What is Brown dwarf: Definition and 22 Discussions

Brown dwarfs are substellar objects which are not massive enough to sustain nuclear fusion of ordinary hydrogen (1H) into helium in their cores, unlike main sequence stars. They have a mass between the most massive gas giant planets and the least massive stars, approximately 13 to 80 times that of Jupiter (MJ). However, they are able to fuse deuterium (2H), and the most massive (> 65 MJ) are able to fuse lithium (7Li).Astronomers classify self-luminous objects by spectral class, a distinction intimately tied to the surface temperature, and brown dwarfs occupy types M, L, T, and Y. As brown dwarfs do not undergo stable hydrogen fusion they cool down over time, progressively passing through later spectral types as they age.
Despite their name, to the naked eye brown dwarfs would appear different colors depending on their temperature. The warmest are possibly orange or red, while cooler brown dwarfs would likely appear magenta to the human eye. Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth.Though originally theorized in the 1960s to exist, it was not until the mid-1990s that the first unambiguous brown dwarfs were discovered. As brown dwarfs have relatively low surface temperatures they are not very bright at visible wavelengths, emitting the majority of their light in the infrared. With the advent of more capable infrared detecting devices thousands of brown dwarfs have been identified. The nearest known brown dwarfs are located in the Luhman 16 system, a binary of L and T type brown dwarfs at a distance of about 6.5 light years. Luhman 16 is the third closest system to the Sun after Alpha Centauri and Barnard's Star.

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  1. F

    B Forming Stars/ Brown Dwarfs by photo-erosion

    Hello, do anybody knows something about the formation of Stars and brown Dwarfs due to photo-erosion? If prestellar cores form in a molekular cloud with some O- and B-stars, the gas or the hydrogen gets ionised and this somehow stops the protostar from akkreting more mass. Why does that stop...
  2. F

    B Can a T-tauri star degenerate into a Brown dwarf?

    Can T-tauri stars, due to the fact that they loose matter, become a Brown dwarf?
  3. F

    B Formation of Brown Dwarfs in filaments?

    Hello, I'm in grade 12, writing a term paper on brown dwarfs and am currently looking at their formation. I have now come across the formation of brown dwarfs in so-called "filaments" (link to the page below), but can't find out anything about them, except for the fact that they are filamentary...
  4. ZX.Liang

    I Is there a difference between an ultracool dwarf and a brown dwarf?

    After reading the introduction of ultracool dwarf and brown dwarf in Wikipedia, I can't see the difference between them. Besides, do they all belong to the main sequence stars?
  5. T

    I How does a brown dwarf's temperature decrease over time?

    A brown dwarf is not quite a star whose core temperatures are only a few million degrees and can't initiate fusion. After billions of years it has to cool down. Does the hydrogen just dissipate or does the hydrogen cool down to the temperature of the universe, a few degrees kelvin, and form...
  6. mollwollfumble

    B Would lightning be possible on brown dwarfs?

    Lightning is well known from planets, and to some extent the bigger the planet, the more powerful the lightning. Would it also be possible on brown dwarfs (Y, T, L, M)? What about red dwarfs (M)? Other stars?
  7. Skyland

    Could an Interstellar Gas Planet Heat its Moon Without Fusion Ignition?

    Summary: Can an interstellar planet be hot enough to heat it's terrestrial moon without igniting fusion? I am a science fiction writer, however I am studying astrophysics to better captivate audiences with real and believable plots, The idea in question is an interstellar sub brown dwarf gas...
  8. T

    B Brown Dwarf Mass Gain: Does Radius Increase?

    Why wouldn't a brown dwarf grow in radius if it started to gain mass?
  9. |Glitch|

    B What is the relationship between brown dwarfs and giant gas planets?

