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

Source: Inconsistent Sleep Times Linked to Higher BMI Percentile in Toddlers – Scents of Science (myfusimotors.com)

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