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Astronomers detect signs of "galactic cannibalism"
One galaxy may have eaten one of its slightly smaller, more primitive neighbors.
Among the most primitive of these galactic fossils is Tucana II — an ultrafaint dwarf galaxy that is about 50 kiloparsecs, or 163,000 light years, from Earth.
Now MIT astrophysicists have detected stars at the edge of Tucana II, in a configuration that is surprisingly far from its center but nevertheless caught up in the tiny galaxy's gravitational pull. This is the first evidence that Tucana II hosts an extended dark matter halo — a region of gravitationally bound matter that the researchers calculated to be three to five times more massive than scientists had estimated. This discovery of far-flung stars in an ancient dwarf galaxy implies that the very first galaxies in the universe were also likely extended and more massive than previously thought.
"Tucana II has a lot more mass than we thought, in order to bound these stars that are so far away," says MIT graduate student Anirudh Chiti. "This means that other relic first galaxies probably have these kinds of extended halos too."
The researchers also determined that the stars on the outskirts of Tucana II are more primitive than the stars at the galaxy's core. This is the first evidence of such a stellar imbalance in an ultrafaint dwarf galaxy.
The unique configuration suggests that the ancient galaxy may have been the product of one of the first mergers in the universe, between two infant galaxies — one slightly less primitive than the other.
"We may be seeing the first signature of galactic cannibalism," says Anna Frebel, the Silverman Family Career Development Associate Professor of Physics at MIT. "One galaxy may have eaten one of its slightly smaller, more primitive neighbors, that then spilled all its stars into the outskirts."
Frebel, Chiti, and their colleagues have published their results today in Nature Astronomy.
Tucana II is one of the most primitive dwarf galaxies known, based on the metal content of its stars. Stars with low metal content likely formed very early on, when the universe was not yet producing heavy elements. In the case of Tucana II, astronomers had previously identified a handful of stars around the galaxy's core with such low metal content that the galaxy was deemed the most chemically primitive of the known ultrafaint dwarf galaxies.
Chiti and Frebel wondered whether the ancient galaxy might harbor other, even older stars, that might shed light on the formation of the universe's first galaxies. To test this idea, they obtained observations of Tucana II through the SkyMapper Telescope, an optical ground-based telescope in Australia that takes in wide views of the southern sky.
The team used an imaging filter on the telescope to spot primitive, metal-poor stars beyond the galaxy's core. The team ran an algorithm, developed by Chiti, through the filtered data to efficiently pick out stars with low metal content, including the previously identified stars at the center and nine new stars much further out from the galactic core.
"Ani's analysis shows a kinematic conection, that these far-out stars move in lockstep with the inner stars, like bathwater going down the drain," Frebel adds.
The results suggest that Tucana II must have an extended dark matter halo that is three to five times more massive than previously thought, in order for it to keep a gravitational hold on these far-off stars. Dark matter is a hypothetical type of matter that is thought to make up more than 85 percent of the universe. Every galaxy is thought to be held together by a local concentration, or halo, of dark matter.
"Without dark matter, galaxies would just fly apart," Chiti. says. "[Dark matter] is a crucial ingredient in making a galaxy and holding it together."
The team's results are the first evidence that an ultrafaint dwarf galaxy can harbor an extended dark matter halo.
"This probably also means that the earliest galaxies formed in much larger dark matter halos than previously thought," Frebel says. "We have thought that the first galaxies were the tiniest, wimpiest galaxies. But they actually may have been several times larger than we thought, and not so tiny after all."
"A cannibalistic history"
Chiti and Frebel followed up their initial results with observations of Tucana II taken by the Magellan Telescopes in Chile. With Magellan, the team focused in on the galaxy's metal-poor stars to derive their relative metallicities, and discovered the outer stars were three times more metal-poor, and therefore more primitive, than those at the center.
"This is the first time we've seen something that looks like a chemical difference beween the inner and outer stars in an ancient galaxy," Chiti says.
A likely explanation for the imbalance may be an early galactic merger, in which a small galaxy — possibly among the first generation of galaxies to form in the universe — swallowed another nearby galaxy. This galactic cannibalism occurs constantly throughout the universe today, but it was unclear whether early galaxies merged in a similar way.
"Tucana II will eventually be eaten by the Milky Way, no mercy," Frebel says. "And it turns out this ancient galaxy may have its own cannibalistic history."
The team plans to use their approach to observe other ultrafaint dwarf galaxies around the Milky Way, in hopes of discovering even older, farther-flung stars.
"There are likely many more systems, perhaps all of them, that have these stars blinking in their outskirts," Frebel says.
This research was supported, in part, by NASA and the National Science Foundation.
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Scientists are using bioelectronic medicine to treat inflammatory diseases, an approach that capitalizes on the ancient "hardwiring" of the nervous system.
- Bioelectronic medicine is an emerging field that focuses on manipulating the nervous system to treat diseases.
- Clinical studies show that using electronic devices to stimulate the vagus nerve is effective at treating inflammatory diseases like rheumatoid arthritis.
