4636 - UNIVERSE - according to the Standard Model?

 

-  4636  -   UNIVERSE  -  according to the Standard Model?       Describes how the Universe has evolved at large scale. There are six numbers that define the model and a team of researchers have used them to build simulations of the Universe. The results of these simulations were then fed to a machine learning algorithm to train it before it was set the task of estimating five of the cosmological constants, a task which it completed with incredible precision.

---------------------------------------   4636  -   UNIVERSE  -  according to the Standard Model?

-    The “Standard Model” incorporates a number of elements; the Big Bang, dark energy, cold dark matter, ordinary matter and the cosmic background radiation. It works well to describe the large scale structure of the Universe but there are gaps in our understanding.

-

-     Quantum physics can describe the small scale of the Universe but struggles with gravity and there are questions around dark matter and dark energy too. Understanding these can help in our understanding of the evolution and structure of the Universe.

-

-    Some new information in the distribution of galaxiesis used to estimate the values of five of the parameters. Using AI technology the team’s results had less than half the uncertainty for the element that describes the clumpiness of the Universe than in the previous attempt. Their results also revealed estimates of other parameters that closely resembled observation.

-

-    They generated 2,000 simulated universes after carefully specifying their cosmological parameters. These included expansion rate, the distribution and clumpiness of ordinary matter, dark matter and dark energy and using these the team ran the simulations. The output was then compressed into manageable data sets and this was used to compare against over one hundred thousand real galaxies data. 

-

-    The parameters are those that describe how the Universe operates at the largest scale. These are essentially, the settings for the Universe and include the amount of ordinary matter, dark matter, dark energy, the conditions following the Big Bang and just how clumpy the matter is. Previously these settings were calculated using observations from the structure of galaxy clusters.

-

-   Instead of using observations, the team used their AI approach to extract the small scale information that was hidden in the existing observational data. The AI system learned how to correlate the parameters with the observed structure of the Universe, but at small scale.

-

-   The uncertainty about the Hubble Constant expansion of the Universe is an example where  AI can help to fine tune its value. Over the next few years the Universe will become far better understood.

-

-

December 7, 2024          UNIVERSE  -  according to the Standard Model?           4636

------------------------------------------------------------------------------------------                                                                                                                       

--------  Comments appreciated and Pass it on to whomever is interested. ---

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 

--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Saturday, December 7, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4633 - WEBB DISCOVERIES

 

-  4633  -   WEBB  DISCOVERIES -   The James Webb Space Telescope since coming online in mid-2022, the most powerful telescope ever built has both blown our minds with its stunning images and swept away many of our preconceptions about the early universe.

-

------------------------------------------   4633  -  WEBB  DISCOVERIES

-

-     The oldest ever black holes, a preview of our solar system's gory demise, and a measurement of distant starlight that threatens to bring the standard of cosmology crashing down, here are the JWST's wildest discoveries of 2023.

-

-    Not long after coming online, the JWST immediately discovered six enormous "universe breaker" galaxies, containing what seemed to be almost as many stars as the Milky Way, dating to just 500 million years after the Big Bang.

-

-   The strange discovery pointed to a deepening mystery around how large galaxies first bloomed in our universe. After running simulations, other astronomers suggested that the galaxies might not contain as many stars as first seemed, and could instead just be glowing unusually brightly.

-

-    The universe is expanding, but depending on where cosmologists look, it's doing so at different rates. In the past, the two best experiments to measure the expansion rate were the European Space Agency's Planck satellite (which gave a most likely expansion rate of 67 kilometers per second per megaparsec) and the Hubble Space telescope, which studied pulsating stars called Cepheids and found a higher value of 73 km/s/Mpc.

-

-    Cosmologists thought this tension might be down to uncertainty caused by Hubble not distinguishing between Cepheids and background stars, but the JWST snuffed out that hope with a result of 74 km/s/Mpc.

-

-     There weren't just inexplicably large ancient galaxies on the JWST's list of discoveries this year, but whopping black holes too. The first, CEERS 1019, had a mass 10 million times that of our sun and was found by the JWST just 570 million years after the Big Bang, making it the oldest black hole ever spotted at the time of its discovery in April 2023.

