Why do some stars still not reach Earth? How big is the universe?

We know that in the huge universe, human imagination cannot fill the greatness of the universe, and it is precisely because of this that human beings desperately want to explore the huge universe, want to surprise human beings from it, and also want to obtain important resources from it. After all, if human beings, as a living being, want to develop sustainably in the universe, they must obtain other resources. At this time, they will go to find other resources, and it is inevitable that they will explore the planet.

The answers are as follows. <>

1. The propagation of light requires a medium. First of all, the first point is that the propagation of light requires a medium, although in the vacuum of the universe, it still needs a medium substance for its propagation. As for the propagation speed of light, it can reach nearly 300,000 kilometers per second, and it is conceivable that this speed can travel nearly 20 circumferences of the earth in one second for us humans, and how fast the speed of light is.

But why the light of some stars cannot reach the Earth is a medium that may be lost in the process of propagation, so it cannot be propagated. <>

Second, there is also some light that is swallowed up by black holes. Secondly, there are some lights, and they may have encountered black holes. Black holes are one of the more peculiar phenomena in the universe, which can devour light and everything around them.

And its gravitational pull is also inescapable of light, and when light enters the black hole, it will not be seen in other parts of the black hole. Therefore, when the light passes through the black hole, we cannot see the existence of light, and the light disappears directly into the black hole. <>

Third, there are also some lights that are too faint for humans to pass through our eyeballs**. Last but not least, there are some stars that shine so far away that our eyes can't reach the Earth directly. After all, the light emitted by the sun is strong enough, not to mention that the light emitted by other stars may be directly obscured by the sun's light.

Because these stars are too far away from Earth to reach Earth. The diameter of the universe is about 160 billion light-years.

Because the universe is so big, the universe is too big to be described by the current units of measurement, it can only be said to be boundless.

Those stars were born late, too far away, and the light emitted from the birth time could not reach the earth. The universe is endless, but scientists have observed stars that are said to be the edge of the universe.

Because the universe is very large, with countless planets, the light emitted by some stars will be blocked by other planets, so it has not reached the earth so far.

The main reason is that the imaginary type is very far away from the earth, and the universe has been expanding, and the distance between the stars and the earth is also increasing, so it has never been illuminated to the earth.

It's because those photons never reach Earth.

There is a binary star system in the Milky Way galaxy that behaves very strangely. It consists of two stars: a relatively cold giant star and a relatively hot white dwarf.

They are 16,000 light-years away from Earth (a light-year is the distance that light travels in a year, meaning everything we see on these stars happened 16,000 years ago). This distance makes them difficult to observe in detail, but using science and technology and knowledge is something we do know about them.

The two stars may be interacting, with material flowing from the large, cold surface to the small, hot surface. Every once a year, they become active every once in a while, about every 9 to 15 years, dating back to the 90s of the 19th century, after a few years of clamour, and once a year, they become brighter at a specific wavelength that can be detected in the Earth's telescope. They are now in an active period, detecting flashes (or "bursts" of energy) in April 2016, May 2017, and April 2018 (the 2016 eruption itself is a bit odd, with two peaks two weeks apart).

Researchers expect another eruption in May and June 2019, but it's too early to publish any reports and can only be seen if it actually happens. But, as the researchers did in the study published in ARXIV, there was something strange about the activity during this period. In the past, binary activity cycles almost always followed a simple pattern:

The first few eruptions were "cold", and the white dwarf temperature seemed to drop with each eruption. Then, sometimes, as the temperature of the star rises, the next round of eruptions is a "hot" eruption.

Cold bursts tend to be much brighter than hot bursts, and cold bursts occur when a white dwarf begins to expand, its outermost atmosphere-like region grows and cools at the same time, a situation that doesn't happen during the lesser-known thermal bursts. But the current cycle is strange, it happened just 7 years after a small outbreak in 2008 and consisted entirely of "hot" outbursts. In the observation of this celestial body for almost 130 years in history, this behavior is rather peculiar, and there is no explanation as to why this phenomenon occurs.

Why do these "outbreaks" happen?

Another study, published in Arxiv, offers a popular explanation derived from a different star system. When the gravitational pull of a white dwarf traps material from its giant twin brother, an "accretion disk" is formed – it is made up of material that revolves around the white dwarf, waiting to fall on its surface. But this disc is unstable.

Because this behemoth sometimes injects it with more substance, and sometimes it injects it with less substance. Every once in a while, too much material will fall on the surface of the dwarf star, and there will be a peak of thermonuclear combustion on the outside of the star, and there should be quite little material there.

Modern scientists generally believe that stars originated from nebulae. The nebula collapses under its own gravitational pull, and the temperature in the center becomes higher and higher, and the pressure increases. Stars are born when the temperature and pressure in the center reach enough for a hydrogen molecule to undergo a nuclear fusion reaction.

There are no stars in the universe with a diameter of 1 light-year. 1 light-year is a very large distance. The speed of light is 300,000 kilometers per second.

The distance that light travels in a straight line in a cosmic vacuum in a year is 1 light-year. The distance of 1 light year is about 9,460.7 billion kilometers when converted into kilometers. It is about 63,241 times the average distance from the Earth to the Sun.

So how big are the stars currently known in the universe? The largest known star is called Stevenson 2-18. According to astronomers, Stevenson's diameter from 2 to 18 is 2,158 times the diameter of the Sun.

