3203 - SUPERNOVAE - new supernova discovery?

  -  3203  -  SUPERNOVAE  -  new supernova discovery?  Astronomers may have finally discovered convincing evidence of an elusive kind of supernova, one that could explain a bright explosion that lit up the night sky on Earth nearly 1,000 years ago and birthed the beautiful Crab Nebula.  

-- -------------------  3203  -   SUPERNOVAE  -  new supernova discovery?  

-  Supernovas are giant explosions that can occur when stars die. These outbursts can briefly outshine all of the other suns in these stars' galaxies, making them visible from halfway across the universe.

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-   Supernovae happen when massive stars’ gravity collects so much mass and gravity gets so strong that the atom’s electrons collapse into the protons creating neutrons.  The collapse is so violent that the collapse rebounds off the core into a giant supernova explosion.  

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-  For decades, scientists have known of two main supernova types. Large stars more than 10 times the mass of the sun collapse in their centers when their cores burn all their fuel, causing the outer layers to explode and leaving behind a neutron star or black hole.

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-   In contrast, stars less than 8 times the sun's mass burn out over time to leave a dense core of ash known as a white dwarf, and these remnants can pull fuel onto themselves off companion stars until they detonate in a thermonuclear explosion.

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-  This is a different kind of supernova.  These stars, around 8-10 solar masses, can explode in so-called “electron-capture supernovas“.  Stars between 8 and 10 solar masses should theoretically explode in a different way. 

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-  Electron-capture Supernova have gigantic internal pressures that would force electrons to fuse with atomic nuclei. These electrons normally repel each other, so their removal leads to a drop in pressure inside the star. The star's core then collapses, setting off an explosion of the surrounding layers and leaving behind a neutron star slightly more massive than the sun.

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-  Over decades, scientists developed predictions of what to look for in an electron-capture supernova and its progenitor star, but they had never actually confirmed a star detonating in this manner.

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- There is a thousand-year old mystery, a supernova in 1054 AD that, according to Chinese and Japanese records, was so bright it could be seen during the daytime for 23 days, and at night for nearly two years. 

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-  Its remnants became the “Crab Nebula“.   SN 1054 was an electron-capture supernova. 

SN 1054 was such a spectacular event that people recorded it around the world and preserved the records for 1,000 years.

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-  Now this exploding star first detected in 2018 may be the first strong example of an electron-capture supernova.  This is an important milestone in our understanding of stellar evolution and supernova physics.  

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-   Shortly after the supernova was discovered a research scientist at the California Institute of Technology in Pasadena, got a hold of a Hubble Space Telescope picture of the supernova. 

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-  After comparing this photo with archival Hubble Space Telescope images previously taken of that area of the sky, they identified the supernova's progenitor star in the galaxy NGC 2146, about 31 million light years from Earth.

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-  Knowing the identity of SN 2018zd's progenitor star helped the researchers compare the star and the supernova with decades worth of electron-capture supernovas models. 

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-  There are six key criteria for a progenitor star of an electron-capture supernova:

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-----------------  It should possess between eight and 10 solar masses. Candidates include super-asymptotic giant branch stars, that is, old bloated red giants, the widest possible stars.  

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-----------------  It should shed most of its mass before exploding.  This shed material should mostly be in the form of helium, carbon and nitrogen, but contain little oxygen.

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-   This has to do with very complicated fusion reactions during the star's life,  as well as churning in the outer layers of the star, and which elements from deep in the star get dredged up to its surface.  The star has a somewhat layered structure just before it explodes, with lighter elements on top of heavier ones. The heaviest oxygen layer was deeper down.

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-------------------  The explosion should be relatively weak compared with other supernovas.  The kinetic energy of the ejected gases is about one-tenth that of other supernovae.

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-------------------   The supernova should have little radioactive fallout compared to other supernovas. For instance, when it comes to radioactive nickel, the major radioactive element that supernovas produce, electron-capture supernovas produce only about one-tenth as much radioactive nickel as a normal core-collapse supernova, and about one-hundredth as much radioactive nickel as a normal thermonuclear supernova.  The progenitor should possess lots of neutron-rich elements in its core. 

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-  The scientists found SN 2018zd and its progenitor matched the predictions for an electron-capture supernova and its origin star. The progenitor was an old bloated red giant that had shed a significant fraction of its mass before the explosion, and the gas surrounding this star matched the expected composition. The explosion was relatively weak, produced little radioactive nickel, and possessed neutron-rich elements such as nickel within its core.

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-  Electron-capture supernovas generally have long-lasting glows because their progenitor stars typically shed a lot of mass before exploding. The expanding gas from the supernova then collides with this earlier shed mass, lighting it. 

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-   Electron-capture supernovas also fade rapidly after a plateau lasting a few months, because they do not produce much radioactive nickel. So they are brighter than standard core-collapse supernovas at first and then fainter after a few months. 

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-    This is compelling support for the idea that the Crab Nebula was produced by an electron-capture supernova.

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-  Your body mass is 72% material created in a supernova.  Understanding how supernovae cook and spew elements into the universe helps us understand ourselves.

You really came from stars.  So did everything else we know.  But, we don’t know everything. 

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---------------------------------  Other Reviews available:

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-    3186   -   SUPERNOVA  -  is what we are made of?   Always, somewhere in the universe a star is reaching the end of its life.   If it is a massive star it collapsing under its own gravity and becomes a supernovae.  If it is much smaller it collapses into a dense cinder of a star, stealing matter from a companion star until it can’t handle its own mass and it goes supernovae

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-   3160   -  SUPERNOVAE  -   are what we are made of!  Supernovae, stars that explode when they can no longer continue fusion radiation, are rare events.   In the Observable Universe the event happens every second. We are living in and made of star dust and gas.  When you look at the night sky and see those stars say “ that is where I came from”.  

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-  3159   -  SUPERNOVA  -  why do stars explode?   Astronomers have problems explaining how the supernova explosion actually occurs.  A theory is that the explosion happens because of sound waves?  That is what computer simulations are telling astronomers today.  All the math remains to be worked out, but, computer simulations are getting closer to the observations they see in supernova explosions.

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-  3013 -   SUPERNOVA  -  one explosion nearby?   At that same time, there was also an extinction event on Earth, called the “Pliocene marine mega fauna” extinction. Up to a third of the large marine species on Earth were wiped out at the time, most of them living in shallow coastal waters.

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-  2997 -   SUPERNOVA  -  gold forged in exploding stars?  -  Astronomers are winding back the clock on the expanding remains of a nearby, exploded star. By using our Hubble Space Telescope, they retraced the speedy shrapnel from the blast to calculate a more accurate estimate of the location and time of the exploding star.

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- 2650  -  SUPERNOVAE  -  are what we are made of!  -  Supernovae, stars that explode when they can no longer continue fusion radiation, are rare events.  They are likely to happen only once per year in our Milky Way Galaxy.  But, in the Observable Universe the event happens every second.

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-  2649  -  SUPERNOVA  -  the runaway universe?  Nuclear fusion will occur when a star’s central temperature reaches 10,000,000 degrees.  The collisions of the atoms are so rapid at that temperature that all electrons are stripped away from their nucleus.  And, nuclei collide to such an extent as to overcome the repulsive electric force of their mutual positive charges.

