The early launch of the deep space probe, Voyager 1, is rapidly moving away from the sun and Earth. Launched by NASA in 1977, it has been in space for more than 40 years, but has flown more than 20 billion kilometers but still hasn't flown out of the solar system. It will take a long, long time to fly out of the solar system and reach the nearest star system.
The earth was too big for the ancients, but when we went to space, we found that the distance on the earth was nothing, and the solar system was really big. Pluto is not the outermost object of the solar system, and further afield, there is a celestial body called the Ault Nebula, which is the true boundary of the solar system, according to which the radius of the solar system can be estimated to be up to one light-year.
Voyager 1 is one of the fastest probes in human history, but it is only 17 kilometers per second, and it will take tens of thousands of years to fly out of the solar system. But even if it flies out of the solar system, humans can only walk out of the novice village.
Because the solar system is really not big in the universe, just a star system, and above it there is a Milky Way. The Milky Way is a stellar aggregate of hundreds of billions of stars, and the Sun is just one of the hundreds of billions of stars in the Milky Way, like a speck of dust.
Where are the current boundaries of the Milky Way? The scientific community is inconclusive, but at least it is certain that the diameter of the Milky Way is at least a hundred thousand light-years across. Compared with the solar system, the Milky Way is too big, even if it is flying at the speed of light, it will take at least tens of thousands of years to fly out of the Milky Way, but it is less than 10,000 years before humans entered the era of civilization.
The Milky Way is so big, it's really so big that it's desperate. Speed can be used as a yardstick to measure the level of development of a civilization, and the fastest speed that humans can barely reach now is only 1/10,000 of the speed of light. If human civilization wants to develop into a cosmic civilization, it must break through the limit of the speed of light, otherwise even the galaxy will not be able to go out. Because even if there is enough time, the speed must reach hundreds of kilometers per second (the fourth cosmic speed) to break through the gravitational bondage of the Milky Way.
The largest galaxy in the universe
You think the Milky Way is already very large, and in fact it is only a fraction of the largest galaxy in the universe.
In the Abel 2029 galaxy group, 1 billion light-years away from Earth, there is a central galaxy with a diameter (including a halo) of about 4 million light-years, IC 1101. IC 1101 is one of the largest galaxies in the universe, with a diameter of about 20 times that of the Milky Way, containing tens of millions of stars, and having tens of thousands of times the mass of the Milky Way.
But that's not all, the largest galaxy in the known universe is the Alcuonius galaxy, which was only discovered not long ago, and the conclusion comes from a paper published in the journal Astronomy and Astrophysics on February 16, 2022.
The galaxy is 3 billion light-years away and has an estimated diameter of 16.3 million light-years, a circle larger than IC 1101. In terms of diameter alone, it is about 4 times the diameter of IC 1101 and more than 100 times that of the Milky Way. For this big Mac, even if it is crossed at the speed of light, it will take more than 16 million years.
Interestingly, the Alcuonius galaxy is fat, and although its volume is large, its mass is estimated to be only 27% of that of the Milky Way, and it should be the sparsest known star density in the universe. As for why its volume is so large? Scientists don't know at the moment.
The top celestial structure in the universe
Above the planets are stars, above the stars are galaxies, above galaxies are galaxy clusters, and above galaxies are superclusters.
There are first-class celestial structures in the universe, and now scientists have discovered that the local galaxy group in which the Milky Way is located is only a small part of the Raniakea supercluster. To illustrate here, galaxy groups and galaxy clusters are celestial structures of the same level, but galaxy clusters contain more galaxies.
Previously, scientists thought that the Milky Way's home group of local galaxies was a member of the Virgo Supercluster , also known as the Native Supercluster. The Virgo Supercluster spans about 110 million light-years and contains about 100 galaxy clusters (groups) with its center about 60 million light-years from Earth and located in the constellation Virgo.
In 2014, scientists redefined the concept of a supercluster by the apparent velocity of galaxies and defined the Raniakea supercluster. According to the new definition, the Virgo supercluster is only part of the Raniakea supercluster.
At the level of the galaxy cluster, the distribution of celestial bodies is relatively scattered. The Raniakea Supercluster is a relatively evacuated celestial structure that is sustained by the enormous gravitational pull between different galaxy clusters, spanning 530 million light-years. As shown in the image below, the Milky Way is located on a tassel on this evacuation structure.
The three superclusters previously thought to have separated from each other are only a part of it, and these three parts include the Serpent-Centauri supercluster and the Peacock-Indian supercluster in addition to the aforementioned Virgo supercluster. Among them, the gravitational center of the Raniakea supercluster , the " giant source " , is located in the Serpent - Centaurus supercluster.
It is estimated that the Ranyakea Supercluster contains about hundreds of galaxy clusters and galaxy groups, and the number of galaxies is as high as 100,000. The mass of the Ranyakea Supercluster is estimated to be 100,000 times that of the Milky Way, and it can be seen that the Milky Way is just a speck of dust from the Ranyakea Supercluster.
In the vast universe, there is more than one celestial structure as large as the Raniakea Supercluster, such as the size of the Constellation Supercluster. However, there is a larger celestial structure above the Ranyakea Supercluster, the Pisces-Cetus Supercluster complex.
The Pisces-Cetus supercluster complex, which is a large-scale fibrous structure. It is estimated to be 1 billion light-years long and 150 million light-years wide, and the mass of the Virgo Supercluster is estimated to be only 1% of it. The fibrous structure is the largest known structure in the universe, in addition to this complex, other fibrous structures include the Shi long Great Wall (about 1.37 billion light years long), the Wuxian-Northern Corona Great Wall (about 10 billion light years long) and so on.
In short, the universe is simply too big. Pessimistically, the end of the history of human civilization may be difficult to break through the shackles of this top celestial structure, let alone travel through the entire universe. Because the diameter of the entire known universe is as high as 93 billion light-years, and the universe is still accelerating and expanding, the future will only be larger.
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