious detailby the Hubble Space Telescope. But the ZTF camera has a considerably larger field of view compared with Hubble’s — each image captures an area on the sky measuring 47 square degrees, or about 247 times the area of the full moon, according to the statement.  

Photographing huge areas of the sky extremely quickly is ZTF’s primary function. By comparing images of the same region of the sky taken within a few hours or a few days of one another, scientists can look for cosmic objects that are moving or changing in brightness over those short timescales.

Of course, most stars, galaxies, nebulas and other large cosmic objects remain more or less stagnant — in brightness and position — over a few hours or days. But the universe is also full of so-called variable objects (those that change in brightness) and transient objects (that appear to move relatively quickly). These include things like dying stars that explode as supernovasand, in a matter of hours, become exponentially brighter than they were the day before; asteroids that zip through the solar system; black holes that devour entire stars, causing the material from the star to rapidly change in brightness; and pairs of neutron stars, the densest objects in the universe, that mergeand release great bursts of radiation.

“The universe is an extremely dynamic place,” Mansi Kasliwal, an assistant professor of astronomy at Caltech and a member of the ZTF team, said in a video from Caltech. Referring specifically to supernovas and other brief eruptions of light, Kasliwal said, “These short-lived explosions — they could last for seconds, for minutes, for months, but [eventually], they disappear on us. And catching these flashes of light, catching these cosmic fireworks, that’s what ZTF can uniquely do.”

The ZTF science survey, scheduled to run from early 2018 until the end of 2020, will turn up objects that are of interest to a wide range of astronomy subfields. Supernovas are obviously interesting to astronomers who study the life cycles of stars, but they are also used by cosmologists to measure cosmic distances. ZTF’s ability to find comets and asteroids will be of interest to astronomers who look for space rocks that could come dangerously close to Earth. But mostly, ZTF will increase the volume of transient and variable objects that astronomers have to study.

“There’s a lot of activity happening in our night skies,” Shrinivas Kulkarni, the principal investigator for ZTF and a professor of astronomy and planetary science at Caltech, said in the statement. “In fact, every second, somewhere in the universe, there’s a supernova that’s exploding. Of course, we can’t see them all, but with ZTF, we will see up to tens of thousands of explosive transients every year over the three-year lifetime of the project.”

Identifying objects in the night sky that flicker, flash, move or change in other ways is a game of comparison. Scientists take an image of the sky, then wait a few hours or a full day, and image the same area again. With ZTF, researchers can use computer software to literally subtract one image from the other, eliminating objects that haven’t changed in the time between when the two images were taken.

“The universe is so dynamic that if you subtract two identical [images] of the sky, separated by an hour or a night, [you can] see new flashes of light that weren’t there in the image from an hour before or a night before,” Kasliwal said in the video. “Those new flashes of light in the subtracted images are what we are after.”

Before astronomers could take digital images of the sky and utilize software to look for these variable objects, this comparison of identical regions of the sky was done manually. Astronomers would take two images of the same patch of the sky (separated by some period of time) using glass photographic plates. Then, the scientists would set these plates next to one another and look for differences. An instrument called a blink comparator, introduced in the early 20th century, would rapidly flip between the images to make it easier to spot transient objects. Astronomer Clyde Tombaugh used a blink comparator to discover Pluto.

ZTF is named after Caltech astrophysicist Fritz Zwicky, who arrived at the university in 1925 and did a great deal of work to systematically search the sky for variable objects; he discovered 120 supernovas in his lifetime, according to the statement

ZTF is a successor to the Palomar Transient Factory (PTF), which ran from 2009 until earlier this year, and also had a camera installed on the 48-inch telescope at Palomar. Astronomers then used the other two telescopes at the observatory, as well as the telescopes at the Keck Observatory in Hawaii (which is co-managed by Caltech), to conduct follow-up observations of particularly interesting objects.

“Going from one telescope to the next allowed us to perform a sort of triage and pick out the most interesting objects for further study; it was a vertically integrated observatory,” Kulkarni said in the statement. “The reason we called it the Palomar Transient Factory is because it did astronomy on an industrial scale.”

ZTF will utilize those same resources to conduct follow-up studies of variable objects that it identifies. But its wide-field camera also gives it some significant improvements over its predecessor program. For example, ZTF can image an area of the sky seven times larger than PTF could, and it can resolve objects out to greater distances, according to the ZTF scientists. Plus, its “upgraded electronics and telescope-drive systems” enable the ZTF camera to take 2.5 times as many exposures each night, according to the statement.

Combined, that means ZTF can scan the sky on the order of 10 times faster than PTF could, the project scientists said in the statement. But there is yet another all-sky survey on the horizon, and it will be about 10 times faster than ZTF. It’s called the Large Synoptic Survey Telescope, and it’s set to come online in 2023. 

“ZTF is a step toward the future,” Kulkarni said

Courtesy-Space

Astronomers Find New Alien Planet Suitable For Life

November 21, 2017 by  
Filed under Around The Net

A newfound exoplanet may be one of the best bets to host alien life ever discovered — and it’s right in Earth’s backyard, cosmically speaking.

Astronomers have spotted a roughly Earth-mass world circling the small, dim star Ross 128, which lies just 11 light-years from the sun. The planet, known as Ross 128b, may have surface temperatures amenable to life as we know it, the researchers announced in a new study that will appear in the journal Astronomy & Astrophysics.

Ross 128b is 2.6 times more distant from Earth than Proxima b, the potentially habitable planet found in the nearest solar system to the sun. But Proxima b’s parent star, Proxima Centauri, blasts out a lot of powerful flares, potentially bathing that planet in enough radiation to stunt the emergence and evolution of life, scientists have said. [10 Exoplanets That Could Host Alien Life]

Radiation is likely much less of an issue for Ross 128b, because its parent star is not an active flarer, said discovery team leader Xavier Bonfils, of the Institute of Planetology and Astrophysics of Grenoble and the University of Grenoble Alpes in France.

“This is the closest Earth-mass planet potentially in the habitable zone that orbits a quiet star,” Bonfils told Space.com

Bonfils and his colleagues found Ross 128b using the High Accuracy Radial velocity Planet Searcher (HARPS), an instrument at the European Southern Observatory’s La Silla Observatory in Chile.

