What is the difference between the stars in the early days of the universe and the stars of today?

The first generation of stars is also known as Constellation III stars. The biggest difference between these stars and the present is that they do not contain heavy elements。According to the theory of the synthesis of elements in the universe,Early nucleosynthesis in the universe formed only hydrogen, helium, and very small amounts of lithium.

The baryonic component of the universe, hydrogen accounts for 3 4, helium accounts for 1 4 (so there will be no formation of stars with hydrogen accounting for 9 into 9 well).

But even so,Just looking at the mass, heavy elements are still negligible in today's stars. But this little bit of heavy element has a big impact。Because these heavy elements can generate emission lines with complex energy levels, they are very effective in cooling the gas cloud before the formation of the protostar.

So the stars that form today are much less massive than the first generation of stars.

So how big can the first generation of stars be, and the general estimate is that they can reach hundreds or even hundreds of solar masses. These stars burn up quickly and die quickly. So today, we haven't observed a single first-generation star with certainty.

However, it is theorized that some of the high-redshift gamma-ray bursts were most likely created when the first generation of stars died.

Extremely high productivity efficiency results in the need for more gravity to resist the radiation pressure, so only by gathering more hydrogen can a stable sphere be formed, so early stars are very large, potentially thousands of times the diameter of the sun;

As far as star formation is concerned. The biggest difference between the early days of the universe and the current environment is that there are very few or no heavy elements, and if memory serves, hydrogen accounts for more than 9 out of 9, and almost all of the rest is helium. First formed:

Since the first batch of stars contains several = 100% hydrogen, this results in extremely efficient core capacityToday's star cores have a significant proportion of heavy elements that do not participate in fusion, and they extrude some of the hydrogen, so they are less efficient

But in fact, the accumulation of mass creates a cycle, the greater the mass, the higher the core pressure, the higher the temperature, and the stronger the agglomerationThen it takes a greater mass to hold it down. In the end, it is a super-giant.

In fact, there are many blue supergiants that can be observed in the universe today, and they are very similar to early stars, for example: Betelgeuse and then the middle:The brightness is extremely high, and the surface is generally blue; The temperature is extremely high, with a surface temperature of tens of thousands of degrees Celsius；A high combustion rate means a lot of consumption, don't look at the mass, the consumption is even greater, and the lifetime of these stars is generally millions to tens of millions of years.

The matter in this universe was released through the universe 13.8 billion years ago. And the material that formed these stars also appeared, of course, at the beginning of the universe. The composition of the first generation of stars was particularly simple.

One is young, the other is not very young anymore and has been running for many years.

They were young at first, but now they are old.

The stellar nuclei of the early universe reacted violently.

There is a difference, the current one has matured.

Stars in the early universe were not stable.

There may be a lot more potholes on it.

Now the sidereal cycle and so on are relatively stable.

Absolute zero is, and is also 0 degrees Celsius at the Kelvin scale, which is the lowest temperature that exists in theory, and the temperature of any space in the universe can only be infinitely close to this temperature, but cannot reach or exceed it.

Because from a microscopic perspective, the temperature of matter is determined by the rate of motion of the microscopic particles that make up the matter. The more intense the microscopic particle movement, the higher the temperature of the matter on the macroscopic scale. Absolute zero, on the other hand, means that all particles of matter are at rest and no longer have any motion – since there is no absolute stillness in the universe, it is impossible to reach absolute zero.

And there are many burning stars in the universe, constantly releasing energy, why is the temperature in the universe still generally low, close to absolute zero? Or from a microscopic point of view, that is, in the universe, there is almost no matter in the vacuum state (a few atoms per cubic meter), so it also leads to the extremely low temperature in most of the space in the universe, except for some places near some celestial bodies.

The material that formed these stars was, of course, also at the beginning of the universe. The composition of the first generation of stars was particularly simple.

Three conditions are required for star formation: hydrogen, gravity, and time.

Stars undergo nuclear fusion at their cores to produce energy that is transmitted outward, then radiated from the surface into outer space. Once the nuclear reaction in the core is exhausted, the life of the star is coming to an end. At the end of life, stars also contain degenerate matter.

