Page 33 - EngineerIT April 2022

SPACE SCIENCE
What causes ORCs?

Researchers aren’t sure and are testing several models. However, the magnetic field
ASKAP
patterns hint at a shell of gas blown out from a central galaxy. This could be from
ASKAP is a radio telescope owned
a gigantic explosion (such as might be caused by two super-massive black holes
and operated by Australia’s national
merging), or by a violent burst of star formation that took place about a billion
science agency, CSIRO. ASKAP is
years ago.
an SKA-precursor telescope. This
means it has been testing out novel
technologies on a future SKA site,
which will enhance our view of the
sky. ASKAP’s special ability is scanning
the sky (called a survey) to find new,
rare, faint or hard-to-detect objects in
our universe, like fast radio bursts. It
is the fastest sky-scanning telescope
in the world, undertaking the feat in
less than two weeks. Other telescopes
would take nearly two years to
complete such a task in such detail.
Above: ASKAP and MeerKAT: (Left) The ASKAP image of ORC1, adapted from Norris et al. (2021b) at 944 With 36 dishes at 12 metres
MHz. The resolution is 11 arcsec, and the rms sensitivity is 25 µJy/beam. (Right) The new Meerkat image diameter, ASKAP covers six km of
of ORC1 at 1284 MHz. The resolution is 6 arcsec, and the rms sensitivity is 2.4 µJy/beam.
the Murchison Radio-Astronomy
Observatory in Western Australia,
“We know that ORCs are rings of faint located on the traditional lands of
radio emissions surrounding a galaxy with a the Wajarri Yamatji people. ASKAP
highly active black hole at its centre, but we is part of the Australia Telescope
don’t yet know what causes them, or why National Facility, assisting scientists
they are so rare,” Professor Norris said. all over the world.
Dr Fernando Camilo, chief scientist
of the South African Radio Astronomy MeerKAT
Observatory, which built and operates MeerKAT is a radio telescope owned
MeerKAT, said that “the ORC project is a and operated by the South African
great example of the clever use of MeerKAT Radio Astronomy Observatory
by its users, playing to its strengths. ASKAP (SARAO), situated 90 km outside
observes large swaths of the sky and can the small Northern Cape town of
discover relatively rare types of objects; Ray Norris Carnarvon. MeerKAT is a precursor
MeerKAT can then follow up to study them to the SKA telescope and will be
in greater detail.” able to tell us more about the life cycle of integrated into SKA-mid, while SKA-low
To really understand odd radio circles, galaxies,” Professor Norris said. is situated in Australia.
scientists will need access to even more “Until the SKA becomes operational, The MeerKAT telescope is an array
sensitive radio telescopes such as those of ASKAP and MeerKAT are set to of 64 antennas. Its special ability is to
the SKA Observatory, which is supported revolutionise our understanding of the look deep into space and obtain more
by more than a dozen countries including universe faster than ever before.” detailed data of our universe than
South Africa, Australia, the UK, France, ASKAP is located in Wajarri Yamatji ever before.
Canada, China and India. country in Western Australia, and MeerKAT The telescope was originally
“No doubt the SKA telescopes, once is located in the Northern Cape province of known as the Karoo Array Telescope
built, will find many more ORCs and be South Africa. n (KAT) that would consist of 20
receptors. When the South African
government increased the budget
ASKAP and MeerKAT collaboration improved the to build 64 receptors, the team re-
knowledge of ORCs named it MeerKAT (“more of KAT” in
Afrikaans). The meerkat is also a much
Because odd radio circles are so faint and rare, ASKAP is the telescope most capable
loved small mammal that lives in the
of finding them. Once an odd radio circle has been found, the MeerKAT radio
Karoo region.
telescope is the best telescope for studying them. ASKAP is great for searching large
The San and Khoi are the
areas of sky, and MeerKAT is great for probing small areas with enormous sensitivity.
traditional peoples of the land where
MeerKAT’s observations show the detailed structure of an odd radio circle.
the MeerKAT is situated.

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