Alien4 Posted at 2024-07-03 21:19:06(12Wks ago) Report Permalink URL | ||
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| Astronomers observe a strong shock front in galaxy cluster SPT-CLJ 2031-4037 by Tomasz Nowakowski  The exposure corrected image of SPT J2031. Credit: Diwanji et al., 2024. Using NASA's Chandra X-ray spacecraft, astronomers from the University of Alabama in Huntsville have observed a merging galaxy cluster known as SPT-CLJ 2031-4037. They detected a rarely seen strong shock front in this galaxy cluster. The finding was reported in a research paper published June 27 on the pre-print server arXiv. Galaxy clusters are formed through hierarchical mergers of smaller subclusters and contain up to thousands of galaxies bound together by gravity. They are the largest known gravitationally bound structures in the universe, and could serve as excellent laboratories for studying galaxy evolution and cosmology. Mergers of galaxy clusters are the most energetic events in the universe after the Big Bang. A fraction of the kinetic energy released during these mergers is dissipated into the intracluster medium via shocks and turbulence. The so-called shock fronts, seen as sharp discontinuities in X-ray brightness and temperature, give astronomers a rare opportunity to observe and investigate such merger systems and their geometry. SPT-CLJ 2031-4037 (or SPT J2031 for short) is a merging galaxy cluster at a redshift of 0.34. It is a massive system with an estimated mass of about 800 trillion solar masses and X-ray luminosity at a level of 1.04 quattuordecillion erg/s. A team of astronomers led by University of Alabama's Purva Diwanji has conducted a search for shock fronts in SPT J2031 with the help of the Chandra X-ray observatory. "SPT J2031 was observed by the Chandra Advanced CCD Imaging Spectrometer (ACIS) detector in the Very Faint (VFAINT) mode for a total of 256 ks spread over 10 observations," the researchers wrote in the paper. The observation allowed the team to detect two shock fronts in SPT J2031—the stronger one to the northwest and the weaker one to the southeast (the southeastern edge). The stronger shock front has a density jump of 3.16 across the sharp surface brightness edge and a Mach number of 3.36, while the weaker one has a density jump of 1.53 and a Mach number of 1.36. The authors of the paper underline that the finding makes SPT J2031 one of the rare merging systems with a Mach number of over 2.0. They note that only a handful of merger shock fronts with such a high Mach number have been discovered by Chandra. The study also found that SPT J2031 exhibits merger geometry and that the post-shock electron temperature of the stronger shock front is lower than the temperature predicted for the instant shock heating model and favors the collisional equilibration model. These findings are consistent with results provided by previous studies. | |
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| Alien4Posted at 2024-07-04 01:54:47(12Wks ago) Report Permalink URL | ||
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| Research intern helps discover a new pulsar buried in a mountain of data by Naval Research Laboratory  VLITE 340 MHz image of GLIMPSE-C01 from February 27, 2021. The clean beam is shown as a white ellipse in the lower left corner and has dimensions of 5 0 × 4 7 with a position angle of 52°. The cross denotes the central position of GLIMPSE-C01. The dashed white circle shows the core radius of 36″. The location of the pulsar candidate is shown with a solid white circle. A scale bar indicating a linear size of 0.2 pc (12 5), assuming a distance to GLIMPSE-C01 of 3.3 kpc, is shown in the lower right corner. Credit: National Radio Astronomy Observatory/NRL/Texas Tech U.S. Naval Research Laboratory (NRL) Remote Sensing Division intern Amaris McCarver, along with a team of astronomers, has discovered the first millisecond pulsar in the stellar cluster Glimpse-CO1 and recently published findings in The Astrophysical Journal. Pulsars are natural laboratories for studying the behavior of matter under extreme gravitational and magnetic fields—conditions difficult or impossible to replicate on Earth. They also function as natural timekeepers. Precise timing of the observed pulses from an array of pulsars offers a means to detect gravitational waves propagating through our galaxy from the merging supermassive black holes that result from galaxy collisions. Some pulsars are observed to have an accuracy and stability comparable to our most precise atomic clocks. These pulsars hold the potential to establish a "celestial GPS" system for satellite navigation in space. McCarver's team used images from the Karl G. Jansky Very Large Array (VLA) Low-band Ionosphere and Transient Experiment (VLITE) to search for new pulsars in 97 stellar clusters. "It was exciting so early in my career to see a speculative project work out so successfully," said McCarver. Her new approach of using VLITE images coupled with images from several radio surveys at different frequencies identified multiple candidate pulsars, with the strongest candidate residing in a system known as GLIMPSE-C01. "This type of scientific discovery is only possible thanks to the collaboration between NRL and the National Radio Astronomy Observatory that enabled this continual dual-frequency capability on the VLA," said Tracy E. Clarke, Ph.D., NRL Remote Sensing Division astronomer. "This research highlights how we can use measures of radio brightness at different frequencies to find new pulsars efficiently, and that available sky surveys combined with the mountain of VLITE data mean those measurements are essentially always available. This opens the door to a new era of searches for highly dispersed and highly accelerated pulsars." The presence of a millisecond pulsar, designated GLIMPSE-C01A, was confirmed through re-processing of archival data from the Robert C. Byrd Green Bank Telescope. Millisecond pulsars, such as GLIMPSE-C01A, are born in supernova explosions and are spun up by consuming material from a companion star. "Millisecond pulsars, or MSP, offer a promising method for autonomously navigating spacecraft from low Earth orbit to interstellar space, independent of ground contact and GPS availability," said Emil Polisensky, Ph.D., an NRL Remote Sensing Division astronomer. "The confirmation of a new MSP identified by Amaris highlights the exciting potential for discovery with NRL's VLITE data and the key role student interns play in cutting edge research." McCarver received the Robert S. Hyer Research Award from the Texas Section of the American Physical Society (APS). McCarver was one of 16 summer of 2023 interns in the Radio, Infrared, Optical Sensors Branch at NRL DC that participated in internships through the Science Engineering Apprenticeship Program and NREIP, Historically Black College and University/Minority Institution High Performance Computing Internship Program, and the U.S. Naval Academy Midshipmen Internship Program. She will graduate with a degree in Physics and Astronomy and plans to pursue her graduate education in astronomy. | |
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| SoupPosted at 2024-07-08 23:45:13(11Wks ago) Report Permalink URL | ||
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| Webb admires bejeweled ring of the lensed quasar RX J1131-1231 by European Space Agency  A small image of a galaxy distorted by gravitational lensing into a dim ring. At the top of the ring are three very bright spots with diffraction spikes coming off them, right next to each other: these are copies of a single quasar in the lensed galaxy, duplicated by the gravitational lens. In the centre of the ring, the elliptical galaxy doing the lensing appears as a small blue dot. The background is black and empty. Credit: ESA/Webb, NASA & CSA, A. Nierenberg This new picture of the month from the NASA/ESA/CSA James Webb Space Telescope features the gravitational lensing of the quasar known as RX J1131-1231, located roughly six billion light-years from Earth in the constellation Crater. It is considered one of the best lensed quasars discovered to date, as the foreground galaxy smears the image of the background quasar into a bright arc and creates four images of the object. Gravitational lensing, first predicted by Einstein, offers a rare opportunity to study regions close to the black hole in distant quasars, by acting as a natural telescope and magnifying the light from these sources. All matter in the universe warps the space around itself, with larger masses producing a stronger effect. Around very massive objects, such as galaxies, light that passes close by follows this warped space, appearing to bend away from its original path by a clearly visible amount. One of the consequences of gravitational lensing is that it can magnify distant astronomical objects, letting astronomers study objects that would otherwise be too faint or far away. Measurements of the X-ray emission from quasars can provide an indication of how fast the central black hole is spinning and this gives researchers important clues about how black holes grow over time. For example, if a black hole grows primarily from collisions and mergers between galaxies, it should accumulate material in a stable disk, and the steady supply of new material from the disk should lead to a rapidly spinning black hole. On the other hand, if the black hole grew through many small accretion episodes, it would accumulate material from random directions. Observations have indicated that the black hole in this particular quasar is spinning at over half the speed of light, which suggests that this black hole has grown via mergers, rather than pulling material in from different directions. This image was captured with Webb's MIRI (Mid-Infrared Instrument) as part of an observation program to study dark matter. Dark matter is an invisible form of matter that accounts for most of the universe's mass. Webb's observations of quasars are allowing astronomers to probe the nature of dark matter at smaller scales than ever before. Provided by European Space Agency | |
