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Washington D.C., Feb 6: An international team of astronomers has found an unusual monster galaxy that existed about 12 billion years ago when the universe was only 1.8 billion years old.

The team of astronomers was led by scientists at the University of California, Riverside.

Dubbed XMM-2599, the galaxy formed stars at a high rate and then died. Why it suddenly stopped forming stars is unclear.

"Even before the universe was 2 billion years old, XMM-2599 had already formed a mass of more than 300 billion suns, making it an ultra massive galaxy," said Benjamin Forrest, a postdoctoral researcher in the UC Riverside Department of Physics and Astronomy and the study's lead author.

"More remarkably, we show that XMM-2599 formed most of its stars in a huge frenzy when the universe was less than 1 billion years old and then became inactive by the time the universe was only 1.8 billion years old," Forrest added.

The team used spectroscopic observations from the W. M. Keck Observatory's powerful Multi-Object Spectrograph for Infrared Exploration or MOSFIRE, to make detailed measurements of XMM-2599 and precisely quantify its distance.

The study results appear in the Astrophysical Journal.

"In this epoch, very few galaxies have stopped forming stars, and none are as massive as XMM-2599," said Gillian Wilson, a professor of physics and astronomy at UCR in whose lab Forrest works.

"The mere existence of ultramassive galaxies like XMM-2599 proves quite a challenge to numerical models. Even though such massive galaxies are incredibly rare at this epoch, the models do predict them."

"The predicted galaxies, however, are expected to be actively forming stars. What makes XMM-2599 so interesting, unusual, and surprising is that it is no longer forming stars, perhaps because it stopped getting fuel or its black hole began to turn on. Our results call for changes in how models turn off star formation in early galaxies," the professor stated.

The research team found XMM-2599 formed more than 1,000 solar masses a year in stars at its peak of activity -- an extremely high rate of star formation. In contrast, the Milky Way forms about one new star a year.

"XMM-2599 may be a descendant of a population of highly star-forming dusty galaxies in the very early universe that new infrared telescopes have recently discovered," said Danilo Marchesini, an associate professor of astronomy at Tufts University and a co-author on the study.

"We have caught XMM-2599 in its inactive phase," Wilson said, who led the W. M. Keck Observatory data acquisition
Co-author Michael Cooper, a professor of astronomy at UC Irvine, said this outcome is a strong possibility.

"Perhaps during the following 11.7 billion years of cosmic history, XMM-2599 will become the central member of one of the brightest and most massive clusters of galaxies in the local universe," he said.

"Alternatively, it could continue to exist in isolation. Or we could have a scenario that lies between these two outcomes," he stated.

The study was supported by grants from the National Science Foundation and NASA.

London, Feb 21: Scientists have discovered a new species of land snail, and have named it Craspedotropis Greta Thunberg in honour of the Swedish activist Greta Thunberg for her efforts to raise awareness about climate change.

According to the study, published in the Biodiversity Data Journal, the newly discovered species belongs to the so-called caenogastropods -- a group of land snails known to be sensitive to drought, temperature extremes, and forest degradation.

The scientists, including evolutionary ecologist Menno Schilthuizen from Naturalis Biodiversity Center in the Netherlands, said the snails were found very close to the research field station at Kuala Belalong Field Studies Centre in Brunei.

They added that the snails were discovered at the foot of a steep hill-slope, next to a river bank, foraging at night on the green leaves of understorey plants.

The effort aided by amateur scientist J.P. Lim, who found the first individual of the snail said, "Naming this snail after Greta Thunberg is our way of acknowledging that her generation will be responsible for fixing problems that they did not create."

"And it's a promise that people from all generations will join her to help," Lim said.

The researchers said they approached Thunberg who said that she would be "delighted" to have this species named after her.

The study work including, fieldwork, morphological study, and classification of identified specimen was carried out in a field centre with basic equipment and no internet access, the scientists said.

According to the study, the work was done by untrained ‘citizen scientists’ guided by experts, on a 10-day taxon expedition.

"While we are aware that this way of working has its limitations in terms of the quality of the output (for example, we were unable to perform dissections or to do extensive literature searches), the benefits include rapid species discovery and on-site processing of materials," the researchers wrote in the study.

Denser places, assumed by many to be more conducive to the spread of the coronavirus that causes COVID-19, are not linked to higher infection rates, say researchers.

The study, led by Johns Hopkins University, published in the Journal of the American Planning Association, also found that dense areas were associated with lower COVID-19 death rates.

"These findings suggest that urban planners should continue to practice and advocate for compact places rather than sprawling ones, due to the myriad well-established benefits of the former, including health benefits," says study lead author Shima Hamidi from Johns Hopkins Bloomberg School of Public Health in the US.

For their analysis, the researchers examined SARS-CoV-2 infection rates and COVID-19 death rates in 913 metropolitan counties in the US.

When other factors such as race and education were taken into account, the authors found that county density was not significantly associated with county infection rate.

The findings also showed that denser counties, as compared to more sprawling ones, tended to have lower death rates--possibly because they enjoyed a higher level of development including better health care systems.

On the other hand, the research found that higher coronavirus infection and COVID-19 mortality rates in counties are more related to the larger context of metropolitan size in which counties are located.

Large metropolitan areas with a higher number of counties tightly linked together through economic, social, and commuting relationships are the most vulnerable to the pandemic outbreaks.

According to the researchers, recent polls suggest that many US citizens now consider an exodus from big cities likely, possibly due to the belief that more density equals more infection risk.

Some government officials have posited that urban density is linked to the transmissibility of the virus.

"The fact that density is unrelated to confirmed virus infection rates and inversely related to confirmed COVID-19 death rates is important, unexpected, and profound," said Hamidi.

"It counters a narrative that, absent data and analysis, would challenge the foundation of modern cities and could lead to a population shift from urban centres to suburban and exurban areas," Hamidi added.

The analysis found that after controlling for factors such as metropolitan size, education, race, and age, doubling the activity density was associated with an 11.3 per cent lower death rate.

The authors said that this is possibly due to faster and more widespread adoption of social distancing practices and better quality of health care in areas of denser population.

The researchers concluded that a higher county population, a higher proportion of people age 60 and up, a lower proportion of college-educated people, and a higher proportion of African Americans were all associated with a greater infection rate and mortality rate.