- Although it's not yet approved by the US Food and Drug Administration, vagus nerve stimulation may also prove effective at treating other diseases like cancer, diabetes and depression.
The nervous system’s ancient reflexes<p>You accidentally place your hand on a hot stove. Almost instantaneously, your hand withdraws.</p><p>What triggered your hand to move? The answer is <em>not</em> that you consciously decided the stove was hot and you should move your hand. Rather, it was a reflex: Skin receptors on your hand sent nerve impulses to the spinal cord, which ultimately sent back motor neurons that caused your hand to move away. This all occurred before your "conscious brain" realized what happened.</p><p>Similarly, the nervous system has reflexes that protect individual cells in the body.</p><p>"The nervous system evolved because we need to respond to stimuli in the environment," said Dr. Tracey. "Neural signals don't come from the brain down first. Instead, when something happens in the environment, our peripheral nervous system senses it and sends a signal to the central nervous system, which comprises the brain and spinal cord. And then the nervous system responds to correct the problem."</p><p>So, what if scientists could "hack" into the nervous system, manipulating the electrical activity in the nervous system to control molecular processes and produce desirable outcomes? That's the chief goal of bioelectronic medicine.</p><p>"There are billions of neurons in the body that interact with almost every cell in the body, and at each of those nerve endings, molecular signals control molecular mechanisms that can be defined and mapped, and potentially put under control," Dr. Tracey said in a <a href="https://www.youtube.com/watch?v=AJH9KsMKi5M" target="_blank">TED Talk</a>.</p><p>"Many of these mechanisms are also involved in important diseases, like cancer, Alzheimer's, diabetes, hypertension and shock. It's very plausible that finding neural signals to control those mechanisms will hold promises for devices replacing some of today's medication for those diseases."</p><p>How can scientists hack the nervous system? For years, researchers in the field of bioelectronic medicine have zeroed in on the longest cranial nerve in the body: the vagus nerve.</p>
The vagus nerve<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTYyOTM5OC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0NTIwNzk0NX0.UCy-3UNpomb3DQZMhyOw_SQG4ThwACXW_rMnc9mLAe8/img.jpg?width=1245&coordinates=0%2C0%2C0%2C0&height=700" id="09add" class="rm-shortcode" data-rm-shortcode-id="f38dbfbbfe470ad85a3b023dd5083557" data-rm-shortcode-name="rebelmouse-image" data-width="1245" data-height="700" />
Electrical signals, seen here in a synapse, travel along the vagus nerve to trigger an inflammatory response.
Credit: Adobe Stock via solvod<p>The vagus nerve ("vagus" meaning "wandering" in Latin) comprises two nerve branches that stretch from the brainstem down to the chest and abdomen, where nerve fibers connect to organs. Electrical signals constantly travel up and down the vagus nerve, facilitating communication between the brain and other parts of the body.</p><p>One aspect of this back-and-forth communication is inflammation. When the immune system detects injury or attack, it automatically triggers an inflammatory response, which helps heal injuries and fend off invaders. But when not deployed properly, inflammation can become excessive, exacerbating the original problem and potentially contributing to diseases.</p><p>In 2002, Dr. Tracey and his colleagues discovered that the nervous system plays a key role in monitoring and modifying inflammation. This occurs through a process called the <a href="https://www.nature.com/articles/nature01321" target="_blank" rel="noopener noreferrer">inflammatory reflex</a>. In simple terms, it works like this: When the nervous system detects inflammatory stimuli, it reflexively (and subconsciously) deploys electrical signals through the vagus nerve that trigger anti-inflammatory molecular processes.</p><p>In rodent experiments, Dr. Tracey and his colleagues observed that electrical signals traveling through the vagus nerve control TNF, a protein that, in excess, causes inflammation. These electrical signals travel through the vagus nerve to the spleen. There, electrical signals are converted to chemical signals, triggering a molecular process that ultimately makes TNF, which exacerbates conditions like rheumatoid arthritis.</p><p>The incredible chain reaction of the inflammatory reflex was observed by Dr. Tracey and his colleagues in greater detail through rodent experiments. When inflammatory stimuli are detected, the nervous system sends electrical signals that travel through the vagus nerve to the spleen. There, the electrical signals are converted to chemical signals, which trigger the spleen to create a white blood cell called a T cell, which then creates a neurotransmitter called acetylcholine. The acetylcholine interacts with macrophages, which are a specific type of white blood cell that creates TNF, a protein that, in excess, causes inflammation. At that point, the acetylcholine triggers the macrophages to stop overproducing TNF – or inflammation.</p><p>Experiments showed that when a specific part of the body is inflamed, specific fibers within the vagus nerve start firing. Dr. Tracey and his colleagues were able to map these relationships. More importantly, they were able to stimulate specific parts of the vagus nerve to "shut off" inflammation.</p><p>What's more, clinical trials show that vagus nerve stimulation not only "shuts off" inflammation, but also triggers the production of cells that promote healing.</p><p>"In animal experiments, we understand how this works," Dr. Tracey said. "And now we have clinical trials showing that the human response is what's predicted by the lab experiments. Many scientific thresholds have been crossed in the clinic and the lab. We're literally at the point of regulatory steps and stages, and then marketing and distribution before this idea takes off."<br></p>
The future of bioelectronic medicine<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTYxMDYxMy9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzNjQwOTExNH0.uBY1TnEs_kv9Dal7zmA_i9L7T0wnIuf9gGtdRXcNNxo/img.jpg?width=980" id="8b5b2" class="rm-shortcode" data-rm-shortcode-id="c005e615e5f23c2817483862354d2cc4" data-rm-shortcode-name="rebelmouse-image" data-width="2000" data-height="1125" />
Vagus nerve stimulation can already treat Crohn's disease and other inflammatory diseases. In the future, it may also be used to treat cancer, diabetes, and depression.