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-  2648  -  SUPERNOVA  -  what is the youngest?  A supernova normally goes off in a galaxy every 50 to 100 years.  However, we have not seen one in several hundred years.  It could be that they are going off and they are out of sight.  The last one astronomers had recorded for the Milky Way  is Cassiopeia A. It went supernova 330 years ago, that would be in 1678. 

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-  2646  -  SUPERNOVAE  - how life is being created?  Betelgeuse is still deep in the red supergiant phase of its life. Even though it has dimmed significantly of recent, it isn’t on the verge of exploding. 

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-  2636  -  SUPERNOVA   -  2 explosions being studied?  Astronomers have detected the fallout of the biggest known explosion in the universe since it was born more than 13 billion years ago.  The blast came from a supermassive black hole in the Ophiuchus galaxy cluster, located nearly 400 million light years from Earth.

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-  2149  -  Supernovae from blue super giant stars.  Summarizes 15 more reviews about supernovae.

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-  2299  -  You are made of stardust.   A Supernova is a sun, a star, that explodes because it becomes unstable after it exhaust all of its nuclear fuel.  Our Sun will not become a Supernovae because it is not big enough.  A bigger star will have the gravity necessary to overcome the electromagnetic force between the electron and nucleus of atoms and when its fuel is gone it goes supernova. 

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- 2300  -  Supernovae you can see. If you have read 2299 - “ You Were Made from Star Dust - Supernova”, you are probably anxious to learn more about Supernova.  It turns out that in the last 1000 years at least six, maybe eight supernova explosions have been seen by naked eye observers.  

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-  2345  -  Scientists estimate it takes 100,000,000 to 200,000,000 years for intelligent life to emerge and colonize a planet.  65,000,000 years ago, at the end of the Cretaceous-Tertiary (K-T) period, 50% of life on Earth was extinguished.  The dinosaurs did not survive.  But, some half of marine invertebrates, plankton, marine reptiles did survive.  65,000,000 years later here we are and you are reading about it.

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-  2426  -  LIFE  -  Exploding stars create life , and destroy life. Our galaxy is big and mostly empty space, but it harbors millions of blackholes that are remnants of supernovas and collapsing stars.  When a giant star burns all it’s fuel, no heat remains to create the pressure withstanding the compression of gravity.  The force of gravity collapses the stars mass into a singularity at the center of a blackhole.   These creators of life are every where.  

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-  June 28, 2021      SUPERNOVAE  -  new supernova discovery?          3203                                                                                                                                                     

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-----  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”  -----------

--------------------- ---  Wednesday, June 30, 2021  ---------------------------

3202 - GALAXIES - with and without Dark Matter?

  -  3202  -  GALAXIES  -  with and without Dark Matter?   Dark matter is invisible and its nature is unknown, but its existence is inferred from galaxies behaving as if they were shrouded in significantly more mass than we can see. There is thought to be about five times as much dark matter in the Universe as ordinary, visible matter.  This is assuming that the laws of gravity are the same everywhere.

---------------------  3202  -  GALAXIES  -  with and without Dark Matter?    

-  14 June 2021.  The spin of the Milky Way’s galactic bar, which is made up of billions of clustered stars, has slowed by about 25% since its formation.  What causes that?

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-  For 30 years, astrophysicists have predicted such a slowdown, but this is the first time it has been measured.  Dark Matter acts like a counterweight slowing the galaxy spin.

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-  The “Gaia Space Telescope” was used to observe a large group of stars, the Hercules Stream, which are in resonance with the bar, revolving around the galaxy at the same rate as the bar’s spin.

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-  These Hercules Stream stars are gravitationally trapped by the spinning bar. The same phenomenon occurs with Jupiter's Trojan and Greek asteroids, which orbit Jupiter's Lagrange points ahead and behind Jupiter. 

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-  If the bar’s spin slows down, these stars would be expected to move further out in the galaxy, keeping their orbital period matched to that of the bar’s spin.

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-  The stars in the stream carry a chemical fingerprint, richer in heavier elements, proving that they have traveled away from the galactic center, where stars and star-forming gas are about 10 times as rich in metals compared to the outer galaxy.

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-  Using this data, they calculated that the bar, made up of billions of stars and trillions of solar masses, had slowed down its spin by at least 24% since it first formed.

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-  The counterweight slowing this spin must be “dark matter”.  Astronomers have only been able to infer dark matter by mapping the gravitational potential of galaxies and subtracting the contribution from visible matter.  This new measurement of dark matter was not of its gravitational energy, but of its inertial mass, which slows the bar’s spin.

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-  The Milky Way, like other galaxies, is thought to be embedded in a ‘halo’ of dark matter that extends well beyond its visible edge.

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-    The Milky Way is a barred spiral galaxy, with a thick bar of stars in the middle and spiral arms extending through the disc outside the bar. The bar rotates in the same direction as the galaxy.

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-  ‘Supermassive blackholes” are blackholes with masses that are several million to billion times the mass of our sun. The Milky Way hosts a blackhole that is much smaller with mass 4 million times the solar mass. 

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-  Billion solar mass blackholes are found when the universe was just 6% of its current age which 6% of 13.7 billion years. 

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-  A “Dark Matter Halo” is the halo of invisible matter surrounding a galaxy or a cluster of galaxies. Although dark matter has never been detected in laboratories, physicists remain confident this mysterious matter that makes up 85% of the universe’s matter exists. Were the visible matter of a galaxy not embedded in a dark matter halo, this matter would fly apart. 

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-    A “seed blackhole” is a blackhole at its initial stage.  The seed blackhole is either much more massive or it grows much faster than we thought, or both. The question that then arises is what are the physical mechanisms for producing a massive enough seed blackhole or achieving a fast enough growth rate?”

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-  It takes time for blackholes to grow massive by accreting surrounding matter.  If dark matter has self-interactions then the “gravothermal” collapse of a halo can lead to a massive enough seed blackhole. 

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-  A mechanism used to explain blackholes is the collapse of pristine gas in protogalaxies in the early universe.   This mechanism, however, cannot produce a massive enough seed blackhole to accommodate newly observed Supermassie Blackholes,  unless the seed blackhole experienced an extremely fast growth rate.

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-  An alternative explanation is a self-interacting dark matter halo that experiences gravothermal instability and its central region collapses into a seed blackhole. 

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-  Dark matter particles first cluster together under the influence of gravity and form a dark matter halo. During the evolution of the halo there are two competing forces, gravity and pressure.

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-   While gravity pulls dark matter particles inward, pressure pushes them outward. If dark matter particles have no self-interactions, then, as gravity pulls them toward the central halo, they become hotter, that is, they move faster, the pressure increases effectively, and they bounce back.

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-   In the case of self-interacting dark matter, dark matter self-interactions can transport the heat from those “hotter” particles to nearby colder ones. This makes it difficult for the dark matter particles to bounce back. 

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-  The central halo, which would collapse into a blackhole, has angular momentum with its rotation. The self-interactions can induce viscosity, or “friction,” that dissipates this angular momentum. During the collapse process, the central halo, which has a fixed mass, shrinks in radius and slows down in rotation due to its viscosity. 

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-  The central halo eventually collapses into a singular state or a seed blackhole. This seed can grow more massive by accreting surrounding baryonic, visible matter, such as gas and stars. 

