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Halo of warm gas explains massive size of the Magellanic Stream

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Sept. 9 (UPI) — Billions of years ago, a pair of dwarf galaxies known as the Magellanic Clouds were pulled into orbit around the Milky Way. Along the way, the Milky Way stripped a massive stream of gas called the Magellanic Stream from the dwarf galaxies.

Until now, scientists weren’t sure how the stream came to be so massive, but new models suggest a halo of warm gas surrounding the Magellanic Clouds fueled the growth of the Magellanic Stream.

Scientists detailed the predictions of the new models in a new paper, published Wednesday in the journal Nature.

“[Our] theory predicts that a high-mass Large Magellanic Cloud should be surrounded by a warm halo, and we believe that its existence will be confirmed from next observations at the Hubble Space Telescope,” study co-author Elena D’Onghia, professor of astronomy at University of Wisconsin, told UPI.

Previous models showed a combination of gravitational tides and forces exerted by the dwarf galaxies surrounding the Milky Way helped to pull the Magellanic Stream out of the Magellanic Clouds. These models did a good job of explaining the stream’s shape and size, researchers say.

“Previous models failed in explaining such a massive system,” D’Onghia said.

Using numerical simulations, scientists were able to show that a corona of warm gas surrounding the two Magellanic Clouds, the Large Magellanic Cloud and Small Magellanic Cloud, came to be massive, totaling 2 billion solar masses.

Though the new research is primarily based on computer simulations, researchers suggest they were motivated by a several recent astronomical observations hinting at the presence of large amounts of highly ionized gas at coronal temperatures surrounding the Magellanic Clouds.

The presence of coronal gas not only explains the Magellanic Stream’s hulking mass, it also helps explain the formation and evolution of the Magellanic Clouds and Magellanic Stream.

“The corona has a large impact on the formation and evolution of the stream, for several reasons,” D’Onghia said.

“First, the corona surrounding the Clouds heats the cool gas pulled out of the Small Magellanic Cloud several billion years ago, before the clouds fall into the Milky Way, thus feeding the nascent stream,” she said. “Second, it protects the stream from disruption by the Milky Way’s own hot corona, acting as a protective cocoon. Finally, the corona provides most of the mass of the stream.”

By more accurately modeling the formation and evolution of the Magellanic Stream, astronomers can improve their understanding of how the Milky Way accretes gas from its population of satellite galaxies.

In future studies, scientists plan to test their theory and models using direct Hubble Space Telescope observations of the Magellanic Stream and the Leading Arm of the Stream.

“This gas structure is very complex,” D’Onghia said. “Its morphology, metal content and spatial location is still controversial and poses challenges to the tidal origin of the Magellanic Stream.”



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Eight nations, including U.S., sign accords for moon missions

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ORLANDO, Fla., Oct. 13 (UPI) — Eight nations have signed NASA’s new framework to govern lunar exploration missions, the agency’s administrator, Jim Bridenstine, announced Tuesday.

By signing the agreement, the eight nations commit to peaceful activities on the moon and in travel to the moon.

Provisions in the Artemis Accords stipulate that nations, and private companies in those nations, will openly disclose plans for lunar missions, and mine resources on the moon in accordance with the international Outer Space Treaty that dates to 1967.

The accords also commit signing nations to render aid to other nations on the moon if necessary, to minimize space debris and to register all objects taken to the lunar surface.

In addition to the United States, Australia, Canada, Italy, Japan, Luxembourg, United Arab Emirates and Britain signed the Artemis Accords.

“We are one human race and we are in this together. The Accords help us to work together to benefit all,” Sarah Al Amiri, chair of the United Arab Emirates Council of Scientists, said in a live broadcast Tuesday.

Bridenstine had said in a press conference Monday that more nations are expected to sign the accords this year, and that he hopes all nations eventually will.

“As NASA, we always try to be very transparent and what our plans and policies are, and we think it’s good for all nations to be transparent with their plans,” Bridenstine said.

The new agreement comes as NASA plans to return astronauts to the moon in 2024, with further plans to establish a lunar base to tap water ice for possible long-term habitation.

NASA officials on Monday acknowledged they didn’t approach all space-faring nations in drafting the accords because the agency wanted to move quickly. NASA sought a few nations believed to have common values, said Mike Gold, associate administrator for NASA’s Office of International and Interagency Relations.

