From the primitive era of eating raw meat and drinking blood to the technological era of flying into space, human technology has only been truly developed for more than 300 years.
But the achievements we have made are amazing, people's quality of life has greatly improved, and also turned their attention to the sky , and launched a comprehensive exploration of the universe.
We often use "universal" to describe the universe, but if we ask how vast the universe is, there seems to be no more specific concept. For a long time in the past, the Earth's atmosphere has seriously limited human observation ability of the depths of the universe. Only by walking out of the earth can we truly appreciate the silence and vastness of space.
A series of photos sent back through a large optical space telescope, we see stars and galaxies shining deep in the universe. So another question arises: How many galaxies are there in the universe?
We cannot see every corner of the universe , so how do we get the specific data?
To answer this question, we cannot do without the already old Hubble Telescope . In the past 30 years of working hours, the number of effective observations of has exceeded 1 million . In the face of the questions we raised today, it has also given answers again and again, and has constantly refreshed people's cognition.
1995, five years after the Hubble Space Telescope was launched, scientists aimed its direction at a sky area above the Beidou Spoon. On the earth, it looked at it with the naked eye, and there was almost nothing there. This small area is only the size of a coin, and accounts for one-26 million of the day.
Hubble took a total of 342 shots in this void area in 10 days, covering ultraviolet, visible light and infrared . In order to obtain more light input, the shooting time of Hubble usually takes 20-40 minutes for each time , and the researchers finally obtained 342 photos. After superimposing these photos, we saw the first Hubble Deep Space Field.
In this radius of only the size of a coin, there are at least 1,500 galaxies of large and small sizes. Each of them is similar to the size of the Milky Way . These galaxies are far and near to the earth. The distance between and the distance between the earth ranges from millions to tens of millions of light years. They are displayed in bright blue and purple. The galaxies far away from the earth have reached tens of billions of light years. The wavelengths they emit have been stretched to the infrared band at a long distance, so there is a dim red light in the figure.
Through this photo, scientists estimate that in the current observable universe , there are at least 1,100 billion galaxies. This is the first time that humans have estimated the lower limit of the universe galaxy. We seem to have no idea about this number, but this is just the beginning.
After the Hubble Deep Space Field was successful, the Hubble Telescope conducted several deep space observations one after another.
2003, Hubble aimed the lens at the day furnace seat direction. This area is located in ascension 3h 32m 40.0s, declination -27°47' 29", its range is only 3 square angle seconds, stretch your arms straight towards space, At this time, the size of the fingernail is the area taken by the Hubble Telescope. cannot see any celestial bodies here with the naked eye. It is far away from many stars in the Milky Way, which reduces interference.
This observation work is divided into two stages. In the second stage, Hubble's newly installed third-generation wide-angle camera and infrared camera came in handy, and 97 was carried out. 800 exposures were shot in 60,000 seconds. The results of analysis show that there are at least 10,000 galaxies in this Hubble Super Deep Field, and most of them are 1 billion to 4 billion times darker than the darkest celestial bodies visible to humans with naked eyes. Among them, the farthest galaxies from the earth reached 13 billion light years.
Based on the number of galaxies contained in this super deep space field, scientists have re-estimated the number of galaxies contained in the universe.In the observable universe, the number of galaxies in the universe has reached at least 150 billion . So how do scientists estimate the number of galaxies in the entire universe through deep field photos?
Modern astronomy believes that the distribution density of matter in the universe is generally relatively uniform. That is to say, count how many galaxies are in the photo and then calculate the proportion of the shooting area to the entire sky, and you can roughly estimate how many galaxies are in the entire universe.
Initially, scientists estimated this value to 176 billion
However, later, a research team from the University of Nottingham simulated the universe in a computer. Based on the theory of Big Bang , it added various mathematical models and physical parameters, combined with the observation data of the Hubble Telescope, and finally calculated that within the current range of 93 billion observable universes, there are at least two trillion galaxies , which is ten times the previous estimate.
In fact, due to the obstacles of cosmic dust and the distance, we cannot observe many galaxies. And the above statistics are based on the current observable universe.
In addition to the observable universe, there is also a universe that we cannot see. The light emitted there has not reached the earth yet. Judging from the current expansion speed of the universe, their light may never be able to transmit. Therefore, the real size of the universe has long exceeded our cognition.
