10 | New Scientist | 27 July 2019SpaceLeah CraneIT HAS long been a mystery why
planets tend to spin in the same
direction as their stars do. The
answer may lie in whether they are
made from huge rocks or pebbles.
The standard model of planetary
growth states that planets coalesce
from giant rocks that are kilometres
across. But models of that process
result in planets that barely spin
at all because similar amounts of
boulders hit the fledgling planet
from all sides.
Rico Visser at the University
of Amsterdam in the Netherlands
and his colleagues examined an
alternative model of planetary
formation called pebble accretion.
In this, planets form from lumps
that are between a millimetre
and a metre across. These rocks
are more affected by friction
from gas surrounding stars than
bigger boulders would be.Visser and his colleagues
simulated individual pebbles
on trajectories around a growing
planet. “For pebbles to be swept
up by the protoplanet, the key is
long-lasting encounters of pebbles
with protoplanets,” he says.
The team’s models suggest
that small rocks circulating between
a nascent planet and its star
keep being pushed back towards
the planet by the friction they
experience from the surrounding
gas. This increases the time they
spend near the planet.
This means that when the rocks
fall onto the protoplanet, they tend
to hit it at an angle that spins it in
the same direction that the star is
turning – called a prograde direction.
Rocks coming in from the other side
of the planet, away from the star,
tend to fly past without colliding. ❚Planets spin the
right way when
made from pebblesPRELIMINARY figures from the
Centers for Disease Control and
Prevention (CDC) suggest that
there has been a 5 per cent fall
in the number of annual drug
overdose deaths in the US. The
drop is almost entirely due to a
fall in deaths from prescription
opioid painkillers, prompting
questions over whether the
worst may finally be over.
The numbers indicate that
there were 68,500 drug overdose
deaths in the US in 2018, down
from 72,000 the previous year.
However, it isn’t known
whether overdose deaths will
continue to fall, says Tisamarie
Sherry at the Rand Corporation
think tank in California.
“The CDC data shows that
overdose deaths from fentanyl,
synthetic opioids, cocaine
and methamphetamines are
still increasing, which is an
ominous sign.”
US drug overdose deaths
related to prescription opioids
rose from just over 3400 in
1999 to about 17,000 in 2017.
This dramatic upwards trend
reflects a nationwide epidemic
of opioid use and abuse. Recentnumbers from the US Drug
Enforcement Administration
revealed that, between 2006
and 2012, 76 billion pills
of common prescription
painkillers oxycodone
and hydrocodone were
distributed in the US. That
is about 248 pills per person.
The epidemic has hit US
states differently, and the new
numbers bear that out. Deaths
have continued to rise in some
eastern states where the illicit
use of fentanyl, a highly potent
synthetic opioid, is spreading.
But deaths are dropping in some
Midwestern states where local
governments have expanded
treatments for addiction and
monitoring of prescriptions.
Despite this recent reduction
in overdoses, tens of thousands
of people are still overdosing
on opioids each year in the US.
The recent decrease may be
due to increased availability
of naloxone – which blocks
the effects of opioids and is
used by emergency medical
practitioners to reverse
overdoses – and better training
in how to use it.If emergency treatment,
rather than reduced drug use,
is largely behind the fall, this
would mean an increasing
number of US adults are living
with substance abuse disorders.
Prescribing restrictions mean
that many of these people are
probably being pushed towards
using street drugs.This isn’t the first time the
rate of opioid deaths has slowed.
They appeared to stall in 2011
and 2012, but the death rate then
shot back up as fentanyl made
its way into the US. Fentanyl
deaths in 2018 continued to rise,
but grew at a slower rate than
they have in recent years. So,
it is fair to be only cautiously
optimistic when it comes to
a possible break in the wave
of opioid-related deaths.
The 2018 numbers are
still being finalised, and
may increase when the CDC
publishes its final report later
this year. They also don’t
include deaths related to
infection from intravenous
drug use.
Complicating matters,
renewed attempts to overturn
the Affordable Care Act are
under way. Should these
succeed, many people who
currently receive legal pain
relief may end up turning
to illegal drugs if they lose
their health insurance.
Celebrating the end of the
opioid epidemic now would
be extremely premature. ❚RICHARD
B.
LEVINE/ALA
MYNews
Naloxone can be used
to reverse opioid
overdoses68,
Estimated number of overdose
deaths in the US in 2018“It has long been a
mystery why planets
tend to spin in the same
direction as their stars”
Analysis Opioid crisisAnnual drug overdose deaths have fallen in the US For the
first time since 1990, fatalities from overdoses have dropped.
Has the opioid painkiller crisis peaked, asks Chelsea Whyte