Astronomy

Quantum mechanics means some black hole orbits are impossible to predict

Even if you could measure three black
holes’ locations as precisely as physically possible, you still might not know
where the black holes would go. Such a trio’s complex dance can be so chaotic
that the motions are fundamentally unpredictable, new computer simulations
show.

The paths of three black holes orbiting each other can be calculated based on their positions and velocities at one point in time. But in some cases, the orbits depend so sensitively on the black holes’ exact positions that the uncertainty of quantum physics comes into play. Tiny quantum uncertainties in specifying the locations of objects can explode as the black holes’ gyrations continue over tens of millions of years, astrophysicist Tjarda Boekholt and colleagues report in the April Monthly Notices of the Royal Astronomical Society. So the distant future of the black holes’ orbits is impossible to foresee.

Such extreme sensitivity to initial conditions is known as chaos. The new study suggests, in the case of three black holes, “quantum mechanics imprints into the universe chaos at a fundamental level,” says astrophysicist Nathan Leigh of Universidad de Concepción in Chile, who was not involved with the research.

In chaotic systems, tiny changes can generate
wildly different outcomes. The classic example is a butterfly flapping its wings, thereby altering weather patterns, possibly
producing a distant tornado that otherwise wouldn’t have formed (SN: 9/16/13). This chaos also shows up
in the orbits of three black holes and other collections of three or more objects,
making such orbits difficult to calculate, a conundrum known as the three-body
problem.

To test whether the black holes’ motions
were predictable, Boekholt, of the University of Coimbra in Portugal, and
colleagues checked if they could run computer simulations of the orbits both
forward and backward and achieve the same result. Starting with a given set of
locations for three initially stationary black holes, the researchers evolved
those orbits forward in time to an end point tens of millions of years in the
future. Then, they rewound the simulation, reversing the motions to see if the
black holes ended up where they started from.

Computer simulations have a limited level
of accuracy. In this case, for example, the locations of black holes were known
only to a certain number of decimal places. That tiny imprecision can balloon
over millions of years of the simulation.

According to quantum mechanics, it is
impossible to determine the position of any object better than an utterly tiny
distance called the Planck length, about 1.6
times 10-35 meters, or 16 billionths of a trillionth of a trillionth
of a millimeter (SN: 4/8/11). Yet even
with accuracy the size of the Planck length, the researchers found that about 5
percent of the time the three black holes wouldn’t return to the same spots
when the simulation was reversed. That means, even if you measured where the black
holes were to the quantum mechanical limit, you couldn’t rewind to find out
where they had come from.

“These systems are fundamentally
irreversible,” says Boekholt. “You can’t go forwards and backwards for these 5 percent
of systems in nature. And that was quite a surprising result.”

The result is theoretical and can’t be applied to real black holes, says astrophysicist Nicholas Stone of the Hebrew University of Jerusalem. For example, measurement errors would swamp the importance of quantum physics. But that doesn’t detract from the study’s importance, he says: “It is still quite interesting from a conceptual perspective.”

Algae use flagella to trot, gallop and move with gaits all their own

A microscopic speck of green algae can
trot like a horse. Or gallop. Biophysicist Kirsty Wan  compares the gaits of creatures large and
small.  

Moving diagonally opposite limbs, or flagella
in this case, in unison —
that’s a trot, Wan says. Her lab, at the University of Exeter in England, is
working on the conundrum of how single-celled creatures, with no nervous system
or brain, coordinate “limbs” to create various gaits. Some of those movements
get far trickier than trots and gallops.

Her work echoes that of 19th century
photographer Eadweard Muybridge, who used a then-novel imaging technique to
reveal hoof positions obscured in the blur of a horse galloping. Wan now creates
Muybridge moments for microalgae.
Using a range of microscopy analytics on what she calls “my private collection
of weird algae,” Wan and colleagues have documented microalgae that coordinate from
four to 16 flagella.

In some four-limbed cells, flagella can move
in neighborly pairs, pulling back in a sort of double-vision breaststroke. To
these microscopic critters, water feels thicker than the splashy stuff that giant
humans easily swish aside. So the algal breaststroke has little glide. It’s more
like a slog through molasses.

This single-celled alga activates its four flagella in the pattern used by a galloping horse. Then something not obvious to a human startles the alga (Carteria crucifera) into retreat. The cell pulls itself together though, and presses on.