Credit: Adobe Stock via Maridav<p>Vagus nerve stimulation is currently awaiting approval by the US Food and Drug Administration, but so far, it's proven safe and effective in clinical trials on humans. Dr. Tracey said vagus nerve stimulation could become a common treatment for a wide range of diseases, including cancer, Alzheimer's, diabetes, hypertension, shock, depression and diabetes.</p><p>"To the extent that inflammation is the problem in the disease, then stopping inflammation or suppressing the inflammation with vagus nerve stimulation or bioelectronic approaches will be beneficial and therapeutic," he said.</p><p>Receiving vagus nerve stimulation would require having an electronic device, about the size of lima bean, surgically implanted in your neck during a 30-minute procedure. A couple of weeks later, you'd visit, say, your rheumatologist, who would activate the device and determine the right dosage. The stimulation would take a few minutes each day, and it'd likely be unnoticeable.</p><p>But the most revolutionary aspect of bioelectronic medicine, according to Dr. Tracey, is that approaches like vagus nerve stimulation wouldn't come with harmful and potentially deadly side effects, as many pharmaceutical drugs currently do.</p><p>"A device on a nerve is not going to have systemic side effects on the body like taking a steroid does," Dr. Tracey said. "It's a powerful concept that, frankly, scientists are quite accepting of—it's actually quite amazing. But the idea of adopting this into practice is going to take another 10 or 20 years, because it's hard for physicians, who've spent their lives writing prescriptions for pills or injections, that a computer chip can replace the drug."</p><p>But patients could also play a role in advancing bioelectronic medicine.</p><p>"There's a huge demand in this patient cohort for something better than they're taking now," Dr. Tracey said. "Patients don't want to take a drug with a black-box warning, costs $100,000 a year and works half the time."</p><p>Michael Dowling, president and CEO of Northwell Health, elaborated:</p><p>"Why would patients pursue a drug regimen when they could opt for a few electronic pulses? Is it possible that treatments like this, pulses through electronic devices, could replace some drugs in the coming years as preferred treatments? Tracey believes it is, and that is perhaps why the pharmaceutical industry closely follows his work."</p><p>Over the long term, bioelectronic approaches are unlikely to completely replace pharmaceutical drugs, but they could replace many, or at least be used as supplemental treatments.</p><p>Dr. Tracey is optimistic about the future of the field.</p><p>"It's going to spawn a huge new industry that will rival the pharmaceutical industry in the next 50 years," he said. "This is no longer just a startup industry. [...] It's going to be very interesting to see the explosive growth that's going to occur."</p>
Researchers figure out the average temperatures of the last ice age on Earth.
- A new study analyzes fossil data to find the average temperatures during the last Ice Age.
- This period of time, about 20,000 years ago, had the average temperature of about 46 degrees Fahrenheit (7.8 C).
- The study has implications for understanding climate change.
Surface air temperatures during the last ice age.
Credit: Jessica Tierney, University of Arizona
"The Expanse" is the best vision I've ever seen of a space-faring future that may be just a few generations away.
- Want three reasons why that headline is justified? Characters and acting, universe building, and science.
- For those who don't know, "The Expanse" is a series that's run on SyFy and Amazon Prime set about 200 years in the future in a mostly settled solar system with three waring factions: Earth, Mars, and Belters.
- No other show I know of manages to use real science so adeptly in the service of its story and its grand universe building.
Credit: "The Expanse" / Syfy<p>Now, I get it if you don't agree with me. I love "Star Trek" and I thought "Battlestar Galactica" (the new one) was amazing and I do adore "The Mandalorian". They are all fun and important and worth watching and thinking about. And maybe you love them more than anything else. But when you sum up the acting, the universe building, and the use of real science where it matters, I think nothing can beat "The Expanse". And with a <a href="https://www.rottentomatoes.com/tv/the_expanse" target="_blank">Rotten Tomato</a> average rating of 93%, I'm clearly not the only one who feels this way.</p><p>Best.</p><p>Show.</p><p>Ever. </p>
Contrary to what some might think, the brain is a very plastic organ.
As with many other physicians, recommending physical activity to patients was just a doctor chore for me – until a few years ago. That was because I myself was not very active.