18 July 2020 | New Scientist | 15THE lemurs pictured here were once
common in southern Madagascar,
but the species is now listed as
critically endangered, one step from
extinction. The plight of Verreaux’s
sifaka (Propithecus verreauxi) is
sadly shared by many of its cousins,
says the International Union for
the Conservation of Nature (IUCN).
Due to rampant deforestation
and hunting in their heartland of
Madagascar, 103 of the world’s
107 lemur species are now
threatened by extinction. A growing
lemur pet trade in the country has
also emerged as a new pressure.
“Everything seems to be stacked
up against lemurs,” says Russ
Mittermeier at the IUCN. Local
taboos about hunting Verreaux’s
sifaka had previously helped this
species, but with new people
moving to the forests they occupy,
that protection has evaporated.
“It’s a wonderful, beautiful
animal,” says Mittermeier. ❚
Animals
ADVANCED alien civilisations
could build a machine capable
of moving a star – and we might
be able to catch one in action.
The Star Tug, thought up
by Alexander Svoronos at
Yale University, would allow
extraterrestrial civilisations
to avoid cosmic disasters.
“It’s a megastructure that can
be used to move an entire star
system,” says Svoronos. “If their
star system is going to be in
proximity of a supernova, they
might want to try to avoid it.”
The idea of moving stars isn’t
new. In 1987, Russian physicist
Leonid Shkadov first described
his Shkadov thruster. This giant
mirror would reflect a star’s light
back on its surface to produce
thrust, enabling modest speeds
over a long period of time.
Svoronos’s concept is somewhat
different. Assuming that the star
to be moved is the same mass as
the sun, it would involve placing
a structure at least a fifth the
mass of our moon as close as
10,000 kilometres from the star.
The gravitational pull of the
object, although small, would
accelerate the star towards it.
The Star Tug would have
thrusters, allowing it to move
and drag the star along with it.
Svoronos estimates that it could
accelerate the star to 0.1 per cent
of the speed of light in 5300 years
and 10 per cent of this speed in38 million years – up to a million
times faster than a Shkadov
thruster (Acta Astronautica,
doi. org/d3hg).
One complication is that the
Star Tug would need to extract
material from the star to power
its engines via nuclear fusion.
This could be done with giant
space elevators, but they might
struggle to survive so close to a
star. “You need ridiculously strong
materials,” says Anders Sandberg at
the University of Oxford’s Future
of Humanity Institute.But if all this were possible, the
Star Tug could enable an advanced
alien civilisation to move its solar
system to another part of its
galaxy, colonising other systems
along the way, or even to relocate
to a different galaxy altogether.
“You can actually expand to
another galaxy over hundreds of
millions of years,” says Svoronos.
Although beyond humanity’s
ability for now, we could in theory
look for alien Star Tugs. Most stars
rotate around the galaxy in the
same direction, but some don’t.
“We think they’re natural,” says
Sandberg. “But if you see a lot
of them, that might be a hint that
something weird is going on.” ❚Space
Migrating stars could be sign of alien tech
Adam Vaughan
World’s lemurs threatened
Nearly all lemur species are now officially at risk of extinction
CYRILRUOSO/NAT
UREP
LJonathan O’Callaghan38m
Years it would take a Star Tug to
reach a tenth the speed of light