As its name suggests, HARPS employs the “radial velocity” method, noticing the wobbles in a star’s movement induced by the gravitational tugs of orbiting planets. (NASA’s prolific Kepler space telescope, by contrast, uses the “transit” technique, spotting tiny brightness dips caused when a planet crosses its host star’s face from the spacecraft’s perspective.)

The HARPS observations allowed Bonfils and his team to determine that Ross 128b has a minimum mass 1.35 times that of Earth, and that the planet orbits its host star once every 9.9 Earth days.

Such a tight orbit would render Ross 128b uninhabitable in our own solar system. But Ross 128 is much cooler than the sun, so the newfound world is likely temperate, the researchers said. Determining whether  the planet is actually capable of supporting life as we know it, however, would require a better understanding of its atmosphere, Bonfils said.

“Ross 128b receives 1.38 times [more] irradiation than Earth from our sun,” he said. “Some models made by theorists say that a wet Earth-size planet with such irradiation would form high-altitude clouds. Those clouds would reflect back to space a large fraction of the incident light, hence preventing too much greenhouse heating. With those clouds, the surface would remain cool enough to allow liquid water at the surface. Not all models agree, though, and others predict this new planet is rather like Venus.

Though both Ross 128 and Proxima Centauri are red dwarfs — the most common type of star in the Milky Way galaxy — they are very different objects.

“Proxima Centauri is particularly active, with frequent, powerful flares that may sterilize (if not strip out) its atmosphere,” Bonfils said. “Ross 128 is one of the quietest stars of our sample and, although it is a little further away from us (2.6x), it makes for an excellent alternative target.”

And the star may indeed be targeted in the not-too-distant-future — by giant ground-based instruments such as the European Extremely Large Telescope, the Giant Magellan Telescope and the Thirty Meter Telescope, all of which are scheduled to be up and running by the mid-2020s.

Such megascopes should be able to resolve Ross 128b and even search its atmosphere for oxygen, methane and other possible signs of life, Bonfils said. (NASA’s $8.9 billion James Webb Space Telescope, which is scheduled to launch in early 2019, probably won’t be able to perform such a biosignature search, the researchers said in their discovery paper. If Ross 128b transited its host star from Webb’s perspective, it would likely be a different story, they added.)

Earlier this year, by the way, radio astronomers detected a strange signal that seemed to be emanating from Ross 128. But further investigation revealed that the signal most likely came from an Earth-orbiting satellite, not an alien civilization.

Courtesy-Space

Are Researchers Close To Finding The Evasive Tetraquark

November 17, 2017 by  
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Flit, zip, jitter, boom. Quarks, the tiny particles that make up everything tangible in the universe, remain deeply mysterious to physicists even 53 years after scientists first began to suspect these particles exist. They bop around at the edge of scientific instruments’ sensitivities, are squirreled away inside larger particles, and decay from their higher forms into their simplest in half the time it takes a beam of light to cross a grain of salt. The little buggers don’t give up their secrets easily.

That’s why it took more than five decades for physicists to confirm the existence of an exotic particle they’ve been hunting since the beginning of quark science: the massive (at least in subatomic particle terms), elusive tetraquark.

Physicists Marek Karliner of Tel Aviv University and Jonathan Rosner of the University of Chicago have confirmed that the strange, massive tetraquark can exist in its purest, truest form: four particles, all interacting with one another inside a single, larger particle, with no barriers keeping them apart. It’s stable, they found, and can likely be generated at the Large Hadron Collider, a particle smasher at the CERN particle physics laboratory in Switzerland, they report in a paper to be published in a forthcoming issue of the journal Physical Review Letters.

If you know a little about particle physics, you probably know that everything with mass is made up of atoms. Diving a little deeper into particle physics would reveal that those atoms are made up of subatomic particles — protons, neutrons and electrons. An even deeper look would reveal quarks.

Neutrons and protons are the most common examples of a class of particles known as hadrons. If you could peer into a hadron, you’d find it’s made up of even more basic particles, clinging tightly together. Those are quarks.

Like atoms, which adopt different properties depending on the combinations of protons and neutrons in their nuclei, hadrons derive their properties from combinations of their resident quarks. A proton? That’s two “up” quarks and one “down” quark. Neutrons? Those are made up of two “down” quarks and one “up” quark. [Wacky Physics: The Coolest Little Particles in Nature]

(Electrons aren’t made up of quarks because they aren’t hadrons — they’re leptons, part of a class of distant cousins of quarks.)

“Up” and “down” are the most common flavors of quark, but they’re just two out of six. The other four — “charm,” “top,” “strange” and “bottom” quarks — existed in the moments after the Big Bang, and they appear in extreme situations, such as during high-velocity collisions in particle colliders. But they’re much heavier than up and down quarks, and they tend to decay into their lighter siblings within moments of their creation.

But those heavier quarks can last long enough to bind together into strange hadrons with unusual properties that are stable for the very short lifetimes of the quarks zipping around inside them. Some good examples: the “doubly charmed baryon,” or a hadron made up of two charm quarks and a lighter quark; and its cousin, formed when a hadron made up of two bulky bottom quarks and one lighter quark fuse together in a flash more powerful than the individual fusion reactions inside hydrogen bombs. (Of note, the bottom quark fusion is militarily useless thanks to heavy quarks’ short lifetimes.)

Playing with colors

“The suspicion had been for many years that [the tetraquark] is impossible,” Karliner told Live Science.

That’s because physical laws suggested four quarks couldn’t actually bind together into a stable hadron. Here’s why: Just like in atoms, where the attraction between positively charged protons and negatively charged electrons is what holds them together, hadrons are held together by forces as well. In atoms, positive and negative particles constantly try to neutralize their charges to zero, so protons and electrons stick together, canceling each other out. [7 Strange Facts About Quarks]

Quarks have positive and negative electrodynamic charges, but they also interact with one another via the much more powerful “strong” force. And the strong force also has charges, called color charges: red, green and blue.

