Astronomers Probe Halo
of Starburst Galaxy
Astronomers have used a radio telescope in outback Western
Australia to see the halo of a nearby starburst galaxy in
unprecedented detail.
A starburst galaxy is a galaxy experiencing a period of
intense star formation. This one, known as the Sculptor
Galaxy (NGC 253), is approximately 11.5 million light-
years from Earth. It has an enormous halo of gas, dust and
stars that had not been observed before at frequencies below
300 MHz. The halo originates from galactic “fountains”
caused by star formation in the disk and a super-wind
coming from the galaxy’s core.
“The Sculptor Galaxy is currently forming stars at a rate
of five solar masses each year, which is a many times faster
than our own Milky Way,” said lead researcher Dr Anna
Kapinska of The University of Western Australia node of
the International Centre for Radio Astronomy Research (ICRAR).
The study used data from the “GaLactic and Extragalactic All-
sky MWA” (GLEAM) survey, which was observed by the
Murchison Widefield Array (MWA) radio telescope in remote
Western Australia. The MWA is a precursor to the Square Kilo-
metre Array (SKA) radio telescope, part of which will be built in
Western Australia in the next decade.
“It’s remarkable how easily the MWA detected the diffuse halo,”
Kapinska said. “We managed it with just an hour of observing as
the galaxy passed overhead. We could see radio emission from elec-
trons accelerated by supernova explosions spiralling in magnetic
fields, and absorption by dense electron-ion plasma clouds.”
Co-author Prof Lister Staveley-Smith of ICRAR and the ARC
Centre of Excellence for All-sky Astrophysics said the SKA will be
the largest radio telescope in the world and will be capable of
discovering many new star-forming galaxies when it comes online.
“But before we’re ready to conduct a large-scale survey of star-
forming and starburst galaxies with the SKA we need to know as
much as possible about these galaxies and what triggers their extreme
rate of star formation,” he said.
“By getting to the bottom of what’s causing this galaxy to produce
so many stars, we can better understand how other galaxies form,
grow and change over time throughout the universe.”MAY/JUNE 2017 | | 9University of NSW researchers have identified a critical step in
the molecular process that allows cells to repair damaged DNA.
Their experiments in mice, published in Science, suggest a
treatment for DNA damage from ageing and radiation. This has
attracted the attention of NASA, which believes the treatment can
help its Mars mission.
The scientists identified that the metabolite NAD+, which is
naturally present in every cell of our body, mediates the
interaction between two enzymes that control a cell’s ability to
repair DNA. DBC1 binds to PARP1 outside the nucleus and
prevents it from repairing DNA. However, NAD+ breaks up this
interaction, enabling PARP1 to fulfil its role in DNA repair.
However, NAD levels decline with age, and hence the ability to
repair DNA declines with age. The researchers found that treating
old or irradiated mice with the NAD+ “booster” NMN freed up
PARP1 to repair DNA. “The cells of the old mice were
indistinguishable from the young mice after just 1 week of
treatment,” said lead author Prof David Sinclair.
For the past 4 years, Sinclair and Dr Lindsay Wu have been
working to make NMN into a drug, with human trials to begin this
year at Brigham and Women’s Hospital in Boston. They had
already established that NAD+ could be useful for treating various
diseases of ageing, female infertility and the side-effects ofchemotherapy. “This is the closest we are to a safe and effective
anti-ageing drug that’s perhaps only 3–5 years away from being
on the market if the trials go well,” Sinclair says.
The work has excited NASA, which is considering how to keep
its astronauts healthy during a 4-year mission to Mars. Even on
short missions, astronauts experience accelerated ageing from
cosmic radiation, and experience muscle weakness, memory loss
and other symptoms when they return. On a trip to Mars, the
situation will be far worse: 5% of the astronauts’ cells will die and
their chances of cancer will approach 100%.
Aircraft passengers are also exposed to cosmic radiation, with
a London–Melbourne flight roughly equivalent in radiation
exposure to a chest X-ray. In theory, the NMN treatment could
mitigate any effects of DNA damage for frequent flyers.
The other group that could benefit from this work is survivors
of childhood cancers. Wu says 96% of childhood cancer survivors
suffer a chronic illness by age 45, including cardiovascular
disease, type 2 diabetes, Alzheimer’s disease and cancers
unrelated to the original cancer.
“All of this adds up to the fact they have accelerated ageing,
which is devastating,” Wu says. “It would be great to do something
about that, and we believe we can with this molecule.”The NGC 253 starburst galaxy observed at optical (green) and
radio (red) wavelengths. The H-alpha line emission, which
indicates regions of active star formation, is highlighted in blue.
Credits: A.D. Kapinska, G. Meurer. ICRAR/UWA/CAASTROAge-Reversing Metabolite (^) Interests Mars Mission