-

-    The telescope later discovered an even older massive black hole 440 million years after the universe began.   How these gigantic space-time ruptures swelled to such staggering scales so early on is an ongoing mystery. Astrophysicists are currently exploring options that include the black holes being formed from the rapid collapse of giant gas clouds.

-

-   The telescope's ultrapowerful eye has also revealed glimpses of completely new, unexplainable objects. After being trained on the Orion Nebula, the JWST found 42 pairs of Jupiter-mass binary objects, or "JuMBOs", Jupiter-sized planets drifting through space in pairs, some as far apart from each other as 390 times the distance between Earth and the sun.

-

-     The JuMBOs are too small to be stars, but as they bafflingly exist in pairs, they are unlikely to be rogue planets ejected from solar systems. Their discovery has alerted astronomers to a brand-new formation mechanism for planets or even for failed stars.

-

-   Another feature of the JWST is its ability to measure a spectrum of the atmospheres of distant exoplanets, a toolkit which enabled it to spot the potential signs of life in "alien farts" on a Goldilocks water world 120 light-years away.

-

-    The exoplanet it found, “K2-18 b”, is a sub-Neptune planet (weighing in somewhere between the mass of Earth and Neptune) orbiting the habitable zone of a red dwarf star. After taking an atmospheric spectrum, the JWST found it rich with hydrogen, methane and carbon dioxide, all chemical markers of a hydrogen-rich hycean world that is a prime contender for extraterrestrial life.

-

-   More tantalizing still was the detection of dimethyl sulfide (DMS), a cabbage-smelling compound only known to be produced by microscopic algae in Earth's oceans.

-

-    Stars and galaxies aren't evenly spread throughout our universe. Instead, they're connected by an enormous cosmic web, a gigantic network of crisscrossing celestial superhighways paved with hydrogen gas and dark matter.

-

-   Taking shape in the chaotic aftermath of the Big Bang, the web's tendrils formed as clumps from the roiling broth of the young universe; where multiple strands of the web intersected, galaxies eventually formed.

-

-    Insights into the structure of this web not only give us a glimpse of the chaotic particle interactions that led to a universe existing in the first place, so astronomers using the JWST were stunned when they spotted the earliest strand of this web ever seen a gassy tendril made of of 10 closely packed galaxies spanning more than 3 million light-years in length.

-

-    The filament formed when the universe was just 830 million years old, and is partially wrapped around a bright black hole.   In the field of one of JWST's largest-area surveys, COSMOS-Web, an Einstein ring was discovered around a compact, distant galaxy. It is the most distant gravitational lens ever discovered by a few billion light-years.

-

-    Besides making for a very pretty picture, distantly-lensed light shows like this could help astronomers to understand the puzzling nature of dark matter: the unseen substance believed to make up 70% of the universe's matter.

-

-    The donut-shaped Ring Nebula, also known as Messier 57 (M57), is a 2,200 light-years distant corpse of an exploded star, harboring at its center a tiny pinprick of a white dwarf that is the last remaining piece of the star's core.

-

-    As it reached the end of its life, the star exploded outwards, hurling its innards far and wide to form what looks like a gigantic eye. The explosion likely obliterated or ejected any unfortunate planets in its way, a fate that will similarly befall our own solar system in 5 billion years time.

-

-

December 4, 2024             WEBB  DISCOVERIES                              4633

------------------------------------------------------------------------------------------                                                                                                                       

--------  Comments appreciated and Pass it on to whomever is interested. ---

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 

--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Saturday, December 7, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4634 - WEBB - discoveries Brown Dwarf Stars?

 

-  4634  -  WEBB  -  discoveries Brown Dwarf Stars?    James Webb telescope finds 1st possible 'failed stars' beyond the Milky Way. They could reveal new secrets of the early universe.   The Space Telescope may have found dozens of elusive brown dwarfs, strange objects larger than planets but smaller than stars, beyond the Milky Way.

