Scientists map earliest glow of hydrogen, opening a new window to the universe

1. At a Glance

• The Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope has, for the first time, picked up the faint radio glow of hydrogen from when the universe was about 5 billion years old. It did this using only its own data. [1]
• CHIME is an interferometric radio telescope in Canada. It was built to map how hydrogen gas is spread across the early universe. That map lets astronomers measure cosmic expansion and study dark energy. [1]
• Indian angle: researchers at the Raman Research Institute (RRI) are part of the collaboration. RRI is an autonomous institute of the Department of Science and Technology (DST). [1]
• Why UPSC cares: the topic falls under GS-III (Science & Technology: space, awareness in astronomy) and shows India taking part in international big-science projects. It also links to RRI's own mission, PRATUSH. [1][2]

2. Why in the News

• 30 Sep 2026: PIB announced CHIME's first standalone detection of the hydrogen glow from about 5 billion years after the Big Bang. The results were published the same day in The Astrophysical Journal (DOI 10.3847/1538-4357/ae9835). [1]
• A companion paper estimated that about 2% of the hydrogen in the universe was in neutral atomic form at that time. This is broadly consistent with other measurements. [1]

3. Background & Evolution

• Driving rationale: CHIME was built specifically to map hydrogen and investigate dark energy. PIB calls this detection "a milestone for the telescope, built for this very reason." [1]
• Earlier method: CHIME used to cross-correlate its data with galaxy surveys from other telescopes. Galaxy surveys use light, focus in fine detail and "cost millions more dollars." They also cover only regions hot and dense enough to form stars. [1]
• 2019: CHIME collected the 94 nights of observation data used in this detection. [1]
• Verification: the finding was "not a Eureka moment." New analysis techniques pulled the signal out from noise coming from space, human technology and the instrument itself. The team then spent more than a year testing the result. [1]
• July 2023 (related Indian work): RRI developed STARFIRE (Simulation of TerrestriAl Radio Frequency Interference in oRbits around Earth). It estimates how much man-made radio interference (RFI) reaches Earth orbit, for radio astronomy experiments in the 40–200 MHz range. [3]
• 2025 (related Indian work): RRI built a Raspberry Pi-based single-board computer to act as the master controller for PRATUSH. [2]

4. Core Static Facts

Item	Fact
Full form	Canadian Hydrogen Intensity Mapping Experiment [1]
Type	Interferometric radio telescope, located in Canada [1]
Design	No moving parts. It scans a large part of the sky as the sky drifts over it and produces a daily radio-wavelength snapshot of the sky [1]
Target signal	Combined radio glow of hydrogen, which acts as a "cosmic tracer" of how matter is distributed [1]
Epoch detected	Universe about 5 billion years old [1]
Data used	94 nights (2019), a small fraction of nearly 7 years of data collected so far [1]
Neutral atomic hydrogen share	About 2% at that time [1]
Journal	The Astrophysical Journal, DOI 10.3847/1538-4357/ae9835 [1]
Indian institution	Raman Research Institute (RRI), autonomous institute under DST, Ministry of Science & Technology [1]
Indian co-author	Dr. Saurabh Singh, Associate Professor, RRI [1]
CHIME Principal Investigator	Dr. Mark Halpern, University of British Columbia [1]
Proposed the finding	Dr. Arnab Chakraborty, University of Toronto [1]
Companion paper co-author	Dr. Shabbir Shaikh, Arizona State University [1]
Next goal	Extend the analysis back to when the universe was about 3 billion years old [1]
Related RRI mission	PRATUSH: Probing ReionizATion of the Universe using Signal from Hydrogen. A planned radiometer in lunar far-side orbit to study the 21-cm hydrogen signal from Cosmic Dawn [2]

5. Multi-Dimensional Analysis

Scientific / Technological

• Hydrogen is the most common element in the universe and the raw material stars form from. Its radio emission shows how matter is spread across space. [1]
• The glow of hydrogen spread across large regions is mapped as a whole, without resolving individual galaxies. This lets CHIME study the same questions as galaxy surveys at a greater scale and further back in time. [1]
• Scientists disagree about what dark energy is. CHIME can now test these rival theories independently. [1]
• Signal extraction is the main technical challenge. The team needed new techniques to separate the signal from background, man-made and instrument noise. [1]

Economic

• The method is described as "faster, less expensive" than galaxy surveys and works "at a fraction of the cost." [1]

Geopolitical / Strategic (science diplomacy)

• The collaboration spans Canadian, US (Arizona State University) and Indian (RRI) institutions. It shows India's role in multilateral big science. [1]
• The PI stresses that CHIME was "conceived, built and funded by Canadians," which reflects national ownership of large facilities. [1]

Administrative / Governance (Indian S&T ecosystem)

