lepton era
When the energy of particles and photons dropped from 100 MeV to 1 MeV, there were many leptons in the matter. The temperature was high enough to ensure the intense production of electrons, positrons and neutrinos. Baryons (protons and neutrons) that survived the hadron era became much rarer than leptons and photons.
The lepton era begins with the decay of the last hadrons - pions - into muons and muon neutrinos, and ends in a few seconds at a temperature of 1010K, when the photon energy has decreased to 1 MeV and the materialization of electrons and positrons has ceased. During this stage, the independent existence of electron and muon neutrinos, which we call “relic”, begins. The entire space of the Universe was filled with a huge number of relic electron and muon neutrinos. A neutrino sea appears.
Photon era or radiation era
The lepton era was replaced by the era of radiation, as soon as the temperature of the Universe dropped to 1010K, and the energy of gamma photons reached 1 MeV, only the annihilation of electrons and positrons occurred. New electron-positron pairs could not arise as a result of materialization, because the photons did not have sufficient energy. But the annihilation of electrons and positrons continued until the radiation pressure completely separated matter from antimatter. Since the hadron and lepton era, the universe has been filled with photons. By the end of the lepton era, there were two billion times more photons than there were protons and electrons. Photons become the most important component of the Universe after the lepton era, not only in quantity, but also in energy.
In order to be able to compare the role of particles and photons in the Universe, the value of the energy density was introduced. This is the amount of energy in 1 cm3, more precisely, the average amount (based on the premise that matter in the universe is evenly distributed). If we add together the energy h? All photons present in 1 cm3, then we get the energy density of the radiation Er. The sum of the rest energy of all particles in 1 cm3 is the average energy of matter Em in the Universe.
Due to the expansion of the Universe, the energy density of photons and particles decreased. As the distance in the universe doubled, the volume increased eightfold. In other words, the density of particles and photons has decreased by a factor of eight. But photons in the process of expansion behave differently than particles. While the rest energy does not change during the expansion of the Universe, the energy of photons decreases during the expansion. Photons decrease their oscillation frequency, as if they “get tired” with time. As a consequence, the photon energy density (Er) falls faster than the particle energy density (Em). The predominance of the photon component over the particle component (meaning the energy density) in the Universe decreased during the era of radiation until it completely disappeared. By this time, both components have come into equilibrium, that is, (Er=Em). The era of radiation is ending, and with it the period of the Big Bang. This is what the universe looked like at about 300,000 years old. Distances in that period were a thousand times shorter than they are today.
star era
After the "Big Bang" came a long era of matter, the era of the predominance of particles. We call it the stellar era. It has been going on since the end of the Big Bang (approximately 300,000 years) to the present day. Compared to the Big Bang period, its development seems to be slowed down. This is due to the low density and temperature. Thus, the evolution of the universe can be compared to a firework that has ended. There were burning sparks, ashes and smoke. We stand on the cooled ashes, peer into the aging stars and remember the beauty and brilliance of the Universe. A supernova explosion or a giant explosion of a galaxy are insignificant phenomena compared to a big bang.
The fashion industry is constantly changing and changing rapidly. Millions of girls come to the podium, but only a few are able to become the muse of a fashion designer and impress a whimsical audience. Let's see which of the new generation has already succeeded and who we will have to admire on the covers of the gloss in the near future.
Chris Grikaite
Her full name is Kristina, she is only 17 years old and she is our compatriot from Omsk. Quite by chance, as often happens, the owner of the fashion house Miuccia Prada noticed the girl and immediately offered her a contract for three years. Now the expressive face of Chris does not leave the covers of fashion magazines, including Vogue.
@kris_grikaite / Instagram.com 
@kris_grikaite / Instagram.com
Diana Silvers
So far, Diana is still a little-known model. But with such an appearance, the girl obviously will not remain in the shadows for long. She has all the data to become the queen of the catwalk and open the most iconic shows. We hope she will choose the podium, not the camera - they say Diana is seriously interested in photography.