Any quark can have any color charge. And when they bind together to form hadrons, all those charges have to cancel out. So a red quark, for example, has to hook up with either a green quark and a blue quark, or its antimatter twin — an “antiquark” with a color charge of “antired.” (This is your brain on quantum mechanics.) Any combination of a color and its anticolor, or all three colors, sticking together has a neutral color charge. Physicists call these particles “white.”

The tetraquark: It’s like a relationship (in that it doesn’t always work)

So, Karliner said, it’s not hard to imagine a four-quark hadron: Just stick two quarks to two matching antiquarks. But just because you stick four matching quarks together, he said, doesn’t mean they’ll be stable enough to form an actual hadron — they could fly apart.

“Just because you move two men and two women into an apartment,” Karliner said, “doesn’t mean they’ll settle down and form a nuclear family.”

Quarks have mass, which physicists measure in units of energy: megaelectron volts, or MeV. When they bind together, some of that mass converts into the binding energy holding them together, also measured in MeV. (Remember Einstein’s E=mc^2? That’s energy equals mass-times-the-speed-of-light-squared, the equation governing that conversion.)

If the mass is too high compared with the binding force, the energy of the quarks careening around inside the hadron will tear the particle apart. If it’s low enough, the particle will live long enough for the quarks to settle down and develop group properties before they decay. A big, happy quark-foursome family needs to have a mass lower than two mesons (or quark-antiquark pairs) stuck together, according to Karliner.

Unfortunately, the mass of a quark family after some of its bulk is converted into binding force is incredibly difficult to calculate, which makes it hard to figure out whether a given theoretical particle is stable.

Scientists have known for about a decade that mesons can bind to other mesons to form ad-hoc tetraquarks, which is why you might have seen reports touting the existence of tetraquarks before. But in those tetraquarks, each quark interacts primarily with its pair. In a true tetraquark, all four would mix with one another equally.

“It’s charming and interesting, but not the same,” Karliner said. “It’s very different to have two couples in different rooms sharing an apartment, and two men and two women all together with everyone … interacting with everyone else.”

But those double-meson tetraquarks provide the mass threshold that true tetraquarks must cross to be stable, he said.

In theory, Karliner said, it would be possible to predict the existence of a stable tetraquark from pure calculation. But the quantum mechanics involved were just too difficult to make work with any reasonable degree of confidence.

Karliner and Rosner’s key insight was that you could start to figure out the mass and binding energy of rare hadrons by analogy to more common hadrons that had already been measured.

Remember that doubly charmed baryon from earlier? And its explosive cousin with the two bottom quarks? In 2013, Karliner and Rosner began to suspect they could calculate its mass, after thinking carefully about the binding energy inside mesons made up of charm quarks and anticharm quarks.

Quantum mechanics suggests that two different-colored charm quarks — say, a red charm and a green charm — should bind together with exactly half the energy of a charm quark and its antimatter twin — say, a red charm quark and an antired charm antiquark. And scientists have already measured the energy of that bond, so the energy of acharm-charm bond should be half of that.

So Karliner and Rosner worked with those numbers, and they found that the doubly charmed baryon and double-bottom baryon should have a mass of 3627 MeV, plus or minus 12 MeV. They published their papers and pushed the experimentalists at CERN (European Organization for Nuclear Research) to start hunting, Karliner said.

But Karliner and Rosner offered CERN a road map, and eventually, the CERN scientists acceded. In July 2017, the first definite doubly charmed baryons turned up in the Large Hadron Collider (LHC). [Photos: The World’s Largest Atom Smasher (LHC)]”The experimentalists were quite skeptical at first” that it would be possible to find the doubly charmed baryons in the real world, Karliner said. “It’s like looking for a needle not in a haystack, but in a haystack of haystacks.”

“We predicted in 2014 that the mass of this doubly charmed baryon was going to be 3,627 MeV, give or take 12 MeV,” Karliner said. “The LHC measured 3,621 MeV, give or take 1 MeV.”

In other words, they nailed it.

And because their calculation turned out to be correct, Karliner and Rosner had a road map to the true stable tetraquark.

In quantum mechanics, Karliner explained, there’s a general rule that heavier quarks tend to bind much more tightly to each other than lighter quarks do. So if you’re going to find a stable tetraquark, it’s probably going to involve some quarks from the heavier end of the flavor spectrum.

Karliner and Rosner got to work as soon as the doubly charmed baryon measurement was announced. First, they calculated the mass of a tetraquark made up of two charm quarks and two lighter antiquarks; charm quarks, after all, are pretty chunky, at about 1.5 times the mass of a proton. The result? A doubly-charmed tetraquark turns out to be right on the edge of stable and unstable, with room for error on both sides — in other words, too uncertain to call a discovery.

But charm quarks aren’t the heaviest quarks around. Enter the bottom quark, a true monster of an elementary particle at about 3.5 times the mass of its charmed sibling, with an accompanying leap in binding energy.

Fuse two of those together, Karliner and Rosner calculated, along with an up antiquark and a down antiquark, and you’ll end up with a stable foursome — converting so much of their bulk into binding energy that they end up 215 MeV under the maximum mass threshold, with a margin of error of just 12 MeV.

“The upshot of all this is that we now have a robust prediction for the mass of this object which had been the holy grail of this branch of theoretical physics,” Karliner said.

This kind of tetraquark won’t live very long once it’s created; it winks out after just one-tenth of a  picosecond, or the length of time it takes a beam of light to cross a single microscopic skin cell. It then will decay into simpler combinations of up and down quarks. But that 0.1 picoseconds (one ten-trillionth of a second) is plenty long enough on the quantum mechanical scale to be considered a stable particle.

“It’s like if you compared a human lifetime to [the movement of continents],” Karliner said. “If you have some creatures living on the scale of fractions of seconds, a human lifetime would seem almost infinite.”

Onward to Switzerland

The next step, once a particle has been predicted by theorists, is for the experimentalists at CERN to try to create it in the miles-long tubes of their particle smasher, the LHC.

That can be a grueling process, especially because of the specific properties of bottom quarks.

The LHC works by slamming protons together at large fractions of the speed of light, releasing enough energy into the collider that some of it turns back into mass. And some tiny fraction of that mass will condense into rare forms of matter — like that doubly charmed baryon.