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| SoupPosted at 2024-07-16 00:34:00(10Wks ago) Report Permalink URL | ||
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| Surprising ring sheds light on galaxy formation by Linda B. Glaser, Cornell University  The distant galaxy PJ0116-24, a Hyper Luminous Infrared Galaxy (HyLIRG). Cold gas is seen here in blue; warm gas is shown in red. Credit: ALMA (ESO/NAOJ/NRAO)/ESO/D. Liu et al. The question of what triggers the extremely rapid star formation within Hyper Luminous Infrared Galaxies (HyLIRGs), as yet unknown, is of much interest to guide our understanding of the formation and evolution of galaxies in the universe. A new photo released by the European Southern Observatory shows a HyLIRG 10,000 times brighter than our Milky Way (in infrared light)—the distant galaxy PJ0116-24—and was released in conjunction with a newly published paper in Nature Astronomy that sheds light on its formation. Previous studies suggested that such extremely bright galaxies must result from galaxy mergers. These galaxy collisions are thought to create dense gas regions in which rapid star formation is triggered. But isolated galaxies could also become HyLIRGs via internal processes alone, if star-forming gas is rapidly funneled towards the galaxy's center. In the paper titled "Detailed study of a rare hyperluminous rotating disk in an Einstein ring 10 billion years ago," on which Cornell astronomer Amit Vishwas, Ph.D. is a co-author, observations from ESO's Very Large Telescope (VLT) and the Atacama Large Millimetre/submillimetre Array (ALMA) were combined to study the motion of gas within PJ0116-24. ALMA traces cold gas, seen in the photo in blue, whereas the VLT, with its new Enhanced Resolution Imager and Spectrograph (ERIS), traces warm gas, shown in red. Thanks to these detailed observations, the international research team discovered that the gas in this extreme galaxy was rotating in an organized fashion, rather than in the chaotic way expected after a galactic collision––a surprising result. This shows, said the researchers, that mergers aren't always needed for a galaxy to become a HyLIRG. PJ0116-24 is so far away that its light took about 10 billion years to reach us. A foreground galaxy acted as a gravitational lens, bending and magnifying the light of PJ0116-24 behind it into the Einstein ring seen here. This precise cosmic alignment allows astronomers to zoom in on very distant objects and see them in a level of detail that would otherwise be very hard to achieve. Vishwas, a research associate at the Cornell Center for Astrophysics and Planetary Sciences (CCAPS), helped map the emission and kinematics from atomic and molecular gas in PJ0116-24 using ALMA, which provided strong support for the rotating disk scenario. He was also involved with obtaining data with the newly commissioned ERIS instrument on the VLT. The research was led by Daizhong Liu from Max Planck Institute for Extraterrestrial Physics and Purple Mountain Observatory. The interpretation of the gas conditions and elemental abundances in PJ0116-24 are similar to what Vishwas and his co-authors reported last year for another galaxy at an earlier epoch in the universe, using data from the James Webb Space Telescope. PJ0116-24, however, is around five times more massive and luminous than the source studied in last year's paper, said Vishwas. "In both cases, gravitational lensing helped us zoom in to study the details of the interstellar medium of these galaxies. I believe these new observations are helping us build an argument for the way galaxies evolve and build up—efficiently converting gas to stars in rapid growth spurts separated by long periods of relative calm," he explained. | |
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| SoupPosted at 2024-07-24 00:12:51(9Wks ago) Report Permalink URL | ||
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| Opinion: If we want to settle on other planets, we'll have to use genome editing to alter human DNA by Sam McKee, The Conversation  Kate Rubins was the first person to sequence DNA in space. Credit: NASA When considering human settlements on the moon, Mars and further afield, much attention is given to the travel times, food and radiation risk. We'll undoubtedly face a harsh environment in deep space and some thinkers have been pointing to genome editing as a way to ensure that humans can tolerate the severe conditions as they venture further into the solar system. In January, I was fortunate to attend a much-anticipated debate between astronomer royal Lord Martin Rees and Mars exploration advocate Dr. Robert Zubrin. The event at the British Interplanetary Society took on the topic of whether the exploration of Mars should be human or robotic. In a recent book called The End of Astronauts, Lord Rees and co-author Donald Goldsmith outline the benefits of exploration of the solar system using robotic spacecraft and vehicles, without the expense and risk of sending humans along for the ride. Dr. Zubrin supports human exploration. Where there was some agreement was over Rees's advocacy of using gene editing technology to enable humans to overcome the immense challenges of becoming an interplanetary species. Our genome is all the DNA present in our cells. Since 2011, we have been able to easily and accurately edit genomes. First came a molecular tool called Crispr-Cas9, which today can be used in a high school lab for very little cost and has even been used on the International Space Station. Then came techniques called base and prime editing, through which miniscule changes can be made in the genome of any living organism. The potential applications of gene editing for allowing us to travel further are almost limitless. One of the most problematic hazards astronauts will encounter in deep space is a higher dosage of radiation, which can cause havoc with many processes in the body and increase the longer-term risk of cancer. Perhaps, using genome editing, we could insert genes into humans from plants and bacteria that are able to clean up radiation in the event of radioactive waste spills and nuclear fallout. It sounds like science fiction, but eminent thinkers such as Lord Rees believe this is key to our advancement across the solar system. Identifying and then inserting genes into humans that slow down aging and counter cellular breakdown could also help. We could also engineer crops that resist the effects of exposure to radioactivity as crews will need to grow their own food. We could also personalize medicine to an astronaut's needs based on their particular genetic makeup. Imagine a future where the human genome is so well understood it has become pliable under this new, personalized medicine. Genes for extremes Tardigrades are microscopic animals sometimes referred to as "water bears." Experiments have shown that these tiny creatures can tolerate extreme temperatures, pressures, high radiation and starvation. They can even tolerate the vacuum of space. Geneticists are eager to understand their genomes and a paper published in Nature sought to uncover the key genes and proteins that give the miniature creatures this extraordinary stress tolerance. If we could insert some of the genes involved into crops, could we make them tolerant to the highest levels of radiation and environmental stress? It's worth exploring. Even more intriguing is whether inserting tardigrade genes into our own genome could make us more resilient to the harsh conditions in space. Scientists have already shown that human cells in the lab developed increased tolerance to X-ray radiation when tardigrade genes were inserted into them. Transferring genes from tardigrades is just one speculative example of how we might be able to engineer humans and crops to be more suited to space travel. We'll need much more research if scientists are ever to get to this stage. However, in the past, several governments have been keen to enforce tight restrictions on how genome editing is used, as well as on other technologies for inserting genes from one species into another. Germany and Canada are among the most cautious, but elsewhere restrictions seem to be relaxing. In November 2018, the Chinese scientist He Jiankui announced that he had created the first gene-edited babies. He had introduced a gene into the unborn twins that confers resistance to HIV infection. The scientist was subsequently jailed. But he has since been released and allowed to carry out research again. In the new space race, certain countries may go to lengths with genome editing that other nations, especially in the west where restrictions are already tight, may not. Whoever wins would reap enormous scientific and economic benefits. If Rees and the other futurists are right, this field has the potential to advance our expansion into the cosmos. But society will need to agree to it. It's likely there will be opposition, because of the deep-seated fears of altering the human species forever. And with base and prime editing now having advanced the precision of targeted gene editing, it's clear that the technology is moving faster than the conversation. One country or another is likely to take the leap where others pull back from the brink. Only then will we find out just how viable these ideas really are. Until then, we can only speculate with curiosity, and perhaps excitement too. | |