@dianasilvers / Instagram.com 
@dianasilvers / Instagram.com Adwoa Aboah
According to the world's leading agencies, Adwoa is the most promising model of the decade. At the moment, in terms of the number of proposals, she has already surpassed the Hadid sisters and even Kaia Gerber. Which is not surprising: a shaved head and a scattering of freckles, combined with a unisex figure, are ideal for demonstrating the extravagant, futuristic and minimalist looks that are now at the peak of popularity.
@adwoaaboah / Instagram.com 
@adwoaaboah / Instagram.com Ashley Graham
You, of course, are already familiar with this charming muffin. Ashley is the complete opposite in size to her colleagues in the shop. But this does not prevent her from actively participating in the most fashionable shows, creating a line of underwear and even writing memoirs about the career of a plus-size model. Her age is approaching retirement by the standards of the modeling business, but critics are sure that this is far from the limit of her capabilities and only the beginning of a grandiose career.
@theashleygraham / Instagram.com 
@theashleygraham / Instagram.com Mika Arganaraz
This curly girl from Argentina was also brought to the big podium by Prada designers. She conquers with her spontaneity and openness, crazy energy and charm. Combined with her bright appearance, Mika becomes a real treasure for the fashion world.
@micarganaraz / Instagram.com 
@micarganaraz / Instagram.com Imaan Hamam
And another charming curly girl with an exotic appearance, half Egyptian, half Moroccan. Young Imaan has already taken part in numerous prestigious shows and photo shoots, last year she became one of the Victoria's Secret Angels. The new Naomi Campbell is what critics call her.
@imaanhammam / Instagram.com 
@imaanhammam / Instagram.com Stela Lucia
The appearance of the girl is fully consistent with her name - a distant and inaccessible, but very bright star. Stella's unearthly appearance first attracted the attention of Givenchy designers, and then conquered the catwalks of the whole world. By the age of 18, this fragile blonde's list of fashion victories is impressive, and it will have a continuation, no doubt.
@stellaluciadeopito / Instagram.com 
@stellaluciadeopito / Instagram.com Vittoria Ceretti
The track record of this 18-year-old Italian beauty includes contracts with Dolce & Gabbana, Armani and Chanel and a number of other iconic brands. With her bright appearance, the girl has been pleasing designers since the age of 14, so Vittoria has enough experience to break into the ranks of super-models.
@vittoceretti / Instagram.com 
@vittoceretti / Instagram.com Kaia Gerber
With such a star mother, the fate of the girl was sealed from the cradle - many will say. And they will be wrong! Model appearance, innate grace and grace, enviable perseverance and rare performance - these are the features that step by step help the young and fragile Kaya conquer the modeling world step by step. To date, she is the favorite muse of Karl Lagerfeld, the creator of her own clothing line ... We are looking forward to new achievements!
@kaiagerber / Instagram.com 
@kaiagerber / Instagram.com Starlight illuminates the night sky
wonders of galaxies flickering light.
Starlight illuminates our days
in which we were somewhere in the shadows:
This is the birth and death of a poet,
it is the pain of sunset and the joy of dawn,
these are complete phrases and those that are unanswered,
these are performances of a loner or a duet,
these are our lives, which this one is guilty of -
Beautiful blue planet!
A star that fell in the palm of your hand
This is how I will remember you
When the soul is resurrected in peace,
And I pray in silence....
How dear is the moment to me, the one that
You uttered the tenderness of the words ...
Incessant reproach
Silence will answer you...
But if I, and in the heat of battle,
I will forget your name
Say your prayer
I will remember her...
"Star", "Star", answer, "Star" -
My call sign is "Romashka" field...
"Star", come back to me "Star" -
My soul is in anguish and pain.
You are behind the no-man's land,
You are wearing camouflage protection.
"Star", "Star", live far away,
And then we will crush the bastard!
Answer the call sign, where are you?
We are all waiting here, at least for a word...
Be careful out there, "Star",
Get back "Star" without a fight.
Well, finally, I hear you -
Clearly you are on the air!
Quite bad, you know, things ...
"Star...
Stars are like holes in a black blanket
The stars shine and tear the darkness.
The stars are so close to God and know
What fate he prepares for whom.
The stars are silent in the peacefully dormant cold,
Stars look at planets, worlds.