But the heavier a particle is, the lower the odds it will pop into being in the LHC. And bottom quarks are exceptionally unlikely creations.

In order to build a tetraquark, Karliner said, the LHC has to generate two bottom quarks in close enough proximity to each other that they bind, and then “decorate” them with two light antiquarks. And then it has to do it again, and again — until it’s happened enough times that the researchers can be sure of their results.

But that’s not as unlikely as it may sound.

“It turns out that, if you consider how you would make such things in a lab,” Karliner said, “the probability of making them is only slightly less likely than finding that baryon with two bottom quarks and one light quark.”

And that hunt is already underway.

Once the two-bottom-quark baryon is discovered, Karliner said — a result he expects within the next few years — “the clock starts ticking” on the appearance of the tetraquark.

Somewhere out there in the ether is a hadron that physicists have been hunting for 53 years. But now they’ve caught its scent.

Courtesy-Space

Supernova Baffles Astronomers

November 15, 2017 by  
Filed under Computing

The appearance of a years-long supernova explosion challenges scientist’s current understanding of star formation and death, and work is underway to explain the bizarre phenomenon.

Stars more than eight times the mass of the sun end their lives in fantastic explosions called supernovas. These are among the most energetic phenomena in the universe. The brightness of a single dying star can briefly rival that of an entire galaxy. Supernovas that form from supermassive stars typically rise quickly to a peak brightness and then fade over the course of around 100 days as the shock wave loses energy.

In contrast, the newly analyzed supernova iPTF14hls grew dimmer and brighter over the span of more than two years, according to a statement by Las Cumbres Observatory in Goleta, California, which tracked the object. Details of the discovery appeared on Nov. 8 in the journal Nature.

 Supernova iPTF14hls was unremarkable when first detected by a partner telescope in San Diego on Sept. 22, 2014. The light spectrum was a textbook example of a Type II-P supernova, the most common type astronomers see, lead author Iair Arcavi, an astronomer at the University of California, Santa Barbara, told Space.com. And the supernova looked like it was already fading, he said.

The observatory was in the middle of a 7.5-year collaborative survey, so Arcavi focused on more-promising objects. But in February, 2015, Zheng Chuen Wong, a student working for Arcavi that winter, noticed the object had become brighter over the past five months.

“He showed me the data,” Arcavi said, “and he [asked], ‘Is this normal?’ and I said, ‘Absolutely not. That is very strange. Supernovae don’t do that,'” Arcavi said.

At first, Arcavi thought it might be a local star in our galaxy, which would appear brighter because it was closer, he said. Many stars are also known to have variable brightness. But the light signature revealed that the object was indeed located in a small, irregular galaxy about 500 million light-years from Earth.

And the object only got weirder. After 100 days, the supernova looked just 30 days old. Two years later, the supernova’s spectrum still looked the way it would if the explosion were only 60 days old. The supernova recently emerged from behind Earth’s sun, and Arcavi said it’s still bright, after roughly three years. But at one one-hundredth of its peak brightness, the object appears to finally be fading out.

“Just to be clear, though, there is no existing model or theory that explains all of the observations we have,” said Arcavi. The supernova may fade out; it may grow brighter, or it may suddenly disappear.

One reason for Arcavi’s uncertainty is that a supernova was seen in the same location in 1954. This means that the event Acavi has been observing, whatever it is, may actually be 60 years running. There’s a 1 to 5 percent chance the two events are unrelated, but that would be even more surprising, said Arcavi. Astronomers have never observed unrelated supernova in the same place decades apart. “We are beyond the cutting-edge of models,” Arcavi said.

“I’m not sure, and I don’t think anyone else is sure, just what the hell is happening,” astrophysicist Stanford Woosley, at University of California, Santa Cruz, told Space.com. “And yet it happened, and so it begs explanation.”

Woosley is not affiliated with the study, but he is among the theoreticians working to understand the event. Two hypotheses show promise in explaining it, he said.

The first involves the famous equation E = mc2. With this formula , Albert Einstein demonstrated that matter and energy are fundamentally interchangeable. Stars burn by converting matter into energy, fusing lighter elements like hydrogen and helium into heavier elements, which build up in the star’s core and also release energy. When a star more than 80 times the mass of the sun reaches a temperature of 1 billion degrees Celsius (1.8 billion degrees Fahrenheit), this energy-matter equivalence produces pairs of electrons and their antiparticle counterparts, positrons, Woosley said. The process robs the star of energy, and so the object shrinks.

But as this happens, the temperature rises in the star’s core. At 3 billion C (5.4 billion F), oxygen fuses explosively, blowing off massive amounts of material and resetting the cycle. This process repeats until the star reaches a stable mass, explained Woosley. When the front of an ejected shell of material hits the trailing edge of a previous shell, it releases energy as light.

The star continues to fuse oxygen and the elements of greater masses, up until iron, at which point the reaction fails to release enough energy to keep the star from collapsing in on itself.Eventually, a star like the one that gave rise to iPTF14hls will collapse into a black hole without another explosion, said Woosley.

This phenomenon, called a pulsation pair instability (PPI) supernova, could account for iPTF14hls’ sustained luminosity as well as the object’s varying brightness. This explanation would require the star to have been 105 times the mass of the sun, said Woosley. However, the PPI model cannot account for the tremendous amount of energy iPTF14hls has released. The first explosion of 2014 had more energy than the model predicts for all the explosions combined, said Arcavi.

What’s more, this phenomenon has yet to be verified observationally. “Stars between 80 and 140 solar masses, which do this kind of thing, have to exist,” said Woosley, “and they have to die, and so, somewhere, this has to be going on.” But no one has seen it yet, he said.

A magnetic superstorm

An alternative explanation involves a star 20 to 30 times the mass of Earth’s sun. After a more conventional supernova, such a star could have condensed into a rapidly spinning neutron star, called a magnetar.

A neutron star packs the mass of 1.5 suns into an object with a diameter about the size of New York City. A neutron star rotating at 1,000 times per second would have more energy than a supernova, according to Woosley. It would also generate a magnetic field 100 trillion to 1 quadrillion times the strength of Earth’s field. As the star spun down over the course of several months, its incredible magnetic field could transfer the star’s rotational energy into the remnants of the supernova that it formed from, releasing light, Woosley explained.

