Closest Galaxies in our Universe

March 24, 2018

Canis Major - Closest Galaxy in Our Universe — Image Credits: SciTechDaily

Andromeda is NOT the Closest Galaxy in our Universe.

It is a long-known fact that the Milky Way is surrounded by millions or even billions of other galaxies. A common perception is that our closest galactic neighbor is the Andromeda Galaxy. Despite the overwhelming popularity of this idea, it’s not true. There are many other galaxies (such as Small and Large Magellanic Clouds) that are much closer to us.

NOTE: Andromeda is the closest Spiral galaxy to the Milky Way.

The Milky Way is a part of the Local Group that has 54 galaxies and dwarf galaxies in it. Therefore, it is not very surprising to know that we are much closer to our neighbors. Some of the closest galaxies in our universe are discussed below.

Table of Contents

Canis Major Dwarf Galaxy

It is our closest galactic companion and is a part of our galaxy. This dwarf galaxy is also known as Canis Major Over-density and is 25,000 light-years away from us. Interestingly, the Canis Major is much closer to us than our own galaxy. Yes, you read that right. Observations show that the Milky Way is 30,000 light-years away from our solar system.

The Canis Major Dwarf Galaxy was discovered in 2003 and has a diameter of about 5,200 light-years. The discovery of this galaxy was done during the Two-Micron All Sky Survey (2MASS). This infrared survey allowed the researchers to explore many regions for the first time. This is because these areas were covered by the dust and gas in the disc of the Milky Way.

The shape of Canis Major continues to change due to the presence of a long filament of stars. These tidal tails wrap the Milky Way three times in a ring-like structure called the ‘Monoceros Ring’. The gravitational pull of our galaxy is continuously degrading this dwarf galaxy and a merger is expected within the next billion years.

Sagittarius Dwarf Elliptical Galaxy

This elliptical galaxy is 70,000 light-years away from us and lies in the constellation of Sagittarius. It was discovered in 1994 and has a diameter of 10,000 light-years. At that time, the Sagittarius Dwarf Elliptical Galaxy (Sag DEG) was regarded as the closest galactic formation to the Milky Way. It held this position for several years before Canis Major was discovered.

This dwarf galaxy homes four globular clusters that are responsible for its elliptical shape. One of these clusters is called Messier 54, which was discovered by Charles Messier in 1778. The high concentration of dark matter within this galaxy allowed it to withstand the strong gravitational forces of the Milky Way. However, the accretion process is now in effect as the dwarf galaxy is going towards a merger.

Large Magellanic Cloud

This satellite galaxy of the Milky Way is at a distance of 163,000 light-years from our solar system. The Large Magellanic Cloud (LMC) lies on the border of the constellations Dorado and Mensa. Its diameter is as wide as 30,000 light-years while the mass-count goes up to 10 billion solar masses.

The fourth-largest galaxy is classified as Magellanic Spiral because it contains a bar of stars that are geometrically off-center. This is caused by tidal interactions from the Small Magellanic Cloud and the gravitational forces of the Milky Way. As a result, the Magellanic Cloud has an irregular shape.

There is no exact information about the date of its discovery. However, it is believed that this galaxy was found somewhere in the pre-historic times. Since then, it was considered the closest galaxy to the Earth until the discovery of Sag DEG in 1994.

Small Magellanic Cloud

This irregularly-shaped galaxy has a diameter of 7,000 light-years and it is 190,000 light-years away from the Earth. It is located across the constellations of Hydrus and Tucana. Astronomers believe that the Small Magellanic Cloud (SMC) once had a barred spiral structure. However, the disruption caused by the attractive forces of the Milky Way changed the shape of this galaxy.

The SMC is one of the farthest objects that can be seen with a naked human eye. Unfortunately, it can only be viewed from the Southern Hemisphere. Due to its low surface-level brightness, the SMC is generally only visible in regions that are far from city lights. This dwarf galaxy appears as a faint hazy cloud and is also known as ‘Nubecula Minor’.

The tidal interaction between the SMC and the LMC results in a bridge of gas. This star-forming site and a common envelope of neutral hydrogen suggest that these galaxies are interacting for a long time.

Draco Dwarf Galaxy

Albert George Wilson of Lowell Laboratory is the discoverer of this dwarf galaxy. He did so in 1954 on the photographic plates of the Palomar Observatory Sky Survey (POSS). The name ‘Draco’ came from its location as this galaxy is present in the direction of the Draco constellation.

This spheroidal galaxy is 3,000 light-years wide and is at a distance of 205,000 light-years from us. It is considered one of the faintest neighbors of the Milky Way and homes a lot of dark matter. In fact, the distribution of dark matter within this galaxy is nearly isothermal. Following this revelation, scientists are trying to learn more and more about this galactic neighbor.

Most of the stars in the Draco Galaxy are extremely old and there is hardly any interstellar matter. However, the central region of the galaxy does have some metal-rich stars.

Andromeda Galaxy

This spiral galaxy is about 2.5 million light-years away from the Earth. It is generally considered the closest galaxy in our universe, but that’s not true. This is because many galaxies (including the ones in this list) are present at much lesser distances. However, it is the nearest major galaxy and has almost a trillion stars over a diameter of 220,000 light-years.

The vicious vastness of the Andromeda Galaxy also makes it the largest galactic formation in our Local Group. According to scientists, Andromeda is expected to collide with the Milky Way in around 4.5 billion years. They believe that a giant elliptical galaxy will be the result of that massive clash.

The Andromeda Galaxy is the most distant object that can be seen with the naked eye. However, ideal conditions (clear night and a very dark sky) are necessary to view this beautiful, spiral galaxy.

Conclusion

The title of the closest galaxy (to the Milky Way) has shifted from one galaxy to another in the past few decades. Initially, the Large Magellanic Cloud held this position until the Sagittarius Elliptical Galaxy was discovered in 1994. In 2003, this position was taken away from this galaxy with the discovery of the Canis Major Dwarf Galaxy.

This galaxy is already within the Milky Way and is being pulled apart by the gravitational pull. In fact, scientists believe that the main body of the Canis Major is already damaged. They also mentioned that the accretion process will continue until this dwarf galaxy merges with the Milky Way.

On the other end of the spectrum, we have the Andromeda Galaxy, which is usually regarded as the closest galaxy. Although several other galaxies are closer to Earth than this spiral galaxy, it is the nearest major galaxy. Andromeda is expected to collide with the Milky Way in about 4.5 billion years.

References

Muneeb

Computer Scientist by qualification who loves to read, write, eat, and travel