--------------------------------------   4634  -  WEBB  -  discoveries Brown Dwarf Stars?

-    While zooming in on the young star cluster NGC 602 in the nearby Small Magellanic Cloud (SMC), the researchers spotted what may be the first evidence of brown dwarfs ever seen outside the Milky Way. Brown dwarfs, or "failed stars," are peculiar objects that are bigger than the largest planets but not massive enough to sustain nuclear fusion like stars.

-

-    A stunning new image of the star cluster courtesy of JWST's Near Infrared Camera, reveals fresh insight into how these strange failed stars form.    Brown dwarfs seem to form in the same way as stars, they just don't capture enough mass to become a fully fledged star.

-

-    NGC 602 is a roughly 3 million-year-old star-forming cluster on the outskirts of the SMC, a satellite galaxy of the Milky Way that contains roughly 3 billion stars.   Our galaxy, in comparison, contains an estimated 100 billion to 400 billion stars.   Orbiting about 200,000 light-years from Earth, the SMC is one of the Milky Way's closest intergalactic neighbors .

-

-     The results suggest that 64 stellar objects within the cluster have masses ranging between 50 and 84 times that of Jupiter. Brown dwarfs typically weigh between 13 and 75 Jupiter masses,  making many of these objects prime candidates to be the first brown dwarfs spotted beyond our galaxy.

-

-    These failed stars appear to have formed in much the same way as stars like the sun: through the collapse of massive clouds of gas and dust. However, for a collapsed cloud to become a star, it must continue accumulating mass until it reaches an internal temperature and pressure high enough to trigger hydrogen fusion at its core combining hydrogen atoms into helium and releasing energy as light and heat in the process.

-

-    “Brown dwarfs” never acquire enough mass to sustain permanent fusion, leaving them larger than a planet but smaller and dimmer than a star. This failure to ignite may be a common outcome in the universe: Astronomers have discovered about 3,000 brown dwarfs in the Milky Way but estimate that there may be as many as 100 billion in our galaxy alone, potentially making them as common as stars themselves.

-

-    Studying this group of extragalactic failed stars further could help clarify why so many stars seemingly fail to ignite. But according to the researchers, these oddball objects could also reveal new insights about the early universe.

-

-     NGC 602 is a young cluster containing low abundances of elements heavier than hydrogen and helium, so its composition is thought to be very similar to that of the ancient universe, before later generations of stars peppered the cosmos with elements we see near Earth.

-

-     By studying the young metal-poor brown dwarfs newly discovered in NGC 602, we are getting closer to unlocking the secrets of how stars and planets formed in the harsh conditions of the early Universe.

-

-

December 4, 2024         WEBB  -  discoveries Brown Dwarf Stars?        4634

------------------------------------------------------------------------------------------                                                                                                                       

--------  Comments appreciated and Pass it on to whomever is interested. ---

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 

--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Thursday, December 5, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4632 - EARTH WATER WORLD ?

 

-  4632  -  EARTH  WATER  WORLD ?    Our planet started off bone dry. Then space sent ice balls and 'water balloons' to give us water.  Each time you take a sip of water, you’re imbibing liquid that, in all likelihood, is up to 4.5 billion years old. Earth is awash in a life-sustaining substance about as ancient as the planet itself.

------------------------------------------------   4632  -  EARTH  WATER  WORLD ?

-     Astrophysicists don’t completely know where the stuff came from, but circumstantial evidence suggests that water-containing meteorites might have pummeled an infant Earth. Those rocky showers would have helped transform a bone-dry place into a unique wet world.

-

-    Although our planet is covered by an estimated 326 quintillion gallons of H2O, it’s drier than you’d imagine comparing Earth, which could be as little as 0.023 percent water, to crackers, which are around 2 percent water. That’s still a lot more moisture than we had at the beginning.

-

-   When the solar system first came together, some of the young planets were too hot for water. Earth and Mars should have formed extremely dry due to their locations in the solar system’s frost line.