“It’s like there’s a lighthouse down in the middle of the supernova,” said Woolsey.

But the magnetar explanation is not perfect, either. It has trouble explaining the dips and peaks in iPTF14hls’ brightness, and the physics behind how such a phenomenon might work is still uncertain, said Woosley.

As iPTF14hls sheds energy, Arcavi said he hopes to be able to see deeper into the object’s structure. If it is a magnetar, then he expects to see X-rays, previously obscured by the supernova itself, beginning to break through, he said. “Maybe by combining pulsation pair instability with [a magnetar], you can start to explain the supernova,” Arcavi said. 

Keeping busy while keeping watch

The existence of iPTF14hls has far-reaching implications, the researchers said. At 500 million light-years away, the supernova is still relatively close to Earth, and the universe is practically the same today — in terms of composition and organization —as it was when this event occurred,  according to Arcavi. If the event was a PPI supernova, it tells astronomers that stars more than 100 times the mass of the sun — thought to be more prevalent in the early universe — are still forming today.

The event also had far more hydrogen than researchers expected to see. The explosion in 1954 should have expelled nearly all of the star’s hydrogen, said Arcavi. Astrophysicists will have to revisit their models of supernovas to understand how this can occur, he said.

The finding has ramifications for the study of galaxies as well. “The energy of the gravity that’s keeping that galaxy together is about the same order of magnitude as the energy that was released in the supernova,” Arcavi said. “So, a few of these in a galaxy could actually unbind the entire galaxy.”

Arcavi and his team plan to continue monitoring iPTF14hls for at least one to two years. And a suite of international telescopes and observatories will join the effort. Swedish colleagues at the Nordic Optical Telescope, in the Canary Islands, will track the object as it continues to dim beyond what Arcavi’s telescope array can detect. NASA’s Swift spacecraft will look for X-ray emissions, while the Hubble Space Telescope is scheduled to image the location beginning in December, and others will follow, Arcavi said.

For now, the event remains a mystery.

“It’s just a puzzle in the sky,” said Woosley. “That’s what we live for, what astronomers love.”

Courtesy-Space

Did Astronomers Discover Two Merging Black Holes

November 6, 2017 by  
Filed under Around The Net

Scientists on the hunt for colliding black holes should turn their eyes to the quiet, outer regions of galaxies like the Milky Way, a new study suggests.

In late 2015, researchers made the first-ever direct detection of gravitational waves — ripples in the universal fabric known as space-time. Astronomers have now detected four separate gravitational-wave signals coming from pairs of black holes colliding and merging together. The fusion of black holes this size — about 20 to 50 times the mass of the sun — had never been directly observed in nature before.

Unfortunately, gravitational-wave detectors have a tough time narrowing down where those merging black holes are located. This makes it difficult for scientists to do follow-up studies, or to look for possible sources of light around the black holes.  

Previous work had suggested that pairs of black holes in this mass range are more likely to form in dim dwarf galaxies. But the new study shows that the quiet outer regions of larger, spiral-shaped galaxies — like our own Milky Way — may be better places to look.

“If our calculation is correct, the advantage is that if you’re trying to localize the signal, it’s a lot easier to find big galaxies, right? That’s pretty obvious,” said study lead author Sukanya Chakrabarti, a professor of physics and astronomy at the Rochester Institute of Technology (RIT).

Determining the precise location or home galaxy of these black hole pairs has multiple advantages for astrophysics. First, it would increase the odds of seeing light signals created by the merger of two black holes. While the black holes themselves are completely dark, nearby matter (such as a disk of gas and dust swirling around it) could radiate light. Studying this light could provide scientists with more information about these events. 

Additionally, scientists want to use gravitational waves to make a measurement of the expansion rate of the universe — a value known as the Hubble Constant, named after the astronomer Edwin Hubble. Right now, there are two ways to measure this value, but they have produced slightly different values, and scientists don’t know why. Measurements from gravitational waves might solve the discrepancy.

“It’s the holy grail of gravitational wave cosmology,” Chakrabarti told Space.com.

Black holes can form when massive stars run out fuel and explode as supernovas. Much of the material that made up the living star collapses down onto a single point, and a black hole forms. Black holes with 10 to 50 times the mass of the sun must form from stars with masses between about 40 and 100 solar masses, according to scientists with the Laser Interferometry Gravitational-Wave Observatory (LIGO) project, which spotted space-time ripples from the four black hole mergers (as well as those generated by a different kind of event — the collision of two neutron stars). 

So where are these massive stars born?

To make a truly massive star requires a very simple starting mixture consisting almost exclusively of hydrogen and helium. “Heavier” elements (those with numbers higher than 2 on the periodic table) can dampen the formation of very massive stars. This happens because those elements give off more intense radiation compared to hydrogen; that radiation exerts an outward force that pushes gas and other material away, so the star doesn’t accumulate more matter and grow bigger.

The bright regions of large galaxies — like the beautiful, swirling arms of the Milky Way — are low on the list of possibilities, because they are so rich in heavy elements. 

But nearly all spiral galaxies possess an outer disk consisting mainly of hydrogen, Chakrabarti said. These co-called “H1 regions” have very low overall star-formation rates, and are thus fairly dim compared to the bright central disks. In the case of the Milky Way, the H1 region is about as thick as the main disk is wide — about 30 kiloparsecs, or about 100,000 light-years across. In some galaxies examined in the paper, the H1 disk is 80 kiloparsecs across, Chakrabarti told Space.com — plenty of room for massive stars to be born.

The new paper calculates the rate at which these heavy black hole collisions are likely to occur in these H1 regions. They find that the number of collisions in a given area, over a given time, is comparable, if not better than, for dwarf galaxies. 

Dwarf galaxies are small collections of stars that look more like sparkly clouds than bright disks of light. A pervious paper showed that dwarf galaxies are more likely to host these black hole pairs than large spiral galaxies like the Milky Way. But that paper did not consider distinct regions in those galaxies, like the H1 region, Chakrabarti told Space.com. 

