10 | New Scientist | 15 June 2019FOR at least five years, a distant star
stayed constant. Then, it lost 70 per
cent of its brightness over two days,
returning to normal two days later.
Astronomers aren’t sure why.
The All-Sky Automated Survey
for Supernovae (ASAS-SN) project
takes pictures of the entire sky each
night. It searches for supernovae
and other objects that suddenly
brighten. On 1 June, ASAS-SN
astronomers saw a star begin to
dim. The diameter of the star, called
ASASSN-V J213939.3-702817.4,
is about 3.4 times larger than the
sun’s and it is 3590 light years
away from Earth. By 3 June, it
had dimmed by 70 per cent.
“Why that happened, we don’t
know yet,” says Tharindu Jayasinghe
at ASAS-SN. The star was back at
its normal brightness by 5 June.
A dip this significant couldn’t be
caused by something within the star
itself, says Jayasinghe. Potential
explanations include a planet ordust cloud obscuring the star, but
none fit exactly, he says. “That’s
what makes this star really weird.”
Tabetha Boyajian at Louisiana
State University thinks this dimming
may have occurred because what
appeared to be a single star could
actually be a pair. “Anything that
blocks out 70 per cent of the star’s
light would have to be bigger than
a planet,” says Boyajian. “Once you
get much bigger than Jupiter, you
get a star.”
If there was a companion star and
one eclipsed the other, the light from
two stars would appear to come
from only one. But the dip in light
lasted longer than these sorts of
eclipses usually do, says Jayasinghe.
More observations of the star could
tell us what the dimming really is. ❚Field notes Australian Microbiome InitiativeWAVES submerge the algae,
forcing us to hop onto higher
ground to avoid getting wet
feet. For the next few months,
the rocky beach outcrop I am on
in the Kamay Botany Bay National
Park, Sydney, will be a lab for
Kim Lema at the University of
New South Wales, Australia.
She is studying a type of
algae whose chemicals attract
certain microbes, forming a
microscopic community on its
surface that plays an important
role in its health.
To identify these microbes,
Lema is getting their DNA
sequenced. These sequences
will then be logged on a public
database. There, they will join
information on 1.7 million
bacteria, 1.8 million tiny
eukaryotes and nearly
1.2 million fungi from across
Australia as part of the first
concerted effort to catalogue an
entire continent’s microbiome.
Around 40 organisations
are involved in the Australian
Microbiome Initiative, which
hopes to determine what
healthy ecosystems look like
at the microscopic level beforeclimate change and habitat
destruction alter them irreversibly.
It is a very ambitious project,
according to Martin Ostrowski
at the University of Technology,
Sydney, who is contributing
marine microbial sequences
to the database. “All the data
that we’re collecting is a really
important resource,” he says.
“One way of thinking about
it is that it gathers three and a
half billion years of evolution
of a whole range of different
solutions to different problems,”
says Ostrowski. This could help
us in various ways, he says, from
microbial methods of cleaning
up pollution to developing
new antibiotics.
Ostrowski and his colleagues
have used drones to sample
microbes living in the breath
expelled from the blowholes
of dozens of humpback whales
migrating off the coast of Sydney.
They used the database to identify
precisely which species came
from the whales’ breath andwhich were captured from the
environment, he says. In doing
so, they identified six new virus
species to add to the evolutionary
tree and established a baseline
to inform future studies of whale
respiratory health.
Andrew Bissett at the
Commonwealth Scientific and
Industrial Research Organisation
in Canberra has been using the
database to help farmers navigate
Australia’s strict biosecurity
regulations. The island nation
has notoriously tight import
rules, designed to protect its
native species and agriculture
from invasive alien organisms.
However, overseas companies
are developing bacteria that can
be added to soils to boost crop
growth. Until now, local farmers
have had to find and isolate
such organisms from within the
country to ensure that they weren’t
importing a potentially damaging
version. But now, Bissett says he
has helped to identify the overseas
organisms in the database,
demonstrating to the authorities
that they are naturally found within
Australian soils and are, therefore,
safe to import and use on farms.
So far, the collaboration has
sequenced only a small fractionof the billions of microbes that
live in Australia. But even this is
helpful, says Anna Fitzgerald at
Bioplatforms Australia, the group
overseeing the initiative.
The project team hopes to
study several thousand more
sites in Australia over the next
three years. “At this stage, we’re
just trying to understand what’s
out there,” says Lema. “To build
a dictionary of what we have.” ❚AstronomyLeah CraneCAMERON^ SPE
NC
ER/GETT
Y^ IMAG
ESMicrobes recently
found in whale breath
are new to science4.7m
microorganisms have
been recorded so far“There are several potential
explanations, including a
planet or dust cloud, but
none of them exactly fit”
Weird star dimmed
for a few days for
unknown reasonsNews
Mapping every microbe
The ambitious attempt to identify every Australian microorganism
Ruby Prosser Scully