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| SoupPosted at 2024-08-01 00:38:14(8Wks ago) Report Permalink URL | ||
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| Discovery of ancient stars on the stellar thin disk of the Milky Way by Tilo Bergemann, Leibniz Institute for Astrophysics Potsdam  Rotational motion of young (blue) and old (red) stars similar to the Sun (orange). Credit: Background image by NASA/JPL-Caltech/R. Hurt (SSC/Caltech) A surprising discovery about the evolution of our galaxy using data from the Gaia mission found a large number of ancient stars on orbits similar to that of our sun. They formed the Milky Way's thin disk less than 1 billion years after the Big Bang, several billion years earlier than previously believed. The Milky Way galaxy has a large halo, a central bulge and bar, a thick disk and a thin disk. Most stars are located in the so-called thin disk of our Milky Way and follow an organized rotation around the galactic center. Middle-aged stars such as our 4.6-billion-year-old sun belong to the thin disk, which was generally thought to have started forming around 8 to 10 billion years ago. Understanding how the Milky Way was formed is a major goal of galactic archaeology. To achieve this, detailed maps of the galaxy that show the ages, chemical compositions, and movements of stars are needed. These maps, known as chrono-chemo-kinematical maps, help to piece together the history of our galaxy. Creating these detailed maps is challenging because it requires large datasets of stars with accurately known ages. One common approach to overcome this challenge is to study very metal-poor stars, which are old, to provide a window into the early Milky Way. Very metal-poor stars are known to be old because they were among the first stars to form when the universe was still largely composed of hydrogen and helium, before many of the heavier elements were created and distributed by successive generations of stars. Using a data set from the European Space Agency (ESA) Gaia Mission, an international team led by astronomers from the Leibniz Institute for Astrophysics Potsdam (AIP) studied stars in the solar neighborhood, about 3,200 light years around the sun. They discovered a surprising number of very old stars in thin disk orbits; the majority of these are older than 10 billion years, some of them even older than 13 billion years. These ancient stars show a wide range of metal compositions: some are very metal-poor (as expected), while others have twice the metal content of our much younger sun, indicating that a rapid metal enrichment took place in the early phase of the Milky Way's evolution. "These ancient stars in the disk suggest that the formation of the Milky Way's thin disk began much earlier than previously believed, by about 4–5 billion years," explains Samir Nepal from AIP and first author of the study, which has been accepted for publication by Astronomy and Astrophysics and is available on the arXiv preprint server. "This study also highlights that our galaxy had an intense star formation at early epochs leading to very fast metal enrichment in the inner regions and the formation of the disk. This discovery aligns the Milky Way's disk formation timeline with those of high-redshift galaxies observed by the James Webb Space Telescope (JWST) and Atacama Large Millimeter Array (ALMA) Radio Telescope. "It indicates that cold disks can form and stabilize very early in the universe's history, providing new insights into the evolution of galaxies." "Our study suggests that the thin disk of the Milky Way may have formed much earlier than we had thought, and that its formation is strongly related to the early chemical enrichment of the innermost regions of our galaxy," explains Cristina Chiappini. "The combination of data from different sources and the application of advanced machine learning techniques have enabled us to increase the number of stars with high quality stellar parameters, a key step to lead our team to these new insights." The results were made possible by the third data release of the Gaia mission. The team analyzed the stellar parameters of more than 800,000 stars using a novel machine learning method that combines information from different types of data to provide improved stellar parameters with high precision. These precise measurements include gravity, temperature, metal content, distances, kinematics and the age of the stars. In the future, a similar machine learning technique will be used to analyze millions of spectra, collected by the 4MIDABLE-LR survey with the 4-meter Multi-Object Spectroscopic Telescope (4MOST), starting operations in 2025. | |
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| SoupPosted at 2024-08-06 23:24:40(7Wks ago) Report Permalink URL | ||
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| Astronomy 'Olympics' is being hosted in Africa for the first time: Four big talking points by James Okwe Chibueze, The Conversation  The South African Astronomical Observatory in Sutherland, in the country’s Northern Cape province. Credit: IAU General Assembly 2024 Cutting-edge telescopes, gravitational waves, black holes and our solar system's central star, the sun, are just a few of the topics that will be on the table in Cape Town, South Africa, for an event that's a scientific version of the Olympic Games—though the world's leading astronomy researchers in attendance will be showcasing their brains rather than their brawn. The International Astronomical Union (IAU) was established in 1919 and held its first General Assembly in Rome, Italy, in 1922. These assemblies, held every four years, are a chance for the organization's members and affiliates to meet in person, and for researchers to share their work with their peers from around the globe. The 32nd General Assembly, which kicks off on 6 August and concludes nine days later, marks the meeting's first outing in Africa. This is a significant milestone for the continent; astronomy has grown and strengthened tremendously over the past decade. This is largely, though not entirely, a result of South Africa's status as co-host, with Australia, of what will be the world's largest radio telescope, the Square Kilometer Array (SKA), operated and managed by the Square Kilometer Array Observatory. Its first phase is set for completion in 2027; its precursor, the MeerKAT telescope, is already making huge contributions to both South African and international science. Additional SKA dishes will be located in eight other African countries: Ghana, Zambia, Madagascar, Botswana, Namibia, Kenya, Mauritius and Mozambique. As an astronomer—and the member of the assembly's national organizing committee tasked with coordinating its scientific activities—I am very excited to see this meeting come to the African continent for the first time. The program is packed with symposia, focus meetings dedicated to a variety of astronomical subjects, poster presentations and more. Here, I've chosen just four of the scientific topics under discussion during the assembly. 1. The James Webb Space Telescope The astronomy world rejoiced on 25 December 2021 when the James Webb Space Telescope was successfully launched. Months later, the telescope went into testing and verification phases; it is now in full science operations mode and producing discoveries at an astonishing rate. What makes it especially effective is that it offers astronomers the high sensitivity—the ability to detect faint, distant objects—required to study the early universe. One of the assembly's symposia, titled "The first chapters of our cosmic history with JWST" features some of the new results in the exploration of the early universe, when the first stars and galaxies were formed. This is fascinating for astronomers and non-astronomers alike: we're all interested in knowing whether there's another planet like ours out there, and the James Webb Space Telescope has already been used to discover many new exoplanets (planets that orbit outside our own solar system). Could any of these planets be habitable for humans? We may have answers sooner than we expected as the telescope continues its remarkable work. 2. The incoming king of radio astronomy Neutral hydrogen is the most abundant element in the universe and is an essential part of the makeup of galaxies in the universe. When the spin direction of the electron in the hydrogen atom flips, radio emissions are produced. These emissions can be detected by radio telescopes and are crucial for understanding the distribution and kinematics (motion) of gases in galaxies. MeerKAT, a precursor to the SKA, is already producing groundbreaking neutral hydrogen science because it is currently the most sensitive telescope for neutral hydrogen observations. Of course, a project the size and scope of the SKA won't only be discussed in one or two sessions. An entire focus meeting at the assembly is dedicated to delving into the history of astronomy in South Africa and how it evolved to the point that it was chosen to host the world's biggest radio astronomy project. 3. Gravitational waves It's been nine years since scientists announced that they had, for the first time ever, detected gravitational waves. This provided clear evidence to support Albert Einstein's prediction, a century earlier, that gravitational waves existed. Since that first confirmation, a variety of new science has emerged in the field of gravitational wave astrophysics. Astronomers are able to explore our observable universe using not just electromagnetic waves, but gravitational waves—"ripples" in space-time—too. Many of these results will be showcased in a symposium at the general assembly. 