Astronomy: Brown Dwarfs

Wikimedia Commons, CC BY-SA

Brown Dwarfs Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main-sequence stars. Their mass is approximately 13 to 80 times that of Jupiter (MJ)—not big enough to sustain nuclear fusion of hydrogen into helium in their cores, but massive enough to emit some light and heat from the fusion of deuterium, 2H, an isotope of hydrogen with a neutron as well as a proton, that can undergo fusion at lower temperatures.

Commentary

Source: Wikipedia (CC BY-SA)

Commentary

Source: Internal

Why Brown Dwarfs matters: Stars are the engines of the cosmos -- they forge the chemical elements, light up galaxies, and create the conditions that make planets and life possible. Astronomers classify self-luminous objects by spectral type, a distinction intimately tied to the surface temperature , and brown dwarfs occupy types M (2100–3500 K), L (1300–2100 K), T (600–1300 K), and Y (< 600 K). As brown dwarfs do not undergo stable hydrogen fusion, they cool down over time, progressively passing through later spectral types as they age. The "brown" in brown dwarf was meant to name a color between red and black. To the naked eye, most brown dwarfs would appear to be magenta or purple with others in different colors depending on their temperature. Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth. Though their existence was initially theorized in the 1960s, it was not until 1994 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 most of their light in the infrared. However, 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 about 6.5 light-years (2.0 parsecs) from the Sun. Luhman 16 is the third closest system to the Sun after Alpha Centauri and Barnard's Star.

Commentary

Source: Internal

Deep dive: Brown Dwarfs As brown dwarfs do not undergo stable hydrogen fusion, they cool down over time, progressively passing through later spectral types as they age. The "brown" in brown dwarf was meant to name a color between red and b lack. To the naked eye, most brown dwarfs would appear to be magenta or purple with others in different colors depending on their temperature. Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth. Though their existence was initially theorized in the 1960s, it was not until 1994 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 most of their light in the infrared. However, 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 about 6.5 light-years (2.0 parsecs) from the Sun. Luhman 16 is the third closest system to the Sun after Alpha Centauri and Barnard's Star. Source: https://en.wikipedia.org/wiki/Brown_dwarf (Wikipedia, CC BY-SA)