Radio Astronomers Discovered Radio Jets In The Phoenix Galaxy Cluster Center (Astronomy)

Radio astronomers have detected jets of hot gas blasted out by a black hole in the galaxy at the heart of the Phoenix Galaxy Cluster, located 5.9 billion light-years away in the constellation Phoenix. This is an important result for understanding the coevolution of galaxies, gas, and black holes in galaxy clusters.

Artist’s illustration of the structures seen in the observations. Credit: NAOJ

Galaxies are not distributed randomly in space. Through mutual gravitational attraction, galaxies gather together to form collections known as clusters. The space between galaxies is not entirely empty. There is very dilute gas throughout a cluster that can be detected by X-ray observations.

If this intra-cluster gas cooled, it would condense under its own gravity to form stars at the center of the cluster. However, cooled gas and stars are not usually observed in the hearts of nearby clusters, indicating that some mechanism must be heating the intra-cluster gas and preventing star formation. One potential candidate for the heat source is jets of high-speed gas accelerated by a super-massive black hole in the central galaxy.

The Phoenix Cluster is unusual in that it does show signs of dense cooled gas and massive star formation around the central galaxy. This raises the question: Does the central galaxy have black hole jets as well?

Radio observations of the center of the Phoenix Galaxy Cluster showing jet structures extending out from the central galaxy. Credit: Akahori et al

A team led by Takaya Akahori at the National Astronomical Observatory of Japan used the Australia Telescope Compact Array (ATCA) to search for black hole jets in the Phoenix Galaxy Cluster with the highest resolution to date. They detected matching structures extending out from opposite sides of the central galaxy. Comparing with observations of the region taken from the Chandra X-ray Observatory archive data shows that the structures detected by ATCA correspond to cavities of less dense gas, indicating that they are a pair of bipolar jets emitted by a black hole in the galaxy. Therefore, the team discovered the first example, in which intra-cluster gas cooling and black hole jets coexist, in the distant universe.

Further details of the galaxy and jets could be elucidated through higher-resolution observations with next generation observational facilities, such as the Square Kilometer Array scheduled to start observations in the late 2020s..


References: Takuya Akahori, Tetsu Kitayama, Shutaro Ueda, Takuma Izumi, Kianhong Lee, Ryohei Kawabe, Kotaro Kohno, Masamune Oguri, Motokazu Takizawa, Discovery of radio jets in the Phoenix galaxy cluster center, Publications of the Astronomical Society of Japan, Volume 72, Issue 4, August 2020, 62, https://doi.org/10.1093/pasj/psaa039

The Phoenix Cluster Is A Record Breaking Galaxy Cluster (Astronomy)

The Phoenix Cluster is impressive enough to make anyone’s head spin. It’s one of the biggest, brightest galaxy clusters ever discovered, and, trust us, that’s just the beginning.

The Phoenix cluster —formally known as SPT-CLJ2344-4243, so be thankful for its nickname—sits about 5.7 billion light years from Earth. Discovered in 2010, this cluster boasts some seriously impressive stats. Here’s a quick rundown from NASA: “Stars are forming in the Phoenix Cluster at the highest rate ever observed for the middle of a galaxy cluster. The object is also the most powerful producer of X-rays of any known cluster, and among the most massive of clusters. The data also suggest that the rate of hot gas cooling in the central regions of the cluster is the largest ever observed.”

But it doesn’t stop there. Here are some more astonishing numbers to gawk over, as reported by Space.com:

• The cluster’s central galaxy contains about 3 trillion stars. Compare that to the Milky Way’s 200 billion or so.
• The estimated mass of the black hole at the cluster’s center is roughly 10 billion solar masses. In other words, it’s about as massive as the biggest black hole ever discovered. The Milky Way’s central black hole weighs a puny 4 million solar masses.
• The galaxy in Phoenix’s center generates about 740 new stars annually, a new high for the middle of a cluster. The Milky Way creates just one or two new stars on average ever year.

Seven years after the Phoenix Cluster was first discovered, scientists noticed more strange and amazing things going on here. A team of astronomers led by the University of Cambridge published their findings in the Astrophysical Journal: an unexpected connection between the supermassive black hole inside the Phoenix Cluster and the giant galaxy in which it sits. The team observed that “radio jets from the black hole—which normally suppress star formation—are stimulating the production of star-forming molecular gas in the galaxy’s halo,” reported Sci-News. Lead author of the research paper, Dr. Helen Russell from the University of Cambridge, said “This gives us new insights into how a black hole can regulate future star birth and how a galaxy can acquire additional material to fuel an active black hole.”