Differences in the size and mass of stars lead to different outcomes: white dwarfs, neutron stars, black holes.

The energy source of a star is produced by nuclear fusion. The issue of stellar energy has always been a point of contention for mankind. In 1926, the British astronomer Eddington raised the issue of stellar energy.

He firmly believed that the energy produced by stellar fusion was enough to bring the star to a state of equilibrium between gravity and gas pressure. However, physicists at the time did not think so. They feel that fusion reactions cannot take place inside the star.

Fortunately, the development of quantum mechanics (the proposed tunneling effect) solved this problem.

In 1938, American physicist Hans Bette and German physicist von Weizsäcker independently discovered the specific path of nuclear fusion inside stars, that is, through the "proton-proton reaction" and "carbon, nitrogen and oxygen cycle", the hydrogen in the star can be fused into helium and release energy.

The density of most voids in a galaxy is about 1 atom per cubic centimeter, but the density of a megamolecular cloud is millions of atoms per cubic centimeter. A giant molecular cloud contains hundreds of thousands to tens of millions of solar masses and is 50 to 300 light-years in diameter. As the megamolecular cloud orbits a galaxy, events may cause its gravitational collapse to collapse.

Macromolecular clouds may collide with each other or pass through dense parts of the spiral arms. The high-velocity mass thrown by a nearby supernova explosion may also be a trigger. Finally, nebulae compression and perturbations caused by galaxial collisions may also form a large number of stars.

The conservation of angular momentum during exploration causes the fragments of the giant molecular cloud to break down into smaller pieces. Debris with a mass of less than about 50 solar masses will form stars. In this process, the gas is heated by the potential energy released, and the conservation of angular momentum causes the nebula to begin to rotate and form a primordial star.

The initial stages of star formation are almost completely obscured by dense nebulae gas and dust. Often, star-producing sources are observed by creating shadows on the surrounding bright clouds of gas.

Stellar adulthood:

From cool red to hot blue, from up to 150 solar masses. The brightness and color of a star depend on its surface temperature, which in turn depends on the mass of the star. Massive stars require more energy to resist the gravitational pull on the outer shell and therefore burn hydrogen much faster.

After star formation, it falls at a specific point in the main sequence of the Herrault diagram. Small, cold M-type red dwarfs burn hydrogen slowly and may stay in this sequence for 100 billion to trillions of years, while large, hot O-type supergiants leave the main sequence after just a few million years.

Medium stars like the Sun will stay on this sequence for 10 billion years. The Sun is also located on the main sequence and is considered to be in middle age. After the star burns off the hydrogen in its core, it leaves the main sequence.

Stars originate from interstellar matter. After a certain amount of interstellar matter is subjected to gravitational disturbances (such as supernova explosions), the gravitational pull between interstellar matter will play a dominant role in causing them to collapse into denser nebulae, as long as certain conditions (Kins mass) are met. When a thermonuclear reaction can maintain the thermal equilibrium of the star's own dynamics, the star is fully born.

Molecular clouds are condensed by clouds of neutral hydrogen under the influence of gravitational waves or shock waves from supernova explosions. In addition to being filled with a lot of gas, molecular clouds also have a lot of interstellar dust. These dusts are able to absorb high-energy photons from the environment to protect the molecular cloud from being shattered by attack.

Moreover, the chemical elements composed of interstellar dust are relatively rich and diverse, which is also conducive to the formation of stars.

Stellar position measurements.

To determine the position of a star on Earth, it is only necessary to determine its coordinates on the celestial sphere and its distance from Earth.

Determining the coordinates of a star on the celestial sphere usually requires a definition of the celestial coordinate system. Generally, there are horizon coordinate system, equatorial coordinate system, ecliptic coordinate system and galactic coordinate system. All celestial coordinate systems specify the cardinal axes, cardinal points, and ranges of metric directions.

Now with large-scale survey data, it is easy to obtain the celestial coordinates of stars. The difficulty lies in measuring the sidereal distance.

The standard candle method uses type IA supernovae to measure the distances of distant galaxies. Type IA supernovae have a constant luminosity, so the distance of this galaxy can be easily measured as long as a type IA supernova is found in an extragalactic galaxy.

