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Why in news?

Recently, Astronomers have detected in the stellar halo that represents the Milky Way's outer limits a group of stars more distant from Earth than any known within our own galaxy - almost halfway to a neighbouring galaxy.

About Stellar Halo:

  • A stellar halo is an essentially spherical population of stars and globular clusters thought to surround most disk galaxies and the cD class of elliptical galaxies.
  • Only about 1% of a galaxy’s stellar mass resides in its halo, and due to this low luminosity, the observation of halos in other galaxies is extremely difficult.
  • In contrast to the thin and thick disk of disk galaxies, the halo generally has no net rotation and is supported almost entirely by velocity dispersion.
  • The halo stars in the Milky Way are generally old, with most having ages greater than 12 billion years.
  • These ages are similar to those of bulge and globular cluster stars, meaning that stars in the halo were probably among the first Galactic objects to form.
  • Due to its old age, understanding the processes which led to the formation of the stellar halo is key in unravelling the evolutionary history of the Milky Way.
  • The halo stars of the Milky Way are generally metal-poor, with a metallicity distribution that peaks at around 1/30 of the solar value.
  • The lowest metallicity star found in the Milky Way to date, is a halo star with a metallicity of approximately 1/200,000 of the solar value.



Source: https://www.thehindu.com/sci-tech/science/astronomers-discover-milky-way-galaxys-most-distant-stars/article66373980.ece