Context
Astronomers propose to place high-resolution telescopes on the moon’s surface and its orbit which includes the Pratush Radio Telescope from India.
- Objective: To study the Cosmic Dawn and Epoch of Reionization and spot signals from the Dark Ages (which would be essentially free from the influence of any starlight).
The Cosmic Dawn and Epoch of Reionization
- Cosmic Dawn: It is a period in cosmology, when the first sources of radiation (such as stars and galaxies) first formed.
- Epoch of Reionization: It is the duration over which the radiation from the cosmic dawn re-ionized most of the Hydrogen atoms to once again result in mostly protons and electrons.
- First Ionization of universe: In the early Universe after the Big Bang all matter existed in the form of constituent particles, primarily protons, electrons, some Helium nuclei and trace amounts of some other elements.
- As the Universe expanded and cooled, these particles combined to form the very first atoms – Hydrogen and Helium, and the ionized Universe became almost fully neutral.
- Beginning of the dark ages: It is a period after the initial ionization of the universe where there are no sources of radiation other than the light released in the initial moments of the Universe which is called the Cosmic Microwave Background (CMB).
- CMB is observed at microwave frequencies and is the oldest light in the universe which can be captured by radio telescopes.
- How to study and understand EoR? Radiation from neutral hydrogen gas is a promising tool to understand the EoR. The neutral hydrogen atom naturally emits a signal at a wavelength of 21-cm.
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Why Renewed Push for Moon Based Telescopes?
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Limitations of Earth Based Telescopes:
- Atmospheric disturbances: Optical telescopes (collect visible light at longer wavelengths) have to peer through layers of the planet’s atmosphere which makes it increasingly difficult for optical instruments to see through the polluted skies.
- Electromagnetic interference: Radio telescopes (collect radio waves with the shortest wavelengths) have to contend with earth based Radio Frequency interference from the communications channels used by radar systems, aircraft, and satellites, adding to the cacophony of the electromagnetic ‘hiss’.
- Earth’s ionosphere also blocks radio waves coming from outer space.
- Earth orbiting telescopes: They receive radio noise from the planet along with the signals from outer space.
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Advantages of Lunar Surface for Observation:
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- Radio -quiet location: Moon provides a pristine and airless desolation to the optical telescopes for crystal-clear viewing conditions throughout the lunar night lasting for two weeks at a time.
- No earth based RFI: Radio telescopes on the lunar far side will be protected by the moon itself as it will block out the radio transmissions from the earth and electrically charged plasma winds blowing from the Sun.
PRATUSH (Probing ReionizATion of the Universe using Signal from Hydrogen)
- About: Pratush Radio Telescope is a future radiometer in lunar orbit.
- Built by: The Raman Research Institute (RRI) in Bengaluru with active collaboration from the Indian Space Research Organisation (ISRO).
- Payloads: Pratush Radio Telescope will carry a wideband frequency-independent antenna, a self-calibrating analog receiver and a digital correlator
- Placed at: Initially will be placed around earth orbit and after some fine-tuning, ISRO will be placed into moon’s orbit.
- Objective: To reveal the Cosmic Dawn of our Universe and answer the question of when the first stars formed in our universe, the nature of the first stars, the color of the light of Cosmic Dawn and will inform us of the first rays of the first suns in the infant universe.
Upcoming Missions to Study the Cosmic Dawn from Moon Surface
- Lunar Surface Electromagnetic Experiment (LuSEE Night): It is a joint NASA-Berkeley Lab project, scheduled for launch in December 2025.
- It will land on the far side of the moon, near the equator. This location shields radio frequency noise coming from the earth
- It will study magnetic activity on stars and the centres of active galaxies in visible and ultraviolet wavelengths.
- European Space Agency:
- To launch a radio telescope to the moon’s far side on board its lunar lander, ‘Argonaut’ by 2030.
- Other European projects include an infrared telescope located inside a permanently shadowed crater near the lunar south pole.
- China: To launch a moon-orbiting radio telescope scheduled in 2026.
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Also Read: Thirty Meter Telescope (TMT) Project
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April 4, 2024