Odd Radio Circles (ORCs)

Context : Odd Radio Circles (ORCs) are rare, mysterious, ring-shaped astronomical structures that appear only in radio wavelengths. These vast circular emissions are believed to form from powerful shockwaves triggered by dramatic galactic events such as black hole mergers or massive energy outflows from galaxies.

Discovery:
ORCs were first detected in 2019 using data from the Australian Square Kilometre Array Pathfinder (ASKAP) telescope. Since then, they have been further studied with international radio observatories, including LOFAR and India’s Giant Metrewave Radio Telescope (GMRT).

Key Characteristics:

• Radio-exclusive visibility: ORCs are observed only in radio frequencies, with no corresponding signals in visible, X-ray, or infrared light.

• Distinct circular shape: They appear as faint, bubble-like rings, often brighter along their outer edges.

• Enormous scale: These structures are among the universe’s largest, stretching across millions of light-years.

• Central galaxy connection: Some ORCs are centered around galaxies, while others float independently, deepening their mystery.

• Twin ORCs: The newly discovered “double ORC” — featuring two opposing plasma rings — may have originated from a massive galactic explosion or collision.

Significance:

• Scientific relevance: ORCs provide valuable clues about galaxy evolution, black hole activity, and the dynamics of intergalactic shockwaves.

• Collaborative achievement: The discovery showcases the power of combining citizen science with advanced telescopes like LOFAR and GMRT.

• Indian contribution: The find, led by citizen scientists from India’s RAD@home network under Prof. Ananda Hota (University of Mumbai), highlights India’s expanding footprint in global radio astronomy and community-driven scientific research.