4. Our star: The sun and its massive counterparts The sun, the central star of our solar system, is the nearest stellar laboratory available to scientists studying the true nature and environmental impact of solar winds and coronal mass ejections, otherwise referred to as space storms that cause aurora. Stars of masses eight times or more than that of the sun are referred to as massive stars. Such high-mass stars evolve faster than their low-mass counterparts. They end their lives in an explosive process, a supernova, and leave behind a fast-spinning neutron star, known as a pulsar. One of the focus meetings will concentrate on exploring new results that bridge the gap between massive stars, supernovae and transients from pulsars. Understanding the full evolutionary sequence of massive stars is key to understanding the evolution of galaxies, since massive stars influence the chemical composition, structure and morphology of their host galaxy. And a symposium has been dedicated to considering recent advances in solar observations. Side meetings The general assembly is also a chance for groups of astronomers to organize side meetings. Some of the science under discussion at these meetings in 2024 includes the Event Horizon Telescope, a global array which is used for black hole imaging, and the African Millimeter Telescope in Namibia. Other meetings will focus on the South African Radio Astronomy Observatory and how to keep night skies dark and quiet for optimal radio astronomy. | |
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| SoupPosted at 2024-08-13 20:53:10(6Wks ago) Report Permalink URL | ||
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| A galactic 'comet' called Terzan 5 illuminates a 100-year-old puzzle about cosmic rays by Mark Krumholz, The Conversation  The star cluster Terzan 5. Credit: ESA / Hubble, CC BY When my colleagues and I set to work on a century-old cosmic mystery, we found an unexpected celestial laboratory in Terzan 5, a dense star cluster currently plunging through our galaxy at breakneck speed. This stellar oddity has allowed us to study the behavior of cosmic rays—high-energy particles whose erratic paths through space have baffled astronomers since their discovery in 1912. By observing radiation produced by Terzan 5's cosmic rays, we've achieved a scientific first: measuring how quickly these particles change direction due to fluctuations in interstellar magnetic fields. Our research is published in Nature Astronomy. Fast-moving radiation from outer space Cosmic rays are something no one expected to be there. When radioactivity was first discovered in the 1890s, scientists thought all sources of radiation were on Earth. But in 1912, Austrian-American physicist Victor Hess measured the ambient radiation level in a high-altitude balloon and discovered it was much higher than at ground level, even during an eclipse when the sun was blocked. This meant the radiation had to be coming from space. Today we know the mysterious radiation Hess discovered as cosmic rays: atomic nuclei and elementary particles such as protons and electrons that have somehow been accelerated to nearly the speed of light. These particles zip through interstellar space, and thanks to their high energies, a small fraction of them can penetrate the upper atmosphere, as Hess discovered. But we cannot easily tell where they come from. Cosmic rays are charged particles, which means their direction of travel changes when they encounter a magnetic field. The staticky picture of the cosmic ray cosmos The magnetic deflection effect provides the basic technology for old cathode ray tube (CRT) monitors and televisions, which use it to steer electrons toward the screen to create a picture. Interstellar space is full of magnetic fields, and those fields are constantly fluctuating, deflecting cosmic rays in random directions—sort of like a broken CRT in an old TV that only shows static. So, instead of cosmic rays coming straight to us from their source like light does, they wind up spreading out almost uniformly across the galaxy. Here on Earth we see them coming almost equally from all directions in the sky. While we now understand this general picture, most of the details are missing. The uniformity of cosmic rays across the sky tells us that cosmic ray directions randomly change, but we have no good way of measuring how fast this process happens. Nor do we understand the ultimate source of the magnetic fluctuations. Or we didn't, until now. Terzan 5 and the displaced gamma rays That's where Terzan 5 comes in. This star cluster is a copious producer of cosmic rays, because it contains a large population of rapidly rotating, incredibly dense and magnetized stars called millisecond pulsars—which accelerate cosmic rays up to extremely high speeds. These cosmic rays don't make it all the way to Earth, thanks to those fluctuating magnetic fields. However, we can see a telltale sign of their presence: some of the cosmic rays collide with photons of starlight and convert them into high-energy uncharged particles called gamma rays. The gamma rays travel in the same direction as the cosmic ray that created them, but unlike the cosmic rays, the gamma rays are not deflected by magnetic fields. They can travel in a straight line and reach Earth. Because of this effect, we often see gamma rays coming from powerful sources of cosmic rays. But in Terzan 5, for some reason, the gamma rays don't exactly line up with the positions of the stars. Instead, they seem to be coming from a region about 30 light-years away, where there is no obvious source. A galactic-scale 'comet' This displacement has been an unexplained curiosity since it was discovered in 2011, until we came up with an explanation. Terzan 5 is close to the center of our galaxy today, but it isn't always. The star cluster is actually moving in a very wide orbit that keeps it far off the plane of the galaxy most of the time. It just happens to be plunging through the galaxy right now. Because this plunge takes place at hundreds of kilometers per second, the cluster sweeps up a cloak of magnetic fields around itself, like the tail of a comet plunging through the solar wind. Cosmic rays launched by the cluster initially travel along the tail. We don't see any of the gamma rays these cosmic rays produce, because the tail isn't pointed directly at us—these gamma rays are beamed along the tail and away from us. And here is where the magnetic fluctuations come in. If the cosmic rays stayed well-aligned with the tail, we would never see them, but thanks to magnetic fluctuations their directions start to change. Eventually, some of them start to point toward us, producing gamma rays we can see. But this takes roughly 30 years, which is why the gamma rays don't seem to be coming from the cluster itself. By the time enough of them are pointing at us for their gamma rays to be bright enough to be visible, they have traveled 30 light-years down the magnetic tail of the cluster. Cosmic rays and interstellar magnetic fields So, thanks to Terzan 5, for the first time we have been able to measure how long it takes magnetic fluctuations to change cosmic ray directions. We can use this information to test theories about how interstellar magnetic fields work and where their fluctuations come from. This brings us a big step closer to understanding the mysterious radiation from space discovered by Hess more than 100 years ago. | |
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| SoupPosted at 2024-08-14 01:16:16(6Wks ago) Report Permalink URL | ||
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| Research team finds evidence of hydration on the asteroid Psyche by Southwest Research Institute  An SwRI-led team used NASA's Webb telescope, shown in the bottom right corner of this illustration, to confirm the presence of hydrated minerals on the surface of Psyche, a massive and heavily metallic body in the main asteroid belt. These findings suggest a complex history for this interesting asteroid, which many scientists think could be the remnant core of a protoplanet, including impacts with hydrated asteroids. Credit: Southwest Research Institute Using data from NASA's James Webb Space Telescope, a Southwest Research Institute-led team has confirmed hydroxyl molecules on the surface of the metallic asteroid Psyche. The presence of hydrated minerals suggests a complex history for Psyche, important context for the NASA spacecraft en route to this interesting asteroid orbiting the sun between Mars and Jupiter. At about 140 miles in diameter, Psyche is one of the most massive objects in the main asteroid belt. Previous observations indicate that Psyche is a dense, largely metallic object that could be a leftover core from a planet that experienced a catastrophic collision. On Oct. 13, 2023, NASA launched the Psyche spacecraft, which is traveling 2.2 billion miles to arrive at the asteroid in August 2029. "Using telescopes at different wavelengths of infrared light, the SwRI-led research will provide different but complementary information to what the Psyche spacecraft is designed to study," said SwRI's Dr. Tracy Becker, second author of a new Planetary Science Journal paper discussing these findings. "Our understanding of solar system evolution is closely tied to interpretations of asteroid composition, particularly the M-class asteroids that contain higher concentrations of metal," said Center for Astrophysics | Harvard & Smithsonian's Dr. Stephanie