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  • richardmitnick 11:18 am on May 7, 2019 Permalink | Reply
    Tags: "A universe is born", , , , , , , , Galaxies, , , , , The Planck epoch   

    From Symmetry: “A universe is born” 

    Symmetry Mag
    From Symmetry

    05/07/19
    Diana Kwon

    Take a (brief) journey through the early history of our cosmos.

    Timeline of the Inflationary Universe WMAP

    The universe was a busy place during the first three minutes. The cosmos we see today expanded from a tiny speck to much closer to its current massive size; the elementary particles appeared; and protons and neutrons combined into the first nuclei, filling the universe with the precursors of elements.

    By developing clever theories and conducting experiments with particle colliders, telescopes and satellites, physicists have been able to wind the film of the universe back billions of years—and glimpse the details of the very first moments in the history of our cosmic home.

    Take an abridged tour through this history:

    The Planck epoch
    Time: < 10^-43 seconds

    The Planck Epoch https:// http://www.slideshare.net ericgolob the-big-bang-10535251

    Welcome to the Planck epoch, named after the smallest scale of measurements possible in particle physics today. This is currently the closet scientists can get to the beginning of time.

    Theoretical physicists don’t know much about the earliest moments of the universe. After the Big Bang theory gained popularity, scientists thought that in the first moments, the cosmos was at its hottest and densest and that all four fundamental forces—electromagnetic, weak, strong and gravitational—were combined into a single, unified force. But the current leading theoretical framework for our universe’s beginning doesn’t necessarily require these conditions.

    The universe expands
    Time: From 10^-43 seconds to about 10^-36 seconds

    In this stage, which began either at Planck time or shortly after it, scientists think the universe underwent superfast, exponential expansion in a process known as inflation.

    Inflation

    4
    Alan Guth, from Highland Park High School and M.I.T., who first proposed cosmic inflation

    HPHS Owls

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex MittelmannColdcreation

    Alan Guth’s notes:
    5

    Physicists first proposed the theory of inflation in the 1980s to address the shortcomings of the Big Bang theory, which, despite its popularity, could not explain why the universe was so flat and uniform, and why its different parts began expanding simultaneously.

    During inflation, quantum fluctuations could have stretched out to produce a pattern that later determined the locations of galaxies. It might have been only after this period of inflation the universe became a hot, dense fireball as described in the Big Bang theory.

    The elementary particles are born
    Time: ~10^-36 seconds

    When the universe was still very hot, the cosmos was like a gigantic accelerator, much more powerful than the Large Hadron Collider, running at extremely high energies. In it, the elementary particles we know today were born.

    Scientists think that first came exotic particles, followed by more familiar ones, such as electrons, neutrinos and quarks. It could be that dark matter particles came about during this time.

    3
    Quarks APS/Alan Stonebraker

    The quarks soon combined, forming the familiar protons and neutrons, which are collectively known as baryons. Neutrinos were able to escape this plasma of charged particles and began traveling freely through space, while photons continued to be trapped by the plasma.

    Standard Model of Particle Physics

    The first nuclei emerge
    Time: ~1 second to 3 minutes

    Scientists think that when the universe cooled enough for violent collisions to subside, protons and neutrons clumped together into nuclei of the light elements—hydrogen, helium and lithium—in a process known as Big Bang nucleosynthesis.

    Protons are more stable than neutrons, due to their lower mass. In fact, a free neutron decays with a 15-minute half-life, while protons may not decay at all, as far as we know.

    So as the particles combined, many protons remained unpaired. As a result, hydrogen—protons that never found a partner—make up around 74% of the mass of “normal” matter in our cosmos. The second most abundant element is helium, which makes up approximately 24%, followed by trace amounts of deuterium, lithium, and helium-3 (helium with a three-baryon core).

    Periodic table Sept 2017. Wikipedia

    Scientists have been able to accurately measure the density of baryons in our universe. Most of those measurements line up with theorists’ estimations of what the quantities ought to be, but there is one lingering issue: Lithium calculations are off by a factor of three. It could be that the measurements are off, but it could also be that something we don’t yet know about happened during this time period to change the abundance of lithium.

    The cosmic microwave background becomes visible
    Time: 380,000 years

    Hundreds of thousands of years after inflation, the particle soup had cooled enough for electrons to bind to nuclei to form electrically neutral atoms. Through this process, which is also known as recombination, photons became free to traverse the universe, creating the cosmic microwave background.

    CMB per ESA/Planck


    ESA/Planck 2009 to 2013

    Today, the CMB is one of the most valuable tools for cosmologists, who probe its depths in search of answers for many of the universe’s lingering secrets, including the nature of inflation and the cause of matter-antimatter asymmetry.

    Shortly after the CMB became detectable, neutral hydrogen particles formed into a gas that filled the universe. Without any objects emitting high-energy photons, the cosmos was plunged into the dark ages for millions of years.

    Dark Energy Camera Enables Astronomers a Glimpse at the Cosmic Dawn. CREDIT National Astronomical Observatory of Japan

    The earliest stars shine
    Time: ~100 million years

    The dark ages ended with the formation of the first stars and the occurrence of reionization, a process through which highly energetic photons stripped electrons off neutral hydrogen atoms.

