Saturday, February 27, 2021
Friday, February 26, 2021
Rare Blast’s Remains Discovered in Milky Way Center - UNIVERSE
Astronomers may have found our galaxy’s first example of an unusual kind of stellar explosion. This discovery, made with NASA’s Chandra X-ray Observatory, adds to the understanding of how some stars shatter and seed the universe with elements critical for life on Earth.
This intriguing object, located near the center of the
Milky Way, is a supernova remnant called Sagittarius A East, or Sgr A East for
short. Based on Chandra data, astronomers previously classified the object as
the remains of a massive star that exploded as a supernova, one of many kinds
of exploded stars that scientists have catalogued.
Using longer Chandra observations, a team of
astronomers has now instead concluded that the object is left over from a
different type of supernova. It is the explosion of a white dwarf, a shrunken
stellar ember from a fuel-depleted star like our Sun. When a white dwarf pulls
too much material from a companion star or merges with another white dwarf, the
white dwarf is destroyed, accompanied by a stunning flash of light.
Astronomers use these “Type Ia supernovae” because
most of them mete out almost the same amount of light every time no matter
where they are located. This allows scientists to use them to accurately
measure distances across space and study the expansion of the universe.
Data from Chandra have revealed that Sgr A East, however,
did not come from an ordinary Type Ia. Instead, it appears that it belongs to a
special group of supernovae that produce different relative amounts of elements
than traditional Type Ias do, and less powerful explosions. This subset is
referred to as “Type Iax,” a potentially important member of the supernova
family.
“While we’ve found Type Iax supernovae in other
galaxies, we haven’t identified evidence for one in the Milky Way until now,”
said Ping Zhou of Nanjing University in China, who led the new study while at
the University of Amsterdam. “This discovery is important for getting a handle
of the myriad ways white dwarfs explode.”
The explosions of white dwarfs is one of the most
important sources in the universe of elements like iron, nickel, and chromium.
The only place that scientists know these elements can be created is inside the
nuclear furnace of stars or when they explode.
“This result shows us the diversity of types and
causes of white dwarf explosions, and the different ways that they make these
essential elements,” said co-author Shing-Chi Leung of Caltech in Pasadena,
California. “If we’re right about the identity of this supernova’s remains, it
would be the nearest known example to Earth.”
Astronomers are still debating the cause of Type Iax
supernova explosions, but the leading theory is that they involve thermonuclear
reactions that travel much more slowly through the star than in Type Ia
supernovae. This relatively slow walk of the blast leads to weaker explosions
and, hence, different amounts of elements produced in the explosion. It is also
possible that part of the white dwarf is left behind.
Sgr A East is located
very close to Sagittarius A*, the supermassive black hole in the center of our
Milky Way galaxy, and likely intersects with the disk of material surrounding
the black hole. The team was able to use Chandra observations targeting the
supermassive black hole and the region around it for a total of about 35 days
to study Sgr A East and find the unusual pattern of elements in the X-ray data.
The Chandra results agree with computer models predicting a white dwarf that
has undergone slow-moving nuclear reactions, making it a strong candidate for a
Type Iax supernova remnant.
“This supernova remnant is in the background of many Chandra images of our
galaxy’s supermassive black hole taken over the last 20 years,” said Zhiyuan
Li, also of Nanjing University. “We finally may have worked out what this
object is and how it came to be.”
In other galaxies, scientists observe that Type Iax
supernovae occur at a rate that is about one third that of Type Ia supernovae.
In the Milky Way, there have been three confirmed Type Ia supernova remnants
and two candidates that are younger than 2,000 years, corresponding to an age
when remnants are still relatively bright before fading later. If Sgr A East is
younger than 2,000 years and resulted from a Type Iax supernova, this study
suggests that our galaxy is in alignment with respect to the relative numbers
of Type Iax supernovae seen in other galaxies.
Along with the suggestion that Sgr A East is the
remnant from the collapse of a massive star, previous studies have also pointed
out that a normal Type Ia supernova had not been ruled out. The latest study
conducted with this deep Chandra data argue against both the massive star and
the normal Type Ia interpretations.
These results have been published today in The Astrophysical Journal, and a
preprint is available online.
