Category: 7. Science

Researchers have found clouds of cold gas embedded deep within larger, superheated gas clouds – or Fermi bubbles – at the Milky Way’s center. The finding challenges current models of Fermi bubble formation and reveals that the bubbles are much younger than previously estimated.

“The Fermi bubbles are enormous structures of hot gas that extend above and below the disk of the Milky Way, reaching about 25,000 light years in each direction from the galaxy’s center – spanning a total height of 50,000 light years,” says Rongmon Bordoloi, associate professor of physics at North Carolina State University and corresponding author of the research.

“Fermi bubbles are a relatively recent discovery – they were first identified by telescopes that ‘see’ gamma rays in 2010 – there are different theories about how it happened, but we do know that it was an extremely sudden and violent event, like a volcanic eruption but on a massive scale.”

Bordoloi and the research team used the U.S. National Science Foundation Green Bank Telescope (NSF GBT) to observe the Fermi bubbles and get high resolution data about the composition of the gas within and the speed at which it is moving. These measurements were twice as sensitive as previous radio telescope surveys of the Fermi bubbles and allowed them to observe finer detail within the bubbles.

Most of the gas inside the Fermi bubbles is around 1 million degrees Kelvin. However, the research team also found something surprising: dense clouds of neutral hydrogen gas, each one measuring several thousand solar masses, dotted within the bubbles 12,000 light years above the center of the Milky Way.

“These clouds of neutral hydrogen are cold, relative to the rest of the Fermi bubble,” says Andrew Fox, ESA-AURA Astronomer at the Space Telescope Science Institute and coauthor of the paper.

“They’re around 10,000 degrees Kelvin, so cooler than their surroundings by at least a factor of 100. Finding those clouds within the Fermi bubble is like finding ice cubes in a volcano.”

Their existence is surprising because the hot (over 1 million degrees Kelvin), high-velocity environment of the nuclear outflow should have rapidly destroyed any cooler gas.

“Computer models of cool gas interacting with hot outflowing gas in extreme environments like the Fermi bubbles show that cool clouds should be rapidly destroyed, usually within a few million years, a timescale that aligns with independent estimates of the Fermi bubbles’ age,” Bordoloi says. “It wouldn’t be possible for the clouds to be present at all if the Fermi bubbles were 10 million years old or older.

“What makes this discovery even more remarkable is its synergy with ultraviolet observations from the Hubble Space Telescope (HST),” Bordoloi says. “The clouds lie along a sightline previously observed with HST, which detected highly ionized multiphase gas, ranging in temperatures from a million to 100,000 Kelvin – which is what you’d expect to see if a cold gas is getting evaporated.”

The team was also able to calculate the speed at which the gases are moving, which further confirmed the age.

“These gases are moving around a million miles per hour, which also marks the Fermi bubbles as a recent development,” Bordoloi says. “These clouds weren’t here when dinosaurs roamed Earth. In cosmic time scales, a million years is the blink of an eye.”

“We believe that these cold clouds were swept up from the Milky Way’s center and carried aloft by the very hot wind that formed the Fermi bubbles,” says Jay Lockman, an astronomer at the Green Bank Observatory and coauthor of the paper. “Just as you can’t see the motion of the wind on Earth unless there are clouds to track it, we can’t see the hot wind from the Milky Way but can detect radio emission from the cold clouds it carries along.”

This discovery challenges current understanding of how cold clouds can survive the extreme energetic environment of the Galactic Center, placing strong empirical constraints on how outflows interact with their surroundings. The findings provide a crucial benchmark for simulations of galactic feedback and evolution, reshaping our view of how energy and matter cycle through galaxies.

The work appears in Astrophysical Journal Letters and is supported by the National Science Foundation under grant number AST-2206853.

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University of Sydney researchers have harnessed human-made lightning to develop a more efficient method of generating ammonia.

The current method to generate ammonia, the Haber-Bosch process, comes at great climate cost, leaving a huge carbon footprint. It also needs to happen on a large scale and close to sources of cheap natural gas to make it cost effective.

Lead researcher Professor PJ Cullen from the University of Sydney’s School of Chemical and Biomolecular Engineering and the Net Zero Institute, said industry’s appetite for ammonia is only growing.

