Deep space objects > Galaxies
Galaxies are sprawling cosmic systems made up of dust, gas, and many stars. The exact number cannot be calculated, because there are 100 billion of them in the observable universe alone.
Some of the galaxies are very similar to the Milky Way, but there are also completely different specimens.
If there are less than a billion stars in a galaxy, then such a galactic type is called “small”. In the Milky Way, the Sun is only one of a billion stars.
Scientists have not fully understood the formation and evolution of galaxies, since the initial stages took place very early. The age of the ancients practically reaches the universal age – 10-13 billion years. Watch the galaxies video for more interesting and useful information about classification and age.
Milky Way Galaxy
We live in a barred spiral galaxy 100,000 years in diameter. The disk-shaped core bulges 30,000 light-years and houses a huge number of old stars and a black hole. Of the four spiral arms, our system is located in the Orion arm. It is distant from the center by 30,000 light years.
The solar system revolves around the galactic center of the Milky Way at a speed of 250 km / s and spends 220 million years on one pass.
There are three main types of galaxies in total: spiral, elliptical and irregular. The former include, for example, the Milky Way and Andromeda. In the center are objects and a black hole, around which a halo of stars and dark matter revolve. Sleeves branch off from the core. The spiral shape is formed because the galaxy does not stop rotating. Many representatives have only one sleeve, but some have three or more.
Table of characteristics of the main types of galaxies
|Elliptical galaxy||Spiral galaxy||Wrong galaxy|
|Spheroidal component||Whole galaxy||There is||Very weak|
|Star disk||No or mild||Main component||Main component|
|Gas and dust disk||No||There is||There is|
|Spiral branches||No or only near the core||There is||No|
|Percentage of the total number of galaxies||twenty%||55%||five%|
Spirals are available with or without a bridge. In the first type, the center is crossed by a dense bar of stars. And in the latter, such a formation is not observed.
Elliptical galaxies are home to the oldest stars and there is not enough dust and gas to create young ones. They can resemble a circle, oval or spiral type, but without sleeves.
About a quarter of the galaxies represent a group of irregular galaxies. They are smaller than spiral and display sometimes bizarre shapes. They can be explained by the appearance of new stars or by gravitational contact with a neighboring galaxy. Among the wrong ones are the Magellanic Clouds.
There are also many galactic subtypes: Seyfert (fast-moving spirals), bright elliptical supergiants (swallowing others), ring (no core), and others.
Types of galaxies
Spiral (like the Milky Way) is a galaxy with a flat disk, a convex center and spiral arms. The disk contains stars, planets, dust and gas, which revolve around the center. The speed can reach 100 km / s, which is why the material on the disk is formed in the form of a spiral. Some of them can create special shapes, due to which they receive their original names (like the Sombrero Galaxy).
Closer to the center of the bulge, older stars are concentrated, and new ones are formed in spiral systems. Their discs are surrounded by halos of mysterious dark matter.
You can learn more about spiral galaxies thanks to our article…
Messier spiral galaxies
Spiral galaxies with large bright stripes of stars and material cutting through the central sections are called “Barred Galaxies”. Most of these galaxies have bars – bars. Astronomers are interested in studying them because they still cannot understand what function they perform in galaxies. The bars can house supermassive black holes. They are divided into subgroups according to bulges, spiral arms and their density.
In addition, we have a separate article dedicated to barred spiral galaxies.
Messier barred spiral galaxies
Elliptical – an elliptical galaxy. As a rule, they are round, but slightly elongated along one axis. They can be elongated and resemble a cigar. This type contains many old stars (1 trillion), but lacks dust and other interstellar material. The stars are centered around the center but move in a random direction. Few new objects are formed.
The most famous are giant elliptical galaxies that can extend over 2 million light years. But this type can also be small – dwarf elliptical galaxies.
You can find out more about elliptical galaxies in our article…
Messier elliptical galaxies
Incorrect – a galaxy that does not fall into the first two types. They appear to be deformed or lack a specific shape because they are in contact with other objects.
