8 | New Scientist | 24 August 2019
CosmologyPLANETS that glow could be a
telltale sign they are home to life.
Most of the nearest potentially
habitable planets we have found are
orbiting a type of star called a red
dwarf. When these stars are young,
they tend to blast out ultraviolet
(UV) light that can be deadly to life
as we know it. That has made some
astronomers question whetherlife can survive near these stars.
If it can, Lisa Kaltenegger and Jack
O’Malley-James at Cornell University
in Ithaca, New York, have an idea
about what it might look like.
They realised that there are some
species of coral that have adapted
to deal with UV light. These coral
get their energy from algae, and to
protect the algae from UV damage,
the coral absorbs the light and
re-emits it at a lower, safer
wavelength. This gives the coral
an ethereal glow.
On a planet subjected to far moreUV radiation, this sort of adaptation
might be more common, says
Kaltenegger. The glow would be
tied to the star’s activity, making
it easier to disentangle from other
factors that might make a planet
appear brighter than expected but
wouldn’t indicate life (Monthly
Notices of the Royal Astronomical
Society, doi.org/c9mp). Dependingon factors like whether the planet
has clouds, the glowing could make
the planet more than 100 times
brighter, says Kaltenegger.
“If you and I would have evolved
on such a world, we would probably
glow too, as that would have had
advantages in survival,” she says.
That means that planets around
red dwarfs are more likely to glow,
and we might see it someday. “This
counterintuitively makes highly
active flaring stars good places to
look [for life],” says Kaltenegger. ❚WEIRD blasts from space called
fast radio bursts are among the
most mysterious phenomena in
the universe. Now astronomers
have spotted eight particularly
unusual ones – including one that
may be the closest to us we have
spotted so far.
Fast radio bursts (FRBs) are
flashes of radio waves from distant
space that last a few milliseconds.
Many hypotheses have been
suggested for what causes
them, but none is a perfect fit.
What makes FRBs so puzzling
is that there seem to be two types:
some that happen once, and
others that repeat. Until now, we
had only detected two so-called
repeaters, but the Canadian
Hydrogen Intensity Mapping
Experiment (CHIME) has found
eight more.
Bursts that repeat are easier
to study than those that occur
once. “Repeaters are nice because
you can follow them up and
observe the source for a long time
and see if there are any changes,
which can give us clues about
what the emission mechanism
could be,” says CHIME team
member Shriharsh Tendulkar
at McGill University in Montreal.That is why the first repeater we
saw, FRB 121102, was also the first
burst that was traced to its home
galaxy. Most of our ideas to
explain repeaters are based on it.
These new bursts seem to be
different to FRB 121102. Their radio
waves don’t show signs of being
scrambled by their environment
like those from FRB 121102. Also,
that burst is in the same spot as
another source of radio waves that
glows constantly. None of the new
repeaters are like that (arxiv.org/
abs/1908.03507).“This demonstrates that there
is a vast diversity even in what
the repeaters are,” says Tendulkar.
“Maybe some of them are older,
some of them have stronger
magnetic fields, they’re in
different environments.”
It has been suggested that there
are two ways to produce FRBs, for
repeaters and for non-repeaters,
but maybe there are more.These new bursts may help
astronomers unravel those
origins. One, which CHIME
saw repeating 10 times over four
months, appears to be the closest
FRB we have yet seen. We may
be able to work out this burst’s
location accurately and so
understand its environment
better than has been possible
for other FRBs.
“You want to be able to
characterise the galaxy and
pinpoint exactly where these
bursts are coming from, and that’s
impossible if the galaxy is halfway
across the universe,” says Gregg
Hallinan at the California Institute
of Technology.
If we can tell exactly where
bursts come from, that helps
narrow down the possible
causes. For example, one idea
is that FRBs are caused by highly
magnetised neutron stars, which
we expect to mainly exist in
star-forming regions of relatively
young galaxies.
“Getting a precise location is
really the future of the FRB science
game,” says Hallinan. Teams have
already started tracking down
the home galaxies of CHIME’s
eight repeaters. ❚Exoplanets
The CHIME telescope
has spotted eight more
fast radio burstsLeah CraneJAMES
SMITH/ALAMY^ STO
CK
PHOTONews
More clues in radio burst mystery
A haul of fast radio bursts that are easier to study could help us work out their cause
We might find alien
life by searching for
its luminous glowLeah Crane“ If we had evolved on such a
planet, we would probably
glow too. There would be
survival advantages”Are we alone? Hear Avi Loeb talk about the
hunt for alien messages from outer space
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