• DST's autonomous institutes, such as RRI, support both international participation (CHIME) and home-grown missions (PRATUSH, STARFIRE). [1][2][3]
• Radio astronomy is increasingly threatened by RFI from FM stations, WiFi, mobile towers, radar and satellites. This is a policy issue around radio-quiet zones and spectrum management. [3]

6. Recent Developments (last 12–18 months)

• Sep 2025: DST reported RRI's Raspberry Pi-based single-board computer as the master controller for PRATUSH. It coordinates the antenna, receiver and FPGA (Field Programmable Gate Array). The work is published in Experimental Astronomy (DOI 10.1007/s10686-025-10013-z). [2]
• 30 Sep 2026: CHIME's standalone hydrogen detection was published in The Astrophysical Journal, with a companion paper on the neutral hydrogen fraction. [1]
• Ongoing: the team is extending the analysis over nearly 7 years of CHIME data, towards the era when the universe was about 3 billion years old. [1]

7. Prelims Hooks

• CHIME stands for Canadian Hydrogen Intensity Mapping Experiment. It is a radio interferometer located in Canada. [1]
• CHIME's main science goal is to study dark energy by measuring cosmic expansion. [1]
• CHIME has no moving parts. It surveys the sky as the sky drifts overhead. [1]
• The first standalone detection is of hydrogen glow from when the universe was about 5 billion years old. [1]
• The detection is based on 94 nights of 2019 data. [1]
• About 2% of the universe's hydrogen was neutral atomic at that epoch. [1]
• The results were published in The Astrophysical Journal (30 Sep 2026). [1]
• Indian participant: Raman Research Institute, an autonomous institute of DST (not ISRO). [1]
• Before this, CHIME detections needed cross-correlation with galaxy surveys. [1]
• PRATUSH stands for Probing ReionizATion of the Universe using Signal from Hydrogen. It is planned for lunar far-side orbit, described as "the most radio-quiet place in the inner Solar System." [2]
• PRATUSH targets the 21-cm hydrogen signal from Cosmic Dawn, when the first stars and galaxies formed. [2]
• STARFIRE is an RRI algorithm that estimates terrestrial RFI in Earth orbits in the 40–200 MHz band. It was tested at 400 km (LEO), 3,795 km (MEO) and 36,000 km (GEO). [3]

8. What This Result Proves, and What It Does Not Yet

• The result is a first step. It does not yet answer the dark energy question
• The detection uses only 94 nights of 2019 data. That is a small part of the nearly 7 years of data CHIME has collected [1].
• PIB says CHIME can now test rival dark energy theories on its own. The testing is still ahead. It has not been done yet [1].

• In an answer, write "a milestone that makes the test possible". Do not write "CHIME has explained dark energy".

• The signal is very faint, so the result needed a lot of checking

• Radio noise from space, from human technology and from the instrument itself is far stronger than the hydrogen glow. New analysis methods were needed to pull the signal out [1].
• The team spent more than a year testing the result before publishing it. PIB calls it "not a Eureka moment" [1].

• Why this matters: when the noise is this strong, a small error in removing it can create a false signal. That is why long checking was needed.

• The 2% figure is a cross-check, not a new discovery on its own

• The companion paper found about 2% of hydrogen was neutral atomic hydrogen (single, uncharged hydrogen atoms). This is broadly in line with other measurements [1].
• Agreement with older methods is what makes the new method believable. This is its real value today.

9. Why Cheaper Does Not Mean Galaxy Surveys Become Useless

• Intensity mapping gives a wide, blurred picture. Galaxy surveys give a sharp, narrow one
• Intensity mapping (measuring the combined glow of hydrogen over a large area, without picking out single galaxies) covers more sky and reaches further back in time [1].
• Galaxy surveys use light and see fine detail. But they cost "millions more dollars" and only see places hot and dense enough to form stars [1].

• So each method sees what the other misses. They work best together, not as replacements.

• Until now, the cheaper method needed the costly one

• Earlier, CHIME's signal could only be confirmed by cross-correlation (matching CHIME's map against a galaxy survey map of the same sky) [1].
• The standalone detection removes that dependence. CHIME can now check its own work.
• Still, galaxy surveys remain the independent referee when two methods disagree.

10. Radio Noise Is Taking the Sky Away From Astronomers

• The signal astronomers want sits among signals our phones and radios use
• FM stations, WiFi, mobile towers, radar and satellites all create RFI (radio frequency interference: unwanted man-made radio signals) [3].
• FM transmissions alone can drown out faint signals from space [2].

• This is why CHIME needed new techniques to remove man-made noise before it could see hydrogen [1].

• Even going to space does not fully escape the noise

• RRI's STARFIRE model shows that man-made RFI reaches Earth orbits, from 400 km (LEO) up to 36,000 km (GEO), in the 40–200 MHz band [3].
• So PRATUSH plans to go to lunar far-side orbit. There the Moon blocks Earth's radio signals. It also avoids the ionosphere (the charged upper layer of Earth's air that bends and distorts radio waves) [2].