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-  The mass of the seed blackhole can be high since it is produced by the collapse of a dark matter halo.  It can grow into a supermassive blackhole in a relatively short timescale

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-  The presence of baryons, such as gas and stars, can significantly speed up the onset of this gravothermal collapse of a halo.  The self-interactions can induce viscosity that dissipates the angular momentum remnant of the central halo. General relativistic instability of the collapsed halo ensures a seed blackhole could form. 

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-  Self-interacting dark matter can provide a good explanation for the observed motion of stars and gas in galaxies.  Stars and gas dominate their central regions.    The presence of this baryonic matter affects the collapse process by speeding up the onset of the collapse. The self-interactions also lead to viscosity that can dissipate angular momentum of the central halo and further help the collapse process.

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-  Once we think all galaxies have central blackholes  and are surrounded by dark matter we find a “see through” galaxy with no evidence of dark matter? 

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-  The galaxy is a giant cosmic cotton ball  so diffuse with ancient stars so spread out that distant galaxies in the background can be seen through it. Called an “ultra-diffuse galaxy“, this galactic oddball is almost as wide as the Milky Way, but it contains only 1/200th the number of stars as our galaxy. 

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-  The ghostly galaxy doesn't appear to have a noticeable central region, spiral arms, or a disk. Researchers calculated a more accurate distance to the galaxy using Hubble telescope to observe about 5,400 aging red giant stars.

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-   Red giant stars all reach the same peak brightness, so they are reliable yardsticks to measure distances to galaxies. The research team estimates that this galaxy is 72 million light-years from Earth. 

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-  This galaxy lacks dark matter, the invisible glue that makes up the bulk of the universe's contents. The galaxy contains at most 1/400th the amount of dark matter that the astronomers had expected.

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-    Dark matter is thought to be the invisible glue that makes up the bulk of the universe's matter. All galaxies appear to be dominated by it; in fact, galaxies are thought to form inside immense halos of dark matter.

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-  Determining the amount of the galaxy's dark matter hinges on accurate measurements of how far away it is from Earth.   If this galaxy is as far from Earth as these measurements then galaxy's dark-matter content may only be a few percent. 

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-  This measurement is based on the motions of the stars within the galaxy and how their velocities are influenced by the pull of gravity. The researchers found that the observed number of stars accounts for the galaxy's total mass, and there's not room left for dark matter.

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-   The research team targeted aging red giant stars on the outskirts of the galaxy that all reach the same peak brightness in their evolution. Astronomers can use the stars' intrinsic brightness to calculate their vast intergalactic distances. 

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-  For almost every other galaxy we look at, we say that we can't see most of the mass because it's dark matter.  This stealthy Galaxy is a giant cosmic cotton ball  where the stars are spread out. The galactic oddball is almost as wide as the Milky Way, but it contains only 1/200th the number of stars as our galaxy.

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-  The researchers are hunting for more of these oddball galaxies.  In 2020, a group of researchers uncovered 19 unusual dwarf galaxies they say are deficient in dark matter.  However, it will take uncovering many more dark matter-less galaxies to resolve this mystery.

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-  Finding a galaxy lacking dark matter tells astronomers something about the invisible substance.  If you have a galaxy without dark matter, and other similar galaxies seem to have it, that means that dark matter is actually real and it exists.   "It's not a mirage."

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-    3146   -   GALAXIES  - millions more discovered ?   In the universe, galaxies are distributed along extremely tenuous filaments of gas millions of light years long separated by voids, forming the cosmic web. Astronomers have captured an image of several filaments in the early universe, revealing the unexpected presence of billions of dwarf galaxies in the filaments.

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 -  3100  - GALAXIES  -  Don’t  Follow the Laws of Gravity?    Astronomers do not have a good idea of what Dark Matter really is.  It is something that has mass and is an attractive force for gravity.  But, it does not interact with the electromagnetic forces.  It does not absorb or emit light or any other part of the electromagnetic spectrum.

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-  3018 -  GALAXIES  -  the most distant galaxies?    Most of the galaxies in the Universe are “ over the horizon” and beyond what we can see.  Astronomers estimate that 98.4% of the galaxies in the Universe lie in the zone that we can never observe. (Unless we find something we can detect traveling faster that the speed of light.)

-  June 29, 2021    GALAXIES  -  with and without Dark Matter?           3200                                                                                                                                                       

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-----  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, June 29, 2021  ---------------------------

3201 - EARTH’S - core and how life began?

  -  3201   -  EARTH’S -  core and how life began?   We may never know exactly what led to the appearance of life on Earth. But we can at least build a trail of evidence that leads to the necessities for it to appear.  The creation of some of the chemicals necessary for life might be more common than originally thought.

-- ---------------------------  3201  -   EARTH’S -  core and how life began? 

-  Despite being quite close to us, the Earth’s core is still a mysterious place. We can divide it into the inner core and the outer core. We also know it’s mostly composed of iron, and it’s responsible for the magnetic field of our planet. 

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-  The Earth’s structure is quite similar to an onion. It is made of at least four layers. Each layer has a different structure and plays a different role in the Earth’s geology. Two of the layers of Earth create the core.

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-  The outer core lies about 3,000 kilometers from the surface, and it is the only liquid layer of the Earth. That is because it’s not under enough pressure to be solid. It is made mostly of iron, nickel, with sulfur and oxygen. 

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-  The temperature inside is extremely high- up to 6,000°C (10,832 °F). Due to the convection of fluid ferromagnetic substances, the Earth creates a magnetic field. This, in turn, leads to a stable atmosphere and conditions for life.

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-  The innermost layers of the Earth comprise the inner core. It is probably a solid sphere with about a 1,200 kilometers radius (70% of the Moon’s radius), and it is as hot as the surface of the Sun (about 5,600°C). 

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-  Quite like the outer layer, it is made of iron and nickel.   The inner core has two layers. 

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-  The data collected in 2015 showed that the crystals in the inner layer are in an east-to-west direction.   Those in the outer line up north to south. This implies a phenomenon that flipped the core’s orientation, turning the crystals in the ‘outer’ inner core.

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-  In our planet’s core the moving iron and nickel create a magnetic field. That magnetic field protects the layer from the solar wind and UV radiation. Therefore, it protects life on our planet from harmful particles.

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-   The core’s radiating heat keeps the Earth’s surface warm. Sometimes people use that geothermal energy to warm their houses.  This is done in Iceland.

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-   Earth’s layers are just a few kilometers down from us, but , we know more about the Moon than our own planet’s interior. 

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-  The deepest human-made core, the Kola Superdeep Borehole, reaches only 12.2 kilometers into our planet. That’s not even halfway through the lithosphere which is the outermost layer!

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-  All studies of the Earth’s inner and outer core come from seismic data. Another unknown is the periodic reversals of the Earth’s magnetic field. 

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-   Even though scientists estimated the temperatures,  there is no way to go directly down to the core because of both the temperature and the pressure.

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-  In the 1940s, scientists  calculated the original balance of minerals on Earth and concluded that the missing iron and nickel must be in the core.

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-   However, only 10 years later, the gravity measurements proved them wrong. The core must be heavier and denser than originally thought, though we don’t know which elements occur inside.

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-  The asteroid “Psyche” might be a naked iron core floating in space. The “2022 Psyche Mission” may give us some answers on the structure of the Earth’s core. Moreover, it will help us compare other solid planets’ iron cores and show their most common properties.

