Giant Metrewave Radio Telescope

In News: A radio signal originating from atomic hydrogen in an extremely distant galaxy was detected by the Giant Metrewave Radio Telescope (GMRT) located in Pune, as per the scientific journal Monthly Notices of the Royal Astronomical Society.

• This is the largest astronomical distance over which such a signal has been picked up.

Giant Metrewave Radio Telescope(GMRT):

• GMRT is a low-frequency radio telescope that helps investigate various radio astrophysical problems ranging from nearby solar systems to the edge of the observable universe.
• It is located in Pune, India
• Using GMRT data, scientists have detected a radio signal from atomic hydrogen in a distant galaxy at redshift z=1.29.
• The signal detected by the team was emitted from this galaxy when the universe was only 4.9 billion years old; in other words, the look-back time for this source is 8.8 billion years.
• The atomic hydrogen mass of this galaxy is almost twice as high as its stellar mass.
• These results demonstrate the feasibility of observing atomic gas from galaxies at cosmological distances in similar lensed systems with a modest amount of observing time.

Redshift:

• Redshift represents the signal’s wavelength change depending on the object’s location and movement; a greater value of z indicates a farther object.

Atomic hydrogen:

• It is the basic fuel required for star formation in a galaxy. When hot ionised gas from the surrounding medium of a galaxy falls onto the universe, the gas cools and forms atomic hydrogen. This then becomes molecular hydrogen and eventually leads to the formation of stars.

• Understanding the evolution of galaxies over cosmic time requires tracing the evolution of neutral gas at different cosmological periods.
• Atomic hydrogen emits radio waves of 21 cm wavelength, meaning the wavelength is a direct tracer of the atomic gas content in nearby and distant galaxies.
• However, this radio signal is feeble and nearly impossible to detect the emission from a distant galaxy using current telescopes due to their limited sensitivity.
• Until now, the most distant galaxy detected using 21 cm emission was at redshift z=0.376, corresponding to a look-back time – the time elapsed between detecting the signal and its original emission – of 4.1 billion years.

Source: DTE

Previous Year Question

Q1) Which of the following is/are cited by the scientists as evidence/evidences for the continued expansion of universe? (2012)

1. Detection of microwaves in space
2. Observation of redshift phenomenon in space
3. Movement of asteroids in space

Occurrence of supernova explosions in space code

1. 1 and 2 only
2. 2 only
3. 1, 3 and 4
4. None of the above