The other co-authors of the paper are Ken’ichi Nomoto of The University of
Tokyo in Japan, Jacco Vink of the University of Amsterdam in The Netherlands,
and Yang Chen, also of Nanjing University.
Article via NASA & Chandra Obs.
Source: Rare
Blast’s Remains Discovered in Milky Way Center – Scents of Science
(myfusimotors.com)
Inconsistent Sleep Times Linked to Higher BMI Percentile in Toddlers
Establishing a consistent sleep schedule for a toddler can be one of the most challenging aspects of child rearing, but it also may be one of the most important.
Research findings from a team
including Lauren Covington, an assistant professor in the University of
Delaware School of Nursing, suggest that children with inconsistent sleep
schedules have higher body mass index (BMI) percentiles. Their findings,
published in the Annals of Behavioral Medicine,
suggest sleep could help explain the association between household poverty and
BMI.
“We’ve known for a while that
physical activity and diet quality are very strong predictors of weight and
BMI,” said Covington, the lead author of the article. “I think it’s really
highlighting that sleep may be playing a bigger role here than it’s been given
credit for.”
The study used data from an
obesity prevention trial for mothers and their children living in Baltimore.
All of the families were eligible for the Special Supplemental Nutrition
Program for Women, Infants, and Children (WIC) and 70% were living at or below
the poverty line. As part of the trial, 207 toddlers wore accelerometers that
measured their sleep and physical activity for up to a week at a time. Mothers
also completed a food diary that was compared with the Healthy Eating Index, a
measure of diet quality based on the recommendations from the Dietary
Guidelines for Americans.
Researchers wanted to examine
the relationship between poverty and BMI, specifically looking at whether the
consistency of when toddlers went to bed, their level of physical activity and
diet quality could explain the association. They found that children from
households with greater poverty had more overall inconsistent sleep onset
times. And those with more inconsistent bedtimes had higher BMI percentages.
Covington said it is likely a
bidirectional relationship. “There’s a lot of teasing out the relationships of
the mechanisms that are at play here, which is really difficult to do because I
think they’re all influencing each other,” she said.
Sleep recommendations suggest
children go to bed within an hour of their usual bedtime on a nightly basis.
But for families living in poverty, such scheduling may not be so easily done,
Covington said, especially if a caregiver is the only parent, juggling multiple
jobs, parenting multiple children or dealing with a tenuous housing situation.
“There’s so many factors that
are at play and not necessarily controllable, especially in disadvantaged
communities,” said Covington, who hopes in the future to develop interventions
for families that support healthy routines.
Covington, who joined the UD
faculty in 2018, became interested in sleep research while working as a
pediatric intensive care nurse. She encountered several families who lost a
baby to sudden infant death syndrome (SIDS) as a result of their sleep
environment.
“There’s so much stigma and
stereotypes out there and people are just so quick to judge,” she said. “These
families just want to do what’s right for their child. They just either don’t
personally know how to or they don’t have the resources to do it.”
Covington is currently
working on a study comparing the sleep similarities between children and their
caregivers. She and other researchers, including Associate Professor Freda
Patterson from the Department of Behavioral Health and Nutrition, School of
Nursing professor Emily Hauenstein and UD graduate students Angeni Cordova and
Shannon Mayberry, also completed a systematic review of the existing research
literature looking at the influence of the family context in early childhood
health sleep health.
Their findings, published in
the peer-reviewed journal Sleep Health, found that the
presence of household chaos and poor-quality marital relationships were
directly associated with early childhood sleep problems and variable sleep
timing.
For families who have been
struggling during the coronavirus (COVID-19) pandemic, creating a regular
evening routine may be a doable way to make a difference in a child’s health,
despite the other upheaval going on at this time.
“Implementing a consistent
bedtime could be one behavioral change that a family could potentially do,”
said Covington, who came to UD because of the opportunity to work with other
sleep and disparity researchers. “It’s more attainable than maybe getting
healthy food at the grocery store or playing outside on the playground,
especially now with the cold weather. Just having a consistent bedtime can help
provide some sense of structure, but then maybe have better implications for
health and BMI as well.”
Source: https://www.udel.edu/
Journal article: https://academic.oup.com/abm/advance-article-abstract/doi/10.1093/abm/kaaa100/5983318?redirectedFrom=fulltext
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