Wan looked hard for microalgae with
eight flagella and found three species. One, Pyramimonus octopus, has a gait unlike any Muybridge ever saw. Wan
calls it rotary breaststroke. Flagella across from each other in the array of eight
will curl in for the stroke as their neighbors are uncurling a few beats behind.

P.
octopus
is a twitchy microbe that
goes through “shocks,” Wan says. An alga swims along, then “like a knee-jerk
reaction,” it changes direction, though she can’t see what spooks it. In
comparison, when she watches a two-flagella Chlamydomonas
species, “sometimes it twirls; sometimes it spins,” but there’s nothing so dramatic
as the abrupt pullback.

The single-celled Arctic alga Pyramimonus octopus coordinates eight flagella when it swims. Even when tethered in place, the cell’s opposite pairs curl and uncurl in what biophysicist Kirsty Wan, of the University of Exeter in England, calls a rotary breaststroke. 

The trickiest example she’s seen may have been lost to science. Wan once grew the Arctic’s P. cyrtoptera, the only microalgal species she knows of with an array of 16 flagella. Sometimes opposite pairs of flagella stroke in unison as the motion ripples around and around the array in a gait she calls a “wave.” Her colony died, however, and so did her supplier’s. “I hope it still exists somewhere in the world,” she says. “Otherwise, I might have … taken the last footage.”

Saturn’s auroras may explain the planet’s weirdly hot upper atmosphere

Saturn’s auroras may heat
its atmosphere like an electric toaster.

Measurements from NASA’s Cassini
spacecraft’s final orbits show that Saturn’s upper atmosphere is hottest where its auroras shine, a finding that could help solve a long-standing
mystery about the outer planets.

Saturn’s upper atmosphere is
much hotter than scientists first expected based on the planet’s distance from
the sun. In fact, all the gas giant planets — Saturn, Jupiter, Uranus and
Neptune — were thought to have chilly upper atmospheres of around 150 kelvins (–123° Celsius). But data from the Voyager spacecraft, which flew past the outer planets in the 1970s and 1980s (SN:
8/7/17
), showed surprisingly toasty upper atmospheres of 400 to 600 kelvins
(125° to 325° C).

Planetary scientists dub this
mismatch an “energy crisis.” Something injects extra energy into the gas
giants’ atmospheres, but no one knew what. “Trying to explain why these
temperatures are so high has long been a goal in planetary atmospheric
physics,” says planetary scientist Ron Vervack of Johns Hopkins University’s
Applied Physics Laboratory.

Data from the Cassini
spacecraft’s waning weeks might point to an answer, planetary scientist Zarah
Brown of the University of Arizona in Tucson and colleagues report April 6 in
Nature Astronomy.

After orbiting Saturn for 13
years, Cassini finished its mission with a daredevil series of dips between the
planet and its rings before plunging into Saturn’s atmosphere in September 2017 (SN: 9/15/17). During those
final orbits, the spacecraft probed the planet’s upper atmosphere by watching stars
in the background. Measuring the amount of starlight that the atmosphere blocks
told Brown and colleagues how dense the atmosphere is at different points, a
clue to its temperatures.

Using 30 of these stellar
measurements, 22 of which came from the last six weeks of Cassini’s mission,
the team mapped Saturn’s atmospheric temperatures across the whole planet and
at different depths. “For the outer planets, this is an unprecedented data
set,” says planetary scientist Tommi Koskinen, also of the University of
Arizona.

The atmosphere was hottest around
60° N and 60° S latitudes — roughly
where Saturn’s glowing auroras show up (SN: 2/16/05). Auroras are brilliant lights
that sparkle when charged particles from the sun interact with a planet’s
magnetosphere, the region defined by a planet’s magnetic field. Unlike Earth’s
visible auroras, Saturn’s auroras glow mainly in ultraviolet light.

The auroras’ light doesn’t
emit much heat on its own, but is accompanied by electric currents that can generate
heat like the wires in a toaster. This process, called Joule heating, also
happens in Earth’s atmosphere.

If Jupiter, Uranus and
Neptune’s auroras also coincide with extra heat, then auroras may solve the
mystery of hot atmospheres across the solar system. The same process could even
take place on exoplanets, Brown says.

Vervack, who has worked with
the Voyager dataset but was not involved in the new work, thinks this study
marks “a big step in our understanding” of these hot upper atmospheres.