The First Galaxy Discovered Was Called A “Universe Beyond Our Own” (Astronomy)

Imagine if you’d lived your whole life indoors, believing your little room was all of reality, only to wake up one morning to learn that there are millions of other buildings just like yours and that the world was much, much bigger than you thought. That’s what happened to planet Earth in 1925 when Edwin Hubble confirmed that the smudges of light in the sky that astronomers had been puzzling over were indeed spirals of stars outside of the Milky Way — their own “island universes,” as some called them (or galaxies, as we call them today). The story of their discovery is one of dramatic intrigue, media sensationalism, and just a little spite.

The Andromeda nebula, photographed at the Yerkes Observatory around 1900. To modern eyes, this object is clearly a galaxy. At the time, though, it was described as “a mass of glowing gas,” its true identity unknown. (From the book Astronomy of To-Day, 1909)

A century ago, astronomers were mired in a fierce debate over what they saw in the night sky. The heavens were dotted with swirling pinwheels of light they called spiral nebulae. Most could only be seen with a telescope, but one, the Andromeda nebula, could be seen with the naked eye if the night was dark enough. What exactly were they?

The answer depended on who you asked. One camp speculated that the nebulae were massive, faraway clusters of stars a lot like our own Milky Way. The other camp thought they were smaller, closer clouds of gas, akin to our modern definition of the word “nebula.” This debate was formalized in what literally came to be called “The Great Debate,” with astronomer Heber Curtis in one corner and Harlow Shapley in the other. One fateful night in 1920, the two men presented their published papers, Heber arguing that the universe is composed of many galaxies like our own while Shapley argued that the entire universe is one big galaxy.

There was no winner that night, and both scientists would prove to be right on some points and wrong on others. But as for the main argument, it would take a few more years before the world had an answer. That would come from a name you’ve certainly heard before: Edwin Hubble, an arch-rival of Shapley who just so happened to be studying the heavens via the world’s biggest stargazer, the 100-inch Hooker Telescope.

Previous research had suggested that these nebulae were actually moving away from us at a dramatic speed, and that made Hubble a quiet advocate of the many-galaxies theory. He spent long periods aiming the Hooker Telescope at the Andromeda nebula, hoping to capture extra detail that could reveal its secrets. His patience paid off; images revealed that the nebula was not a cloud of gas, but a cluster of stars.

Then in 1923, Hubble got his smoking-gun evidence: He spotted a Cepheid variable, a particular type of star that shines and dims in a predictable way that can tell you how far away it is. Hubble estimated that this star within the Andromeda galaxy was an eye-watering 930,000 light-years away, farther than anything detected at that time.

But Hubble was a cautious scientist, and it wasn’t until his discovery leaked to the media and other astronomers suggested he publish his results that he eventually agreed to. On January 1, 1925, the world finally heard about his discovery. The universe was 100,000 times larger than we’d previously believed. Our small place in space got even smaller.

The media paid less attention than you might think, but those who did notice advertised the news in lights. “Offers Proof of Complete Universe Beyond Our Own,” announced one headline in Baltimore’s Evening Sun, atop an article that sensationalized the discovery as “proof that beyond this entire universe … is another Earth in another universe separate from our own.”

As Corey Powell points out in Discover Magazine, it was oddly Shapley, not Hubble, who suggested everyone stop calling these pinwheels “nebulae” or “island universes.” They were just like the Milky Way galaxy, he said, so they should be called “galaxies.” But Hubble had won the fight; he wasn’t about to take suggestions from the losing side. For the rest of his life, he called these objects “extra-galactic nebulae.”


Ultra-Diffuse Galaxies Are The Ghosts Of The Cosmos (Astronomy)

When talking about space, people often gravitate to the biggest, the brightest, and the closest to us. But sometimes it’s just as fascinating to learn about the other end: the faint and seemingly insignificant. Ultra-diffuse galaxies are in the latter camp. These dim, wispy galaxies have caught the attention of astronomers, who have sought to find out how they formed.

Ultra diffuse galaxy. Credit: Nasa/ESA

WHY THEY’RE INTERESTING?