Seeing in the hands of our weapons spears
They don't understand why we are so angry.
We are not given to comprehend being.
We enjoy garbage, rubbish,
And we are ruled by cruelty and revenge ...
So in the century we are dragging from the century
A heavy thought that gave birth to a spleen
The stars look at people, we look at the stars;
But there is no salvation for either...
The star of midnight shines over the earth,
Giving light of hope to villages and cities.
I always loved to watch, as over a mountain
This midnight star is rising.
Already more than half left behind:
Flickering of events and losses of a series.
Only invariably shone in the midnight sky
A cherished star, a magical star.
And now she shines in the darkness of heaven,
Beam slightly touching the mirror of the pond,
And again awakens hope in my soul
A cherished star, a midnight star.
stars
looking everywhere at once
stars live a long, long time
they have their own life, their own destiny
the stars are flying, waiting for no one
you will not believe
you are a star too
own planid, own orbit
great beauty in you
only need one
for her to show up
need, as in childhood
swirl in a whirlwind
in a whirlwind of white quickly - quickly
and scream out loud
and feel beautiful
unthinkable
Star of my love shine!
Burn and never go out.
You lit up my night
The path through troubles and misfortunes,
You melted with kindness
Hearts frozen in pain...
Star of my love, alas,
Yesterday I fell like a stone into the sea.
And again I stand in the night
Darkness and cold around me
And I scream to the star: "Burn!
I need your light more than ever."
And the star of love shines on me
From the depths of the cold abyss
And gives a golden ray
All-conquering hope.
star in the sky
star on earth
The touch of your lips
You can only feel in a dream!
The warmth of your body
It comes from the heart
Perhaps boldly
Warm you and mine!
Stars don't age
Love never gets old...
They don't know how
You will be loved again and again!
I whisper to you with my eyes...
How good are you...
You give me lips...
Happiness, thoughts and warmth!!!
I trust the sky, the stars...
I will say that you are a star
You will shine brighter
I will shine too!
After " big bang” a long era of matter has begun. We call her stellar era. It has been going on since the end of " big bang" to the present day. Compared to the period big bang”, its development seems to be too slow. This is due to the low density and temperature.
Thus, the evolution of the universe can be compared to a firework that has ended. There were burning sparks, ashes and smoke. We stand on the cooled ashes, peer into the aging stars and remember the beauty and brilliance of the Universe. A supernova explosion or a giant explosion of a galaxy are insignificant phenomena compared to a big bang.
The process of the formation of the first stars is simpler than the process of formation of stars of the modern type, due to the chemical purity of the source material - a hydrogen-helium mixture. A gas of atomic composition was mixed with a dark mass. It began to shrink, following the action of the gravitational forces of dark matter condensation. The formation of a star depends on the temperature of the environment, the mass of the condensing gas formation and the presence of molecular hydrogen in it, which has the ability to remove heat from condensation, radiating it into the surrounding space. Molecular hydrogen cannot arise from atomic hydrogen during random collisions of atoms; nature has a rather complicated process in store for its formation. Therefore, at z > 15–20, hydrogen remained mainly in the atomic phase. When compressed, the temperature of the gas in the condensation rises to 1000 K or more, and the fraction of molecular hydrogen somewhat increases. At this temperature, further condensation is not possible. But due to molecular hydrogen, the temperature in the densest part of the condensation decreases to 200-300 K and the compression continues, overcoming the pressure of the gas. Gradually, ordinary matter separates from dark matter and concentrates in the center. The minimum mass of gaseous condensation required to form a star, the Jeans mass, is determined by a power-law dependence on gas temperature, so the first stars had a mass 500-1000 times greater than the Sun. In the modern Universe, during the formation of stars, the temperature in the dense part of condensation can be only 10 K, because, firstly, the functions of heat removal are more successfully performed by the heavy elements and dust particles that have appeared, and secondly, the temperature of the environment (relic radiation) is only 2 .7 K, not nearly 100 K, as it was at the end of the Dark Age. Jeans' second measure of mass is pressure (more precisely, the square root of pressure). In the Dark Age, this parameter was about the same as now.
