Sky & Telescope - January 2025 - 34

JAYANNE ENGLISH (UNIVERSITY OF MANITOBA), WITH SUPPORT FROM RAY NORRIS, JORDAN
COLLIER AND THE EVOLUTIONARY MAP OF THE UNIVERSE TEAM, DATA FROM MEERKAT AND THE
DARK ENERGY SURVEY AT CERRO TOLOLO INTER-AMERICAN OBSERVATORY
A TALE OF ORCS by Monica Young
Odd Radio Circles
G
When astronomers discovered monstrous rings in the radio sky, they began
a journey to uncover the objects' origins.
igantic circles of radio emission, spanning an
arcminute or more, popped out of the first images
from an ambitious survey called the Evolutionary
Map of the Universe (EMU). The features look like round,
edge-brightened thumbprints in fields otherwise covered in
the smaller blots and dots that mark entire galaxies.
Undertaken with the Australian Square Kilometre
Array Pathfinder (ASKAP), EMU's aims include tracing the
cosmic history of stars and black holes in galaxies as they
evolve over time. Ray Norris (Commonwealth Scientific and
Industrial Research Organisation, Australia), who founded
the unprecedentedly sensitive survey, knew one thing
before the project even started: It would find novel things.
" I actually predicted in a paper, we're almost certain to
find new types of objects, " Norris says. But he thought it
would be difficult, requiring advanced computing techniques.
He continues with a smile: " So the first bit of my
prediction was right; the second bit was totally wrong. "
In fact, members of the EMU team were reviewing
the very first tiles of the survey by eye when they found
what are now called odd radio circles, or ORCs for short.
But while those initial discoveries may have been eureka
moments, understanding the oddly symmetrical shapes
has taken years. Now, after observing the rings with other
telescopes, analyzing additional data, and running simulations,
the team thinks they've arrived at an explanation:
SMOKE RING Radio data (green) superimposed on a visible-light
view shows Odd Radio Circle 1, or ORC 1. The radio data, which come
from a sensitive array known as MeerKAT, fill in details in the circle discovered
by the Australian Square Kilometre Array Pathfinder (ASKAP).
34 JANUARY 2025 * SKY & TELESCOPE

Sky & Telescope - January 2025

Table of Contents for the Digital Edition of Sky & Telescope - January 2025

Contents
Sky & Telescope - January 2025 - Cover1
Sky & Telescope - January 2025 - Cover2
Sky & Telescope - January 2025 - 1
Sky & Telescope - January 2025 - Contents
Sky & Telescope - January 2025 - 3
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Sky & Telescope - January 2025 - Cover3
Sky & Telescope - January 2025 - Cover4
Sky & Telescope - January 2025 - SGA1
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