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-  After knowing what the Earth is made of there is an even greater question: How did life begin on Earth?    Did the heat from asteroid impacts help life get started?

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-  The focus is on asteroids impacting Earth and delivering water and chemicals.  It is possible that the heat from those impacts generated water and life-origin chemicals on the asteroid’s surface, then delivered them to Earth.

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-  An earlier Earth would not have liquid water on its surface because it would hsve boile away.  

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-  A laboratory asteroid proxy was made of porous gypsum. They placed thermocouples inside this asteroid moel to measure heat. Then they created high-velocity impacts by accelerating projectiles with a gas gun. 

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-   “Aqueous alteration”  is when minerals in rock change because of chemical reactions with water. Those reactions can create organic solids.

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-   But for those reactions to take place, there must be heat to melt the asteroid’s ice. In larger bodies, scientists think that the decay of Aluminum 26, a radioactive isotope, can provide this needed heat for aqueous alteration. 

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-  But that only occurs in larger asteroids of about 10 kilometers in diameter and may only have occurred in the Solar System’s first 10 million years or so before all of the Al 26 had decayed. 

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-  Could aqueous alteration have occurred due to impacts on smaller asteroids much later into the Solar System’s life?

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-  The scientists monitored the temperature created by the impacts as they raised the velocity of their projectiles. They wanted to know not only how much heat was generated but how long that heat would persist. Could asteroid impacts create enough heat to create life-origin chemicals without destroying the asteroids themselves? 

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-  How widespread are these conditions in the Solar System, and could these chemicals still be generated in older Solar Systems like ours?

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-   In the main asteroid belt the relative velocity among asteroids is about 4 to 5 kilometers / second. The shock of these collisions would have immediately raised the temperature around the resulting crater. Collisions like these were common in our Solar System’s youth, long after all of the Al 26 had decayed. 

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-  The heat from these impacts would have been most pronounced on more porous asteroid bodies.  The researchers used different types of projectiles traveling at different velocities to develop a model of impact heating. 

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-   The researchers found that the potential for asteroid impacts to create chemicals necessary for life is more widespread than previously thought. It’s more widespread both spatially and temporally, and the necessary heat can be created from impacts that create craters as small as 100 meters in diameter.

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-   These results increase the number of astronomical bodies that could have delivered water and organic substances for the origin of life on Earth.

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-  Another interesting result of their work involves organic solids that originated in the nebular cloud at the very beginning of our Solar System’s formation. This research showed that the heat from impacts may be like a double-edged sword. Not only can that heat forge new organic materials, but it can destroy the same type of materials present on asteroids and asteroid parent bodies since the early days.-----  See other reviews:

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-  3105 --  EARTH  -  finely tuned for life?    How did it get that way?  Are we here as a result of random collusions and mutations?  We only know life that is us.  That is a sample size of one. Regardless,  Earth's history demonstrates that life can take root and evolve.  Here is what we have  learned.

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-  3068  -  EARTH  -  magnetic field flips N. to S.?  -  The end of the world as we know it could come in any number of ways. Some believe global cataclysm will occur when Earth's magnetic poles reverse. When north goes south, the continents will lurch in one direction or the other, triggering massive earthquakes, rapid climate change and species extinctions.  We are a species too.

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-  3055  -   EARTH  -  magnetic pole shift.   The temporary breakdown of Earth's magnetic field 42,000 years ago sparked major climate shifts that led to global environmental change and mass extinctions.  The Earth suffered electrical storms, widespread auroras, and cosmic radiation, all triggered by the reversal of Earth's magnetic poles.

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-  3040  -   EARTH  -  evolution of the Solar System?  - To carry our lineage back further this review is about the geological history of our Solar System.  We do not have many rocks to work with, a few meteorites, so the history lesson takes more imagination.  By studying the rocks, gas , and stars within 6,500 lightyears of Earth with detailed observations.

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-  2970 - EARTH  -  unusual places?   Our Earth is a dynamic planet, and there is much about its history and ongoing processes  on land, in the oceans and deep under the surface that scientists are still discovering.  Here are several examples that should interest you:

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-  2927  -  EARTH  -  Revolutions and orbits are how we tell time.   We not only know that Earth’s orbit slightly changes over time, but we can quantify and confidently state exactly what those changes will be. What does this mean for the speed of Earth around the Sun?  Are years getting longer or shorter?

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-  2903 - PREHISTORIC  EARTH  -  how did life get started?    Four billion years ago, Earth was covered in a watery sludge swarming with primordial molecules, gases, and minerals, nothing that biologists would recognize as alive. Out of that prebiotic stew emerged the first critical building blocks, proteins, sugars, amino acids, cell walls,  that would combine over the next billion years to form the first specks of life on the planet.

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-    2875   -  EARTH   -   climate change got us here?  A coupled increase in atmospheric CO2 and decrease in surface ocean pH, global warming, changes in productivity and oxygen depletion have been reported worldwide, which suggests that the scenario outlined here may be relevant to understanding future environmental and climatic trends.

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-  2869  -  EARTH  -  waster, water everywhere?   There remains a number of mysteries on our planet including the elusive origin of  the blue water on the Earth.  Scientists have found the interstellar organic matter could produce an abundant supply of water by heating, suggesting that “organic matter” could be the source of terrestrial water.

-

-   2486  -  EARTH  -  Third Rock from the Sun.  The Sun’s energy itself is changing in its light energy.  It has several cycles of its own , “Could Our Sun Be a Variable Star?”  .  Today we are considered to be in a normal warming trend.  Global warming is claimed to be exacerbating this warming trend with human burning of fossil fuels and putting greenhouse gases into the atmosphere.

-

-  June 27, 2021      EARTH’S -  core and how life began?                 3201                                                                                                                                                      

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

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

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

--------------------- ---  Sunday, June 27, 2021  ---------------------------

3200 - DARK ENERGY - latest survey results?

  -  3200  -  DARK  ENERGY  -  latest survey results?  Survey results from the DES fit well with the predicted model that is used to map the universe from the beginning of time.  In fact, it contradicts previous claims that there was a few percentage difference between the observed universe and the predicted one.   

- ---------------------------  3200  -   DARK  ENERGY  -  latest survey results?

-  DES is the largest cosmological survey ever released.   The Dark Energy Survey (DES)  took place over 6 years from 2013 to 2019, and looked at over 1/8th of the night sky for a total of 758 nights. 

-

-   Results released on May 27, 2021,  contain analysis of the data from the first half of that observational period, having already released results from the first year back in 2017.

-

-  The survey was reviewed by 400 individual scientists from 25 institutions in 7 countries after observations of over 226 million galaxies.  Observations were done with the Victor M “Blanco telescope” at Cerro Tololo Inter-American Observatory in Chile. 

-

-   Measuring 4 meters in width, the Blanco telescope has a resolution of 570 mega pixels,  almost 50 times as much as a standard iPhone camera.

-

-  The goal of the survey was to “quantify the distribution of ‘dark matter’ and the effect of “dark energy”.   These two hardly understood cosmic features make up 95% of all the known “stuff” in the universe.  

-

-  Despite their 95% prevalence, they are very hard to detect, hence the name “dark”.  However, DES provides more insight that ever before into some characteristics  of these little understood phenomena.  In particular, two cosmological features were central to the survey’s efforts.  The first was the “cosmic web”, while the second were “weak gravitational lenses“.