Jarmak, the paper's lead author, who conducted much of this research while at SwRI. "These asteroids were initially thought to be the exposed cores of differentiated planetesimals, a hypothesis based on their spectral similarity to iron meteorites." The Webb data points to hydroxyl and perhaps water on Psyche's surface. The hydrated minerals could result from external sources, including impactors. If the hydration is native or endogenous, then Psyche may have a different evolutionary history than current models suggest. "Asteroids are leftovers from the planetary formation process, so their compositions vary depending on where they formed in the solar nebula," said SwRI's Dr. Anicia Arredondo, another co-author. "Hydration that is endogenous could suggest that Psyche is not the remnant core of a protoplanet. Instead, it could suggest that Psyche originated beyond the 'snow line,' the minimum distance from the sun where protoplanetary disk temperatures are low enough for volatile compounds to condense into solids, before migrating to the outer main belt." However, the paper found the variability in the strength of the hydration features across the observations implies a heterogeneous distribution of hydrated minerals. This variability suggests a complex surface history that could be explained by impacts from carbonaceous chondrite asteroids thought to be very hydrated. Understanding the location of asteroids and their compositions tells us how materials in the solar nebula were distributed and have evolved since formation. How water is distributed in our solar system will provide insight into the distribution of water in other solar systems, and because water is necessary for all life on Earth, will drive where to look for potential life, both in our solar system and beyond. | |
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| SoupPosted at 2024-08-21 01:31:20(5Wks ago) Report Permalink URL | ||
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| New view of North Star reveals spotted surface by Georgia State University  CHARA Array false-color image of Polaris from April 2021 that reveals large bright and dark spots on the surface. Polaris appears about 600,000 times smaller than the full moon in the sky. Credit: Georgia State University / CHARA Array Researchers using Georgia State University's Center for High Angular Resolution Astronomy (CHARA) Array have identified new details about the size and appearance of the North Star, also known as Polaris. The new research is published in The Astrophysical Journal. Earth's North Pole points to a direction in space marked by the North Star. Polaris is both a navigation aid and a remarkable star in its own right. It is the brightest member of a triple-star system and is a pulsating variable star. Polaris gets brighter and fainter periodically as the star's diameter grows and shrinks over a four-day cycle. Polaris is a kind of star known as a Cepheid variable. Astronomers use these stars as "standard candles" because their true brightness depends on their period of pulsation: Brighter stars pulsate slower than fainter stars. How bright a star appears in the sky depends on the star's true brightness and the distance to the star. Because we know the true brightness of a Cepheid based on its pulsational period, astronomers can use them to measure the distances to their host galaxies and to infer the expansion rate of the universe. A team of astronomers led by Nancy Evans at the Center for Astrophysics | Harvard & Smithsonian observed Polaris using the CHARA optical interferometric array of six telescopes at Mount Wilson, Calif. The goal of the investigation was to map the orbit of the close, faint companion that orbits Polaris every 30 years. "The small separation and large contrast in brightness between the two stars makes it extremely challenging to resolve the binary system during their closest approach," Evans said.  The CHARA Array is located at the Mount Wilson Observatory in the San Gabriel Mountains of southern California. The six telescopes of the CHARA Array are arranged along three arms. The light from each telescope is transported through vacuum pipes to the central beam combining lab. All the beams converge on the MIRC-X camera in the lab. Credit: Georgia State University The CHARA Array combines the light of six telescopes that are spread across the mountaintop at the historic Mount Wilson Observatory. By combining the light, the CHARA Array acted like a 330-meter telescope to detect the faint companion as it passed close to Polaris. The observations of Polaris were recorded using the MIRC-X camera built by astronomers at the University of Michigan and Exeter University in the U.K. The MIRC-X camera has the remarkable ability to capture details of stellar surfaces. The team successfully tracked the orbit of the close companion and measured changes in the size of the Cepheid as it pulsated. The orbital motion showed that Polaris has a mass five times larger than that of the sun. The images of Polaris showed that it has a diameter 46 times the size of the sun. The biggest surprise was the appearance of Polaris in close-up images. The CHARA observations provided the first glimpse of what the surface of a Cepheid variable looks like. "The CHARA images revealed large bright and dark spots on the surface of Polaris that changed over time," said Gail Schaefer, director of the CHARA Array. The presence of spots and the rotation of the star might be linked to a 120-day variation in measured velocity. "We plan to continue imaging Polaris in the future," said John Monnier, an astronomy professor at the University of Michigan. "We hope to better understand the mechanism that generates the spots on the surface of Polaris." The new observations of Polaris were made and recorded as part of the open access program at the CHARA Array, where astronomers from around the world can apply for time through the National Optical-Infrared Astronomy Research Laboratory (NOIRLab). | |
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| SoupPosted at 2024-09-10 01:42:54(2Wks ago) Report Permalink URL | ||
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| Pluto mission: South African astronomers join forces with NASA to learn more about the dwarf planet by Nico Orce, The Conversation  Pluto nearly fills the frame in this image from the Long Range Reconnaissance Imager (LORRI) aboard NASA’s New Horizons spacecraft, taken on July 13, 2015 when the spacecraft was 476,000 miles (768,000 kilometers) from the surface. This is the last and most detailed image sent to Earth before the spacecraft’s closest approach to Pluto on July 14. The color image has been combined with lower-resolution color information from the Ralph instrument that was acquired earlier on July 13. This view is dominated by the large, bright feature informally named the “heart,” which measures approximately 1,000 miles (1,600 kilometers) across. The heart borders darker equatorial terrains, and the mottled terrain to its east (right) are complex. However, even at this resolution, much of the heart’s interior appears remarkably featureless—possibly a sign of ongoing geologic processes. Credit: NASA/APL/SwRI When the International Astronomical Union announced in 2006 that Pluto was being demoted from its status as the sun's ninth planet, many astronomers and non-experts alike were shocked. Pluto remains an important object for study, though. Today it is considered one of many dwarf planets beyond Neptune, in a doughnut-shaped region of mostly icy debris orbiting the sun called the Kuiper Belt. These outskirts of the solar system remain largely unexplored. They were first reached by US space agency NASA's New Horizons spacecraft; it flew close to Pluto in 2015, revealing spectacular images of the dwarf planet's surface and atmosphere. But there's still plenty to learn. That's why my colleagues and I at South Africa's University of the Western Cape (UWC) were over the moon when we were invited to participate in an international mission funded by Nasa. We are a group of experienced nuclear physicists with groundbreaking research that spans astronomy and stellar explosions. Pluto reached its closest point to our sun in 1989. As it moves away from the sun along its 248-year-long oval-shaped orbit, its atmosphere will likely collapse and freeze onto its surface in the next few years. We were asked to observe a rare event that would provide insights into the dwarf planet's atmosphere and particularly this likely freezing scenario. The event is called occultation, and occurs when any celestial object passes in front of a distant star, temporarily blocking or dimming the star's light. This allows the object's atmosphere to—just for a second or so—act as a lens that amplifies the starlight. In this case, the occultation was a chance to capture information about Pluto's atmosphere, as explained below. A single telescope We used a single state-of-the-art 0.5-meter Newtonian telescope that was generously donated to UWC by the University of Virginia. When scientists are trying to capture an occultation, they might use a single telescope that tracks the shadow of the object's passage, or up to 100 telescopes strategically distributed to map out the shape of an object and discover or characterize satellites and asteroids. These telescopes need to be smaller and more mobile than their more static, larger equivalents used for other research. Setting up the telescope and commissioning it was a major operation that required state-of-the-art facilities and human power. Students and staff from UWC's Physics & Astronomy department worked hard to prepare for the observation, learning