Ultra-diffuse galaxies are fairly large, sometimes stretching to the size of our own Milky Way galaxy. But they contain the same number of stars as your average dwarf galaxy; that is, as little as one one-thousandth the number in the Milky Way. That makes them incredibly dim and hard for astronomers to spot, which is why nearly all of the ultra-diffuse galaxies we’ve discovered so far have been in clusters of other galaxies. The telescopes were already looking at the clusters and spotted those galaxies by happenstance.

But how does a galaxy with so few stars get to be so big? Since the discovery of the first ultra-diffuse galaxy in 2015, astronomers have been split. Some thought that they were ordinary spiral galaxies that contained an unusually large amount of dark matter, while others thought they were just dwarf galaxies that had spread out over a larger area. In November 2016, scientists solved the mystery. By using computer simulations, researchers in Copenhagen and Abu Dhabi were able to watch the formation of nearly 100 virtual galaxies from characteristics they had observed in real ones. What they saw was that young ultra-diffuse galaxies start out like dwarf galaxies but contain a large number of supernovae, whose vast explosions blow other stars and dark matter outward until the whole galaxy is extra large and extra faint. Like a housecat that inexplicably takes up half of a queen-size bed, ultra-diffuse galaxies are dwarf galaxies that have spread out and gotten comfortable.

WHY THEY’RE IMPORTANT?

Dwarf galaxies are the most numerous type of galaxy in the universe. The fact that ultra-diffuse galaxies are dwarf galaxies’ larger sisters means that there are probably many, many more of them out there that we haven’t spotted. Add that to the list of things we never knew we didn’t know.


We’re In The Milky Way’s Second Life (Astronomy)

Call it a second life, a mid-life crisis, or a zombie uprising — whatever you call it, it seems that our home galaxy died once before and has come back to life. That’s according to Japanese astronomer Masafumi Noguchi. His idea solves a long-standing mystery about the stars in the Milky Way.

Here’s something strange: The Milky Way is made up of two types of stars, and scientists haven’t been sure why that is. One type is made up of what are known as α (“alpha”) elements, such as oxygen, magnesium, and silicon. The other type is rich in iron. That suggests that they formed in different ways — but how?

To answer that, Noguchi relied on a concept proposed in 2006 called cold-flow accretion, which describes how stars form in galaxies via the influx of cold streams of gas. Noguchi came up with a model of the Milky Way’s evolution over a 10-billion-year period, starting with a period where cold gas streams flowed into the baby galaxy and made it possible for new stars to form. Over time, these stars began to explode in type II supernovae — the kind of death that happens when a star runs out of fuel and collapses under its own gravity. Those type II supernovae gave off lots of α-elements, thereby giving rise to even more stars rich in α-elements.

But around 7 billion years ago, those cold gas flows collided with other clouds of gas and produced shock waves that heated the whole shebang to a much higher temperature. At that point, gas stopped flowing into the galaxy and stars stopped forming — but they kept on dying. This time, more mature stars exploded in type Ia supernovae. These supernovae only happen when a star is in a tight binary orbit with a white dwarf, which pulls gas from its larger companion until it’s compressed to such a degree that it triggers a runaway nuclear reaction. This cataclysmic explosion produces — you guessed it — iron, which is jettisoned into the gas of the galaxy.

Finally, around 5 billion years ago, the gas in the Milky Way emitted enough radiation to start cooling down again. Cold gas began flowing back into the galaxy again, and new stars began forming once more. But this time, they used the surrounding iron in their formation. (Shout-out to our sun! It formed during this period.) That explains why some stars in our galaxy are rich in iron and some aren’t.

So there you have it: There was a 2-billion-year period where the Milky Way completely stopped making stars, and we’re currently on its comeback tour. Even cooler, this appears to be true of a whole lot of galaxies: Andromeda, our closest neighbor, also formed stars in two separate periods, and the same is true of other galaxies that are much more massive than ours. But this is the first time we’ve confirmed that a galaxy of our size formed this way. Noguchi’s model doesn’t extend to all galaxies — smaller galaxies appear to make stars continuously. But with this information under our belts, we can learn even more from watching other galaxies. “… future observations of nearby galaxies may revolutionize our view about galaxy formation,” he says.


You’ve Never Seen A Picture Of The Entire Milky Way (Astronomy)

Search the internet for pictures of the Milky Way — our home galaxy — and you’ll find all sorts of images: bright smudges across the night sky taken by high-end cameras, a horizontal streak taken by powerful telescopes, and an entire spiral galaxy taken by — wait a second. If we live inside of the Milky Way, how do we have pictures of the entire Milky Way? Spoiler alert: We don’t. Not real ones, anyway.

