Brown Dwarf

## Properties

### Diameter range

around 100,000 kilometers to around 1,000,000 kilometers

## Kurzgesagt

### First appearance

The Last Star in the Universe – Red Dwarfs Explained

### Latest appearance

The Largest Star in the Universe – Size Comparison

## General Information

Brown dwarfs are failed stars from the same components, but does not have enough mass for nuclear fusion. Because of this, brown dwarfs glow dimly. Scientists believe there are many brown dwarfs, but it is hard to find.

They are around 13-90 times more massive than Jupiter. Brown dwarfs with only 13 times the mass can fuse deuterium, with 65 Jupiters being lithium. These make brown dwarfs not stars but also not planets since they are too massive.

Brown dwarfs are multiple colors based on their temperature. The warmest ones are red or orange, while the colder ones are magenta.

### Forming

Protoplanetary disks are dense clouds of gas and dusts that surrounds a star. Because the formation of brown dwarfs are similar to stars, disks around brown dwarfs are also similar to those around stars.

These disks may also form planets around the brown dwarfs. Since brown dwarfs have low mass, planets around them are expected to be low terrestrial. These bands can sometimes form ionized jets.

### History

Brown dwarfs were first proposed in the 1960s and were called black dwarfs, a type for dark objects floating freely in space that were not massive enough to fuse hydrogen. However, black dwarfs also refer to white dwarfs after it no longer emits light and heat. To prevent a mix up, other names, including planetar and substar, were made. In 1975, Jill Tarter proposed brown dwarf.

Scientists theorized that an object less than 0.09 solar masses would never go through a normal star evolution. The discovery of deuterium fusion brought it down to less than 0.012 solar masses and formation of dusts in the cold outer atmospheres of brown dwarfs made brown dwarfs seem impossible.

Brown dwarfs were hard to find because they emit almost no visible light. Their strongest light emissions are in the infrared spectrum. However, infrared detectors were too inaccurate to find brown dwarfs during that time.

Attempts to discover brown dwarfs were unsuccessful until 1988, when astronomers found a star named GD 165B. However, whether it would be classified as a brown dwarf or a low-mass star was debated because it was hard to distinguish between the two. Nowadays, GD 165B is confirmed to be a brown dwarf and is the prototype of a class of objects now called "L dwarfs".

After the discovery of GD 165B, other brown dwarf candidates were reported, although most candidates were disputed due to the absence of lithium that showed them to be actual stars. Stars would burn their lithium quickly, while brown dwarfs would not. So, if we discovered lithium in the atmosphere of an object older than 100 million years, it is safe to assume that it is a brown dwarf.

In 1994, the study of brown dwarfs changed with the discovery of two substellar objects, named Teide 1 and Gliese 229B. Gliese 229B was the first T dwarf discovered, in 1994 scientists from the John Hopkins University. In the same year, Spanish astrophysicists discovered Teide 1, the first M dwarf. They are significant because they were the first brown dwarfs to be fully verified and exhibits a feature that had only been observed in gas giants.

### Structure

Brown dwarfs form similarly to stars and are surrounded by protoplanetary disks made of gas, dust and a bunch of space rocks.

Protoplanetary disks are dense clouds of gas and dusts that surrounds a star. Because the formation of brown dwarfs are similar to stars, disks around brown dwarfs are also similar to those around stars.

These disks may also form planets around the brown dwarfs. Since brown dwarfs have low mass, planets around them are expected to be low mass planets — terrestrial planets. The infalling material from the disk also causes some brown dwarfs also produces jets of ionized material, such as Mayrit 1701117.

* Class M
* Class L
* Class T
* Class Y

Classes
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 Band
* Vanadium oxide

Classes
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 Band

Classes
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* Carbon monoxide

Classes
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