Our galaxy, the Milky Way, is very typical: it has hundreds of billions of stars, enough gas and dust to form billions of stars, and the dark matter is at least ten times that of all the stars and gases here. All this is gathered here by gravity.
Like more than two-thirds of known galaxies, the Milky Way is spiral. At the center of the vortex, a lot of energy is being generated, and occasionally there will be a strong flash. We need great gravity to explain the motion and energy burst of stars. Astronomers infer that the center of the Milky Way is a supermassive black hole.
Some other galaxies are elliptical, while others are unusual toothpick shapes or rings. However, Hubble's ultra-deep open field of vision (HUDF) image shows a different picture. Hubble observed a small point in the sky (one ninth of the diameter of the moon) for one million seconds (1 1.6 days) and found about 10000 galaxies of different sizes, shapes and colors. On the ground, we can see a small part of this place, which is located on the hearth.
Illustration: Hubble ultra-deep space image galaxy: Source: NASA, ESA, S. Beckwith (STScI) and Hubble ultra-deep space team.
form
The universe after the Big Bang consists of radiation and subatomic debris. People have different views on what will happen next-will small pieces slowly combine to form stars, clusters and eventually galaxies, or will the universe first form huge blocks of matter and then subdivide them into galaxies?
collide
The shape of a galaxy is influenced by its neighbors and is often influenced by galaxy collisions. The Milky Way itself is experiencing a collision with Andromeda, our nearest neighbor. Although it is the same age as the Milky Way, Hubble observation still reveals that the stars in Andromeda's ring are much younger than those in the Milky Way. Based on this and other evidence, astronomers infer that Andromeda has split into one and possibly several other galaxies.
relevant knowledge
Galaxy is a gravitational binding system composed of stars, star residues, interstellar gas, dust and dark matter. The word "Galaxy" comes from the Greek word galaxy (γ α λ α ξ? α? ), which literally means "milky white", is quoted by the word Yinhe. Galaxies vary in size, from dwarf galaxies with hundreds of millions of stars (108) to giant galaxies with 100 trillion stars (10/4), and each galaxy rotates around the center of mass of its own galaxy.
Galaxies are divided into oval, spiral and irregular shapes according to their visual forms. Many galaxies are thought to have supermassive black holes at their centers. The black hole in the center of the Milky Way, Sagittarius A *, has a mass four million times that of the sun. By March of 20 16, GN-z 1 1 was the oldest and farthest galaxy observed, 32 billion light years away from the Earth, and it was not observed until 400 million years after BIGBANG.
A study published on 20 16 revised the number of galaxies in the Hubble volume from the previous estimate of 200 billion (2× 10 1) to 2 trillion (2×10/2) or more, which contained more stars than all the grains of sand on the earth. Most galaxies have a diameter of 1000 to 100000 seconds (about 3000 to 300000 light years), and the distance between them is several million seconds. In contrast, the Milky Way is at least 30,000 seconds (65,438+million light years) in diameter and 780,000 seconds (2.5 million light years) away from its nearest neighbor, Andromeda.
Illustration: Parsec (English Parsec, abbreviated as pc) is a unit of length in astronomy. Parsec is one of the oldest and most standard methods to measure the distance between stars.
(The picture shows the Andromeda galaxy)
The space between galaxies is filled with thin gas (intergalactic medium) with an average density of less than one atom per cubic meter. Most galaxies are organized into galaxy clusters, galaxy clusters and supercluster due to gravity. The Milky Way is a part of the local galaxy group, which is mainly composed of the Milky Way and Andromeda, and is a part of virgo supercluster. On the largest scale, these combinations are usually arranged in sheets and filaments surrounded by huge gaps. The largest known galaxy structure is a supercluster called Laniakea, which includes virgo supercluster.
reference data
1. Wikipedia
2. Astronomical terminology
3. Grasshopper/Sue
Please also get authorization for reprinting, and pay attention to maintaining integrity and indicating the source.