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Andromeda galaxy has a humongous halo of gas – BBC Focus Magazine

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Astronomers using the Hubble Space Telescope have mapped the enormous halo of gas surrounding the Andromeda galaxy – the closest large galaxy to our Milky Way.

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The map – the most detailed of its kind – shows that the halo of plasma (electrically charged gas) surrounding this spiral galaxy extends about 1.3 million light-years towards the Milky Way (about half of the distance), and as much as 2 million light-years in some directions.

The halo is invisible, but the researchers say that if it could be seen, it’d be about three times the width of ‘the Plough’, making it the biggest feature in the night sky.

Read more about galaxies

“Understanding the huge halos of gas surrounding galaxies is immensely important,” said team member Samantha Berek at Yale University in Connecticut, US.

“This reservoir of gas contains fuel for future star formation within the galaxy, as well as outflows from events such as supernovae. It’s full of clues regarding the past and future evolution of the galaxy, and we’re finally able to study it in great detail in our closest galactic neighbour.”

The team found that Andromeda’s halo is composed of two distinct layers. The inner ‘shell’ has a more complex structure than the outer shell, which is likely the result of supernovae in the galaxy’s disk. These violent explosions – the death throes of giant stars – also eject heavy elements into space, which were detected in high amounts in the halo.

Illustration showing the halo, with quasars marked in orange © NASA, ESA, and E. Wheatley (STScI)

The halo was mapped by studying the ultraviolet light from 43 distant quasars – extremely luminous galactic cores that are powered by black holes – located behind the halo.

The researchers used Hubble’s ‘Cosmic Origins Spectrograph’ to analyse how this background light was absorbed by the halo’s gas in different regions, revealing variations in the gas’s structure.

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Andromeda is thought to be similar in size and shape to our Milky Way, so these findings also provide insights into our own galactic halo, which is much trickier to map from inside the galaxy.

Reader Q&A: If the Universe is expanding, why is the Andromeda galaxy on course to collide with the Milky Way?

Asked by: Bazrry Cull, Taumarunui, New Zealand

The expansion of the Universe is a large-scale phenomenon: in general, the further away a galaxy is, the faster it recedes from us. But over small regions of space, this expansion is negligible compared to the motion of individual galaxies.

The Andromeda and Milky Way galaxies are sufficiently large – and sufficiently close together – to create a gravitational force that overcomes the general expansion and pulls them together. But don’t worry, the collision won’t happen for another four billion years.

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NASA says bus-sized asteroid safely buzzed Earth | TheHill – The Hill

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NASA reported that an asteroid roughly the size of a school bus passed by Earth early Thursday morning, traveling from about 13,000 miles away. 

According to the government space agency, the rock made its closest approach to Earth around 7 a.m. EDT on Thursday, passing over the Southeastern Pacific Ocean. 

NASA first reported on the asteroid on Tuesday, saying that scientists estimated the space rock was about 15 to 30 feet wide. Scientists predict that the asteroid will now travel around the sun and not make its way back into the Earth’s vicinity until 2041. 

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Paul Chodas, director of the Center for Near-Earth Object Studies at NASA’s Jet Propulsion Laboratory in Southern California, said Tuesday that space rocks such as these are relatively common and are not considered a threat to life on Earth. 

“There are a large number of tiny asteroids like this one, and several of them approach our planet as close as this several times every year,” Chodas said. “In fact, asteroids of this size impact our atmosphere at an average rate of about once every year or two.”

He added that “the detection capabilities of NASA’s asteroid surveys are continually improving, and we should now expect to find asteroids of this size a couple days before they come near our planet.” 

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NASA said that while Thursday’s asteroid was not on a trajectory to hit Earth, it would have likely broken up in the atmosphere and become a bright meteor, known as a fireball, before causing any damage. 

This comes a month after NASA reported that an asteroid is on a path toward Earth one day before the U.S. presidential election, although the agency said that the chances of it actually hitting the Earth’s surface are less than 1 percent. NASA confirmed in a statement to The Hill last month that the rock would not pose a threat. 