“For the past decade, the global scientific community, including our lab, wants to uncover a more sustainable way to produce ammonia that doesn’t rely on fossil fuels,” he said.

“Currently, generating ammonia requires centralised production and long-distance transportation of the product. We need a low-cost, decentralised and scalable green ammonia.”

The research is the culmination of six years’ work.

“In this research we’ve successfully developed a method that allows air to be converted to ammonia in its gaseous form using electricity,” he said.

Professor Cullen’s team’s new method to generate ammonia works by harnessing the power of plasma, by electrifying or exciting the air.

But the star is a membrane-based electrolyser, a seemingly non-descript silver box, where the conversion to gaseous ammonia happens.

During the Haber-Bosch process, ammonia is made by combining nitrogen and hydrogen gases under high temperatures and pressure in the presence of catalyst.

The plasma-based method Professor Cullen’s team developed uses electricity to excite nitrogen and oxygen molecules in the air. The team then passes these molecules to the membrane-based electrolyser to convert them to ammonia.

Professor Cullen said the findings signal a new phase in making green ammonia possible and his team is now working on making the method more energy efficient and competitive compared to the Haber-Bosch process.

“This new approach is a two-step process, namely combining plasma and electrolysis. We have already made the plasma component viable in terms of energy efficiency and scalability,” he said.

“To create a more complete solution to a sustainable ammonia productive, we need to push the energy efficiency of the electrolyser component.”

Earth is expected to spin more quickly in the coming weeks, making some of our days unusually short. On July 9, July 22 and Aug. 5, the position of the moon is expected to affect Earth’s rotation so that each day is between 1.3 and 1.51 milliseconds shorter than normal.

A day on Earth is the length of time needed for our planet to fully rotate on its axis — approximately 86,400 seconds, or 24 hours. But Earth’s rotation is affected by a number of things, including the positions of the sun and moon, changes to Earth’s magnetic field, and the balance of mass on the planet.

NASA’s Lucy mission is key to helping us understand the early history of our solar system as it studies asteroids like the Donaldjohanson.

What is it?

Named after the paleoanthropologist who co-discovered the Lucy skeleton, NASA’s Lucy space probe is key to helping scientists understand the early history of our solar system. Launched on Oct. 16, 2021, Lucy is the first space mission designed specifically to study Trojan asteroids, which are ancient remnants from the early solar system that share orbits with the sun and Jupiter.

NASA’s Lucy mission is key to helping us understand the early history of our solar system as it studies asteroids like the Donaldjohanson.

What is it?

Named after the paleoanthropologist who co-discovered the Lucy skeleton, NASA’s Lucy space probe is key to helping scientists understand the early history of our solar system. Launched on Oct. 16, 2021, Lucy is the first space mission designed specifically to study Trojan asteroids, which are ancient remnants from the early solar system that share orbits with the sun and Jupiter.

Researchers have found clouds of cold gas embedded deep within larger, superheated gas clouds – or Fermi bubbles – at the Milky Way’s center. The finding challenges current models of Fermi bubble formation and reveals that the bubbles are much younger than previously estimated.

“The Fermi bubbles are enormous structures of hot gas that extend above and below the disk of the Milky Way, reaching about 25,000 light years in each direction from the galaxy’s center – spanning a total height of 50,000 light years,” says Rongmon Bordoloi, associate professor of physics at North Carolina State University and corresponding author of the research.

“Fermi bubbles are a relatively recent discovery – they were first identified by telescopes that ‘see’ gamma rays in 2010 – there are different theories about how it happened, but we do know that it was an extremely sudden and violent event, like a volcanic eruption but on a massive scale.”

Bordoloi and the research team used the U.S. National Science Foundation Green Bank Telescope (NSF GBT) to observe the Fermi bubbles and get high resolution data about the composition of the gas within and the speed at which it is moving. These measurements were twice as sensitive as previous radio telescope surveys of the Fermi bubbles and allowed them to observe finer detail within the bubbles.

Most of the gas inside the Fermi bubbles is around 1 million degrees Kelvin. However, the research team also found something surprising: dense clouds of neutral hydrogen gas, each one measuring several thousand solar masses, dotted within the bubbles 12,000 light years above the center of the Milky Way.