The previous study was co-authored by Richard O’Shaughnessy, an assistant professor of mathematics at RIT and a member of the LIGO collaboration — and one of Chakrabarti’s co-authors on the new paper. Chakrabarti said she talked with O’Shaughnessy after the publication of the earlier paper, telling him he should consider regions of galaxies, and not just galaxies as a whole. 

“This is a new field,” said Chakrabarti, referring to the direct detection of these black hole mergers. “Our paper is really the third to have looked at this question of what are the host galaxies of binary black holes. It’s sort of a new question, and it does require the confluence of two fields that have been somewhat distinct.”

The authors state in the paper that their numerical estimations for black hole collisions in these different environments aren’t very precise, because there is still very little data to work with — only four detections of gravitational-wave signals from black holes so far. But, Chakrabarti said the overall conclusion is that, when it comes to black holes in this mass range, the H1 regions of these galaxies are just as fertile as dwarf galaxies, or even more so. 

“No one has proposed that, in fact, binary black holes could form more abundantly in the outskirts of big galaxies like our own,” Chakrabarti said. “Even considering all of the uncertainties [in the calculated rate], I think it’s clear that the outskirts of spirals will produce as many massive binary black hole mergers as any other galactic environment.”

Courtesy-Space

Astrophysicist Research Supernova Explosions

November 1, 2017 by  
Filed under Around The Net

Everything in the universe someday comes to an end. Even stars. Though some might last for trillions of years, steadily sipping away at their hydrogen reserves and converting them to helium, they eventually run out of fuel. And when they do, the results can be pretty spectacular.

Our own sun will make a mess of the solar system when it enters the last stages of its life in 4 billion years or so. It will swell, turn red (consuming Earth in the process) and cast off its outer layers, giving one last gasp as a planetary nebula before it settles down into post-fusion retirement as a white dwarf.

The most spectacular deaths, though, are reserved for the most massive stars. Once an object builds up to at least eight times the mass of the sun, interesting games can be played inside the core, with … explosive results.

Any star, no matter how massive, walks a thin tightrope. On one side is the crushing gravity of the star’s own weight, which provides the pressures and temperatures necessary to achieve nuclear fusion in the core and turn hydrogen into helium. But that fusion process releases energy, which puts the star in a more expansive mood than gravity does alone. 

To understand how this works, let’s work through a thought experiment. Imagine that the gravity were to increase a tiny bit, then the increased pressure would raise the intensity level of the fusion reactions, which, in turn, would release more energy and thus prevent further collapse of the star. And on the opposite end, if the fusion party were to get just a little bit wilder, it would cause to star to overinflate, lessening the grip of gravity and easing the pressure in the core, cooling things off.

This balancing act enables a star to last millions, billions and even trillions of years.

Until it doesn’t.

The game can be played as long as there’s fuel to keep the lights on. As long as there’s a sufficient supply of hydrogen near the core, the star can keep cranking out the helium and keep resisting the inevitable crush of gravity.

I’m not just using a flair of language when I describe the crush of gravity as inevitable. Gravity never stops, never sleeps, never halts. It can be resisted for a long time, but not forever.

As a star ages, it builds up a core of inert helium. Once the hydrogen supply exhausts itself, there’s nothing to stop the infalling weight of the surrounding material. That is, until the core reaches a scorching temperature of 100 million kelvins (180 million degrees Fahrenheit), at which point helium itself begins to fuse.

Hooray, the party’s back on! Well, for a while, at least. Helium fusion isn’t as efficient as good ol’ hydrogen, so the reactions happen at an even faster pace to compete with gravity.

While the “main sequence” of a star’s life may last hundreds of millions of years as it happily burns hydrogen, the helium phase barely lasts a single million.

The product of helium fusion is carbon and oxygen, and the same game gets played again, but at even higher temperatures and shorter timescales. Once the helium is sucked dry, the core collapses and intensifies to 1 billion K (1.8 billion degrees F), allowing those new elements to get their turn.

Out of control

Then, silicon fuses at around 3 billion K (5.4 billion degrees F) in the core, generating iron. Surrounded by plasmatic onion-like layers of oxygen, neon, carbon, helium and hydrogen, the situation at the center starts to get dicey.

The problem is that, due to its internal nuclear configuration, fusing iron consumes energy rather than releases it. Gravity keeps pressing in, shoving iron atoms together, but there’s no longer anything to oppose its push.

In less than a day, after millions of years of peaceful nuclear regime changes, the star forms a solid core of iron, and everything goes haywire.

In a matter of minutes, the intense gravitational pressure slams electrons into the iron nuclei, transforming protons into neutrons. The small, dense neutron core finally has the courage to resist gravity, not by releasing energy but through an effect called degeneracy pressure. You can only pack so many neutrons into a box; eventually, they won’t squeeze any tighter without overwhelming force, and in the first stages of a supernova explosion, even gravity can’t muster enough pull.

So now you have, say, a couple dozen suns’ worth of material collapsing inward onto an implacable core. Collapse. Bounce. Boom.

Except there’s a stall. The shock front, ready to blast out from the core and shred the star to stellar pieces, loses energy and slows down. There’s a bounce but no boom.

To be perfectly honest, we’re not exactly sure what happens next. Our earliest simulations of this process failed to make stars actually blow up. Since they do blow up in reality, we know we’re missing something.

For a while, astrophysicists assumed neutrinos might come to the rescue. These ghostly particles hardly ever interact with normal matter, but they’re manufactured in such ridiculously quantities during the “bounce” phase that they can reinvigorate the shock front, filling its sails so it can finish the job.

But more sophisticated simulations in the past decade have revealed that not even neutrinos can do the trick. There’s plenty of energy to power a supernova blast, but it’s not in the right place at the right time.

The initial moments of a supernova are a very difficult time to understand, with plasma physics, nuclear reactions, radiation, neutrinos, radiation — a whole textbook’s worth of processes happening all at once. Only further observations and better simulations can fully unlock the final moments of a star’s life. Until then, we can only sit back and enjoy the show.

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Is Another Mission To Pluto Being Planned

October 31, 2017 by  
Filed under Around The Net

A grassroots movement seeks to build momentum for a second NASA mission to the outer solar system, a generation after a similar effort helped give rise to the first one.

