Context: A group of international astrophysicists have identified cloud bands on the surface of Luhman 16A, one of a pair of binary brown dwarfs in the Vela constellation.
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- They have used an idea put forth nearly two decades ago by Indian astrophysicist Sujan Sengupta that the light emitted by a cloudy brown dwarf, or reflected off an extrasolar planet, will be polarised.
- He suggested that a polarimetric technique could help in probing the environment of these objects.
- Polarisation of brown dwarfs have been detected in the past but what makes Luhman 16 study special is detection of actual structure of clouds over one of pairs (Luhman 16A).
- The group, by using the Very Large Telescope at European Southern Observatory, Chile, found that Luhman 16A had band-like clouds in its atmosphere, whereas the same was not true of Luhman 16B.
- Understanding the cloud system over a brown dwarf can shed light on the pressure, temperature and climate on the surface of the celestial body.
- A brown dwarf is a type of substellar object that has a mass between those of the heaviest gas giant planets and the least massive stars, i.e., approximately 13 to 75–80 times that of Jupiter(MJ).
- Below this range are the sub-brown dwarfs (sometimes referred to as rogue planets), and above it are the least massive red dwarfs.
- Brown dwarfs may be fully convective, with no layers or chemical differentiation by depth.
- Unlike the stars , brown dwarfs are not massive enough to sustain nuclear fusion of ordinary hydrogen (1H) to helium in their cores.
- They are, however, thought to fuse deuterium (2H), and to fuse lithium (7Li) if their mass is > 65 (MJ) and glow faintly.
- It is a binary star system, the third closest system to the Sun after Alpha Centauri and Barnard’s star.
- At a distance of about 6.5 light years from the Sun, this pair of brown dwarfs referred to as Luhman 16A and Luhman 16B orbit each other, casting a dim light.
- It is located in the southern constellation Vela and is the closest known brown dwarfs.
- It is the measurement and interpretation of the polarization of transverse waves, most notably electromagnetic waves, such as radio or light waves.
- Polarization is a property applying to transverse waves that specifies the geometrical orientation of the oscillations.
- In a transverse wave, the direction of the oscillation is perpendicular to the direction of motion of the wave
- Typically polarimetry is done on electromagnetic waves that have traveled through or have been reflected, refracted or diffracted by some material in order to characterize that object.
- Polarimetry is used in -
- remote sensing applications, such as planetary science, astronomy,
- weather radar.
- computational analysis of waves etc.