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Don't Miss It: Jupiter, Saturn Will Look Like Double Planet for First Time Since Middle Ages - SciTechDaily

Just after sunset on the evening of December 21, 2020, Jupiter and Saturn will appear closer together in Earth’s night sky than they have been since the Middle Ages, offering people the world over a celestial treat to ring in the winter solstice. “Alignments …

Just after sunset on the evening of December 21, 2020, Jupiter and Saturn will appear closer together in Earth’s night sky than they have been since the Middle Ages, offering people the world over a celestial treat to ring in the winter solstice. “Alignments between these two planets are rather rare, occurring once every 20 years or so, but this conjunction is exceptionally rare because of how close the planets will appear to one another,” said Rice University astronomer Patrick Hartigan. “You’d have to go all the way back to just before dawn on March 4, 1226, to see a closer alignment between these objects visible in the night sky.” Jupiter and Saturn have been approaching one another in Earth’s sky since the summer. From December 16-25, the two will be separated by less than the diameter of a full moon. A view showing how the Jupiter-Saturn conjunction will appear in a telescope pointed toward the western horizon at 6 p.m. CST, December 21, 2020. The image is adapted from graphics by open-source planetarium software Stellarium. Credit: This work, “jupsat1,” is adapted from Stellarium by Patrick Hartigan, used under GPL-2.0, and provided under CC BY 4.0 courtesy of Patrick Hartigan “On the evening of closest approach on December 21 they will look like a double planet, separated by only 1/5th the diameter of the full moon,” said Hartigan, a professor of physics and astronomy. “For most telescope viewers, each planet and several of their largest moons will be visible in the same field of view that evening.” Though the best viewing conditions will be near the equator, the event will be observable anywhere on Earth, weather-permitting. Hartigan said the planetary duo will appear low in the western sky for about an hour after sunset each evening. “The further north a viewer is, the less time they’ll have to catch a glimpse of the conjunction before the planets sink below the horizon,” he said. Fortunately, the planets will be bright enough to be viewed in twilight, which may be the best time for many U.S. viewers to observe the conjunction. “By the time skies are fully dark in Houston, for example, the conjunction will be just 9 degrees above the horizon,” Hartigan said. “Viewing that would be manageable if the weather cooperates and you have an unobstructed view to the southwest.” But an hour after sunset, people looking skyward in New York or London will find the planets even closer to the horizon, about 7.5 degrees and 5.3 degrees respectively. Viewers there, and in similar latitudes, would do well to catch a glimpse of the rare astronomical sight as soon after sunset as possible, he said. Those who prefer to wait and see Jupiter and Saturn this close together and higher in the night sky will need to stick around until March 15, 2080, Hartigan said. After that, the pair won’t make such an appearance until sometime after the year 2400.

Hubble Captures Edge of the Cygnus Supernova Blast Wave - SciTechDaily

While appearing as a delicate and light veil draped across the sky, this image from the NASA/ESA Hubble Space Telescope actually depicts a small section of the Cygnus supernova blast wave, located around 2400 light-years away. The name of the supernova remnan…

This image from the NASA/ESA Hubble Space Telescope actually depicts a small section of the Cygnus supernova blast wave, located around 2400 light-years away. Credit: ESA/Hubble & NASA, W. Blair, Acknowledgement: Leo Shatz While appearing as a delicate and light veil draped across the sky, this image from the NASA/ESA Hubble Space Telescope actually depicts a small section of the Cygnus supernova blast wave, located around 2400 light-years away. The name of the supernova remnant comes from its position in the northern constellation of Cygnus (The Swan), where it covers an area 36 times larger than the full moon. The original supernova explosion blasted apart a dying star about 20 times more massive than our Sun between 10,000 and 20,000 years ago. Since then, the remnant has expanded 60 light-years from its center. The shockwave marks the outer edge of the supernova remnant and continues to expand at around 350 kilometers per second. The interaction of the ejected material and the low-density interstellar material swept up by the shockwave forms the distinctive veil-like structure seen in this image.

Long-Standing Tension in the Standard Model of Particle Physics Addressed by ATLAS Experiment at CERN - SciTechDaily

A new ATLAS measurement of a key feature of the Standard Model known as lepton flavor universality suggests that a previous discrepancy measured by the LEP collider in W boson decays may be due to a fluctuation. The best-known particle in the lepton family is…