That first mission, of course, was New Horizons, which in July 2015 performed the first-ever flyby of Pluto and is currently cruising toward a January 2019 close encounter with a small object known as 2014 MU69.

New Horizons got its start with letter-writing campaigns in the late 1980s, and the new project hopes to duplicate that success, said campaign co-leader Kelsi Singer, a New Horizons team member who’s based at the Southwest Research Institute (SwRI) in Boulder, Colorado.   

Nearly three dozen scientists have drafted letters in support of a potential return mission to Pluto or to another destination in the Kuiper Belt, the ring of icy bodies beyond Neptune’s orbit, Singer told Space.com.Next Up

These letters have been sent to NASA planetary science chief Jim Green, as well as to the chairs of several committees that advise the agency, she added.

“We need the community to realize that people are interested,” Singer said. “We need the community to realize that there are important, unmet goals. And we need the community to realize that this should have a spot somewhere in the Decadal Survey.”

That would be the Planetary Science Decadal Survey, a report published by the National Academy of Sciences that lays out the nation’s top exploration priorities for the coming decade.

“This is the way it normally works,” said New Horizons principal investigator Alan Stern, who’s also based at SwRI.

“First it bubbles up in the community and then, when there’s enough action, the agency starts to get behind it,” Stern, who has been the driving force behind New Horizons since the very beginning, told Space.com. “Then it lets the Decadal Survey sort things out.”

Stern contributed a letter to the new campaign, and he has voiced support for a dedicated Pluto orbiter. Singer would also be happy if NASA went back to the dwarf planet.

“Pluto just has so much going on,” she said.

But there are other exciting options available as well, Singer said. For example, NASA could do a flyby of a different faraway dwarf planet — Eris, perhaps — to get a better idea of the variety and diversity of these intriguing worlds.

Or the agency could target Kuiper Belt objects (KBOs) that have diameters of a few hundred kilometers or so, she added. New Horizons has flown by one “big” KBO (Pluto) and will soon see a small one — 2014 MU69 is just 20 miles (32 km) or so across — but there are no plans at the moment to study anything of an intermediate size up close.

The last Decadal Survey was put out in 2011, and it covers the years 2013 to 2022. The next one is due out in five years, and it will help map out NASA’s plans for the 2020s and early 2030s. So Singer knows she and her colleagues must be patient, even if their letter-writing campaign ultimately bears fruit.

“I would say 25 years is the longest I think about,” she said, referring to how long it may be before another Kuiper Belt mission gets to its destination. “And I hope it may be more like 15 years.”

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Scientist Have New Theory On The 3D Universe

October 26, 2017 by  
Filed under Around The Net

We take for granted that we live in a world of three dimensions governed by the laws of physics, and don’t often wonder why. But a group of physicists just hatched a new theory that they think may explain our three-dimensional universe.

The physicists think that their new model could also explain inflation, the exponential expansion of space the universe experienced just moments after the Big Bang.

Thomas Kephart from Vanderbilt University and four of his colleagues from around the world wanted to figure out why our universe seemingly has just three dimensions, especially since, as they wrote, “quantum gravity scenarios such as string theory… assume nine or ten space dimensions at the fundamental level.”

They combined particles physics with mathematical knot theory to try and work this out, borrowing the concept of “flux tubes,” which are flexible strands of energy that link elementary particles together.

Quarks, the elementary particles that  make up  protons and neutrons, are held together by another type of elementary particle called a gluon that “glues” quarks together. Gluons bond positive quarks to matching negative antiquarks with these flux tube energy strands.

Normally, the flux tube that links a quark and antiquark would disappear when the two particles come into contact — they would self-annihilate. But, the team said in a paper published by the European Physical Journal C, if two or more flux tubes become intertwined, it becomes stable. If the tubes take the form of a knot, they become even more stable and can outlive the particles that created it.

“A knot or link between two flux tubes is only classically stable if these are unable to intersect and either reconnect or pass through each other,” the researchers wrote. “Such  intercommutations  lead to the well-known scaling behavior in cosmic string networks, which has been observed in several examples of non-interacting strings.”

In moments of transition, such as what happened during the Big Bang, the linked particles would get pulled apart, and the flux tube would get longer until it reaches a point where it breaks. When it does, it releases enough energy to form a second quark-antiquark pair that splits up and binds with the original particles, producing two pairs of bound particles.

The physicists equated this to how cutting a bar magnet in half produces two smaller magnets that both have north and south poles.

If the tubes were knotted together, they could quickly expand and multiply. The team calculated the energy that this flux tube network might contain and found that it would be enough to power an early period of cosmic inflation.

While this sounds like an incredible amount of action to take place in such a short period of time — inflation theory suggests that the universe expanded exponentially in milliseconds — Kephart told Seeker that flux tubes form naturally during times of transition.

“Flux tubes form in phase transitions where complex forms of matter can arise,” he explained in an email. “For example, water vapor is structurally simple, but if it is rapidly cooled you get a flurry of snowflakes — they all look different and the new phase seems much more complex.”

In an environment of extremely high energy, the team said that the quark-gluon plasma would have been an ideal environment for rapid flux tube formation in the very early universe.

But, crucially, they noted that this would only work if the universe existed in three dimensions. If you add more dimensions, the process becomes unstable.

“Of all possible dimensionalities of space, our mechanism picks out three as the only number of dimensions that can inflate and thus become large,” the team wrote. “This model may explain why we live in three large spatial  dimensions,  since knotted/linked tubes are topologically unstable in higher-dimensional space-times.”

This would technically agree with a computer model from 2012 where Japanese scientists found that at the moment of the Big Bang, the universe had 10 dimensions, but only three of these spatial dimensions expanded. So, the three-dimensional space we experience could have formed from 10 dimensions, just as superstring theory predicts.

Their new theory would also agree with certain gauge theories, which are theories used by physicists that describe the limits of physical laws and how they apply to symmetric transformations.

Kephart noted that this new flux tube theory also encompasses what happened after inflation.

“Not only does our flux tube network provide the energy needed to drive inflation, it also explains why it stopped so abruptly,” he said in a statement. “As the universe began expanding, the flux-tube network began decaying and eventually broke apart, eliminating the energy source that was powering the expansion.”