The first stars formed were not only huge, 4-14 times larger than the Sun, but also very hot. The sun emits light with a temperature of 5780 K. The temperature of the first stars was 100,000-110,000 K, and the radiated energy exceeded the solar energy by millions and tens of millions of times. The sun is called a yellow star; these same stars were ultraviolet. They burned and collapsed in just a few million years, but managed to fulfill at least two functions that determined the properties of the subsequent world. As a result of fusion reactions, some enrichment of their interiors with "metals" (as astronomers call all elements heavier than hydrogen) took place. The "stellar wind" flowing from them enriched the interstellar medium with metals, facilitating the formation of subsequent generations of stars. The main source of metals was the explosions of some stars as supernovae. The most massive part of the first stars at the end of their life path, apparently, formed black holes. Powerful ultraviolet radiation from giant stars caused rapidly developing heating and ionization of interstellar and intergalactic gas. This was their second function. This process is called reionization because it was the reverse of the recombination that ended 250 million years earlier, at z = 1200, when atoms formed and the CMB was released. Studies of distant quasars show that reionization has practically ended at z = 6-6.5. If these two marks, z = 1200 and z = 6.5, are considered the boundaries of the Dark Age, then it lasted 900 million years. The period of complete darkness itself, before the appearance of the first stars, lasted shorter, about 250 million years, and theorists believe that in some, quite exceptional cases, individual stars could have appeared earlier, but the probability of this was very low.
With the formation of the first stars, the Dark Age ended. Giant ultraviolet stars were part of protogalaxies formed mainly by dark matter. The sizes of the protogalaxies were small, and they were close to each other, which caused a strong attraction that united them into galaxies, also small. The dimensions of the first galaxies were 20-30 light years (only 5 times the modern distance to the nearest star, and the diameter of our Galaxy is 100,000 light years). It would be interesting to see these giant ultraviolet stars, but despite their enormous brightness, it is not possible to do this: they are in the z = 8-12 region, and the quasar at z = 6.37 still remains the record for observing distant objects. Now, if you could figure out how to isolate the radiation that arose in a certain period of time. E. Hubble, who sometimes hesitated, admitted that the redshift is simply the result of light aging, and not the Doppler effect.
About an unprecedented phenomenon - first recorded by LIGO and Virgo scientists gravitational waves from the merger of two neutron stars. This event is already called the beginning of a new era in astrophysics, but why is it so important?
We talked with Alan Jay Weinstein- Professor of Physics and Head of the Astrophysical Data Analysis Group from the LIGO laboratory at the California Institute of Technology. He told why what happened is so important, and how it can change the existing understanding of the universe.
Everyone says that an “unprecedented” phenomenon has occurred. What is its significance?
For the first time, our science team and LIGO detectors spotted gravitational waves in September 2015, when two black holes collided. This confirmed the significant hypothesis Einstein's theory of relativity, provided us with new opportunities to study black holes, allowed us to witness the most powerful phenomenon since the Big Bang, and, to some extent, made it possible to hear the vibrations of space-time itself. Since then, we have recorded several more such phenomena.
But on August 17, 2017, we saw something different. It was a merger of two ultra-compact luminaries - not black holes, but neutron stars. They are made of pure nuclear material, so this is a very exotic and interesting topic for physicists and astronomers. But the main thing is that, unlike black holes, they emit light - in large quantities.
Gravitational waves
Gravitational waves predicted general relativity, are changes in the gravitational field that propagate according to the principle of a wave. They can be described as "ripples of space-time".
They were first discovered in 2015 by the detectors of the LIGO observatory. In 2017 American physicists Weiss, Thorne and Barish received the Nobel Prize for the experimental detection of gravitational waves from the merger of two black holes.
The term "gravitational wave" was introduced Poincaré in 1905.
For the first time we have witnessed such a large-scale astronomical phenomenon, which was the source of both gravitational waves and light. We have observed light in all its many manifestations: not only visible radiation, but also ultraviolet, infrared, X-ray and gamma radiation, radio waves.