about telescope operations and the required software. Some modification was also required. The telescope arrived from the factory with a faulty GPS that was replaced and a little too short for our purposes. We used 3D printing technology in the university's Modern African Nuclear Detector Laboratory to rectify the length and match the telescope focal point. Then it was time for the main event. Capturing the moment On 4 August 2024, my UWC colleague Siyambonga Matshawule, together with two of my postdocs, Cebo Ngwetsheni and Craig Mehl, and my Ph.D. student Elijah Akakpo traveled to the viewing spot. They joined professors Michael Skrutskie and Anne Verbiscer from the University of Virginia and Nasa, both principal investigators of Pluto's occultation and other Nasa missions such as New Horizons. The viewing spot was in a remote area in South Africa's Northern Cape province, about 40km north from the town of Upington. This was precisely the central point or dead center of Pluto's shadow on Earth, extending 2,377km in diameter, passing across South Africa and Namibia at 85,000 km/h. Considering that, at the same time, our Earth is also moving at an orbital velocity of 107,000 km/h, nailing just the right timing and position for our telescope was crucial. The temperature reached 0°C and the sky above our viewing point was partially cloudy. But the clouds opened up at just the right time and place—and, while the occultation lasted only a few seconds, it may have been enough to get crucial information about Pluto's atmosphere. The problem was that a sudden and unexpected wind surge briefly shook the telescope (and our hearts) during the occultation. We're doing further processing to remove the resulting noise. Scientific discovery During the occultation, the star light starts dimming as it gets absorbed by Pluto's atmosphere. Shortly after, a central flash occurs right at the dead center of Pluto's shadow, where Pluto's atmosphere acts as a magnifying glass and the star looks brighter than before or after the occultation. After the central flash, the star starts dimming again and eventually returns to its usual brightness. It is that central flash that shows how the star light refracts through Pluto's atmosphere and provides crucial information on its temperature and chemical composition. This information is input to atmospheric models that tells us if the atmosphere is finally contracting. It's still too soon to unpack any findings about Pluto's atmosphere from our observation, and it may well be that we can't see anything quantitative in the data during our first attempt. If not, around the same time next year we'll get another opportunity. And this time we'll be well prepared for sudden wind surges. We'll also bring hot water bottles. Adventure is out there! | |
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| miokPosted at 2024-09-10 01:52:45(2Wks ago) Report Permalink URL | ||
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| Thanks Soup, I love reading your posts  | |
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| SoupPosted at 2024-09-10 01:56:02(2Wks ago) Report Permalink URL | ||
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| Most welcome | |
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| SoupPosted at 2024-09-10 01:56:54(2Wks ago) Report Permalink URL | ||
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| miokPosted at 2024-09-10 02:05:49(2Wks ago) Report Permalink URL | ||
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| Trivia... The creator of Calvin and Hobbes missed out on an estimated $300,000,000 deal by not allowing anyone to release plush toys of his characters. | |
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| SoupPosted at 2024-09-10 02:07:17(2Wks ago) Report Permalink URL | ||
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 never knew that | |
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| SoupPosted at 2024-09-11 00:30:16(2Wks ago) Report Permalink URL | ||
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| Cloud atlas of Mars showcases array of atmospheric phenomena by Europlanet  This image displays two atmospheric phenomena: the white curved lines are gravity wave clouds, while the brown areas are dust lifted from the ground by wind. The color shift visible in the dust lifting event might be indicative of very fast winds, a phenomenon currently under investigation by other members of the team. Credit: ESA/DLR/FU Berlin. Cloud enthusiasts have a new tool to investigate striking formations in the skies above the red planet. A browsable database of 20-years-worth of images of clouds and storms, created by the German Aerospace Centre (DLR) in Berlin, is helping scientists better understand how and where features arise in the Martian atmosphere and what they can tell us about the climate of Mars and other planets. The Mars 'Cloud Atlas', which is available to the public, has been presented this week at the Europlanet Science Congress (EPSC) 2024 in Berlin by Daniela Tirsch of DLR. The images in the Cloud Atlas have been captured by the High Resolution Stereo Camera (HRSC) instrument, which has been in orbit on board the European Space Agency (ESA) Mars Express spacecraft since 2005. Although Mars has a very thin atmosphere, numerous cloud formations and dust storm phenomena can develop from water and carbon dioxide ice crystals as well as dust particles. "Clouds on Mars are just as diverse and fascinating as those we see in our skies on Earth, with some features unique to the red planet. One of my favorite phenomena are the beautiful 'cloud streets'—linear rows of fleecy clouds that develop around the huge volcanic Tharsis rise and the northern lowlands in northern spring and summer. While they resemble cumulus clouds on Earth, they are formed under different atmospheric conditions," said Dr. Tirsch. "We also see impressive dust clouds that can spread hundreds of kilometers—a phenomenon we luckily don't experience on Earth."  This elongated cloud has formed as a result of wind encountering the Arsia Mons mountains. It forms almost every day during a specific season, from early morning until noon. Credit: ESA/DLR/FU Berlin/A. Cowart. Dust plays a major role in the atmosphere and climate of Mars. Rare upwelling events can leave beige, dust-laden blobs hanging in the atmosphere. Large differences in temperature and air pressure at certain seasons can result in stronger-than-usual winds that lift large amounts of dust from the Martian surface. Dust clouds spreading from the tops of giant volcanoes take on the appearance of eruption clouds, although they are no longer active. Large spiral dust storms and cyclone systems can also be observed each year near the Martian north pole. Studying these phenomena is crucial to scientists in understanding the atmosphere and air mass circulation on Mars. Rippling 'gravity clouds' are one of the most common formations on both Mars and the Earth. They are seen at mid-latitudes in winter for both hemispheres, as well as over the Tharsis volcanic plateau in southern winter. Lee waves, a special type of gravity clouds, can build up on the downwind side of ridges, mountains and other obstacles to create repeating ridge formations.  Lee waves are a special type of cloud created by the wind encountering obstacles and build up on the 'leeward' or downwind side. The geometries of the lee waves depend on the shape of the obstacles. Credit: ESA/DLR/FU Berlin.  An example of cloud streets over Vastitas Borealis, a large area near the North Pole mostly devoid of craters. . Credit: ESA/DLR/FU Berlin/A. Cowart  Some types of clouds studied are specific to locations and seasons; others like 'twilight clouds' can appear in the early morning at any place or time of year. The HRSC Cloud Atlas will provide valuable insights into the physical nature and appearance of clouds and storms, the time of their occurrence and their location. This knowledge will help better understand the atmospheric dynamics and the climate cycles on Mars, as well as provide input for studies of the climate on other planets such as Earth and Venus. The DLR team has already used the database to create global maps showing the occurrence of various types of cloud as a function of season and location. "As Mars Express has been extended by ESA until at least 2026, this will enable us keep filling this database and refine even further our understand of Mars atmosphere," said Dr. Tirsch. Papers on the database and scientific applications are currently in preparation. | |
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| SoupPosted at 2024-09-12 00:15:28(2Wks ago) Report Permalink URL | ||
