Cartwheel Galaxy

This galaxy looks like a wheel.

It has a big outer ring. A small galaxy hit it long ago. This hit made a big wave. The wave pushed gas and dust. This helped make many new stars.

There is also a smaller ring inside. Some thin lines look like spokes. They connect the rings together. It is a very busy place in space.

One bright star even exploded there. This makes the galaxy look very special. It is a beautiful sight to see.

The Cartwheel Galaxy looks very strange. It is a ring galaxy. This means it has a shape like a wheel.

This galaxy is far away. It sits in the Sculptor constellation. Fritz Zwicky found it in 1941. It has two main rings. The outer ring is very bright. This is because new stars are forming there. A big wave of gas and dust made them.

How did this happen? A long time ago, a smaller galaxy hit it. This was a head-on hit. The hit sent a shock wave through the galaxy. This wave moved fast. It pushed gas and dust into a ring. Scientists think a galaxy called G3 was the "bullet." It plunged right through the center.

Thin lines connect the rings. We call these spokes. The galaxy might look like a normal spiral again one day. This will happen as the gas and stars move back. The galaxy also has many X-ray sources. These are bright spots. They may be black holes. These black holes pull matter from nearby stars. This makes them shine very bright.

The Cartwheel Galaxy is a very strange and beautiful object. It is a ring galaxy located in the Sculptor constellation. This galaxy sits about 500 million light-years away from us.

It has a shape that looks like a wheel. The galaxy is the biggest member of its own group. This group includes four galaxies that stay close together. The Cartwheel is much larger than the Andromeda Galaxy. Its diameter is about 150,000 light-years across.

This galaxy has a very complicated shape. It has an outer ring and an inner ring. The outer ring is a very bright place. This is where many new stars are forming right now. A shock wave pushed gas and dust into this ring. This process is called a starburst. The ring is a bluish color because it is so bright.

There are also thin lines called spokes. These spokes connect the outer ring to the inner ring. Some spokes can be seen in radio waves. Other spokes can be seen with visible light.

A long time ago, a big event changed this galaxy. It used to be a normal spiral galaxy. Then, a smaller galaxy hit it head-on. This hit happened about 200 to 300 million years ago. The smaller galaxy acted like a bullet. It plunged straight through the disk of the Cartwheel. This collision sent a powerful shock wave outward. The wave swept up gas and dust as it moved.

This movement created the rings we see today.

Scientists have worked hard to understand this galaxy. Fritz Zwicky discovered the Cartwheel Galaxy in 1941. He thought it was a very complicated structure. Today, we think a galaxy named G3 was the bullet. We know this because of a tail of hydrogen gas. This gas tail connects G3 to the Cartwheel.

The gas is very light and easy to pull away. Other nearby galaxies are named G1 and G2. G1 is a small blue spiral galaxy. G2 is a yellow spiral with a long tail.

The Cartwheel Galaxy is a very active place. It has many bright X-ray sources along its rim. These bright spots might be black holes. Some are black holes with a companion star. They pull matter off the star to shine brightly.

One star even exploded as a supernova in 2021. This event was called SN 2021afdx. In the future, the galaxy will change again. The gas and stars will fall back toward the center. The galaxy will likely become a spiral shape again.

The Cartwheel Galaxy, cataloged as ESO 350-40 and PGC 2248, is a striking lenticular ring galaxy. It is located roughly 500 million light-years away within the constellation Sculptor. This galaxy is the dominant member of the Cartwheel Galaxy group. This group consists of four physically associated spiral galaxies. The Cartwheel is quite large, with a diameter of approximately 150,000 light-years. This makes it slightly larger than our neighbor, the Andromeda Galaxy.

The galaxy possesses a highly complicated and disturbed structure. It is defined by two main rings. The outer ring is a site of massive, ongoing star formation. This happens because a shock wave has compressed gas and dust. This compression creates a starburst region, which makes the ring appear bright and bluish. Inside this is an inner ring that surrounds the galactic center. This inner ring also contains a ring of dark, absorbing dust. Connecting these two rings are several optical arms known as "spokes." While both radio and optical spokes exist, they do not seem to overlap.

This unique shape is the result of a violent cosmic event. Originally, the Cartwheel was a normal spiral galaxy. Approximately 200 to 300 million years ago, it underwent a head-on collision. A smaller companion galaxy passed through it in a "bullseye" style impact. This collision generated a powerful gravitational shock wave. As this wave moved outward at high speed, it swept up gas and dust. This process created the bright starburst ring we see today. The central portion of the galaxy remained largely unscathed as the wave expanded.

Astronomers have long studied this complex system. Fritz Zwicky discovered the galaxy in 1941. He described it as one of the most complicated structures requiring an explanation based on stellar dynamics. Today, scientists use HI (neutral hydrogen) tail mapping to understand these collisions. Hydrogen is the lightest and most abundant gas in galaxies. It is easily torn away by gravitational forces. By mapping these tails, researchers can identify the "culprit" galaxy that caused the collision.

In the Cartwheel group, there are three companions labeled G1, G2, and G3. G1 is a smaller, irregular blue Magellanic spiral. G2 is a yellow, compact spiral that features a tidal tail. G3 is a more distant spiral often seen in wide-field images. Most evidence suggests that G3 is the "bullet" galaxy. It is located about 88 kiloparsecs, or 287,000 light-years, away. An HI tail connects G3 to the Cartwheel, supporting this theory. This is more likely than G1 or G2 being the intruder, as they remain much closer to the Cartwheel.

The intense star formation in the ring leads to extreme phenomena. The massive stars created in the starburst eventually explode as supernovas. For example, the ATLAS system discovered a Type II supernova, SN 2021afdx, on November 23, 2021. These explosions leave behind neutron stars and black holes. Some of these objects become ultra or hyperluminous X-ray sources. This happens when a black hole pulls matter off a nearby companion star. The Cartwheel contains an exceptionally large number of these X-ray sources along its rim.

The future of the Cartwheel Galaxy involves a slow return to normalcy. Over the next few hundred million years, the current ring structure is expected to disintegrate. The remaining gas, dust, and stars will begin to fall back toward the center. If the companion galaxies G1, G2, and G3 remain distant, the galaxy will likely regain a spiral shape. This recovery depends on the reformation of spiral density waves. The galaxy's evolution shows how massive gravitational interactions can temporarily transform the fundamental shape of a galactic system.