So we were able to "see" and "hear" this extraordinary phenomenon in a variety of ways. What happened confirmed the connection between the merger of binary neutron stars and gamma-ray bursts (GRB), determined the likely location of the fusion of heavy elements in the universe, allowed us to measure the speed and polarization of gravitational waves for the first time. Thanks to gravitational waves, the event was the beginning of an era multi-messenger astronomy .
Multi-messenger astronomy
Term multi-messenger astronomy there is still no official analogue in Russian. This branch of astronomy is based on the coordinated observation and interpretation of signals, the creation, through various astrophysical processes, of electromagnetic radiation, gravitational waves, neutrinos and cosmic rays. So they reveal various information about their sources.
As a rule, sources are ultra-compact pairs of black holes and neutron stars, supernovae, irregular neutron stars, gamma-ray bursts, active galactic nuclei and relativistic jets.
Now physicists and astronomers have the opportunity to learn a lot about this incredibly multifaceted process, we are still continuing to explore what happened and learn something new. But if we talk about the importance of this event in a practical and universal sense, it provides us with information about the origin of the heaviest chemical elements, including precious metals in our jewelry.
The collision produced gold, lead and platinum. A person who is not too close to the world of science (like me, for example) sees this as similar to an explosion of gold dust, but, of course, everything is much more complicated.
Neutron stars are pure nuclear material, which, upon collision, is ejected into interstellar space in huge quantities. It splits and then fuses into neutron-rich atomic nuclei that become heavy elements—not just gold, lead, and platinum, but uranium, plutonium, and most of the other heaviest elements on the periodic table. They scatter throughout their galaxy (which, in the case of GW170817, very far).
Similar collisions occur in our Milky Way about once every 10-100 thousand years. The fragments of heavy elements left after them fall into our solar system and to the Earth.
neutron stars
neutron star is a dense neutron core with a thin shell, which is formed as a result of a supernova explosion. Neutron stars have a powerful magnetic field and high density, but their size is 10-20 km. Many neutron stars have a huge rotation speed - several hundred revolutions per second.
Collision is important for a number of reasons. Already they say that it will be the beginning of a new era for astronomy. Is it really true?
Yes! We will find many more similar phenomena, different stellar masses in different galactic environments. This will allow us to learn much about the formation, development and extinction of the most massive stars and to strengthen a new understanding of the origin of the heaviest chemical elements. The results of these studies will appear in textbooks, so when we talk about a bright future - or even gold, we really mean it.
The collision provided a new opportunity to study gravitational waves and the universe. What new scientists will learn thanks to such a find?
We will be able to measure the expansion rate of the universe with ever-improving accuracy. There are many ways to do this, but we have another completely new method. If we come to the same conclusions in all cases, we strengthen our understanding of the Big Bang. If not, then we will know that we misunderstood some data, need a better theory, or missed something important.
We will receive more and more accurate information when studying the fundamental properties of gravitational waves. This will allow us to subject Einstein's general theory of relativity, the modern theory of gravity, to even more severe tests. We suspect that we will eventually find that it is not entirely correct, and this will point to a deeper and more accurate theory.
General Relativity (GR)
In 1915 Albert Einstein published his geometric theory of gravity, which became known as the General Theory of Relativity. Its main statement was that gravitational and inertial forces are of the same nature, from which it followed that the deformation of space-time causes gravitational effects.
Einstein used the gravitational field equations to relate matter and the curvature of space-time, in which it existed - this was the difference between the work and other alternative theories of gravity.
General theory of relativity predicted such effects as gravitational time dilation, gravitational deflection of light, gravitational redshift of light, gravitational radiation, signal delay in a gravitational field, etc. In addition, she predicted the existence of black holes.
To date, general relativity remains the most successful theory of gravity.
Something like a neutron star collision is unusually rare. When will scientists witness something like this again?
Such phenomena can be observed in the Milky Way every 10-100 thousand years. We won't have to wait that long! Our current LIGO detectors are capable of observing such collisions in more than a million distant galaxies. We are currently improving the sensitivity of our detectors to be able to detect these phenomena in hundreds of millions of galaxies. So we hope to see something similar every year.
Gravitational waves from neutron star mergers: a golden era for astronomy updated: October 17, 2017 by: Anastasia Belskaya
