Our Moon
doesn’t really look like this. Earth’s Moon, Luna, doesn’t naturally show this rich texture, and
its colors are more subtle. But this digital creation is based on reality. The featured image is a composite of multiple images and enhanced to bring up real surface features. The
enhancements, for example, show more clearly craters that illustrate the tremendous bombardment our Moon has been through during its 4.6-billion-year
history. The dark areas, called maria, have fewer craters and were once seas of molten lava. Additionally, the image colors, although based on the moon’s real composition, are
changed and exaggerated. Here, a blue hue indicates a region that is iron rich,
while orange indicates a slight excess of aluminum. Although the Moon has shown the same side to the Earth for
billions of years, modern technology is allowing humanity to learn much more about it — and how it affects the Earth.
Artist's impression of
waves, with different frequencies, travelling in the inner layers of a star.
P-modes, or pure sound (pressure) waves, in white, spend most of their time in
the outer envelope and are directly visible at the stars' surface. G-modes, or
pure gravity waves, in black, propagate in the radiative interior and hold
information on the stellar core. In red giants, the two are coupled together
and the resulting waves sense all layers, thus revealing information of the
stars' deepest interior. Credit: Tania Cunha (Planetário do Porto - Centro
Ciência Viva)/Instituto de Astrofísica e Ciências do Espaço
Red giants are dying stars, in advanced stages of stellar evolution, which
have depleted the hydrogen in their cores. In a study published today in Nature
Communications, a team of astronomers mainly from Instituto de Astrofísica
e Ciências do Espaço (IA), have found new evidence that red giant stars
experience "glitches"—sharp structural variations—in their inner
core.
Unfortunately, it is impossible to look directly inside a star. However, a
technique dubbed asteroseismology, which measures oscillations similar to
"earthquakes" in stars, can provide indirect glimpses of stellar
interiors. The "glitches" can affect these oscillations, or the
frequencies and paths of gravity and sound waves traveling
through the stellar interior.
As IA researcher Margarida Cunha explains, "Waves propagating inside
stars induce minute stellar brightness variations that can be detected with
highly precise space-based instruments. These waves reveal the conditions of
the medium where they propagate, which is to say, the physical properties of
the stellar interiors."
Animation of
waves, with different frequencies, travelling in the inner layers of a star.
P-modes, or pure sound (pressure) waves, in white, spend most of their time in
the outer envelope and are directly visible at the stars' surface. G-modes, or
pure gravity waves, in black, propagate in the radiative interior and hold
information on the stellar core. In red giants, the two are coupled together
and the resulting waves sense all layers, thus revealing information of the
stars' deepest interior. Credit: Tania Cunha (Planetário do Porto - Centro
Ciência Viva)/Instituto de Astrofísica e Ciências do Espaço
The team used data from the Kepler space telescope (NASA) to detect and
study waves propagating to the deepest layers of evolved stars.
Lead author Mathieu Vrard, currently a postdoctoral research associate in
astronomy at the Ohio State University, explains, "This work presents the
first characterization of structural discontinuities present in the core of
red-giant stars, therefore allowing, for the first time, to precisely sound the
physical processes occurring in this region."
Vrard, who began this work at IA, adds, "By analyzing these
variations, we can obtain not only the global parameters of the star, but also
information on the precise structure of these objects."
Artist's impression of
waves, with different frequencies, travelling in the inner layers of a star.
P-modes, or pure sound (pressure) waves, in white, spend most of their time in
the outer envelope and are directly visible at the stars' surface. G-modes, or
pure gravity waves, in black, propagate in the radiative interior and hold
information on the stellar core. In red giants, the two are coupled together
and the resulting waves sense all layers, thus revealing information of the
stars' deepest interior. Credit: Tania Cunha (Planetário do Porto - Centro
Ciência Viva)/Instituto de Astrofísica e Ciências do Espaço
Low-mass red giants experiencing
helium burning in their cores are often used in astrophysical studies as probes
of distance, to measure aspects like galaxy density, and to learn more about
the physical processes behind stellar
chemical evolution. So it's vital that scientists model them correctly which,
in turn, requires that they understand why these discontinuities happen.
In this work, the team analyzed a sample of 359 red giants that were below
a certain stellar mass, measuring various properties and individual oscillation
frequencies of each star. They discovered that almost 7% of these stars exhibit
structural discontinuities.
Schematic of the
evolution of a main sequence star, to red giant. The stars in this study are at
the end of the evolution track shown, experiencing helium core fusion. The
different evolutionary stages are not to scale. Credit: Thomas Kallinger,
University of British Columbia and University of Vienna
There are two main theories which explain how these disturbances might
work. The first states that "glitches" are present throughout the
star's evolution, but are generally very weak and below the threshold for what
astronomers would categorize as a true discontinuity.
The second suggests that these irregularities are "smoothed out"
by some unknown physical process that later leads to changes in the structure
of the star's core.
As it turns out, the first scenario is not supported by this study, but
more precise data is needed before scientists can confidently subscribe to the
second. Diego Bossini (IA) explains, "This study shows the limits of our
models and it gives us an opportunity to find a way for improving them."