-

-    When the sun was coalescing out of a collapsing cloud of gas and dust 4.6 billion years ago, its tremendous heat made a boundary. Outside of it, space was cool enough for ice grains to solidify.  This helps explain why far-out Jupiter and Saturn have ocean moons.

-

-     Inside of it, heat vaporized water. Earth and the other inner planets clumped together from the dry rock and dense metal that remained. Something must have happened, some millions of years later, to nourish those planets with water. Astronomers have explored several possible scenarios.

-

-    Craters on the surface of our moon indicate that our side of the frost line was constantly hit with space rocks, including a particularly violent shower known as the “Late Heavy Bombardment”. Some experts think those projectiles, specifically meteorites, the bits of asteroids that fall to Earth, might have been more like cosmic water balloons.

-

-    This hypothesis is supported by the 2010 discovery of a thin crust of frost on asteroid          “24 Themis”.     NASA found water-bearing clay minerals in the near-Earth asteroid “Bennu” during a ground-breaking sample-retrieval mission.

-

-    Still, it’s possible that other processes were involved in delivering water to Earth, such as gas from the cloudy solar nebula that dissolved hydrogen into the planet’s magma layer. It’s also possible that there were multiple sources and steps.

-

-    The pieces of the puzzle are not clear.    One major clue that gives us an idea of where the water may be coming from is the type of hydrogen that flows through our aquatic systems.

-

-    The most common form of hydrogen in the universe has a lone proton orbited by an electron. But there’s a slightly different version called “deuterium” with a proton and a neutron squished into the center. Astronomers have measured the proportion of deuterium to regular hydrogen in Earth’s water and looked for that “D-H ratio” in other objects around the solar system.

-

-    “Carbonaceous chondrites”, a kind of meteorite, are a pretty good D-H ratio match. If our solar system was once an ancient construction site, think of the chondrites as the unmelted rubble. They hail from the asteroid belt’s outer section, closer to Jupiter than Mars, which means they probably formed on the wet side of the frost line.

-

-    A single ton of carbonaceous space rocks, rich in ice and watery minerals, could have delivered 110 to 220 pounds of water to Earth. When Jupiter and Saturn’s masses grew big really fast, the gas giant kicked those rocks toward the sun and the inner planets.

-

-    The meteorites “contain a lot of organic goop” like carbon and other molecules associated with life. They also hold volatile materials, substances that evaporate easily when heated, like water, zinc, and hydrogen from the early days of the solar system. While those can be found on our planet today, a few volatile materials are still missing.

-

-    If the carbonaceous chondrites contributed Earth’s water, they would have also contributed Earth’s noble gasses.   But they don’t support those elements, so something else must have filled the gap. “Comet 67P”, closely studied in the mid-2010s has the right noble gas content.

-

-    This lends to the idea that a bunch of space bodies hit Earth with noble gasses, H2O.           If most of the water gets contributed by asteroid impacts and most of the noble gasses are contributed by comets.   Newer evidence emphasizes a different kind of space rock from closer to home.

-

-    “Enstatite chondrites” are meteorites with a similar composition to the original building blocks of Earth. Because they formed within the inner solar system, on our side of the asteroid belt, astronomers classify them as “non-carbonaceous.” While they don’t have as much water as their distant counterparts, they could pack some punch.

-

-       A suite of more recent studies have linked nitrogen and other volatile elements on Earth to enstatite chondrites.    Sn analysis of Martian zinc, indicates that debris from the inner solar system transported the metal to our neighbor. If zinc existed within those meteorites, they probably carried other volatile materials, specifically, water. Mars had liquid water at one point and may have some still lurking under an ice cap.

-

-    If space rocks brought water to the Red Planet, could they have done so elsewhere?  What we’re learning here may not only be applicable to our understanding of what we should expect on Mars,  but about the possibility of water and organic molecules being delivered to planets around other stars, which would give you an environment that could be conducive to the formation of life.

