Sub-brown dwarf

Some things in space are hard to name.

They are like big clouds of gas. These clouds fall in on themselves. This makes a sub-brown dwarf.

They are not quite stars. They are also not quite planets. They are very small. They have a small amount of mass.

Some float all alone in space. Others move around a star. They can even move around a brown dwarf.

Scientists still talk about them. They do not always agree on a name. It is a big mystery.

Space is full of many surprises.

Space has many strange objects. One is the sub-brown dwarf.

These objects form like stars. They start when a gas cloud collapses. A cloud falls in on itself to make the object. But sub-brown dwarfs are very small. They have a planetary mass. This means they weigh less than a brown dwarf. A brown dwarf is a type of small star.

Some sub-brown dwarfs float alone. People call these rogue planets. Others move around a star. Some even orbit a brown dwarf. Scientists do not always agree on their names. Some say they are planets. Others say they are sub-brown dwarfs.

One sub-brown dwarf is called Cha 110913-773444. It has a mass of 5 to 15 times Jupiter. Jupiter is a very large planet in our solar system. Another object is OTS 44. It has a mass of 11.5 times Jupiter. These objects are hard to study. They are often found in young star clusters. They are a big part of the mystery of space.

Space is full of objects that are hard to name. One such object is a sub-brown dwarf. These objects are also called planetary-mass brown dwarfs. They are very interesting because they sit between stars and planets. A sub-brown dwarf forms just like a star does. It starts when a big cloud of gas collapses inward. This collapse creates the object. However, these objects do not have enough mass to become true stars.

How these objects work depends on their weight. To become a star, an object must be heavy enough to start fusion. This is a process where gas creates energy. Sub-brown dwarfs are below the mass needed for this. They lack the mass to start fusion of deuterium. This is a type of fuel for small stars. The smallest mass for these objects is about 1 Jupiter mass. This is because the gas must be able to release heat. If the gas is too thick, it cannot let the heat out.

Scientists have spent a long time debating what to call them. The IAU Working Group on Extra-Solar Planets helped with this. They gave a definition in February 2003. They said a sub-brown dwarf is a free-floating body. These bodies are found in young star clusters. They must be below the mass limit for brown dwarfs. Some researchers call them rogue planets instead. This is because they float alone in space.

There are many real examples of these objects in our sky. One object is named WISE 0855–0714. It is about 3 to 10 Jupiter masses. It is quite close at only 7 light years away. Another example is S Ori 52. This one is 10 to 25 Jupiter masses. It is 13 light years away from us. Cha 110913-773444 is another one. It is 5 to 15 Jupiter masses and 163 light years away.

It can be hard to tell these apart from planets. Some sub-brown dwarfs orbit a star. Others orbit a brown dwarf. For example, 2M1207b orbits a young brown dwarf. This object might even have its own disk of material. Some people think these should be called planets. Others think the way they formed makes them sub-brown dwarfs. It is a big mystery that scientists are still solving.

A sub-brown dwarf is a mysterious type of astronomical object. It is also known as a planetary-mass brown dwarf. These objects exist in a strange middle ground between stars and planets. They are large enough to form like a star, but they lack the mass to act like one. This makes them a unique subject for astronomers to study. Understanding them helps us learn how different parts of our universe are built.

The formation of a sub-brown dwarf follows the same path as a star. It begins when a massive cloud of gas collapses inward due to gravity. This process is sometimes aided by a process called photo-erosion. As the gas cloud shrinks, it becomes much denser. However, a sub-brown dwarf never reaches a specific mass limit. It stays below the mass required for the thermonuclear fusion of deuterium. Deuterium is a type of fuel that small stars use to create energy. Because they cannot start this fusion, they never shine like true stars.

There is a specific limit to how small these objects can be. The smallest mass for a sub-brown dwarf is about 1 Jupiter mass (MJ). This limit exists because of how heat moves through gas. To collapse into an object, the gas must radiate away energy as heat. This process is limited by the opacity of the gas. If the gas is too thick, the heat cannot escape easily. A candidate object with a mass of 3 MJ was described in a 2007 research paper.

Astronomers often debate how to classify these objects. The IAU Working Group on Extra-Solar Planets (WGESP) provided a formal definition in February 2003. They defined a sub-brown dwarf as a free-floating body found in young star clusters. These bodies must be below the lower mass cut-off for brown dwarfs. Some researchers prefer the term "rogue planets" for objects that float alone. This is because they can be very difficult to distinguish from planets through observation alone.

Sub-brown dwarfs can be found in different environments. Some are free-floating, meaning they do not orbit a star. Others may orbit a star or even a brown dwarf. For example, the object 2M1207b orbits a young brown dwarf. This object may even have its own circumstellar disk of material. There is no consensus on whether these companions are planets or sub-brown dwarfs. The IAU definition of an exoplanet often ignores the formation mechanism. This means objects that formed like stars might still be called planets by some scientists.

We have found several examples of these objects in space. One free-floating object is WISE 0855–0714, which is 3 to 10 MJ. It is located only about 7 light years away. Another is S Ori 52, which has a mass of 10 to 25 MJ. It is 13 light years from Earth. Cha 110913-773444 is much further at 163 light years away. It has a mass between 5 and 15 MJ. Other examples include CFBDSIR 2149−0403 and OTS 44.

These objects help us understand the boundaries of celestial bodies. They connect the study of star formation to the study of planet formation. By looking at mass ratios, scientists try to tell them apart. The IAU requires a mass ratio of about q < 0.04 for exoplanets. However, the object WISE J0336−0143AB has a mass ratio of q = 0.61. This makes it a sub-brown dwarf rather than an exoplanet under IAU rules. Studying these objects reveals how much variety exists in the cosmos.