“If it were to enter our planet’s atmosphere, it would disintegrate due to its extremely small size,” a spokesperson said in the statement. “NASA has been directed by Congress to discover 90% of the near-Earth asteroids larger than 140 meters (459 feet) in size and reports on asteroids of any size.”

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UM physicists part of international team for historic first – UM Today

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September 24, 2020 — 

UM researchers on an international team of physicists have made the first precise measurement of the weak force between particles in the universe, verifying a theory of the Standard Model of Particle Physics.

Using a device called the the Spallation Neutron Source at the U.S. Department of Energy’s Oak Ridge National Laboratory, the scientists were able to measure the weak force exerted between protons and neutrons by detecting the miniscule electrical signal produced when a neutron and a helium-3 nucleus combined and then decayed moving through a target. 

The result was published in the journal Physical Review Letters.

As described in the online news site Mirage News

The Standard Model describes the basic building blocks of matter in the universe and fundamental forces acting between them. Calculating and measuring the weak force between protons and neutrons is an extremely difficult task.

Their finding yielded the smallest uncertainty of any comparable weak force measurement in the nucleus of an atom to date, which establishes an important benchmark.

UM physicist Dr. Michael Gericke said:

When a neutron and a helium-3 nucleus combine, the reaction produces an excited, unstable helium-4 isotope, decaying to one proton and one triton (consisting of two neutrons and one proton), both of which produce a tiny but detectable electrical signal as they move through the helium gas in the target cell.”

Gericke led the group that built the combined helium-3 target and detector system designed to pick up the very small signals and led the subsequent analysis.

Read the Mirage News story here.

An analysis and explanation of the discovery is here.

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Teenage British activist stages climate protest on Arctic ice floe – CBC.ca

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Like many of her generation, Mya-Rose Craig feels strongly that adults have failed to take the urgent action needed to tackle global warming and so she has headed to the Arctic Ocean to protest.

Armed with a placard reading “Youth Strike for Climate,” the 18-year-old British activist is staging the most northerly protest in a series of youth strikes worldwide.

The strikes, made famous by Swedish campaigner Greta Thunberg, are resuming after a lull caused by the global coronavirus pandemic to draw public attention back to the threat posed by climate change.

“I’m here to … try and make a statement about how temporary this amazing landscape is and how our leaders have to make a decision now in order to save it,” she told Reuters Television as she stood with her placard on the edge of the Arctic sea ice.

“I absolutely think that my generation has always had to think about climate change … which is why as we’ve got older there’s been this massive wave of just this need for change, this demand for change when we realized the grown-ups aren’t going to solve this, so we have to do it ourselves.”

Environmental activist and campaigner Mya-Rose Craig, 18, holds a cardboard sign reading “youth strike for climate” standing on the ice floe in the middle of the Arctic Ocean, hundreds of miles above the Arctic Circle, September 20, 2020. (Natalie Thomas/Reuters)

Craig, from southwest England, is known as “Birdgirl” online, where her blog chronicling her bird-watching experiences has attracted thousands of followers.

She has traveled hundreds of miles above the Arctic Circle aboard a Greenpeace ship, Arctic Sunrise.

Climate data shows the Arctic is one of the fastest changing ecosystems on the planet, with serious consequences for wildlife from polar bears and seals to plankton and algae, while the melting sea ice contributes to rising sea levels worldwide.

Warming Arctic

Warming in the Arctic shrank the ice covering the polar ocean this year to its second-lowest extent in four decades, scientists said on Monday.

For Craig, getting to the ice floe involved a two-week quarantine in Germany, followed by a three-week voyage to the edge of the sea ice.

Craig said those who dismiss the youth protests as just a rebellious phase by her generation are wrong, and she wants those in power to stop treating climate change as a low-priority issue, raised only to appease “the lefties in the corner.”

“It’s everything now and it has to be treated like that,” she said.

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