The researchers say that when the network broke down, it filled the universe with a gas of subatomic particles and radiation, allowing the evolution of the universe to continue to what we see today.

“This combines knowledge of gauge theories and the possibility that an initial uniform configuration can condense into flux tubes,” Kephart told Seeker, “along with the fact that knots and links for strings can only be stable in 3D, plus the current state of the theory of the early Universe and the need for a natural way to inflate.”

While this is all theoretical, Kephart said that the next step would be to continuing to develop their theory until it can make some predictions about the nature of the universe that can actually be tested.

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Astronomers Discover New Galaxy Collision

October 25, 2017 by  
Filed under Around The Net

The Hubble Space Telescope recently captured a speckled and sparkling image of the Cocoon Galaxy, also known as NGC 4490. Over millions of years, it morphed from an elegant spiral shape, like that of the Milky Way Galaxy, which contains Earth’s solar system, into an elongated system of scattered star births and deaths.

While gravity is a weak force for small objects, it creates a powerful attraction between massive structures like galaxies. In NGC 4490’s case, the smaller galaxy NGC 4485 was drawn in by gravity, moving and colliding through its larger neighbor and altering the properties of them both, according to Hubble’s image caption. The impact from the smaller galaxy stretched out the bigger galaxy, which only has a few remaining signs of its former spiral shape, like the curved arm that connects it with the smaller NGC 4485.

Both galaxies are collectively known as system Arp 269, located in the constellation Canes Venatici, or the Hunting Dogs.

According to the caption, the bright-pink colors throughout the Hubble image are active regions where stars are forming. The galactic impact dislodged gas and dust, which are reassembling as the two galaxies are about 24,000 light years apart from each other. The collision produced ripples packed with dense areas, which are prime for star creation. Clouds of ionized hydrogen are so dense, they radiate a pink glow as they’re lit by the more fully formed young stars nearby.

NGC 4490 is called a starburst galaxy because it is brimming with stellar birth. However, it is also full of supernovas, the dramatic explosions caused by the death of stars. Several supernovas have been spotted within the Cocoon galaxy in the last few decades, in 1982 and 2008, officials wrote in the caption.

In billions of years, it’s likely NGC 4490 and NGC 4485 will tug one another with their gravitational forces and collide once again.

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Astronomers Discover Multiple Black Holes Merging

October 24, 2017 by  
Filed under Around The Net

Astronomers have pinpointed five pairs of merging black holes using three different space- and ground-based instruments and two sky surveys. 

A new study used data from the Chandra X-ray Observatory, the Wide-field Infrared Survey Explorer (WISE), the ground-based Large Binocular Telescope in Arizona, the Sloan Digital Sky Survey (SDSS) and the Mapping Nearby Galaxies at APO (MaNGA) survey to identify the pairs. They are circling one another before they eventually merge. Finding the black holes could help astronomers understand how the objects produce such powerful gravitational waves when they finally combine. 

The pairs of supermassive black holes, each billions of light years from Earth, are millions of times as massive as the sun, researchers said in a new statement from Chandra. The black holes are in pairs because they come from two galaxies that collided and merged with each other, putting their central black holes in close proximity. Theoretical models predicted this kind of giant black hole pairing should be relatively common, but the phenomenon has been difficult to see, the researchers said.

To find those pairs, astronomers first used the SDSS data to spot galaxies that looked like they were undergoing mergers. Researchers picked out the ones whose centers were less than 30,000 light-years apart and applied the WISE data, looking for colors that matched those of a supermassive black hole. 

Then, the scientists used Chandra to see if there was a high level of X-ray emission, which marks a growing black hole. And Chandra had high enough resolution to discern two distinct sources of those emissions, the researchers said. That revealed five black hole pairs that fit the bill. 

Five new pairs of supermassive black holes in the process of merging are identified in data from three different instruments and two sky surveys.

The combination of X-ray data from Chandra and infrared data from WISE suggests that large amounts of dust and gas surrounds these supermassive black holes; the observatories were measuring wavelengths that could pierce that material and reveal the pairs. 

Four of the dual black hole candidates were reported in a paper accepted for publication in The Astrophysical Journal. The other dual black hole candidate was reported in the journal the Monthly Notices of the Royal Astronomical Society and appears online. 

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Astronomers Find Two Black Holes At The Center Of A Spiral Galaxy

September 29, 2017 by  
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Not one but two gigantic black holes lurk at the heart of the distant spiral galaxy NGC 7674, a new study suggests.

These two supermassive black holes are separated by less than 1 light-year and together harbor about 40 million times the mass of the sun, researchers said.

If it holds up, the find would be just the second known system of double supermassive black holes. The other, announced in 2006, is in a galaxy known as 0402+379, whose two giant black holes are separated by about 24 light-years and boast a combined 15 billion solar masses.  

(The Laser Interferometer Gravitational-Wave Observatory project, or LIGO, has spotted the gravitational waves emitted by multiple binary black holes as they spiral toward each other. But the LIGO detections involve objects a few tens of times more massive than the sun, known as stellar-mass black holes.)

The research team analyzed observations of NGC 7674, which lies about 400 million light-years from Earth, that were made by the Very Large Array, a network of radio telescopes in New Mexico. The researchers found two distinct, compact sources of radio-wave emission at the galaxy’s center.

“The two radio sources have properties that are known to be associated with massive black holes that are accreting gas, implying the presence of two black holes,” study lead author Preeti Kharb, of the National Centre for Radio Astrophysics at the Tata Institute of Fundamental Research in India, said in a statement.

These two behemoths orbit their common center of mass about once every 100,000 years, the researchers said.

The two newfound black holes probably sidled up when their former host galaxies merged to form the current NGC 7674. (Most, if not all, galaxies are thought to have supermassive black holes at their centers.) This supposition is bolstered by the twisted, Z-like shape of the galaxy’s radio emission — a large-scale structure thought to be produced by a galaxy collision, study team members said.

“Detection of a binary supermassive black hole in this galaxy also confirms a theoretical prediction that such binaries should be present in so-called Z-shaped radio sources,” co-author David Merritt, of the Rochester Institute of Technology in New York, said in the same statement.

Courtesy-Space

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