Earth is located in the Milky Way, but it’s nowhere near the middle. We’re about 25,000 light-years from the supermassive black hole at the center, and also 25,000 light-years from the outer edge. As Matt Williams writes for Universe Today, if the Milky Way were a vinyl record, we’d be in the groove halfway between the center and the edge. The galaxy itself is shaped like a disc, with a bulge in the center and some warping thanks to the pull of the galaxies nearby.

This isn’t the milky way.. Its actually NGC 4414, a typical spiral galaxy in the constellation Coma Berenices

If you head for an area mostly free of light pollution, like a Dark Sky Park, you can gaze up at and see a faint glowing band streak across the night sky. That’s the cross-section of the Milky Way we can see from our vantage point on Earth. (To return to the metaphor, if you were sitting on the outer edge of a vinyl record, you would see it as a flat line, not a circle. Same goes for our galaxy.)

But that’s from ground level. What about from a spacecraft?

The spacecraft that has traveled the farthest from Earth is Voyager 1. On the 40th anniversary of its launch in 2017, the craft was 13 billion miles (21 billion kilometers) away. To put that in perspective, one light-year is about 5.9 trillion miles (9.5 trillion kilometers), and our region of the Milky Way is 1,000 light-years thick. It’s safe to say we’re not going to leave our galaxy in your lifetime.

But that’s not to say we don’t have some awesome pictures of what we can see — and even some dependably accurate artist’s renderings of what we can’t. Powerful telescopes like Hubble, Chandra, and Spitzer (and soon, James Webb) capture images of our galaxy in many different light wavelengths, which astronomers piece back together so they can see past the gas and dust as far into the center as possible. And those same telescopes can see other galaxies in their entirety, gathering data that artists use to inform their estimations of what our galaxy actually looks like.

In that way, the images you’ve seen of the Milky Way are a lot like the ones you’ve seen of living dinosaurs. No one has seen either with their own eyes, but decades of research has enabled us to make a pretty accurate guess of what they look like.


This Ingestible Device Treat Stomach Ailments (Medicine / Gastroenterology)

Alex Abramson and colleagues created an ingestible device that affixes itself to the stomach wall and treats ailments by delivering electrical pulses. In their paper, they described problems with current devices used to treat certain stomach ailments and how they overcame them to develop a device that they believe will help treat a wide variety of stomach and bowel problems.

Self-Orienting Technology for Injection and electrical Micro-Stimulation (STIMS) Capsule. Credit: Alex Abramson

Over the past several decades, medical scientists have learned that the gastrointestinal tract does a lot more than just digest our food—it is also involved in chemical processes that regulate critical parts of day-to-day living. There is even some evidence that problems in the gut could be behind such conditions as Alzheimer’s, Hirschsprung’s and Parkinson’s. Because of that, scientists have been working to cure or treat conditions that disrupt the GI process, many of which are antagonistic to stomach digestion by interfering with the contraction process—a critical part of breakdown. Unfortunately, treating such conditions has proven to be problematic. The current approach involves surgery to implant devices that send electrical pulses to the stomach wall, inciting them to contract. Surgery on the stomach is considered risky, however, which has led to efforts aimed at surgery-free solutions. In this new effort, the researchers say they have developed an ingestible capsule that latches onto the stomach wall and emits electrical signals.

Capsule schematic and timeline. Credit: Alex Abramson

The new device is slightly larger than medicinal capsules, but it has three properties that allow it to adhere properly to the stomach wall. The first is a bottom weight to ensure that it will be situated right side up when it reaches the stomach. The second is its shape overall; the team designed it to conform to the shape of the wall of the stomach. The final property involves a payload of sharp, tiny hooks modeled on those of a tapeworm. They allow the device to grab hold of the stomach and to stay in place as digestion takes place.

Thus far, the device has worked as intended in test pigs. The researchers plan to continue their work by ensuring it does not produce unwanted side effects in humans.


References: Alex Abramson et al., “Ingestible transiently anchoring electronics for microstimulation and conductive signaling”, Science Advances, Vol. 6, no. 35, eaaz0127
DOI: 10.1126/sciadv.aaz0127 (2020). Link: https://advances.sciencemag.org/content/6/35/eaaz0127

‘Jumping’ DNA Regulates Human Neurons (Neuroscience)

The human genome contains over 4.5 million sequences of DNA called “transposable elements,” virus-like entities that “jump” around and help regulate gene expression. They do this by binding transcription factors, which are proteins that regulate the rate of transcription of DNA to RNA, influencing gene expression in a broad range of biological events.