Read more about the irregular galaxies in our article…
The most famous irregular galaxies
Messier irregular galaxies
List of lesser known galaxies:
- Bootes 1
- Virgo eyes
- Dwarf Galaxy in Pump
- Siamese twins
- Darth Vader’s Galaxy
- Condor Galaxy
- NGC 772
- NGC 1277
- NGC 1365
- NGC 1569
- NGC 1679
Clusters of galaxies
Galaxies can exist alone or in pairs. But in most cases, they are part of large associations, which are called groups, clusters and superclusters. Such objects interact and merge into single galaxies. Because of this, gases flow to the galactic center, which leads to the activation of the birth of stars.
It is believed that the Milky Way will one day merge with the Andromeda galaxy, located 2 million light years away and observed from the northern hemisphere. All these are stages of evolution, when the irregular ones transform into one of the forms, and the spiral ones become elliptical.
Origin of galaxies
Scientists believe that galaxies appeared immediately after the Big Bang, which created the universe 10-20 billion years ago. Already in the first milliseconds, gas clouds began to combine, collapse and shrink due to gravity, forming building blocks.
But if in this moment opinions agree, then disagreements appear in how it happened and how it began. Some people think that the initial stage was the merging of clusters of millions of stars. Others believe that from the very beginning there were galaxies, and only then the stars inside were combined into clusters. The video below about galaxies will tell you how the process of merging and absorption of galactic structures takes place.
It is a type of galaxy that emits more energy than a normal galaxy. The Milky Way is considered stable. Compared to it, active ones release 100 times more energy. This is due to explosions in the core. Energy is released in the form of radio waves. There are several varieties of such galaxies.
Seyfert galaxies resemble spiral galaxies with an extremely active nucleus. Quasars are of most interest, because in 1 second they are able to throw out as much energy as the Sun produces in its entire existence. They resemble stars and are considered the most energetic objects. Many believe that quasars act as active nuclei of distant galaxies in their early evolutionary stages. Light has been moving towards us for billions of years and can come even from the very beginning of the universe.
How did you find out about our galaxy? The ancients observed a light streak in the sky and called it the Milky Way. In the late 1500s. Galileo Galilei first looked at the stars through a telescope and realized that this strip is represented by many separate objects. In 1755, Immanuel Kant suggested that our galaxy is a lenticular stellar group, and there are many more in the Universe.
Years passed and scientists got to know the galaxy closer, but still put the Sun in its center. In 1918, that all changed when Harlow Shapley realized that we were on the periphery of the galaxy.
Hubble, galaxies and the expanding universe
It is worth expressing our deepest gratitude to Edwin Hubble, who in 1924 proved that our galaxy is one of many. With his 100-inch telescope, he noticed that the group of stars that were previously thought to be part of the Milky Way are actually the Andromeda galaxy, located 2.2 million light-years away. In 1927, Jan Oort proved that galaxies rotate around their center.
Hubble also revealed that distant galaxies are moving away from us at high speeds. This observation became Hubble’s law – the universe is expanding.
In 1996, the Hubble Telescope captured images of 1,500 distant galaxies in the process of forming, increasing the estimated number of galaxies. In the 1990s. believed that there could be only 50 billion. Of course, today’s numbers are much higher. On our site you have the opportunity to explore all types of galaxies and view high-quality photos, diagrams and drawings of the cosmic structures of the Universe.
- What is a galaxy ?;
- How many galaxies are there in the universe;
- The largest galaxy;
- The nearest galaxy to us;
- The youngest galaxy;
- Farthest captured object;
- How many galaxies have been found ?;
- How many planets are there in the galaxy ?;
- Distance to Andromeda;
- Who will the Milky Way collide with?
- What is the name of our galaxy?;
- In which galaxy is the Earth located;
- Why is our galaxy called the Milky Way?
- How does the galaxy get its name?
- Names of galaxies;
Superclusters and galaxy clusters
- Great attractor;
- The Virgo Cluster;
- Virgo Supercluster;
- Cluster of galaxies;
- Local group of galaxies;
- Evolution of galaxies;
- Rotation of galaxies;
- How do large galaxies appear ?;
- Galactic center;
- Active galactic nucleus;
- Galactic Plane;
- Galactic equator;
- Galactic alignment;
- What is intergalactic space ?;
Types of galaxies
- Spiral galaxies;
- Barred spiral galaxies;
- Wrong galaxies;
- Elliptical galaxies;
- Dwarf galaxies;
- Dark Matter Galaxy;
- Forms of galaxies;
- Magellanic clouds;
- Large Magellanic Cloud;
- Small Magellanic Cloud;
- Other galaxies;