    Reionization era and first stars, Caltech

    Scientists think that the vast majority of the ionizing photons emerged from the earliest stars. But other processes, such as collisions between dark matter particles, may have also played a role.

    At this time, matter began to form the first galaxies. Our own galaxy, the Milky Way, contains stars that were born when the universe was only several hundred million years old.

    Milky Way NASA/JPL-Caltech /ESO R. Hurt

    Our sun is born
    Time: 9.2 billion years

    3
    NASA

    The sun is one of a few hundred billion stars in the Milky Way. Scientists think it formed from a giant cloud of gas that consisted mostly hydrogen and helium.

    Today
    Time: 13.8 billion years

    Today, our cosmos sits at a cool 2.7 Kelvin (minus 270.42 degrees Celsius). The universe is expanding at an increasing rate, in a manner similar to (but many orders of magnitude slower than) inflation.

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Physicists think that dark energy—a mysterious repulsive force that currently accounts for about 70% of the energy in our universe—is most likely driving that accelerated expansion.

    Dark energy depiction. Image: Volker Springle/Max Planck Institute for Astrophysics/SP)

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.


    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 9:01 am on August 21, 2015 Permalink | Reply
    Tags: , , Galaxies, ,   

    From SPACE.com: Giant Galaxies May Be Better Cradles for Habitable Planets 

    space-dot-com logo

    SPACE.com

    August 21, 2015
    Charles Q. Choi

    1
    This map shows the full extent of the Milky Way galaxy – a spiral galaxy of at least two hundred billion stars. Our Sun is buried deep within the Orion Arm about 26 000 light years from the centre. Towards the centre of the Galaxy the stars are packed together much closer than they are where we live. Notice also the presence of small globular clusters of stars which lie well outside the plane of the Galaxy, and notice too the presence of a nearby dwarf galaxy – the Sagittarius dwarf – which is slowly being swallowed up by our own galaxy. From http://www.atlasoftheuniverse.com/galaxy.html

    Galaxies like the Milky Way may not be the best cradles of life in the universe — giant galaxies devoid of newborn stars and at least twice as massive as the Milky Way could host 10,000 times more habitable planets, researchers say.

    In the past 20 years, astronomers have confirmed the existence of nearly 1,900 planets that orbit stars other than our sun. These findings have led researchers to speculate which moons, planets and stars might be the best at supporting recognizable forms of life. Scientists have even investigated whether there might be a galactic habitable zone in the Milky Way — a region of the galaxy favorable to the formation and evolution of habitable worlds.

    Now, researchers have analyzed more than 140,000 neighboring galaxies to answer the question, “Which type of galaxy might be the most habitable in terms of complex life in the cosmos?”

    One potentially surprising conclusion? The number of habitable planets is not the largest in spiral galaxies like ours, study co-author Anupam Mazumdar, a particle cosmologist at Lancaster University in England, told Space.com.

    The researchers suggested three criteria that might be important in determining a galaxy’s habitability. The first was the total mass of their stars, representing potential homes to planets. The next was the amount of mass in “metals” they had — elements heavier than hydrogen and helium — since this kind of matter is needed to build worlds as well as life as it is known on Earth. The last was their ongoing rate of star formation, since galaxies with high star-formation rateswould pack stars closer together, increasing the chance that any stars with habitable worlds might dwell near massive stars that will eventually die in supernovas that can trigger mass extinctions.

    “This is the first computation ever where we are discussing life in cosmological scales, and not within our own galaxy,” Mazumdar said. “It is fair to say that our paper is the first ‘cosmobiology’ paper, which has perhaps opened a new avenue to understand habitability in the cosmos.”

    The scientists investigated galaxies that astronomers have observed using the Apache Point Observatory in New Mexico as part of the Sloan Digital Sky Survey.

    SDSS Telescope
    SDSS telescope at Apache Point, NM, USA

    About 1,800 of these 140,000 galaxies are comparable to the Milky Way in terms of total mass in stars and ongoing star-formation rates, Mazumdar said. (The Milky Way weighs as much as about 60 billion suns, and gives birth to about three suns per year, the researchers noted.)

    They found that the most habitable kind of galaxy was the metal-rich type at least twice as massive as the Milky Way with less than a tenth of its star-formation rate. In fact, the researchers said this type of galaxy can host 10,000 times as many Earth-like planets as the Milky Way. Such galaxies could also host 1 million times more gas giants, which can, in turn, host potentially habitable moons, the researchers added.

    “The most important implication of our analysis is that our cosmos is actually full of life,” Mazumdar said.

    However, don’t expect astronauts to visit such galaxies anytime soon. The nearest such galaxy is Maffei 1, discovered in 1968, which lies more than 9.5 million light-years from Earth.

    3
    Maffei 1

    About 200 ofthe 140,000 galaxies analyzed were the potentially life-rich kind the scientists defined. Such galaxies are relatively shapeless. “Perhaps they are not eye-catching, looking at their pictures, but they are key to understanding extragalactic life in our universe,” Mazumdar said.

    In the future, computer simulations of these galaxies could investigate where their habitable planets are located, Mazumdar said. He and his colleagues detailed their findings in a paper accepted for publication in Astrophysical Journal Letters.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
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