A new ATLAS measurement of a key feature of the Standard Model known as lepton flavor universality suggests that a previous discrepancy measured by the LEP collider in W boson decays may be due to a fluctuation. The best-known particle in the lepton family is the electron, a key building block of matter and central to our understanding of electricity. But the electron is not an only child. It has two heavier siblings, the muon and the tau lepton, and together they are known as the three lepton flavors. According to the Standard Model of particle physics, the only difference between the siblings should be their mass: the muon is about 200 times heavier than the electron, and the tau-lepton is about 17 times heavier than the muon. It is a remarkable feature of the Standard Model that each flavor is equally likely to interact with a W boson, which results from the so-called lepton flavor universality. Lepton flavor universality has been probed in different processes and energy regimes to high precision. In a new study, described in a paper posted on July 28, 2020, on the arXiv and first presented at the LHCP 2020 conference, the ATLAS collaboration presents a precise measurement of lepton flavor universality using a brand-new technique. Researchers from the ATLAS collaboration explain their new measurement of “lepton flavor universality” – a unique property of the Standard Model of particle physics. Credit: CERN ATLAS physicists examined collision events where pairs of top quarks decay to pairs of W bosons, and subsequently into leptons. “The LHC is a top-quark factory, and produced 100 million top-quark pairs during Run 2,” says Klaus Moenig, ATLAS Physics Coordinator. “This gave us a large unbiased sample of W bosons decaying to muons and tau leptons, which was essential for this high-precision measurement.” They then measured the relative probability that the lepton resulting from a W-boson decay is a muon or a tau-lepton – a ratio known as R(τ/μ). According to the Standard Model, R(τ/μ) should be unity, as the strength of the interaction with a W boson should be the same for a tau-lepton and a muon. But there has been tension about this ever since the 1990s when experiments at the Large Electron-Positron (LEP) collider measured R(τ/μ) to be 1.070 ± 0.026, deviating from the Standard Model expectation by 2.7 standard deviations. The new ATLAS measurement gives a value of R(τ/μ) = 0.992 ± 0.013. This is the most precise measurement of the ratio to date, with an uncertainty half the size of that from the combination of LEP results. The ATLAS measurement is in agreement with the Standard Model expectation and suggests that the previous LEP discrepancy may be due to a fluctuation. “The LHC was designed as a discovery machine for the Higgs boson and heavy new physics,” says ATLAS Spokesperson Karl Jakobs. “But this result further demonstrates that the ATLAS experiment is also capable of measurements at the precision frontier. Our capacity for these types of precision measurements will only improve as we take more data in Run 3 and beyond.” Although it has survived this latest test, the principle of lepton flavor universality will not be completely out of the woods until the anomalies in B-meson decays recorded by the LHCb experiment have also been definitively probed. Reference: “Test of the universality of τ and μ lepton couplings in W-boson decays from tt¯ events with the ATLAS detector” by ATLAS Collaboration, 28 July 2020, High Energy Physics – Experiment.arXiv: 2007.14040

Astronomers Look Back 11 Billion Years and See Unusual “Cosmic Ring of Fire” - SciTechDaily

Unusual galaxy set to prompt rethink on how structures in the universe form. Astronomers have captured an image of a super-rare type of galaxy — described as a "cosmic ring of fire" — as it existed 11 billion years ago. The galaxy, which has roughly the mass …

ByARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D)May 25, 2020This is an artist’s impression of the ring galaxy. Credit: James Josephides, Swinburne Astronomy Productions Unusual galaxy set to prompt rethink on how structures in the universe form. Astronomers have captured an image of a super-rare type of galaxy — described as a “cosmic ring of fire” — as it existed 11 billion years ago. The galaxy, which has roughly the mass of the Milky Way, is circular with a hole in the middle, rather like a titanic doughnut. Its discovery, announced in the journal Nature Astronomy, is set to shake up theories about the earliest formation of galactic structures and how they evolve. “It is a very curious object that we’ve never seen before,” said lead researcher Dr. Tiantian Yuan, from Australia’s ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D). “It looks strange and familiar at the same time.” This is a composite image of the ring galaxy R5519 compiled from single-color images taken by the Hubble Space Telescope. Credit: Tiantian Yuan/Hubble Space Telescope The galaxy, named R5519, is 11 billion light-years from the Solar System. The hole at its center is truly massive, with a diameter two billion times longer than the distance between the Earth and the Sun. To put it another way, it is three million times bigger than the diameter of the supermassive black hole in the galaxy Messier 87, which in 2019 became the first ever to be directly imaged. “It is making stars at a rate 50 times greater than the Milky Way,” said Dr Yuan, who is an ASTRO 3D Fellow based at the Centre for Astrophysics and Supercomputing at Swinburne University of Technology, in the state of Victoria. “Most of that activity is taking place on its ring — so it truly is a ring of fire.” Working with colleagues from around Australia, US, Canada, Belgium and Denmark, Dr Yuan used spectroscopic data gathered by the WM Keck Observatory in Hawaii and images recorded by NASA’s Hubble Space Telescope to identify the unusual structure. The evidence suggests it is a type known as a “collisional ring galaxy”, making it the first one ever located in the early Universe. There are two kinds of ring galaxies. The more common type forms because of internal processes. Collisional ones form — as the name suggests — as a result of immense and violent encounters with other galaxies. In the nearby “local” Universe they are 1000 times rarer than the internally created type. Images of the much more distant R5519 stem from about 10.8 billion years ago, just three billion years after the Big Bang. They indicate that collisional ring galaxies have always been extremely uncommon. ASTRO 3D co-author, Dr. Ahmed Elagali, based at the International Centre for Radio Astronomy Research in Western Australia, said studying R5519 would help determine when spiral galaxies began to develop. “Further, constraining the number density of ring galaxies through cosmic time can also be used to put constraints on the assembly and evolution of local-like galaxy groups,” he added. Another co-author, Professor Kenneth Freeman from the Australian National University, said the discovery had implications for understanding how galaxies like the Milky Way formed. “The collisional formation of ring galaxies requires a thin disk to be present in the ‘victim’ galaxy before the collision occurs,” he explained. “The thin disk is the defining component of spiral galaxies: before it assembled, the galaxies were in a disorderly state, not yet recognizable as spiral galaxies.” “In the case of this ring galaxy, we are looking back into the early universe by 11 billion years, into a time when thin disks were only just assembling. For comparison, the thin disk of our Milky Way began to come together only about nine billion years ago. This discovery is an indication that disk assembly in spiral galaxies occurred over a more extended period than previously thought.” Reference: 25 May 2020, Nature Astronomy.DOI: 10.1038/s41550-020-1102-7 Drs Yuan and Elagali, and Professor Freeman, worked with colleagues from the University of New South Wales, Macquarie University, and University of Queensland, all in Australia, together with others at the Cosmic Dawn Centre (DAWN) in Denmark, Texas A&M University in the US, York University in Canada, and Ghent University in Belgium.