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| Observational study supports century-old theory that challenges the Big Bang by Grant Guggisberg, Kansas State University  Northeastern University researchers have shown that our visible universe and invisible dark matter likely co-evolved from the time of the Big Bang. Credit: Pixabay/CC0 Public Domain A Kansas State University engineer recently published results from an observational study in support of a century-old theory that directly challenges the validity of the Big Bang theory. Lior Shamir, associate professor of computer science, used imaging from a trio of telescopes and more than 30,000 galaxies to measure the redshift of galaxies based on their distance from Earth. Redshift is the change in the frequency of light waves that a galaxy emits, which astronomers use to gauge a galaxy's speed. Shamir's findings lend support to the century-old "tired light" theory instead of the Big Bang. The findings are published in the journal Particles. "In the 1920s, Edwin Hubble and George Lemaitre discovered that the more distant the galaxy is, the faster it moves away from Earth," Shamir said. "That discovery led to the Big Bang theory, suggesting that the universe started to expand around 13.8 billion years ago. At around the same time, preeminent astronomer Fritz Zwicky proposed that galaxies that were more distant from Earth did not really move faster." Zwicky's contention was that the redshift observed from Earth is not because the galaxies move but because the light photons lose their energy as they travel through space. The longer the light travels, the more energy it loses, leading to the illusion that galaxies that are more distant from Earth also move faster. "The tired light theory was largely neglected, as astronomers adopted the Big Bang theory as the consensus model of the universe," Shamir said. "But the confidence of some astronomers in the Big Bang theory started to weaken when the powerful James Webb Space Telescope saw first light. "The JWST provided deep images of the very early universe, but instead of showing an infant early universe as astronomers expected, it showed large and mature galaxies. If the Big Bang happened as scientists initially believed, these galaxies are older than the universe itself." While new imaging casts doubt on the Big Bang, Shamir's study used the constant rotational velocity of the Earth around the center of the Milky Way to examine the redshift of galaxies that move in different velocities relative to Earth and to test how the change in the redshift responds to the change in velocity. "The results showed that galaxies that rotate in the opposite direction relative to the Milky Way have lower redshift compared to galaxies that rotate in the same direction relative to the Milky Way," Shamir said. "That difference reflects the motion of the Earth as it rotates with the Milky Way. But the results also showed that the difference in the redshift increased when the galaxies were more distant from Earth. "Because the rotational velocity of the Earth relative to the galaxies is constant, the reason for the difference can be the distance of the galaxies from Earth. That shows that the redshift of galaxies changes with the distance, which is what Zwicky predicted in his Tired Light theory." | |
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| SoupPosted at 2024-09-16 20:33:46(1Wk ago) Report Permalink URL | ||
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| The skies are about to get a new star as a result of a cosmic cataclysm by Anthony R. Wood, The Philadelphia Inquirer  Credit: Unsplash/CC0 Public Domain Any night now, the astrophysicists tell us, a new star will appear in the night sky—about as bright as the North Star—the result of a cosmic explosion in a distant constellation millennia ago. NASA scientist Rebekah Hounsell has called it "a once-in-a-lifetime event that will create a lot of new astronomers out there." Once you see it, however, don't get too attached to it. The so-called recurring nova star, T. Coronae Borealis, which periodically mutates into an earth-size hydrogen bomb, will flame out in less than a week. But if you're around, you'll get another shot at seeing it at the beginning of the 22nd century. Precisely when the nova, affectionately known as T CrB in the astronomical community, will be visible is unclear, astronomers say, and nailing the timing is a bit more complicated than predicting what time the sun will rise. It could be sometime this month, maybe even this week, or maybe not until winter. But the evidence is unmistakable that it will appear soon. When will the star explosion happen? It already has, about 3,000 years ago, around the time of King David (he who felled Goliath in one of the great upsets in human history); Zoroaster; the Iron Age; and the golden age of the Villanovan people, who overran northern Italy. While that may seem a long time ago, in terms of cosmic time, this qualifies as breaking news, said Edward Sion, astrophysicist at Villanova University, which has no connection with the Villanovans, or the nova in question. He believes its appearance may be imminent. Astronomers know the explosion has occurred because it happens about once every 80 years, and looking into their backward crystal balls, they have observed that T CrB has undergone a signature loss in star power that has preceded previous cataclysms. The nova—not to be confused with a self-destructing supernova—was last observed in February 1946, and before that, in May 1866. A German priest, Abbott Burchard of Upsberg, sighted it all the way back in 1217, according to astrophysicist Brady Bradley, an emeritus professor at Louisiana State University. The priest described it as "a faint star that for a time shone with great light." Sion said that mentions of the nova appear in the Middle Ages writings of Chinese and Korean observers. Of course, they didn't have to contend with light pollution, but they also didn't have the unprecedented observing power that astronomers have these days. The new star poses no threat to us. It is 3,000 light years from Earth, which explains the lag: Light travels about 5.9 trillion miles annually. Do feel free to multiply 3,000 by 5.9 trillion. By comparison, the light from our star, the sun, beamed from a mere 93 million miles away, gets here in about six minutes. Why does the nova keep exploding? The star's nearest neighbor is a gigantic, gaseous nuisance. The nova is a "white dwarf," the lesser half of a binary system in which two stars are bound together by gravity. Its partner is a "red giant" that leaks hydrogen because its gravity can't hold it all, and eventually is lured by the gravitational system of its partner, the white dwarf nova, from the Latin for "new," as in new star. "It's almost like a perfect storm," said Villanova's Sion. The white dwarf is an Earth-sized core of a dead star that is unimaginably hot, perhaps exceeding 180,000 degrees Fahrenheit, by NASA's estimate. When enough hydrogen accumulates on the white dwarf, the result is a nuclear explosion that NASA says is 10 times stronger than the annual output of the sun. Said Sion, "Every 80 years, the white dwarf says 'enough accreted mass already!' I'm going to blow up!" The result is that T CrB becomes visible to earthlings. Where in the sky can you find the 'new' star? To find the nova, follow the tail that trails the "scooper" of the Big Dipper. That will lead you to Arcturus, one of the brightest stars in the sky. Just to the east of Arcturus is the Northern Borealis constellation, of which T CrB is an occasional member. The nova will be just below the apex of the constellation's curved crown of stars, visible to the naked eye, said Sion. When will the nova call it a career? It isn't clear when T CrB will stop being a recurring nova, but it's possible that its career will come to a spectacular end, said Sion. Someday it may undergo an ultimate detonation as a "Type 1a supernova," which would be about 100,000 times as bright as our sun. Even 3,000 light years away, he said, that would be something to see. | |
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| SoupPosted at 2024-09-23 20:17:46(5Days ago) Report Permalink URL | ||
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| Could stars hotter than the sun still support life? by Brian Koberlein, Universe Today  A comparison of typical sizes of main sequence stellar classes. Credit: NASA’s Goddard Space Flight Center Although most potentially habitable worlds orbit red dwarf stars, we know larger and brighter stars can harbor life. One yellow dwarf star, for example, is known to have a planet teaming with life, perhaps even intelligent life. But how large and bright can a star be and still have an inhabited world? That is the question addressed in a recent article in The Astrophysical Journal Supplement Series. Stable main-sequence stars such as the sun are categorized by color or spectral type, with each type assigned a letter designation. For historical reasons, the categories aren't alphabetical. Red dwarf stars, the coolest stars with the smallest mass, are M type. Then with each brighter, bluer, and more massive category is K, G, F, A, B, and finally O. The sun falls into the G category as a yellow star. Each spectral type is then broken into smaller sections, numbered 0–9. The sun is G2 star because it is at the warmer end of G-type stars. As you go up the scale, the potentially habitable zone shifts farther from the star but also gets larger. That makes it more likely for a planet to be in the zone. But larger stars also have shorter lives, which might not give life enough time to evolve on a world. Then there are other factors that can be harmful for life. The largest stars emit a tremendous amount of ionizing radiation, which could strip planets of their atmospheres, or sterilize the surface of a planet. Because of this, the largest stars of the B and O types aren't likely to harbor life.  How habitable zones differ by spectral type. Credit: NASA, ESA and Z. Levy (STScI) But what about F-type stars? They are a bit brighter than the sun and more white than yellow in color. They are also stable for around 4 billion years, which is long enough for life to evolve and thrive. And they also emit more ultraviolet radiation, which may have helped life arise on Earth. What are the odds of a habitable F-type planet? To answer this question, the team went through the database of known exoplanets. About 80 F-type main-sequence stars are known to have at least one planet. Of those, 18 systems have exoplanets that spend at least part of their orbit in the habitable zone of the star. And in one case, the exoplanet 38 Virginis b, the planet is always in the habitable zone. Statistically, around 5%–20% of F-type stars have potential for life. What's interesting about 38 Virginis b is that it is a gas giant about four times more massive than Jupiter, so it isn't likely to be habitable. But it could have Earth-sized moons, similar to the Galilean moons of Jupiter. A world orbiting a Jovian planet could be a perfect home for life. F-type stars only comprise 3% of main-sequence stars in the Milky Way, and it's possible that their excess UV light could rule out habitable worlds. But alien astronomers might make similar arguments about G-type stars like the sun. As this study shows, we shouldn't rule out the sun's brighter cousins in the search for living worlds. | |