-

-    Putting these lines of evidence together gives us a recipe that would have involved lots of damp local rocks and a few of the more distant ice balls. Hydrogen, nitrogen, and zinc isotopes “all tell the same story” of a wet Earth.    Previously overlooked non-carbonaceous meteorites probably supplied about 70 percent of the planet’s water, and just a dash of carbonaceous meteorites touched up its vast blue surface. 

-

-

December 2, 2024            EARTH  WATER  WORLD ?                4632

------------------------------------------------------------------------------------------                                                                                                                       

--------  Comments appreciated and Pass it on to whomever is interested. ---

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 

--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Tuesday, December 3, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4631 - DARK ENERGY - new ways to study it?

 

-  4631  -   DARK  ENERGY  -  new ways to study it?  “Dark Energy Spectroscopic Instrument” (DESI).   Each of its 5,000 robotic positioners are precisely pointing to their celestial targets to within a tenth of the width of a human hair.   The corrector barrel holds DESI’s six large lenses in precise alignment.

-

----------------------------------------   4631  -   DARK  ENERGY  -  new ways to study it?

-

-   The hexapod, designed and built with partners in Italy, focuses the DESI images by moving the barrel-lens system. Both the barrel and hexapod are housed in the cage, which provides the attachment to the telescope structure.

-

-     Charge-coupled devices, or CCD convert the light passing through the lenses from distant galaxies into digital information.   A complex analysis of DESI’s first year of data provides one of the most stringent tests yet of general relativity and how gravity behaves at cosmic scales

-

-    Looking at galaxies and how they cluster across time reveals the growth of cosmic structure, which lets DESI test theories of modified gravity which is an alternative explanation for our universe’s accelerating expansion

-

-    DESI researchers found that the way galaxies cluster is consistent with our standard model of gravity and the predictions from Einstein’s theory of general relativity.   Gravity has shaped our cosmos. Its attractive influence turned tiny differences in the amount of matter present in the early universe into the sprawling strands of galaxies we see today.

-

-    Using data from the “Dark Energy Spectroscopic Instrument” (DESI) has traced how this cosmic structure grew over the past 11 billion years, providing the most precise test to date of gravity at very large scales.

-

-   The result validates our leading model of the universe and limits possible theories of modified gravity, which have been proposed as alternative ways to explain unexpected observations including the accelerating expansion of our universe that is typically attributed to dark energy.

-

-   The study also provided new upper limits on the mass of neutrinos, the only fundamental particles whose masses have not yet been precisely measured. Previous neutrino experiments found that the sum of the masses of the three types of neutrinos should be at least 0.059 eV/c^2. (For comparison, an electron has a mass of about 511,000 eV/c^2.)    DESI’s results indicate that the sum should be less than 0.071 eV/c^2, leaving a narrow window for neutrino masses.

-

-    The complex analysis used nearly 6 million galaxies and quasars lets researchers see up to 11 billion years into the past. With just one year of data, DESI has made the most precise overall measurement of the growth of structure, surpassing previous efforts that took decades to make.

-

-    DESI’s first year of data made the largest 3D map of our universe to date and revealed hints that dark energy might be evolving over time. The results looked at a particular feature of how galaxies cluster known as “baryon acoustic oscillations” (BAO).

-

-    The new analysis, called a “full-shape analysis,” broadens the scope to extract more information from the data, measuring how galaxies and matter are distributed on different scales throughout space.

-

-   DESI is a state-of-the-art instrument that can capture light from 5,000 galaxies simultaneously.   DESI sits atop the U.S. National Science Foundation’s Nicholas U. Mayall    4-meter Telescope at Kitt Peak National Observatory . The experiment is now in its fourth of five years surveying the sky and plans to collect roughly 40 million galaxies and quasars by the time the project ends.

-

-    The collaboration is currently analyzing the first three years of collected data and expects to present updated measurements of dark energy and the expansion history of our universe in spring 2025.

