India’s ASTROSAT discovers oldest galaxy

A global team led by scientists of the Inter University Centre for Astronomy and Astrophysics (IUCAA) has discovered one of the oldest galaxies in extreme ultraviolet light with the aid of ASTROSAT. The team comprises scientists from India, Switzerland, France, USA, Japan and Netherlands.

About the discovery:

  • The team observed the galaxy, which is located in the Extreme Deep field, through AstroSat. These observations lasted for more than 28 hours in October 2016. But it took nearly two years since then to carefully analyse the data to ascertain that the emission is indeed from the galaxy.
  • The team comprises scientists from India, Switzerland, France, USA, Japan and Netherlands.
  • Since UV radiation is absorbed by Earth’s atmosphere, it has to be observed from space.
  • Earlier, NASA’s Hubble Space Telescope (HST), which is significantly larger than the Ultra Violet Imaging Telescope (UVIT) on Astrosat, did not detect any UV emission from this galaxy because it is too faint.AstroSat/UVIT was able to achieve this unique feat because the background noise in the UVIT detector is much less than the ones on HST.


  • ASTROSAT is India’s first dedicated multi wavelength space observatory.
  • One of the unique features of ASTROSAT mission is that enables the simultaneous multi-wavelength observations of various astronomical objects with a single satellite.
  • ASTROSAT observes universe in the optical, Ultraviolet, low and high energy X-ray regions of the electromagnetic spectrum, whereas most other scientific satellites are capable of observing a narrow range of wavelength band.
  • ASTROSAT with a lift-off mass of about 1513 kg was launched into a 650 km near-equatorial  orbit inclined at an angle of 6 deg to the equator by PSLV-C30.
  • After injection into Orbit, the two solar panels of ASTROSAT were automatically deployed in quick succession. The spacecraft control centre at Mission Operations Complex (MOX) of ISRO Telemetry, Tracking and Command Network (ISTRAC) at Bangalore manages the satellite during its mission life.
  • Payloads of ASTROSAT :

    Five payloads of ASTROSAT are chosen to facilitate a deeper insight into the various astrophysical processes occurring in the various types of astronomical objects constituting our universe.  These payloads rely on the visible, Ultraviolet and X-rays coming from distant celestial sources.

The science data gathered by five payloads of ASTROSAT are telemetered to the ground station at MOX. The data is then processed, archived and distributed by Indian Space Science Data Centre (ISSDC) located at Byalalu, near Bangalore.

The scientific objectives of ASTROSAT mission are:

  • To understand high energy processes in binary star systems containing neutron stars and black holes
  • Estimate magnetic fields of neutron stars
  • Study star birth regions and high energy processes in star systems lying beyond our galaxy
  • Detect new briefly bright X-ray sources in the sky
  • Perform a limited deep field survey of the Universe in the Ultraviolet region

Relevance for The Big Bang Theory:

About the origin of Universe. It suggests that about 1370 crore (13.7 billion) years ago, all matter and energy in the universe was concentrated into an area smaller than an atom. At this instant, matter, energy, space and time were not existent. Then suddenly with a bang, the Universe began to expand at an incredible rate and matter, energy, space and time came into being. As the Universe expanded, matter began to coalesce into gas clouds and the stars and planets.

  •  After the Big Bang, the Universe was a hot soup of particles (i.e.,protons, neutrons, and electrons).
  • As the universe started to cool, the protons and neutrons began combining into ionized atoms of hydrogen (and eventually some helium).
  • These ionized atoms of hydrogen and helium attracted electrons, turning them into neutral atoms — which allowed light to travel freely for the first time, since this light was no longer scattering off free electrons.
  • The universe was no longer opaque. But there were no stars, and no galaxies, and the Universe was dark.
  • A while after this, maybe a few hundred million years after the Big Bang, the dark ages ended when the first stars and galaxies formed and the energy pouring out from them ionized the hydrogen and helium, splitting the atoms back again in protons and electrons, — this is the epoch of reionization.
  • Astronomers have been looking for sources that reionized the early universe. The usual suspects have been the first astronomical objects, especially the newborn small galaxies.

Important Topics Prelims

Source:The Indian Express

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