Now, an international team of scientists led by Didier Trono at EPFL has discovered that transposable elements play a significant role in influencing the development of the human brain. The study is published in Science Advances.

The scientists found that transposable elements regulate the brain’s development by partnering up with two specialized proteins from the family of proteins known as “Krüppel-associated box-containing zinc finger proteins, or KZFPs. In 2019, another study led by Trono showed that KZFPs tamed the regulatory activity of transposable elements in the first few days of the fetus’s life. However, they suspected that these regulatory sequences were subsequently re-ignited to orchestrate the development and function of adult organs.

The researchers identified two KZFPs as specific only to primates, and found that they are expressed in specific regions of the human developing and adult brain. They further observed that these proteins kept controlling the activity of transposable elements—at least in neurons and brain organoids cultured in the lab. As a result, these two KZFPs influenced the differentiation and neurotransmission profile of neurons, as well as guarded these cells against inflammatory responses that were otherwise triggered if their target transposable elements were left to be expressed.

These results revealed how two proteins that appeared only recently in evolution have contributed to shape the human brain by facilitating the co-option of transposable elements, these virus-like entities that have been remodeling our ancestral genome since the dawn of times. Their findings also suggest possible pathogenic mechanisms for diseases such as amyotrophic lateral sclerosis or other neurodegenerative or neurodevelopmental disorders, providing leads for the prevention or treatment of these problems.


References: Priscilla Turelli et al., “Primate-restricted KRAB zinc finger proteins and target retrotransposons control gene expression in human neurons”, Science Advances, Vol. 6, no. 35, DOI: 10.1126/sciadv.aba3200 (2020), link: https://advances.sciencemag.org/content/6/35/eaba3200

This ‘Cold Tube’ Can Beat The Summer Heat Without Relying On Air Conditioning (Engineering)

Many people even you, beat the summer heat by cranking the air conditioning. However, air conditioners guzzle power and spew out millions of tons of carbon dioxide daily. They’re also not always good for your health—constant exposure to central A/C can increase risks of recirculating germs and causing breathing problems. Now, Adam Rysanek and colleagues, came up with an even better alternative. They call it the Cold Tube, and they have shown it works.

Schematic of a Cold Tube radiant cooling panel

Unlike air conditioners which work by cooling down and dehumidifying the air around us. The Cold Tube works by absorbing the heat directly emitted by radiation from a person without having to cool the air passing over their skin. This achieves a significant amount of energy savings.

The Cold Tube is a system of rectangular wall or ceiling panels that are kept cold by chilled water circulating within them. Since heat naturally moves by radiation from a hotter surface to a colder surface, when a person stands beside or under the panel, their body heat radiates towards the colder panel. This creates a sensation of cooling like cold air flowing over the body even if the air temperature is quite high.

Radiant heat transfer through the IR-transparent membrane

Although these types of cooling panels have been used in the building industry for several decades, what makes the Cold Tube unique is that it does not need to be combined with a dehumidification system. Just as a cold glass of lemonade would condense water on a hot summer day, cooling down walls and ceilings in buildings would also condense water without first drying out the air around the panels. The researchers behind the Cold Tube conceived of an airtight, humidity-repelling membrane to encase the chilled panels to prevent condensation from forming while still allowing radiation to travel through.

The team built an outdoor demonstration unit last year in Singapore, inviting 55 members of the public to visit and provide feedback. When the system was running, most participants reported feeling “cool” or “comfortable,” despite an average air temperature of 30 degrees Celsius (86 degrees Fahrenheit). The panels also stayed dry, thanks to the special membrane.

The team is currently using the data collected in Singapore to update their projections of the Cold Tube’s effectiveness in indoor spaces globally. They plan to demonstrate a commercially viable version of the technology by 2022.


References: Eric Teitelbaum, Kian Wee Chen, Dorit Aviv, Kipp Bradford, Lea Ruefenacht, Denon Sheppard, Megan Teitelbaum, Forrest Meggers, Jovan Pantelic, and Adam Rysanek, “Membrane-assisted radiant cooling for expanding thermal comfort zones globally without air conditioning”, PNAS, pp. 1-8, 2020 https://doi.org/10.1073/pnas.2001678117 link: https://www.pnas.org/content/early/2020/08/17/2001678117