-

-  The “cosmic web” is what cosmologists use to describe the structure of galaxies.  These massive clusters of gravitationally bound stars aren’t randomly distributed.  They form a pattern, with clumps of galaxies banding together to form “galaxy clusters“. 

-

-  Cosmologists normally attribute those clumped up areas to the presence of higher densities of dark matter and, therefore, gravity.  Mapping where they occur in space provides insight into what areas of the galaxy might feature high concentrations of dark matter to study. 

-

-   Results from universe growth models can then be compared to the cosmic web as a way to check their accuracy in predicting how the universe actually turned out.

-

-  Clustering isn’t the only way to detect dark matter though.  Gravitational lensing effect happens when light is bent around areas of high gravity, which pockets of dark matter certainly are. Strong gravitational lensing, such as that around blackholes, is a common enough feature of cosmology, producing features such as “Einstein rings“.

-

-  “Weak gravitational lensing’ doesn’t have quite as much visual impact but it does provide more insight into that important map of dark matter and dark energy.  

-

-  “Redshifting” is a feature of astronomical observations where things that are far away and getting further away appear to have the light they emit shifted to the red side of the light spectrum.  

-

-   A novel calibration technique ws used on 10 different regions of the sky to perform “deep field” searches  to see galaxies that were even farther away than their normal observational area.  They then used the redshift values calculated in these deep fields to calibrate redshift values in the rest of the surveyed sky.

-

-  Even having removed the redshift, more data is always more useful in understanding cosmological phenomena.  The DES team also analyzed a number of other phenomena, which included baryonic acoustic oscillations, frequency measurements for massive galaxy clusters, and calculations of some of the features of Type Ia supernovae captured in the survey.

-

-  They still have only analyzed half the data, so the other half is expected to add even more detail to the picture of dark energy and dark matter.  In addition, new surveys using new instruments, such as the “Vera Rubin Observatory“, are already planned.   There’s always more cosmological data to be collected.  We still have more to learn.

-

-   3116  -  DARK  ENERGY  -  a mystery for science?  Dark energy is one of the greatest mysteries in science today. We know very little about it, other than it is invisible, yet it fills the whole universe, and it pushes galaxies away from each other. The result of this force is that it is making our cosmos expand at an accelerated rate.  

-

-  3095  -   DARK  ENERGY  -   into WIMPs and MACHOs?   The more we learn the more we know the less we know.   That is certaintly true with astronomy.   We have come to the most recent conclusion that 95% of the Universe is “dark”.  We call it Dark Energy and Dark Matter.  Of course Matter is Energy too, according to energy = mass*c^2 .

-

-  3086  -  DARK ENERGY -  What is the Universe Made of?  Dark Energy was not known until 1998 so we  have only 30 years to think about it.  The most likely answer is vacuum energy.  A vacuum is not really a vacuum but a see of virtual particles and anti-particles going into and out of existence in such a short time they do not defy the laws of physics and cannot be detected using the laws of physics.  

-  June 25, 2021        DARK  ENERGY  -  latest survey results?        3200                                                                                                                                                       

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

-----  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”  -----------

--------------------- ---  Friday, June 25, 2021  ---------------------------

UNIVERSE - mass and energy ratios.

  -  3199  -   UNIVERSE  -  mass and energy ratios.  How do we know the ratios.   With the latest observations and experiments, it’s clear that time has passed. The Universe has only 4.7-5.0% normal matter in it, and the rest, in some form or other, is truly dark matter and dark energy.

All that we see is only 5%bof what is there??

-

-------------------------  3199  -   UNIVERSE  -  mass and energy ratios.    

-  The Universe is made up of only 5% normal matter that we see and understand.  All matter and energy are two forms of the same thing according to E = mc^2.   “c^2” is constant and the it is the constant speed of light squared, that is , times itself.   Therefore “E” =  a constant times “m”   Dark Matter is 20% of the Universe and Dark Energy is 70% of the Universe.  How did we every come up with these numbers?  It all started 100 years ago.

-

-  100 years ago, we began to understand the true nature of the Universe for the very first time. The grand spirals and elliptical galaxies in the sky were determined to be enormous, distant collections of stars well outside of the Milky Way.  They were a variety of galaxies some very similar to our own.  Some very different configuration of stars.  But all moving away from us in an expanding universe.  

-

- These distant galaxies were receding away with more distant galaxies exhibiting faster recession speeds.  This was evidence that the Universe was expanding at an ever increasing rate. 

-

-   If space is expanding today, that means the Universe was smaller, denser, and even hotter in the past. Extrapolate back far enough, and you’ll predict that the Universe began a finite amount of time ago in an event known as the hot “Big Bang“.

-

-  If the Universe was hotter and denser in the past, but cooled, that means there was once a time where neutral atoms couldn’t form, because things were too hot, but then did as the Universe cooled. 

-

-  That expanding cooling condition leads to a prediction of a now cold, but mostly uniform background of radiation which was discovered in the 1960s, validating the picture of the hot Big Bang and ruling out many alternatives. 

-

-  There is an entirely independent way to validate this hot Big Bang theory using the nuclear reactions that must have occurred when the Universe was just minutes old. These predictions are imprinted in the hydrogen gas throughout our Universe, and help us understand the Big Bang from a totally different theory.

-

-  If we were to go back to the very early stages of the hot Big Bang, to when the Universe was just a fraction-of-a-second old, we wouldd see a very different Universe from the one we recognize today. 

-

-  There were lots of free protons and neutrons, at temperatures and densities greater than we find in the Sun’s core.   There were no heavier nuclei, as the photons that were around at the time were so energetic that they would immediately blast a heavier nucleus apart. In order to stably form them, we would have to wait for the Universe to expand and cool. 

-

-   As time went on  electrons and positrons, the lightest charged particles, annihilated away, leaving only enough electrons to balance out the protons (and their positive and negative electric charges) in the Universe.

-

-  Neutrinos stopped interacting with protons and neutrons, causing them to “free stream,” or travel without colliding with other particles.  A fraction of the remnant free neutrons, with a half-life of around 10 minutes, decayed into protons, electrons, and anti-electron neutrinos.

-

-  Only after 3-4 minutes, has the Universe cooled down  enough to successfully take the first step in forming heavy elements: fusing a proton and a neutron into deuterium, the first heavy isotope of hydrogen.

-

-  By the time that 3-to-4 minutes have passed since the hot Big Bang, the Universe is a lot cooler and less dense than it once was. Temperatures are still high enough to initiate nuclear fusion, but the density, due to the expansion of the Universe is only about 0.0000001% of what it is in today’s Sun’s center.

-

-   As a result, most of the neutrons that still remain wind up combining with protons to form helium-4, with a small amount of helium-3, deuterium, tritium (which decays to helium-3), and isotopes of lithium and beryllium (which eventually decay to lithium) also remaining.

-

-  Given the Standard Model of particle physics, and how nuclear processes are known to work, there should be a particular ratio of the light elements that survive today dependent only on the ratio of baryons (protons and neutrons combined) to photons.

-

-   Even completely independent of the radiation from the Cosmic Microwave Background, measuring the relative abundances of the light elements will tell us what the total amount of “normal matter” present in the Universe must be. We can see that measuring deuterium’s abundance will reveal to us the baryon-to-photon ratio of the Universe.