-

-    Dark matter makes up about a quarter of the universe, and dark energy makes up another 70 percent, and we don’t really know what either one is.   The idea that we can take pictures of the universe and tackle these big, fundamental questions is mind-blowing

-

-

December 2, 2024            DARK  ENERGY  -  new ways to study it?         4631

------------------------------------------------------------------------------------------                                                                                                                       

--------  Comments appreciated and Pass it on to whomever is interested. ---

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 

--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Tuesday, December 3, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4630 - HOW PLANETS FORM?

 

-  4630  -  HOW  PLANETS  FORM?  -    Every second in the Universe, more than 3,000 new stars form as clouds of dust and gas undergo gravitational collapse. Afterward, the remaining dust and gas settle into a swirling disk that feeds the star’s growth and eventually accretes to form planets known as a protoplanetary disk.

-----------------------------------------   4630  -   HOW  PLANETS  FORM?

-   This model, known as the “Nebular Hypothesis”, is the most widely accepted theory, the exact processes that give rise to stars and planetary systems are not yet fully understood. Shedding light on these processes is one of the many objectives of the James Webb Space Telescope (JWST).

-

-    Astronomers used the JWST’s advanced infrared optics to examine protoplanetary disks around new stars. These observations provided the most detailed insights into the gas flows that sculpt and shape protoplanetary disks over time.

-

-    In order for young stars to grow, they must draw in gas from the protoplanetary disk surrounding them. For that to happen, the gas must lose angular momentum (inertia); otherwise, it would consistently orbit the star and never accrete onto it.

-

-     Magnetically driven disk winds have emerged as a possible mechanism. Primarily powered by magnetic fields, these “winds” funnel streams of gas away from the planet-forming disk into space at dozens of kilometers per second.

-

-    This causes it to lose angular momentum, allowing the leftover gas to fall inward toward the star.    Researchers selected four protoplanetary disk systems that appear edge-on when viewed from Earth. Using Webb’s Near Infrared Spectrograph (NIRSpec), the team could trace various wind layers by tuning the instrument to detect distinct atoms and molecules in certain transition states.

-

-    The team also obtained spatially resolved spectral information across the entire field of view using the spectrograph’s Integral Field Unit (IFU).

-

-    This allowed the team to trace the disk winds in unprecedented detail and revealed an intricate, three-dimensional layered structure: a central jet nested inside a cone-shaped envelope of winds at increasing distances. There was a pronounced central hole inside the cones in all four protoplanetary disks.   This is one of the most important processes at work is how the star accretes matter from its surrounding disk.

-

-   How a star accretes mass has a big influence on how the surrounding disk evolves over time, including the way planets form later on.   Winds driven by magnetic fields across most of the disk surface could play a very important role.

-

-    However, other processes are also responsible for shaping protoplanetary disks. These include “X-wind,” where the star’s magnetic field pushes material outward at the inner edge of the disk.

-

-    There are also “thermal winds,” which blow at much slower velocities and are caused by intense starlight eroding its outer edge. The high sensitivity and resolution of the JWST were ideally suited to distinguish between the magnetic field-driven wind, the X-wind, and the thermal wind. These observations revealed a nested structure of the various wind components that had never been seen before.

-

-    A crucial distinction between the magnetically driven and the X-winds is how they are located farther out and cover broader regions. These winds cover regions that correspond to the inner rocky planets of our solar system, roughly between Earth and Mars. They also extend farther above the disk than thermal winds, reaching hundreds of times the distance between Earth and the Sun.

-

-    The new JWST observations revealed a nested structure and morphology that matched what astronomers anticipated for magnetically driven disk wind.   These observations strongly suggest that we have obtained the first detailed images of the winds that can remove angular momentum and solve the longstanding problem of how stars and planetary systems form.

-

-    Astronomers want to get a larger sample with JWST and then also see if we can detect changes in these winds as stars assemble and planets form.

-

-

November 30, 2024            HOW  PLANETS  FORM?                        4630

------------------------------------------------------------------------------------------                                                                                                                       

--------  Comments appreciated and Pass it on to whomever is interested. ---

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 

--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Tuesday, December 3, 2024  ---------------------------------

 

 

 

 

 

           

 

 

- 4628 - MILKYWAY GALAXY -

 

-  4628  -  MILKYWAY  GALAXY  -    Astronomers often use the Milky Way as a standard for studying how galaxies form and evolve. Since we’re inside it, astronomers can study it in detail with advanced telescopes. By examining it in different wavelengths, astronomers and astrophysicists can understand its stellar population, its gas dynamics, and its other characteristics in far more detail than distant galaxies.