“We wanted to begin with a group substantive and large enough to make an impact,” Gold said. “It’s very challenging to do that with too large a group. Now that the text of the accords have been finalized we can broaden the coalition.”

Bridenstine said NASA couldn’t approach China, which already has landed two robotic missions on the moon, because federal law prohibits negotiations with China.

When asked how the accords would be enforced, Bridenstine said the intent of the agreement is to pre-empt conflict by being transparent.

“If one of the participants chooses to disregard the guidance, other participants … ultimately could be asked to leave the Artemis program, but I would hope that they will come to a better resolution,” Bridenstine said.

NASA’s 16 women astronauts — at least one likely to walk on moon

Tracy Caldwell Dyson pauses for a portrait in her spacesuit before going underwater in the Neutral Buoyancy Lab at NASA’s Johnson Space Center in Houston on July 8, 2019. Photo by Bill Ingalls/UPI

NASA’s 16 women astronauts — at least one likely to walk on moon

Tracy Caldwell Dyson pauses for a portrait in her spacesuit before going underwater in the Neutral Buoyancy Lab at NASA’s Johnson Space Center in Houston on July 8, 2019. Photo by Bill Ingalls/UPI



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Rising atmospheric dust across the Great Plains recalls lead up to the Dust Bowl

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Oct. 13 (UPI) — Atmospheric dust levels are rising 5 percent per year across the Great Plains, according to a new survey by scientists at the University of Utah.

The research, published this week in the journal Geophysical Research Letters, increased cropland conversion and expanded growing seasons are exposing more and more soil and wind erosion.

Authors of the new study suggest the phenomenon, if combined with drier climate conditions as a result of climate change, could yield conditions comparable to the Dust Bowl, the series of droughts and dust storms that devastated the Midwest during the 1930s.

“We can’t make changes to the earth surface without some kind of consequence just as we can’t burn fossil fuels without consequences,” lead study author Andy Lambert said in a news release.

“So while the agriculture industry is absolutely important, we need to think more carefully about where and how we plant,” said Lambert, a recent graduate of the University of Utah.

In the 1920s, farmers across the Great Plains converted massive amounts of grassland to farm tracts. When drought hit in the 1930s, extensive crop failures left newly plowed fields exposed to the wind, yielding waves of dust storms.

“These dust storms removed nutrients from the soil, making it more difficult for crops to grow and more likely for wind erosion to occur,” Lambert said.

Soaking rains eventually brought an end to the Dust Bowl, but much of the damage caused by erosion was permanent. Soils in some parts of the Great Plains have never recovered.

Three-quarters of a century later, around 2000, as demand for biofuels increased, farmers started clearing additional grassland to biofuel feedstocks.

Between 2006 and 2011, nearly 2,050 square miles of grassland across five Midwestern states was converted to farmland. Meanwhile, droughts have become longer and more across the Great Plains.

To gauge the risk of dust storms in the region, researchers amassed data from a variety of instruments designed to measure atmospheric haziness from both the ground up and space down. The data, from NASA satellites and two federally managed ground monitoring systems, showed the amount of dust in the atmosphere above the Great Plains has steadily increased over the last 20 years.

“The amount of increase is really the story here,” said study co-author Gannet Hallar, associate professor of atmospheric sciences. “That 5 percent a year over two decades, of course, is a hundred percent increase in dust loading. This is not a small signal to find.”

Scientists were also able to link rises in dust levels with crop expansion. Across Iowa, atmospheric dust increased predominantly in June and October, the planting and harvesting months for soybeans, the dominant crop. Across the southern Great Plains, where corn is more popular, the dust increases appeared in March and October.

“I think it’s fair to say that what’s happening with dust trends in the Midwest and the Great Plains is an indicator that the threat is real if crop land expansion continues to occur at this rate and drought risk does increase because of climate change,” Lambert says. “Those would be the ingredients for another Dust Bowl.”

Authors of the new study said their findings should serve as a warning to farmers and policy makers across the Midwest that proactive measures are needed to ensure history doesn’t repeat itself.



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NASA’s Kate Rubins, 2 cosmonauts dock with International Space Station

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Tracy Caldwell Dyson pauses for a portrait in her spacesuit before going underwater in the Neutral Buoyancy Lab at NASA’s Johnson Space Center in Houston on July 8, 2019. Photo by Bill Ingalls/UPI



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