Brown dwarfs. The name “brown dwarf” was coined by Jill Tarter in 1975 , and it designates the interstellar gas groupings that have not achieved a mass large enough to have started continuous nuclear reactions of hydrogen fusion and thus become one star .
Summary
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- 1 Features
- 2 Types of brown dwarfs
- 3 The anomalous brightness of brown dwarfs
- 4 Utility of brown dwarfs
- 5 Sources
Characteristics
Brown dwarfs emit huge amounts of infrared radiation as a result of slow gravitational contraction and sporadic deuterium fusion reactions. Hence, they were called that, given their erratic nature .
The more massive a brown dwarf is, the higher its surface temperature , with a typical value of 700 ° C. Red giants, white dwarfs, and brown dwarfs are different types of stars. Brown dwarfs are not really stars, but they are not planets either, they are halfway between the two. They are not massive enough to shine the way stars do. But they are much larger than the planets , even than Jupiter
Types of brown dwarfs
There are basically two types of brown dwarf or dwarf coffee , as are also known. Those that are in a binary system, orbiting around a star or other brown dwarf, and those that roam through space under the attraction of some type of star within a star system.
The first verified brown dwarf was Teide 1 in 1995 , in the IAC-80 telescope of the Teide Astronomical Observatory (Tenerife). In order to detect brown dwarfs, a combination of the determination of their mass and direct images is used, in addition to the classical mode, the determination of lithium.
Due to its low mass, hydrogen does not reach the temperatures and pressures necessary to trigger the fusion of this element and lithium is not destroyed, remaining in the brown dwarf throughout its existence. This lithium can be detected through its characteristic emission spectra
The best characterized brown dwarf is Gliese 229B. Its luminosity is about one-tenth that of the faintest star. Its spectrum contains large amounts of methane and steam of water . Methane should not exist if the surface temperature was above 1,500ºK (815ºC).
The anomalous glows of brown dwarfs
At least 25,000 times weaker than the sun, brown dwarfs are still incredibly hot, with temperatures as high as 3,410ºF (2,000K, 1,737ºC). At such temperatures, substances like iron and sand are in the gaseous state. When brown dwarfs cool, these gases condense in the atmosphere as liquid droplets that form clouds , similar to water clouds on earth .
When the brown dwarf cools further, weather patterns cause the clouds to rapidly clear, allowing the bright infrared light from the hot atmosphere under the clouds to escape, giving rise to the unusual glow of brown dwarfs. During a relatively short phase, brown dwarfs appear brighter as they cool.
Utility of brown dwarfs
Brown dwarfs are very useful for astronomers who study star formation processes and extrasolar planets, especially their atmosphere , since that of these failed stars is similar to that of giant planets, such as Jupiter. And they are relatively easy to study because they are isolated in space and not orbiting a blinding star like exoplanets.