The diameter of the Sun is 1,392,000 km. So, the diameter of Stevenson 2-18 is about 3 billion kilometers. Stevenson 2-18 is already a very terrifying existence in the universe.

It's big enough to hold 10 billion suns. The sun is not even as good as dust in front of it. If it were placed in the position of the Sun in the solar system, its planetary radius would exceed the orbit of Saturn.

Even so, Stevenson's 2-18 is only light-years in diameter. Is it 1 light-year away in diameter?

Stevenson 2-18 is the largest star in the universe we know of? Is it possible that there are stars in the universe with a diameter of 1 light-year? It's just that we haven't found out yet.

We can infer from the average density and mass of a star whether it is possible or not.

Take the Sun, for example, which is a yellow dwarf star in the main-sequence phase. The average density of the sun is about grams of cubic centimeters. Although the average density of the Sun is only twice that of water, the Sun is a relatively "porcelain" star.

Scientists deduce that the initial mass of Stevenson 2-18 is between 35 and 42 times the mass of the sun. As a rough calculation, if Stevenson's 2-18 now has a mass of 35 times the mass of the Sun, then its average density is now only 1/100 million of the Sun's.

In that case, how can Stevenson 2-18 still be a star? This shows that Stevenson 2-18 is large not because of its mass, but because of its extreme expansion during the red giant phase. Most of its mass is concentrated in the core.

Illustration: Galaxies.

Conversely, if there were a star in the universe with a diameter of 1 light-year, and it was also a red supergiant star with the same size as Stevenson 2-18, how massive would it be? It has a mass of about 1 trillion times that of the Sun. What is this concept?

That's almost two-thirds of the total mass of the Milky Way. Is it possible that a star can make up two-thirds of the total mass of a galaxy? The massive black holes in those galaxies don't have such a large mass!

It is clear that there are no stars in the universe with a diameter of one light year.

The universe is so big that there are no wonders, and it is possible to exist; Stars are formed by the accumulation of large amounts of material in nebulae over a continuous process of evolution.

This cannot exist. Mostly giant spheres made of luminous plasma.

There should be such a star, but we have not found it, and the sky is high and we don't have the scientific and technological power to find it. Of course, it is formed through the accumulation of tens of millions of years.

Judging from the birth of stars and the evolution of spine oak, this is impossible, no matter how big the universe is, it cannot tolerate the existence of such a monster that violates the law.

Stars are not generated in the void, they are born in clouds of gas and dust rich in hydrogen elements, due to gravity or other light pressure disturbances generated by stars, the density of some nebulae becomes uneven, and gradually under the action of gravity, the density of material is condensed more and more densely, with the increase of density, the gravitational effect is stronger and stronger, absorbing and merging the surrounding material clusters into this center of mass, and obtaining angular momentum to form a disk-shaped vortex, in the central region, due to the first law of thermodynamics, the temperature of the entrenched gas will rise, This process takes about several million years, until the pressure and temperature cause the hydrogen to begin to produce fusion reactions, and then the matter in the center of the protostellar cloud obtains the equilibrium of pressure and gravity, and the output is relatively stable for a period of time, which becomes the so-called main-sequence star.

The mass and size of a star depends on the density of material dispersion in the nebula region in which it was born, and the denser the nebula, the more potential it has to nurture massive stars. But there is a limit, if a giant star provokes nuclear fusion in the center of the star and emits more light pressure energy than its own mass provokes gravity, it is called the Eddington limit. Beyond this limit, the star will begin to push itself, and theoretically a grand star cannot sustain such a grand mass because the stellar wind will crowd out too much matter.

When the central star begins to radiate energy outwards rapidly, a large amount of local matter close to the primordial star will be blown away from the center, and the remaining central mass of material that can be called a star cannot reach a diameter of 1 light-year. And once this supermassive star turns on nuclear fusion, its extinguishing speed will be much more violent than our sun, due to the huge mass, the density and temperature of the center of the center are far beyond ordinary stars, the hydrogen element in the center of the star will fuse out of the helium nucleus in a short period of time, the helium nucleus may not be able to withstand the high pressure and high temperature immediately, turn on helium nuclear fusion, the fusion reaction of the helium nucleus will release stronger and faster energy, at this time the hydrogen shell of the star shrinks, it looks more and more grand, but it is also losing mass.

When a supermassive star dies, it may be left with supernova sites that can be more than 1 light-year, but it can no longer be called a "star" at this time.

I don't think there will be a light-year-diameter good brother star in Liang Ye's universe; Because it has not been found in reality, and the existence of such traces is not theoretically supported.

Yes, the universe is very wide, and our exploration is very limited, and our understanding will be limited.

According to the current scientific and technological disappearance of human beings, the largest star measured by Yu Fan is only 2.4 billion kilometers in diameter, far less than the length of a hail light year trillion kilometers distance, but I think that not found it does not mean that it does not exist, and it will be continued by future scientists

One, the sun.

The Milky Way is a barred spiral galaxy about 100,000 light-years in diameter and includes between 100 billion and 400 billion stars. The Sun is a typical star of the Milky Way, located on the branch cantilever Orion Arm, 10,000 light-years away from the center of the Milky Way, and the solar system rotates around the center of the Milky Way at a speed of about 240 s, one revolution in 100 million years.

The eight planets in the solar system all orbit in a near-circular orbit in about the same plane, orbiting the Sun in the same direction. With the exception of Venus, the other planets have the same direction of rotation and revolution. Most comets orbit in the same direction around the Sun, most of them have elliptical orbits, and generally have a long orbital period.