“The real test of whether
they’re right will be when you go out to Uranus or Neptune,” whose magnetospheres
are more complicated than Saturn’s, he says. “Being able to see how our
understanding from Saturn holds up when we get to these more complicated systems
is going to be really key to knowing if we’ve licked this problem or not.”

Beets bleed red but a chemistry tweak can create a blue hue

Beet juice is red. Now chemists turned it blue. It might have potential
for consumers like you.

Natural colorings for food and cosmetics are in demand. Biology’s blue pigments, however, are tough to bottle. The
brilliant blues of jaybirds, butterflies and dragonflies are a consequence of light scattering, so there’s no pigment to isolate (SN:
6/30/17
). Juicing blueberries isn’t an option “because the pigment doesn’t
last, and its blue color can change or fade,” says Erick Leite Bastos,
a chemist at Universidade de São Paulo in Brazil.

Bastos and colleagues instead chemically modified a food
color additive found in red beets
to make blue, the team reports April 3 in Science
Advances
.

Chemists can tune certain molecules’
color by adding alternating single and double bonds to their chemical
structures. That can “create molecules that absorb yellow/orange light and,
consequently, look blue,” Bastos says.

The beet pigment already has some
bonds in that alternating arrangement, but not nearly enough to appear blue.
Bastos hypothesized he could achieve a blue dye by cleaving off part of the
molecular structure of the beet pigment and replacing it with a compound called
2,4-dimethylpyrrole, which itself has alternating bonds, thus extending the
pattern.

A new versatile beet-derived dye tints food products and fibers alike. Chemist Erick Leite Bastos and his team used BeetBlue to add color to hair, a silk moth cocoon, cotton fabric, cellulose (a plant fiber found in celery and other foods), yogurt and the food additive maltodextrin. The white circles are uncolored precursors to the colored materials.B.C. Freitas-Dörr et al/Sci Adv 2020
A new versatile beet-derived dye tints food products and fibers alike. Chemist Erick Leite Bastos and his team used BeetBlue to add color to hair, a silk moth cocoon, cotton fabric, cellulose (a plant fiber found in celery and other foods), yogurt and the food additive maltodextrin. The white circles are uncolored precursors to the colored materials.B.C. Freitas-Dörr et al/Sci Adv 2020

The dye, called BeetBlue, held up
under acidic conditions that fade or alter many blue colorants. It added a pop
of color to fabric, yogurt and hair in lab tests. Some blue dyes contain toxic
metals, but BeetBlue is nontoxic to live zebrafish embryos and human cell
cultures, tests show.

“We still don’t know whether one can eat BeetBlue or not,” he says, because it takes many additional tests to demonstrate that something new is safe to consume. While 2,4-dimethylpyrrole is not of natural origin, Bastos suspects that his team can achieve blue with natural compounds in future work, thus creating a family of blues potentially suited to different tasks.

.image-mobile {
display: none;
}
@media (max-width: 400px) {
.image-mobile {
display: block;
}
.image-desktop {
display: none;
}
}

Can plasma from recovered COVID-19 patients treat the sick?

Since March 28, at least 11
patients critically ill with COVID-19 at hospitals in New York City and Houston
became the first in the United States to receive a promising experimental
treatment. But the therapy, newly authorized for emergency use by the U.S. Food and Drug Administration, wasn’t concocted
in a pharmaceutical laboratory. It came from the blood of other patients, those
who have recovered from the coronavirus infection.

The treatment is convalescent
plasma, the liquid component of blood taken from someone who has survived an
infection, in this case COVID-19. With the United States now leading the world
in confirmed cases of the disease — and no proven
treatments yet — researchers here are
racing to set up clinical trials to test how effective convalescent plasma is against
SARS-CoV-2, the virus that causes COVID-19. If the treatment is beneficial, that
could lead to FDA approval for wider use.

A vaccine against SARS-CoV-2 is at best more than year away (SN: 2/21/20). In trying to manage COVID-19 over the next several months,
the question is, “what kind of treatments could we administer that could
truncate this pandemic?” says pathologist John Roback of Emory University
School of Medicine in Atlanta, who does research on transfusion medicine. The top
candidates are drugs already approved to treat diseases such as malaria
that might be repurposed
for COVID-19
(SN: 3/10/20) and convalescent plasma,
he says.

