International Space Agencies – Missions and Discoveries

Luhman 16A: A binary brown-dwarf system


From UPSC perspective, the following things are important :

Prelims level : Luhman 16A, Binary star system

Mains level : Not Much

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.

Space terminology has gained importance in prelims. The Luhman 16A coupled with few more examples of space concepts like binary star and dwarf star are discussed in this newscard.

Luhman 16A

  • Luhman 16 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.
  • Brown dwarfs are also called failed stars because their masses are intermediate to the largest planets and the smallest main sequence stars.
  • Their masses being too small, they are unable to sustain fusion of their hydrogen to produce energy.
  • It is believed that some of the more massive brown dwarfs fuse deuterium or lithium and glow faintly.

The cloud band over Luhman

  • 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.
  • Many astronomers detected polarization of brown dwarfs.
  • But what is special in the newest study of Luhman 16 is that the researchers have found the actual structure of the clouds — that they form bands over one of the pair.
  • Understanding the cloud system over a brown dwarf can shed light on the pressure, temperature and climate on the surface of the celestial body.

Why it has made into a headline?

  • The researchers have used an idea put forth nearly two decades ago by Indian astrophysicist Sujan Sengupta, who works at the Indian Institute of Astrophysics, Bengaluru.
  • Sengupta had propounded the light emitted by a cloudy brown dwarf, or reflected off an extrasolar planet, will be polarized.
  • He then suggested that a polarimetric technique could serve as a potential tool to probe the environment of these objects.

Back2Basics: Binary Star System

  • A binary star is a star system consisting of two stars orbiting around their common barycenter.
  • Systems of two or more stars are called multiple star systems.
  • These systems, especially when more distant, often appear to the unaided eye as a single point of light, and are then revealed as multiple by other means.
  • Binary star systems are very important in astrophysics because calculations of their orbits allow the masses of their component stars to be directly determined.
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