“These clouds of neutral hydrogen are cold, relative to the rest of the Fermi bubble,” says Andrew Fox, ESA-AURA Astronomer at the Space Telescope Science Institute and coauthor of the paper.

“They’re around 10,000 degrees Kelvin, so cooler than their surroundings by at least a factor of 100. Finding those clouds within the Fermi bubble is like finding ice cubes in a volcano.”

Their existence is surprising because the hot (over 1 million degrees Kelvin), high-velocity environment of the nuclear outflow should have rapidly destroyed any cooler gas.

“Computer models of cool gas interacting with hot outflowing gas in extreme environments like the Fermi bubbles show that cool clouds should be rapidly destroyed, usually within a few million years, a timescale that aligns with independent estimates of the Fermi bubbles’ age,” Bordoloi says. “It wouldn’t be possible for the clouds to be present at all if the Fermi bubbles were 10 million years old or older.

“What makes this discovery even more remarkable is its synergy with ultraviolet observations from the Hubble Space Telescope (HST),” Bordoloi says. “The clouds lie along a sightline previously observed with HST, which detected highly ionized multiphase gas, ranging in temperatures from a million to 100,000 Kelvin – which is what you’d expect to see if a cold gas is getting evaporated.”

The team was also able to calculate the speed at which the gases are moving, which further confirmed the age.

“These gases are moving around a million miles per hour, which also marks the Fermi bubbles as a recent development,” Bordoloi says. “These clouds weren’t here when dinosaurs roamed Earth. In cosmic time scales, a million years is the blink of an eye.”

“We believe that these cold clouds were swept up from the Milky Way’s center and carried aloft by the very hot wind that formed the Fermi bubbles,” says Jay Lockman, an astronomer at the Green Bank Observatory and coauthor of the paper. “Just as you can’t see the motion of the wind on Earth unless there are clouds to track it, we can’t see the hot wind from the Milky Way but can detect radio emission from the cold clouds it carries along.”

This discovery challenges current understanding of how cold clouds can survive the extreme energetic environment of the Galactic Center, placing strong empirical constraints on how outflows interact with their surroundings. The findings provide a crucial benchmark for simulations of galactic feedback and evolution, reshaping our view of how energy and matter cycle through galaxies.

The work appears in Astrophysical Journal Letters and is supported by the National Science Foundation under grant number AST-2206853.

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Note to editors: An abstract follows.

“A New High-latitude H I Cloud Complex Entrained in the Northern Fermi Bubble”

DOI: 10.3847/2041-8213/addd16

Authors: Rongmon Bordoloi, North Carolina State University; Andrew Fox, Space Telescope Science Institute; Felix Lockman, Green Bank Observatory
Published: July 7 in Astrophysical Journal Letters

Abstract:
We report the discovery of eleven high-velocity H I clouds at Galactic latitudes of 25–30 degrees, likely embedded in the Milky Way’s nuclear wind. The clouds are detected with deep Green Bank Telescope 21 cm observations of a 3.2◦×6.2◦ field around QSO 1H1613-097, located behind the northern Fermi Bubble. Our measurements reach 3σ limits on NHI as low as 3.1 × 1017 cm−2, more than twice as sensitive as previous H I studies of the Bubbles. The clouds span −180 ≤ vLSR ≤ −90 kms−1 and are the highest-latitude 21 cm HVCs detected inside the Bubbles. Eight clouds are spatially resolved, showing coherent structures with sizes of 4–28 pc, peak column densities of log(NHI/cm2)=17.9–18.7, and H I masses up to 1470M⊙. Several exhibit internal velocity gradients. Their presence at such high latitudes is surprising, given the short expected survival times for clouds expelled from the Galactic Center. These objects may be fragments of a larger cloud disrupted by interaction with the surrounding hot gas.

The July full moon, known as the ‘Buck Moon’ will rise on Wednesday, July 10 and put on a spectacular show for both stargazers and astrophotographers alike.

A full moon occurs when the moon is positioned opposite the sun in the sky, causing it to appear fully lit from our perspective here on Earth.