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| SoupPosted at 2024-09-24 20:22:38(4Days ago) Report Permalink URL | ||
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| What happens to the climate when Earth passes through interstellar clouds? by Mark Thompson, Universe Today  Orion Molecular Cloud Complex, dominated in the center of this view by the brilliant Flame nebula (NGC 2024). The smaller, glowing cavity falling between the Flame nebula and the Horsehead is called NGC 2023. Credit: NASA/JPL-Caltech. Noctilucent clouds were once thought to be a fairly modern phenomenon. A team of researchers recently calculated that Earth and the entire solar system may well have passed through two dense interstellar clouds, causing global noctilucent clouds that may have driven an ice age. The event is thought to have happened 7 million years ago and would have compressed the heliosphere, exposing Earth to the interstellar medium. Interstellar clouds are vast regions of gas and dust between the stars within galaxies. They are mostly made up of hydrogen along with a little helium and trace elements of heavier elements. They are a key part of the life cycle of stars, providing the materials for new stars to be formed, and are seeded with elements after stars die. The clouds vary significantly in size, density and location and are an important part of the evolution of the galaxy. Earth's journey around the galaxy is not for the impatient, for it takes about 250 million years to complete one full orbit at a speed of 828,000 kilometers per hour. Currently, the solar system is located in the Orion Arm, one of the spiral arms of our galaxy. During the journey, Earth travels through different regions, encountering stars and different densities of the interstellar medium. It experiences gravitational interactions with nearby stars and nebulae, sometimes exerting subtle interactions. Regardless of the immense journey, the stars of our galaxy remain relatively unchanged over a human lifetime. A team of astronomers led by Jess A. Miller from the Department of Astronomy of Boston University have traced the path of the sun back through time. In doing so, they have identified two occasions when the Earth and solar system passed through two dense interstellar clouds. The research is published in Geophysical Research Letters. One of the crossings occurred 2 million years ago, the other 7 million years ago. Exploring the properties of the clouds, the team assert that the clouds are dense enough that they could compress the solar wind to inside the orbit of Earth. The solar wind is a constant stream of charged particles, mostly electrons and protons that are emitted from the upper layer of the sun's atmosphere, the corona. The particles travel through the solar system at speeds between 400 and 800 kilometers per second. The edge of our solar system is defined as the point where the solar wind merges with the interstellar medium. Previous teams have analyzed climate change events due to these interstellar medium interactions with similar findings. Global cooling has been the result, with an ice age being triggered. The study by Miller and team readdressed this very topic using modern technology and processes. The team find that the interactions have indeed played a part in changes to the atmosphere of Earth. They find that levels of hydrogen in the upper atmosphere would have increased substantially. The newly acquired hydrogen would be converted to water molecules in the lower atmosphere and it would also have led to a reduction in mesospheric levels of ozone. These processes would have led to the appearance of global noctilucent clouds in the mesosphere. They would not have been permanent, but may have blocked 7% of sunlight from reaching Earth, plunging our planet into an ice age. | |
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| SoupPosted at 2024-09-25 04:27:57(4Days ago) Report Permalink URL | ||
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| Astronomers catch a glimpse of a uniquely inflated and asymmetric exoplanet by University of Arizona  Artist's illustration of the exoplanet WASP-107 b based on transit observations from NASA's James Webb Space Telescope as well as other space- and ground-based telescopes, led by Matthew Murphy of the University of Arizona and a team of researchers around the world. Credit: Rachel Amaro, University of Arizona An international group of researchers including University of Arizona astronomers, using NASA's James Webb Space Telescope, has observed the atmosphere of a hot and uniquely inflated exoplanet. The exoplanet, which is the size of Jupiter but only a tenth of its mass, is found to have an east-west asymmetry in its atmosphere, meaning that there is a significant difference between the two edges of its atmosphere. The findings are published in the journal Nature Astronomy. "This is the first time the east-west asymmetry of any exoplanet has ever been observed as it transits its star, from space," said lead study author Matthew Murphy, a graduate student at the U of A Steward Observatory. A transit is when a planet passes in front of its star—like the moon does during a solar eclipse. "I think observations made from space have a lot of different advantages versus observations that are made from the ground," Murphy said. East-west asymmetry of an exoplanet refers to differences in atmospheric characteristics, such as temperature or cloud properties, observed between the eastern and western hemispheres of the planet. Determining whether this asymmetry exists or not is crucial for understanding the climate, atmospheric dynamics and weather patterns of exoplanets—planets that exist beyond our solar system. The exoplanet WASP-107b is tidally locked to its star. That means that the exoplanet always shows the same face to the star it is orbiting. One hemisphere of the tidally locked exoplanet perpetually faces the star it orbits, while the other hemisphere always faces away, resulting in a permanent day side and a permanent night side of the exoplanet. Murphy and his team used the transmission spectroscopy technique with the James Webb Space Telescope. This is the primary tool that astronomers use to gain insights into what makes up the atmospheres of other planets, Murphy said. The telescope took a series of snapshots as the planet passed in front of its host star, encoding information about the planet's atmosphere. Taking advantage of new techniques and the unprecedented precision of the James Webb Space Telescope, the researchers were able to separate the signals from the atmosphere's eastern and western sides and get a more focused look at specific processes happening in the exoplanet's atmosphere. "These snapshots tell us a lot about the gases in the exoplanet's atmosphere, the clouds, the structure of the atmosphere, the chemistry and how everything changes when receiving different amounts of sunlight," Murphy said. The exoplanet WASP-107b is unique in that it has a very low density and relatively low gravity, resulting in an atmosphere that is more inflated than other exoplanets of its mass would be. "We don't have anything like it in our own solar system. It is unique, even among the exoplanet population," Murphy said. WASP-107b is roughly 890 degrees Fahrenheit—a temperature that is intermediate between the planets of our solar system and the hottest exoplanets known. "Traditionally, our observing techniques don't work as well for these intermediate planets, so there's been a lot of exciting open questions that we can finally start to answer," Murphy said. "For example, some of our models told us that a planet like WASP-107b shouldn't have this asymmetry at all—so we're already learning something new." Researchers have been looking at exoplanets for almost two decades, and many observations from both the ground and space have helped astronomers guess what the atmosphere of exoplanets would look like, said Thomas Beatty, study co-author and an assistant professor of astronomy at the University of Wisconsin–Madison. "But this is really the first time that we've seen these types of asymmetries directly in the form of transmission spectroscopy from space, which is the primary way in which we understand what exoplanet atmospheres are made of—it's actually amazing," Beatty said. Murphy and his team have been working on the observational data they have gathered, and are planning to take a much more detailed look at what's going on with the exoplanet, including additional observations, to understand what drives this asymmetry. "For almost all exoplanets, we can't even look at them directly, let alone be able to know what's going on one side versus the other," Murphy said. "For the first time, we're able to take a much more localized view of what's going on in an exoplanet's atmosphere." | |
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