-

---------------------------------------------   4628  -   MILKYWAY  GALAXY  -

-

-    The Sloan Digital Sky Survey (SDSS), the Two Micron All Sky Survey (2MASS), and the ESA’s Gaia mission are all prominent examples.  The Satellites Around Galactic Analogs (SAGA) Survey is another, and its third data release features in three new studies. The studies are all based on 101 galaxies similar in mass to the Milky Way.

-

-    Research shows that galaxies form inside gigantic haloes of dark matter, the elusive substance that doesn’t interact with light. 85% of the Universe’s matter is mysterious dark matter, while only 15% is normal or baryonic matter, the type that makes up planets, stars, and galaxies. Though we can’t see these massive haloes, astronomers can observe their effects. Their gravity draws normal together to create galaxies and stars.

-

-     SAGA is aimed at understanding how dark matter haloes work. It examines low-mass satellite galaxies around galaxies similar in mass to the Milky Way. These satellites can be captured and drawn into the dark matter haloes of larger galaxies. SAGA has found several hundred of these satellite galaxies orbiting 101 Milky Way-mass galaxies.

-

-    The Milky Way has been an incredible physics laboratory.  The comparison between the Milky Way and the 101 others revealed some significant differences.   The SAGA Survey’s third data release includes 378 satellites found in 101 MW-mass systems, and the first paper focuses on the satellites. Only a painstaking search was able to uncover them. Four of them belong to the Milky Way, including the well-known Large and Small Magellanic Clouds.

-

-    SAGA found that the number of satellites per galaxy ranges from zero to 13.   The mass of the most massive satellite is a strong predictor of the abundance of satellites.  One-third of the SAGA systems contain LMC-mass satellites, and they tend to have more satellites than the MW.   The Milky Way is an outlier in this regard, it’s atypical.

-

-    The second study focuses on star formation in the satellites. The star formation rate (SFR) is an important metric in understanding galaxy evolution. The research shows that star formation is still active in the satellite galaxies, but the closer they are to the host, the slower their SFR. Is it possible that the greater pull of the dark matter halo close to the galaxy is quenching star formation?

-

-    Our results suggest that lower-mass satellites and satellites inside 100 kpc are more efficiently quenched in a Milky Way–like environment, with these processes acting sufficiently slowly to preserve a population of star-forming satellites at all stellar masses and projected radii.

-

-   However, in the Milky Way’s satellites, only the Magellanic Clouds are still forming stars, with radial distance playing a role.   What in the Milky Way caused these small, lower-mass satellites to have their star formation quenched? Perhaps, unlike a typical host galaxy, the Milky Way has a unique combination of older satellites that have ceased star formation and newer, active ones – the LMC and SMC – that only recently fell into the Milky Way’s dark matter halo.

-

-     This is another reason that our galaxy is atypical.  What about the smaller dark matter haloes around the satellite galaxies? They developed a new model for quenching in galaxies with less-than-or-equal-to 109 solar masses. Their model is constrained by the SAGA data on the 101 galaxies, and the researchers then compared it to isolated field galaxies from the Sloan Digital Sky Survey.

-

-    Those surveys can hopefully answer questions about the role internal feedback plays in the lower-mass satellites, about their mass and gas accretion and the influence dark matter has on them, as well as gas processes specific to the satellites.

-

-     SAGA provides a benchmark to advance our understanding of the universe through the detailed study of satellite galaxies in systems beyond the Milky Way.

-

-

November 30, 2024                 4628

------------------------------------------------------------------------------------------                                                                                                                        

--------  Comments appreciated and Pass it on to whomever is interested. ---

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 

--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Sunday, December 1, 2024  ---------------------------------