    It has been my understanding that a brown dwarf was defined by when an object has achieved sufficient mass to begin deuterium fusion. Much like a star is defined by when it has achieved sufficient mass to begin hydrogen fusion. The minimum mass to begin fusing deuterium is estimated to be...
  10. |Glitch|

    B Exploring the Binary Brown Dwarf Pair Luhman 16AB and Its Orbiting Objects

    I have been reading up on the latest Hubble observations concerning the binary brown dwarf pair Luhman 16AB (officially WISE J104915.57-531906.1AB). It occurred to me that I did not know what to call the objects that most likely are in orbit around both brown dwarfs. Since brown dwarfs are...
  11. C

    B First Direct Measurement of Brown Dwarf Mass Limit: 6.7% Sun

    by Ken Croswell New observations indicate that objects born with a mass just 6.7 per cent that of the Sun can shine for trillions of years rather than fizzle out as failed stars known as brown dwarfs. Link: New Scientist
  12. |Glitch|

    I Could Brown Dwarf Sub-Dwarf Companions Host Habitable Moons?

    The majority of our focus for exoplanets have been around main sequence stars, understandably so. However, one place we have not looked very closely is for exoplanets around brown dwarfs (or would it be exomoons?). Brown dwarfs are not quite planets and not quite stars, so I am not certain...
  13. |Glitch|

    A possible super-Earth or Brown Dwarf in our Solar System

    Below is the arXiv free reprint being referenced by the above magazine article. Ironically, they were using ALMA in order to attempt to confirm the exoplanet previously found orbiting Alpha Centauri B when this object was discovered. The brighter the object the more likely it would have been...
  14. rpthomps

    Calculating Core Temperature of a Brown Dwarf

    To begin with, I am an enthusiastic but very amateur physicist. I am working on my knowledge by taking online open courseware, buying textbooks and doing all the questions. I recently bought Astrophysics of Planet Formation which is no doubt out of my league but I like to pick at it from time to...
  15. T

    Could an Exomoon Survive Permenant Shade from a Gas Giant?

    Hello, thank you for reading my post. For a story I am working on I am wondering about the plausibility of some star and planet configurations. I have done some web research on my own and learned a lot, but for some things I think my vocabulary and knowledge is too limited to search for exactly...
  16. wolram

    What happens to the gravitational energy of a cooling brown dwarf galaxy?

    Brown dwarf galaxies are, i think the coldest systems in the universe, If they continue to loose heat energy they must loose gravitational energy as well, eventually these galaxies will be ripped apart by the tidal effects of more massive galaxies. So if this is correct what happened to the...
  17. Chronos

    Could life arise on a brown dwarf?

    The recent discovery of a warm super-Jupiter [re: https://www.physicsforums.com/showthread.php?t=727440] raises tantalizing questions about the prospects of life being found on, or near, such a body. A quick perusal of the literature reveals [unsurprisingly] this possibility has been considered...
  18. F

    Brown Dwarf more massive than stars?

    Is it possible for some brown dwarves to be more massive than some stars?
  19. D

    Take a stroll on a brown dwarf

    Apparently, you can: http://news.yahoo.com/blogs/technology-blog/nasa-spots-chilled-stars-cooler-human-body-004551421.html At least temperature-wise. Don't know about the gravity... If the brown dwarf is that cool, though, wouldn't it still be a gassy object, too tenuous to walk?
  20. C

    How Do You Calculate the Mass of a Brown Dwarf in a Binary System?

    Hello! I'm struggling with a particular question, and have no idea where to look or seek help at the moment. It's driving me crazy! I have a feel I need to use Kepler's Third Law, but am unsure how to apply it in this situation. Here: Suppose you observe a binary system containing a...
  21. Q

    Beyond brown dwarf mass to sustained fusion

    Did a brown dwarf ever experience fusion? What is the smallest size star, ie., sustained fusion model? ... how do we determine the mass that will sustain fusion of a star.? What effect does plasma in space have on star's fusion reaction? thank you
  22. Loren Booda

    Life on a brown dwarf or a fissioning rouge planet?

    Life on a brown dwarf or a fissioning rogue planet? Is life on a brown dwarf or a rogue planet with a fissioning core any less feasible than life in a solar system?