Antibody defense

To fight a virus, the immune
system develops antibodies, proteins that bind to parts of the virus and impede
the infection. When a person makes antibodies in response to an infection or upon
getting a vaccine, it’s called active immunity. The initial ramp up to antibody
production can take about a week or two, but once that has occurred, the immune
system will be able to quickly respond to the next exposure to the virus. For
some viruses and vaccines, active immunity can last decades or even lifelong.

Convalescent plasma, also
called passive antibody therapy, is a type of passive immunity. It can provide
antibodies immediately, but the proteins will last only for a short amount of
time, weeks to possibly a few months.

“We’re using the antibody-rich
plasma from the convalescent patient … to prevent infection or treat infection
in another patient,” says Jeffrey Henderson, an infectious disease physician
and scientist at Washington University School of Medicine in St. Louis.

Setting up clinical trials

Henderson is part of a group
of U.S. researchers working to set up clinical trials for convalescent plasma,
called the National
COVID-19 Convalescent Plasma Project
.
There are plans to test the plasma in three different groups.

One randomized clinical trial
is designed to investigate whether plasma can prevent infection in people
exposed to COVID-19 by a close contact, such as a family member, says project
member Shmuel Shoham, an infectious disease physician at Johns Hopkins
University School of Medicine. The trial will test plasma from recovered
COVID-19 patients against a placebo — plasma taken from patients prior to the December
2019 start of the epidemic, he says.

Another trial is planned to test
whether plasma can keep people with moderate disease who are in the hospital
from needing intensive care, Shoham says. And a third trial aims to study
whether the therapy helps the most critically ill patients. The project is waiting
on a green light from the FDA to start enrolling patients in all of the trials.

Controlled clinical trials
are necessary to get definitive answers on whether convalescent plasma can stop
disease or improve symptoms of COVID-19, and which people it could help the
most. But a look at the history of infectious diseases, described in a
commentary April 1 in the Journal of
Clinical Investigation
, provides many instances in which passive
antibody therapy appeared to prevent or ameliorate infections
. Convalescent plasma was used to help stop outbreaks
of measles and mumps before vaccines were available, and there’s some evidence
that those who got the plasma during the 1918 influenza pandemic were less
likely to die.

Convalescent plasma has also
been put to use against SARS and MERS, the two other coronavirus epidemics. But
studies that showed some benefit didn’t compare how the treatment worked
against a placebo. That’s also true for the first studies on using the plasma
to treat COVID-19. In one, five patients critically ill with COVID-19 and on
mechanical ventilation received convalescent plasma 10 to 22 days after being admitted
to a hospital in Shenzhen, China. As of March 25, three of the patients had been discharged, after a little over 50 days in the hospital, and two
were in stable condition 37 days after the transfusion, researchers report
March 27 in JAMA. Although the
patients improved, they had also gotten antiviral medications, so it’s unclear
which therapy, if any, had an impact.

Plasma questions

In the United States, some blood
banks and hospitals are gearing up to collect plasma from people who’ve recovered
from COVID-19. The Red Cross has set up a donor request form for people who would like to contribute plasma. The National COVID-19
Convalescent Plasma Project also has information on how to register
to donate
plasma.

For the U.S. clinical
trials, the researchers will be scrutinizing the donated plasma to determine
whether it contains neutralizing antibodies, Henderson says. This type of
antibody prevents the virus from entering a host cell, thereby stopping the
infection. Data so far suggest that the spike protein, a particular protein in
SARS-CoV-2 which the virus uses to bind to a protein on human cells (SN: 2/3/20),
is a target of neutralizing antibody.

Researchers suspect that
this type of antibody is what makes convalescent plasma effective. And it also
hints at when using the plasma may be most beneficial.

Early on in the disease, the
virus is infecting cells and hijacking cell machinery to make many copies of
itself. “But as the disease progresses, the tissue damage done by the virus is
more difficult to reverse and isn’t necessarily reversed by something that is
solely targeted towards the virus itself,” such as antibodies, says Henderson. The
body’s inflammatory response can be contributing to the damage.

It doesn’t mean that passive antibody therapy wouldn’t help someone critically ill with COVID-19, he says. “We have so much to learn, of course, but we’re thinking the antibodies may prevent the virus from expanding its numbers.”

Clinical trials of convalescent plasma are beginning in other countries, too. As doctors await answers from completed trials, additional patients may receive the treatment under the FDA’s emergency authorization. It’s great that critically ill patients and their doctors have that option, Shoham says. In the meantime, “we’re trying to … find out if [convalescent plasma] actually works.