-

-  The problem is that these are predictions for what the Universe was born with, but that’s not the Universe we see today. By the time we get to the stars and galaxies we can observe, the normal matter that exists has gone through processing: stars have formed, lived, burned through their nuclear fuel, transmuted light elements into heavy ones, and have recycled those processed elements back into the interstellar medium. 

-

-  When we look at stars today, they don’t exhibit these predicted ratios, but significantly altered ones. In addition to these light elements, there are also heavy ones showing up in all of the heavier elements, like oxygen, carbon, and iron, etc.

-

-  In a Universe without pristine stars, how could you possibly try and reconstruct how much deuterium was present immediately following the Big Bang?  

-

-  One method is to measure the ratios of elements in a variety of stellar populations. If you measure the oxygen-to-hydrogen , or iron-to-hydrogen ratios, and also measure the deuterium-to-hydrogen ratio, you could graph them together, and use that information to extrapolate backwards to a zero oxygen or iron abundance. 

-

-  This will give an estimate for how much deuterium would be present at a time before heavy elements, like oxygen or iron, had formed.

-

-    Clouds of gas can absorb light, imprinting their unique signature onto it. The brightest, most luminous light sources from the distant universe are “quasars“, supermassive blackholes that are actively feeding in galaxies at great distances. 

-

-  Everywhere there’s an intervening cloud of gas, a portion of that quasar light gets absorbed, as whatever atoms, molecules, or ions that are present will absorb that light at those explicit quantum frequencies particular to whatever particles are present at whatever “redshift” distance they are located at.  

-

-  You would think that deuterium, being an isotope of hydrogen, would be indistinguishable from hydrogen itself. But when it comes to the frequencies that atoms emit or absorb light at, they’re determined by the energy levels of the electrons in that atom, which depend on not just the charge of the atomic nucleus, but on the ratio of the electron mass to the mass of the nucleus itself. 

-

-  With an extra neutron in its nucleus, the deuterium absorption line overlaps with, but its peak is off-center from, the peak of the normal hydrogen.

-

-  By looking at the best quasar data we have in the Universe, and finding the closest-to-unpolluted molecular clouds that exist along their lines-of-sight, we can reconstruct the primordial deuterium abundance to extreme precision. 

-

-  The latest results tell us that the amount of deuterium in the Universe, by mass, was 0.00253% of the initial hydrogen abundance, with an uncertainty of only ±0.00004%.

-

-  This corresponds to a Universe that’s made up of about “4.9% normal matter” which is  consistent within 1% of what the Cosmic Microwave Background reveals, but completely independent of that result. 

-

-   In 2020, at an underground laboratory in Italy, a plasma physics experiment at the Laboratory for Underground Nuclear Astrophysics (LUNA),  recreated the high temperatures and densities that were present during the hot Big Bang, and went to observe the reactions between deuterium and protons directly. 

-

-  It took three years to measure enough different conditions to high-enough precisions to recreate the necessary temperature ranges until they had the best measurement of this particular reaction rate ever with an uncertainty of just 1.6%.

-

-  The results confirmed our expectations. Although the uncertainties were larger, previously, the central value determined the Universe really is made of about 5% normal matter, and no more than that.

-

-  This is a conclusion whose importance cannot be overstated. There’s an awful lot we don’t understand about our Universe today, including why we live in a Universe where so much of what exists lies beyond the reach of our observation. 

-

-  There are a lot of reasons to be skeptical of dark matter and dark energy because  they are tremendously counterintuitive. Just because the Cosmic Microwave Background tells us they must be there doesn’t mean they necessarily exist. 

-

-   The science of Big Bang “Nucleosynthesis” is one of those incredibly important cross-checks. It’s an independent test not only of the Big Bang model of the early Universe, but of our concordance cosmological model.

-

-   It tells us, all on its own, what the total amount of normal matter in the Universe is. Since the other lines of evidence, like colliding galaxy clusters or the large-scale structure of the Universe, require far more matter than the early deuterium tells us can exist, we can be much more confident that dark matter is real.

-

-  When it comes to the Universe, simply starting from the known laws of physics and extrapolating back from our direct observations can get us extremely far. Start with redshifts and distances of galaxies, and General Relativity will give the expanding Universe. Start with the expanding Universe, and the Cosmic Microwave Background can give you the Big Bang. 

-

-  Start with the Big Bang, and the nuclear physics of the light elements will give the total amount of “normal matter” in the Universe. And take the normal matter and our astrophysical observations of how galaxies cluster and merge, and we get a Universe requiring dark matter.

-

-  If we confidently want to know what the Universe is made of, we have to ensure we test it in every way plausible. Although it was one of the earliest predictions to arise from the hot Big Bang scenario, the nucleosynthesis of the light elements is an independent method. 

-

- With the latest observations and experiments, it’s clear that time has passed. The Universe has only 4.7-5.0% normal matter in it, and the rest, in some form or other, is truly dark matter and dark energy.  We have a lot more to learn.

-

-  June 24, 2021        UNIVERSE  -  mass and energy ratios.              3199                                                                                                                                                       

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

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

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

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

--------------------- ---  Thursday, June 24, 2021  ---------------------------

3198 - UNIVERSE - how immense is it?

  -  3198  -  UNIVERSE  -  how immense is it?   Shortly after the Big Bang, the Universe was a relatively small, nearly infinitely dense place. It boggles the mind. That was 13,800,000,000 years ago. The expanding universe means the entirety of what we know is now incredibly large and is getting more immense every day. 

- ---------------------------  3198  -    UNIVERSE  -  how immense is it? 

-  Where does the energy come from to fuel this expansion?  The universe today is an immensely large place. Even distances between the nearest objects are staggering, and the distances across the Milky Way Galaxy and certainly between galaxies in the universe are astonishingly huge to us living beings stuck on a planet.

-

-   A model of the Milky Way wherein the Sun is a grain of sand , stars, I.e. sand grains, are 4 miles apart in the Milky Way’s disk and the disk is about 40,000 miles  across. 

-

-    The Big Bang theory tells us that once the universe was very small. We know the fastest that radiation or any information can travel is the speed of light, 186,000 miles per second . 

-

-  We are confident that the universe is 13.8 billion years old. We also know that a light-year is equal to approximately 6 trillion miles.  In nearly 14 billion years we might expect radiation to expand radially outward to something like 30 billion light-years across. 

-

-   The Big Bang was not like an explosion.  Following the Big Bang, space-time itself expanded radially outward at all points, meaning all of space expanded too, not just the stuff within it.

-

-  As the expansion of the universe began, just 1 centimeter of “empty space” interstitially became 2 centimeters over time, and so on. So the best ideas about the size of the universe allowing for its expansion over time point to a radius of slightly more than 46 billion light-years and therefore a “diameter” for the universe of approximately 93 billion lightyears. 

-

-  This 93 billion lightyear diameter refers to the visible universe we can see from Earth. “Inflation theory“ suggests the portion of the universe we can see is not the entire universe. 

-

-  The seeds of measuring the universe stretch back in time all the way to the Greek astronomer Aristarchus of Samos , 310–230 b.c., who had correct notions of parallax in mind with regard to distances of the Sun and Moon. 

-

-  “Parallax” is the technique of measuring the offset of nearer bodies to the distant background of stars and geometrically calculating a distance. 