• The cost of this is clear: when Earth becomes too noisy, the only fix is a far more expensive mission to the Moon.

• Spectrum rules are where science and telecom meet

• The Department of Telecommunications (DoT) released the National Frequency Allocation Plan 2025 (NFAP-2025). It decides who can use which radio frequencies, from 8.3 kHz to 3000 GHz. It takes effect from 30 December 2025 [4].

• Every new band given to mobile or satellite services adds to the noise that telescopes must work around. More 5G and more satellites mean more noise.

• What should follow

• DoT: when it next revises NFAP, it should consult DST and radio astronomy institutes such as RRI and NCRA-TIFR about which bands and sites to keep quiet.
• DST: tools like STARFIRE can supply the data for this. They can show how much noise reaches a given orbit or band [3].

11. Partner or Paying Member: Two Ways India Joins Big Science

• In CHIME, India contributes scientists, not ownership
• CHIME's PI says the telescope was "conceived, built and funded by Canadians" [1].

• India's role comes through RRI researchers who co-author the analysis [1]. This builds skill at low cost, but India has little say over how the facility is run or what it studies next.

• In SKA, India paid for a seat at the table

• The Government approved ₹1,250 crore for India's part in building the Square Kilometre Array (SKA) over 7 years. The Department of Atomic Energy (DAE) leads, and DST co-funds [5].
• India joined the SKA Observatory Council as a founding member in July 2024 [6].

• Over 20 Indian institutes take part, with NCRA-TIFR as the nodal (lead) institute. India leads the Observatory Monitor & Control system, the software that runs the telescope [6].

• Why the difference matters

• A paying member helps decide how the observatory is run and gets to build key parts of it. This skill stays in India after the project ends.
• Collaborating as a partner, as in CHIME, is cheaper and flexible. But it depends on the host country's choices.
• A balanced answer: India needs both. Low-cost partnerships (CHIME) and home missions (PRATUSH) train people. Paid membership (SKA) gives India a say in how the observatory is run.

12. Anchors for Answers

• Data: About 2% of cosmic hydrogen was neutral atomic hydrogen when the universe was about 5 billion years old. This matches other measurements [1]
• Data: The detection used only 94 nights of 2019 data, out of nearly 7 years collected [1]
• Data: ₹1,250 crore approved for India's role in building SKA, over 7 years, with DAE leading [5]
• Report/Committee: National Frequency Allocation Plan 2025 (DoT), which allocates spectrum from 8.3 kHz to 3000 GHz, effective 30 Dec 2025 [4]
• Comparison: CHIME was fully Canadian-funded, with India contributing scientists. In SKA, India is a paying founding member (July 2024) and leads the Monitor & Control system [1][6]
• Scheme: PRATUSH (RRI) plans a lunar far-side orbit to escape Earth's radio noise. STARFIRE (RRI) measures RFI reaching Earth orbits [2][3]

13. Mains Relevance

• GS-III: Science and Technology: developments and their applications; achievements of Indians in S&T; awareness in the fields of space.
• GS-II (secondary): Bilateral and multilateral relations, through scientific collaboration.
• Question stems: 1. Radio astronomy offers a cost-effective window into cosmic evolution. Discuss with reference to hydrogen intensity mapping and India's participation in global observatories. (15 marks) 2. What is dark energy? How do new observational techniques help resolve competing theories about it? (10 marks) 3. Radio frequency interference is emerging as a threat to astronomy. Examine the challenge and India's technological responses. (10 marks)

14. Related Topics to Study Next

• PRATUSH: RRI's lunar-orbit mission on the hydrogen signal from Cosmic Dawn, the Indian counterpart theme. [2]
• Dark energy and dark matter: the core cosmology concepts behind CHIME's purpose.
• Giant Metrewave Radio Telescope (GMRT), Pune: India's flagship radio telescope for hydrogen and radio observations.
• Square Kilometre Array (SKA): the next-generation global radio observatory in which India participates.
• Radio-quiet zones and spectrum management: links to RFI (STARFIRE). [3]
• Fast Radio Bursts (FRBs): CHIME is also a major FRB detector (verify from a standard source).
• Big Bang, Cosmic Dawn and the Epoch of Reionization: the timeline of the universe.

15. Common Errors / Trap Areas

• Wrong parent body: RRI is under DST, not ISRO or the Department of Space. [1]
• Wrong location: CHIME is in Canada, not India. India is a collaborator, not the host. [1]
• Epoch confusion: CHIME detected hydrogen when the universe was about 5 billion years old, with a future goal of about 3 billion years. PRATUSH targets the much earlier Cosmic Dawn. Do not mix up the two. [1][2]
• "Glow" vs starlight: CHIME detects radio emission from hydrogen, not optical light. Galaxy surveys are the optical, light-based method. [1]
• "First ever" vs "first standalone": CHIME had seen the signal earlier through cross-correlation. The new result is the first standalone detection. [1]