To some, the
dark shape looks like a mythical boogeyman. Scientifically, Lynds’ Dark Nebula (LDN) 1622 appears against a faint background of glowing
hydrogen gas only visible in long telescopic exposures of the region. In
contrast, the brighter reflection nebula vdB 62 is more easily seen just above and to the right
of center in the featured image. LDN 1622 lies near the plane of our Milky Way
Galaxy, close on the sky to Barnard‘s Loop, a large cloud surrounding the rich complex of emission
nebulae found in the Belt and
Sword of Orion. With swept-back outlines, the obscuring dust of LDN 1622 is thought to lie at a similar
distance, perhaps 1,500 light-years away. At that distance, this 2-degree wide field of view would span about 60
light-years. Young stars do lie hidden within the dark expanse and have been revealed in Spitzer Space
Telescopeinfrared images.
Professor
Crystal M. Ripplinger (left) and Post-Doctoral Scholar Jessica L. Caldwell
(right), UC Davis School of Medicine Department of Pharmacology. Credit: UC
Davis
A new study published
in Science Advances shows female and male hearts respond
differently to the stress hormone noradrenaline. The study in mice may have
implications for human heart disorders like arrhythmias and heart failure and
how different sexes respond to medications.
The team built a new type of fluorescence imaging system that
allows them to use light to see how a mouse heart responds to hormones and neurotransmitters in
real time. The mice were exposed to noradrenaline, also known as
norepinephrine. Noradrenaline is both a neurotransmitter and hormone associated
with the body's "fight or flight" response.
The results reveal that male and female
mouse hearts respond uniformly at first after exposure to noradrenaline.
However, some areas of the female heart return to normal more quickly than the
male heart, which produces differences in the heart's electrical activity.
"The differences in electrical
activity that we observed are called repolarization in the female hearts.
Repolarization refers to how the heart resets between each heartbeat and is
closely linked to some types of arrhythmias," said Jessica L. Caldwell,
first author of the study. Caldwell is a postdoctoral scholar in the UC Davis
School of Medicine Department of Pharmacology.
"We know that there are sex
differences in the risk for certain types of arrhythmias. The study reveals a
new factor that may contribute to different arrhythmia susceptibility between
men and women," Caldwell said.
Heart disease is the
leading cause of death in the US
Heart disease is the leading cause of
death for both men and women in the United
States. It accounted for about 1 in every 4 male deaths and 1 in
every 5 female deaths in 2020. Despite the impact on both sexes, cardiology
research has largely been performed on male subjects.
In this study, the researchers were
interested in looking at factors that may contribute to arrhythmias.
Arrhythmias are a type of heart disorder where the electrical impulses that control
heartbeats don't function properly. They affect somewhere between 1.5% to 5% of
the population.
Methods
The novel imaging system uses a mouse,
called the CAMPER mouse, that has been genetically modified to emit light
during a very specific chemical reaction in the heart—cAMP binding.
The cAMP molecule (an abbreviation of
cyclic adenosine 3',5;-monophosphate) is an intermediate messenger that turns
signals from hormones and neurotransmitters, including noradrenaline, into
action from heart cells.
The light signals from the CAMPER mouse
are transmitted by a biosensor that uses fluorescence resonance energy transfer (FRET). This FRET signal
can be picked up at high speed and high resolution by a new imaging system
specially designed for hearts. This allows the researchers to record the
heart's reaction to noradrenaline in real time, along with changes in
electrical activity.
This new imaging approach revealed the
differences in the breakdown of cAMP in female and male mice and the associated
differences in electrical activity.
After being
exposed to noradrenaline, cAMP (cyclic adenosine 3',5;-monophosphate) in the
heart increases. However, the bottom of the heart—the apex—returns to normal
more quickly in females than males. The findings may have implications for
heart disorders like arrhythmias. Credit: UC Davis
Including female mice
leads to discoveries
The researchers had not planned to study
sex-based responses, according to Crystal M. Ripplinger, senior author of the
study. But the researchers started seeing a pattern of different reactions,
which led them to realize the differences were sex-based.
Ripplinger, an electrical and biomedical
engineer, is a professor in the Department of Pharmacology.
When she started her lab at the UC Davis
School of Medicine over a decade ago, she exclusively used male animals. That
was the norm for most research at the time. But several years ago, she began
including male and female animals in her studies.
"Sometimes the data between the two
sexes is the same. But if the data start to show variation, the first thing we
do is look at sex differences. Using both male and female mice has revealed clues
into differences we would never have suspected. Researchers are realizing you
can't extrapolate to both sexes from only studying one," Ripplinger said.
She notes that with the current study,
it's not clear what the differences in cAMP and electrical activity may mean.
"The response in the female mice
may be protective—or it may not. But simply documenting that there is a
measurable difference in the response to a stress hormone is significant. We
are hoping to learn more in future studies," Ripplinger said.
Additional authors on the study include
I-Ju (Eric) Lee, Lena Ngo, Lianguo Wang, Donald M. Bers, Manuel F. Navedo and
Julie Bossuyt from UC Davis; Sherif Bahriz from UC Davis and Mansoura
University; Bing (Rita) Xu and Yang K. Xiang from UC Davis and VA Northern
California.
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