-

-  Little progress took place after Aristarchus until Polish astronomer Nicolas Copernicus (1473–1543) proposed the heliocentric model of the cosmos, and it was one of the last great visual astronomers, Danish nobleman Tycho Brahe (1546–1601), who made the first parallax measurements of comets and helped define a more modern distance scale to nearby objects. 

-

-   Imagine a scale solar system with the Sun on one end and 1 centimeter representing the distance between our star and Earth, called an astronomical unit (AU). That is, 1 AU = 1 centimeter.

-

-  With the Sun at one end, Earth is 1 centimeter away, and Mercury and Venus are in there too at 0.4 centimeter and 0.7 centimeter, respectively. Outward from Earth, we have Mars at 1.5 centimeters, the main-belt asteroids centered around 2.5 centimeters, Jupiter at 5 centimeters, Saturn at 9.5 centimeters, Uranus at 19 centimeters, and Neptune at 30 centimeters. Pluto can be placed at 40 centimeters.

-

-  The outer solar system is sparse, consisting of the Kuiper Belt region from 30 to 50 centimeters from the Sun, and you can even indicate some of the more interesting objects in the area to keep Pluto company, Haumea at 40 centimeters, Makemake at 45 centimeters, and Eris at 60 centimeters.

-

-   Icy asteroids are between 50 and 100 centimeters from the Sun. This gives you a complete scale model of the solar system in a region spanning 1 meter, or 3 feet, across. 

-

-  Now appreciate that on this scale, the inner edge of the Oort Cloud, the vast halo of 2 trillion comets on the solar system’s perimeter, is 100 meters farther away. The outer edge of the Oort Cloud, on this scale, is 1,000 meters (0.6 mile, more than 10 football fields) away.

-

-  Yet as human astronaut-explorers, we only have traveled as far away as the Moon, about 1/389 AU, or on our scale 1/389 centimeter, from Earth, which on this scale is about the size of a human red blood cell. That distance is imperceptibly close to our planet’s “dot” on our scale. 

-

-   The distances to the nearest stars are larger than our imagined scale of the Oort Cloud. And then come perhaps 400 billion stars scattered across the bright disk of our Milky Way Galaxy, 150,000 light-years across, and a hundred billion more galaxies spread across a vast cosmos. 

-

-  We don’t just ue light to study yhe Universe.  Studying thermal history of the universe over the last 10 billion years has found that the mean temperature of gas across the universe has increased more than 10 times over that time period and reached about 2 million degrees Kelvin today, approximately 4 million degrees Fahrenheit.

-

-    The large-scale structure of the universe refers to the global patterns of galaxies and galaxy clusters on scales beyond individual galaxies. It is formed by the gravitational collapse of dark matter and gas.

-

- Astronomers have confirmed that the universe is getting hotter over time due to the gravitational collapse of cosmic structure, and that heating will likely continue.

-

-  The temperature of the universe has changed over time from data on light throughout space collected by two missions, Planck and the Sloan Digital Sky Survey. Planck is the European Space Agency mission that operates with heavy involvement from NASA Sloan collects detailed images and light spectra from the universe.

-

-  They combined data from the two missions and evaluated the distances of the hot gases near and far via measuring redshift, a notion that astrophysicists use to estimate the cosmic age at which distant objects are observed.

-

-   “Redshift” gets its name from the way wavelengths of light lengthen. The farther away something is in the universe, the longer its wavelength of light.  That lengthening  is the redshift effect.

-

-  The concept of redshift works because the light we see from objects farther away from Earth is older than the light we see from objects closer to Earth.   The light from distant objects has traveled a longer journey to reach us.

-

-   That fact, together with a method to estimate temperature from light, allowed the researchers to measure the mean temperature of gases in the early universe, gases that surround objects farther away,  and compare that mean with the mean temperature of gases closer to Earth,  gases today.

-

-  Those gases in the universe today, the researchers found, reach temperatures of about 2 million degrees Kelvin, 4 million degrees Fahrenheit, around objects closer to Earth. That is about 10 times the temperature of the gases around objects farther away and further back in time.

-

-  The universe is warming because of the natural process of galaxy and structure formation. It is unrelated to the warming on Earth.

-

-  At the “very end of the Universe“. The stars, past, present, and future, have all burned out. Stellar corpses like neutron stars and white dwarfs have radiated the last of their remnant energy away, fading to black in color and ceasing to emit any radiation at all. 

-

-  The great gravitational dance of masses within galaxies has come to an end, as every mass has either inspiraled into a blackhole or been ejected into the intergalactic medium.

-

-   And these last remaining structures themselves will decay away, as blackholes evaporate due to Hawking radiation, while dark energy drives every unbound structure apart from every other such structure that it isn’t bound to.

-

-  At this stage, we will have a cold, empty Universe, where the density of matter and radiation has effectively dropped to zero. But our Universe also contains dark energy, an energy inherent to the fabric of space itself. 

-

-  Dark energy doesn’t decay, meaning that even as the Universe relentless expands forever and ever, this form of energy density will remain constant. Surprisingly, this fact alone will keep our Universe’s temperature from dropping to absolute zero, no matter how long we wait. 

-

-   A Universe governed by Einstein’s rules couldn’t, as was commonly thought to be the case, be filled with roughly equal amounts of material everywhere and still be stable and remain the same size. 

-

-  For generations, it was widely believed that the Universe was static and eternal, providing an unchanging “stage” upon which the matter in the Universe would engage in its cosmic performance. But as Einstein’s new theory of gravitation grew to prominence, many realized that this assumption was a physical impossibility.

-

-  If General Relativity governs your Universe, and your Universe is filled with a roughly equal density of “stuff” everywhere.  “Stuff” can encompass any and every form of energy that’s possible, including normal matter, blackholes, dark matter, radiation, neutrinos, cosmic strings, field energy, dark energy, etc.   

-

- There are only two options for what your Universe can do: expand or contract. Every other solution is unstable, and after even an infinitesimal amount of time, will begin expanding or contracting, depending on what your initial conditions were.

-

-  In the 1920s, we began measuring individual stars in other galaxies, confirming their location outside of the Milky Way and their enormous, multi-million, or even multi-billion, light-year distances from Earth. 

-

-  By measuring the spectrum of the light coming from those galaxies, that is; breaking the light up into individual wavelengths and identifying absorption and emission lines from atoms, molecules, and ions.  We could also measure the redshift of that light: by what multiplicative factor every individually identifiable line was shifted by.

-

-  When we put that data together in the late 1920s, a feat independently accomplished first by Georges Lemaître, then Howard Robertson, and finally by Edwin Hubble, it pointed towards an unambiguous conclusion: the Universe was expanding.

-

-   Subsequently, this was put together into a framework that became the modern Big Bang, with the discovery of the cosmic microwave background , which is a leftover bath of radiation from the hot, dense, early stages of the Universe.

-

-  To measure what we called the ‘Hubble constant“, H0, which would tell us how quickly the Universe is expanding today.  HO is a rate of expansion equal to 49,300 miles per hour for every million light years of distance.  The reciprocal of his constant is the age of the Universe 

-

-----------------------------  Velocity = Hubble Constant  *  distance.

-

----------------------------   Time  =  1  /  Hubble Constant 

-

-  To measure what we called the “deceleration parameter“, q0, which would tell us the rate at which a distant galaxy would appear to recede more slowly from us as time went on.