For more distant galaxies (15g parsec), the only way to do this is to use the Hubble relation. If there are more distant galaxies, astronomers can't figure out their distances.

In the early days of the universe, there were various relatively light atoms in the universe, such as hydrogen atoms. Most of them are scattered and scattered, forming nebulae with a diameter of more than a hundred light-years and a particularly large internal mass. Due to the action of gravitation, they will interact with each other, and under the action of internal and external pressure, the volume will become smaller and denser, and eventually the star will be formed.

Stellar classification

Take the mass of the sun as the criterion. It can be divided into several types:

Smaller than the mass of the sun is called a brown dwarf. This kind is a failed star and cannot be counted as a star.

Those greater than 1 and less than twice the mass of the Sun become yellow dwarfs.

Stellar old age

Stars with less than 7 times the mass of the Sun must have evolved into white dwarfs or neutron stars.

Stars with more than 8 solar masses are highly likely to become black holes.

Stars with more than 30 solar masses will become black holes.

And the fate of our sun is to become a white dwarf.

The process of stellar aging

Stars have been burning continuously since they formed, first hydrogen fusion, then helium fusion after hydrogen consumption, and stars of mass like the Sun are almost over here. But the more massive stars will continue to fuse inside, with carbon fusion, oxygen fusion, and even deeper. In the process, the star grows in size, increases in temperature, and eventually releases energy as well.

With the release of energy, the life of the star has also come to an end, the denser ones will continue to invert to form black holes, the less dense ones will become white dwarfs or neutron stars, and then after tens of billions of years will become black dwarfs, completely ending life.

When the sun becomes a supergiant, the diameter can reach the Earth's orbit and completely engulf the Earth. And that's not all, at that time, the boundary of the Sun could even approach the orbit of Mars. But by then, humanity should find a new home!

It seems that at that time, Jupiter's moons were probably in a more comfortable range. However, at that time, the solar radiation was stronger, the temperature was higher, and the outer shell would gradually disperse into space. Therefore, the solar system is no longer suitable for the survival of living things, despite the right temperature.

When that day comes, only other galaxies outside the universe will be humanity's next stop.

Nebulae are the materials that make up stars, but the mass of the matter that really makes up stars is very large, and a nebula cluster with a radius of 90 billion kilometers is required to make up a star like the Sun. The process of clustering from nebulae to stars can be divided into fast contraction phase and slow contraction phase. The former lasted hundreds of thousands of years, and the latter lasted tens of millions of years.

After the nebula shrinks rapidly, the radius is only one percent of the original, and the average density increases by 100 million billion times, and finally forms a "star embryo". It is a thick, dark cloud with a dense nucleus in the center. After that, it enters a slow contraction, also known as the protosidereal phase.

At this time, the temperature of the star embryo continues to rise, and when the temperature rises to a certain extent, it will shimmer and glow to show its existence and enter the juvenile stage of the star. However, the star was still unstable and was still surrounded by diffuse nebulous material that projected material into the world.

Portrait of a star.

In the silent night sky, people see that the stars in the sky are all shining, and there is no difference except for size and light and darkness. Is that actually the case? Of course not, each star has its own unique physiognomy. Back in the Han Dynasty in China, we.

Our wise ancestors, through careful observation, have divided the stars into five colors: white, red, yellow, pale, and black. In 1665, Newton of England discovered the continuous spectrum of the sun using a prism, and thus knew that daylight was made up of a mixture of various colors of light such as red, orange, yellow, green, blue, indigo, and violet.

The "key" to unlock the mysteries of stellar physiognomy

In 1814, the German Francometer and the fee spectrometer were used to study the solar spectrum.

Investigate. They made a slit in the shutter of the darkroom so that sunlight could shine through the slit onto a prism behind which was a small telescope. Through the small telescope, Fu Lang and Fei were surprised to find that many dark lines appeared in the spectrum of the sun's "seven color bands".

After repeated counting, there are as many as 567 such dark lines. Based on several discoveries made by previous people, we have come to understand the true portrait of the star. The difference in the color of the star indicates that the temperature of each star is different, such as the white temperature is high and the red temperature is low, so the spectrum is the "key" to understanding the star.