-

-  The idea is simple: the equations that govern the Universe dictate a relationship between the matter-and-energy present within it and how the expansion rate will change over time. If we can measure the expansion rate today and how quickly the expansion rate is changing, we can not only determine what makes up the Universe, but we can know its past history as well as its future fate

-

-   As the decades went on, new telescopes and observatories were built, and enormous advances in instrumentation occurred, our answers got both more accurate and also more precise.

-

-  In a Universe filled with matter and radiation, there’s a key relationship between our Universe’s expansion rate and its fate. You can imagine the Big Bang as the starting gun of the ultimate cosmic race: between gravity, on the one hand, that works to recollapse the Universe and pull everything back together, and the initial rate of expansion, which works to drive everything apart. You can imagine multiple different fates:

-

---------------------  One where gravity wins, and overcomes the expansion, causing the Universe to recollapse and end in a Big Crunch,

-

--------------------- One where the expansion wins, where gravity is insufficient, and the Universe expands forever, with its density eventually dropping to zero,

-

-------------------- One right on the border between those two, a “Goldilocks” case, where the expansion rate asymptotes to zero but never quite reverses.

-

-  But when the decisive data came in, it pointed to none of these. Instead, gravitation fought the initial expansion, causing distant galaxies to recede from us at a slower and slower rate, and then something strange happened. 

-

-  About 6 billion years ago, these distant, receding galaxies began moving away from us at faster and faster rates.   The Universe’s expansion was accelerating.

-

-   Today, 13.8 billion years after the Big Bang, it’s apparent that the Universe not only contains many different forms of matter and radiation, but also an unexpected component: “dark energy“.

-

-   When we look at the modern Universe, we’re seeing it in perhaps its most interesting state: after an enormous amount of interesting, luminous, large-and-small-scale structures have formed, but before dark energy has driven them all away from us to practically imperceptible distances.

-

-  In today’s Universe, we see stars forming, living, and dying; we see galaxies and galaxy clusters colliding and merging; we see new planets being formed; but we also see these distant objects speeding farther and farther away from one another. After enough time passes:

-

------------------------   Stars will only form from the rare, occasional merger of failed or extinct stars,  all the shining stars will burn through their fuel,

-

-----------------------  Stellar remnants will radiate their energy away,

-

-----------------------  Blackholes will swallow a significant fraction of masses,

-

-----------------------  Galaxies will gravitationally kick out all of the remaining individual masses,

-

----------------------  The leftover radiation from the Big Bang will redshift to arbitrarily low energies,

-

----------------------  Every single blackhole will eventually evaporate,  all while the Universe continues to relentlessly expand due to dark energy.

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-  On the levels of individual particles, there may be some incredibly long-term effects that happen far beyond our means to measure them. Protons may decay, although modern experiments have constrained the proton’s lifetime to be longer than 10^25 times the present age of the Universe.

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-   Atomic nuclei may undergo quantum tunneling to arrive at a more stable configuration: iron-56 or nickel-60, for example. And improbable but not forbidden events, like the ionization of matter due to a stray, energetic photon, may eventually kick all of the electrons off of atoms and ions.

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-  But, at some point, any arbitrarily large region of the Universe will be completely empty: devoid of all forms of normal matter, dark matter, neutrinos, or any of the radiation permeating the Universe today. 

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-  Even that great thermal bath of photons created from the Big Bang will shift to long wavelengths, low densities, and energies that asymptote to zero. All that will remain will be the energy inherent to space itself,  dark energy,  and the consequences that it brings.

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-  Remarkably, one of those consequences of a Universe with a cosmological constant, the form of dark energy that is best supported by the data, where the energy density of dark energy remains constant over time and throughout all of space, is that the temperature of the Universe does not go to zero. 

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-  Instead, the Universe will be filled with a bath of extraordinarily low-energy radiation that will appear everywhere, but at an utterly minuscule temperature: 10^-30 Kelvin. Compare that to the cosmic microwave background today, which is more like 3 Kelvin, or some 10^30 times hotter.

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-  To understand why, we can start by thinking about blackholes. The reason blackholes evaporate is because they radiate energy, owing to the fact that observers close to the event horizon and observers farther from the event horizon disagree as to what the ground state of the quantum vacuum is.

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-   The more severely space is curved near the event horizon of a blackhole, the greater the difference an observer there versus far away will experience for the quantum vacuum.

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-  But quantum fields are continuous throughout all of space, and there exist possible light paths that take you from anyplace outside the event horizon to anywhere else outside the event horizon. 

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-  The difference in the zero-point energy of space between those two locations tells us, as first derived in Hawking’s landmark 1974 paper, that radiation will be emitted from the region around the blackhole, with the blackhole’s event horizon playing a key role.

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-   That radiation will have its temperature set by the mass of the blackhole, with lower-mass black holes having higher temperatures, and will have a perfect blackbody spectrum.

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-  We don’t have an event horizon in a Universe with a cosmological constant, but we have a different type of horizon: a “cosmological horizon“. Two observers in different locations will be able to communicate at the speed of light, but only for a finite amount of time. 

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-  Eventually, they’ll recede from one another fast enough that an emitted light signal from one will never reach the other, similar to how a signal emitted by us today could only reach an observer, 18 billion lightyears distant. Beyond that, they can only receive “older” signals from us, just as we can only receive “old light” from them.

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-  The key that unlocks the entire puzzle is “Einstein’s equivalence principle“: the idea that observers cannot tell the difference between gravitational accelerations and any other form of acceleration of equal magnitude. If you’re in an enclosed rocket ship and you feel yourself pulled down towards one end, you cannot know whether you’re pulled down because the rocket is at rest on Earth, or,  because the rocket is accelerating in the “up” direction.

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-  Similarly, the Universe doesn’t care whether you’ve got an event horizon or a cosmological horizon; it doesn’t matter whether a point mass (like a black hole) or dark energy (like a cosmological constant) is accelerating two observers relative to one another.

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-   In either case, the physics is the same: a continuous amount of thermal radiation gets emitted. Based on the value of the cosmological constant we infer today, that means a blackbody spectrum of radiation with a temperature of 10^-30 Kelvin will always permeate all of space, no matter how far into the future we go.

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-  Even at its very end, no matter how far into the future we go, the Universe will always continue to produce radiation, ensuring that it will never reach absolute zero.

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-   However, this final-state bath of photons should be tremendously difficult to ever observe. With a temperature of 10^-30 K, this cosmic radiation should have a wavelength of 10^28 meters, or about 30 times the size of the observable Universe today.

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-  It may be a long journey to the very end, but if what we think about the Universe today is correct, even empty space, as far into the future as we care to go, can never be completely empty.  If it got any stranger we would not understand it.  Other reviews:

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-    3174   - UNIVERSE  -  age and rotation?  We think our Universe was born about 13.7 billion years ago.  This newborn universe didn’t look like it does today, with elegant, star-filled galaxies strewn in all directions. Instead of stars and galaxies, the early universe was filled with gas and dark matter.

 -  3151   -  UNIVERSE  -  size and beyond?  The universe doesn't need that outside perspective in order to exist. The universe simply is. It is entirely mathematically self-consistent to define a three-dimensional universe without requiring an outside to that universe. 

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-  June 22, 2021          UNIVERSE  -  how immense is it?                 3198                                                                                                                                                       

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--------------------- ---  Wednesday, June 23, 2021  ---------------------------