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Seafloor sediment reveals previously unknown volcanic eruption 520,000 years ago in south Aegean Sea

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theconversation.com – Molly Colleen McCanta, Associate Professor of Petrology and Planetary Geoscience, of Tennessee – 2024-07-23 07:13:32
Researchers obtained cylindrical core samples from almost 3,000 feet – nearly a kilometer – within the seafloor.
Erick Bravo/IODP

Molly Colleen McCanta, University of Tennessee

“Core on deck!”

For two months, whenever I heard that cry, I would up to the deck of the JOIDES Resolution to watch the crew pull up a 30-foot (10-meter) cylindrical tube filled with layered, multicolored rock and sediment drilled from the seafloor beneath our ship.

people in protective gear and hard hats on a ship's deck, raising a long metal tube with water coming out the bottom
The crew drilled more than 780 cores from the seabed on the expedition.
Erick Bravo/IODP

In the winter of 2022, I spent two months cruising the south Aegean Sea on board the International Ocean Discovery Program’s JOIDES Resolution as part of IODP Expedition 398. My geologist colleagues and I used this former oil exploration ship to drill deep into the seafloor and reveal the volcanic history of the area off the coast of Santorini, Greece.

As a scientist who studies the chemistry of volcanic rocks, I use my expertise to correlate volcanic sediments to the eruption that caused them and to understand the conditions that magma experienced both at depth underneath a volcano and during an eruption.

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Our expedition’s drilling of the seafloor revealed a massive but previously unknown volcanic eruption that took place more than 500,000 years ago. This discovery expands our understanding of the volcanic activity in the chain of volcanoes comprising the South Aegean Volcanic Arc, which will allow for a more accurate hazard analysis of this region.

Building a more complete volcanic history

Archaeologists have long been fascinated with the late Bronze Age eruption of Santorini around 1600 BCE. This eruption is associated with the decline of the Minoan civilization on the nearby island of Crete. Geologists also have significant interest in the region, due to the volatility of the volcanic and seismic activity in this area that is home to about 15,000 residents and attracts around 2 million tourists per year.

Although there’s significant on-land documentation of the Santorini volcano, scientists know that this record is incomplete. On land, erosion, vegetation and additional eruptive events often or obscure older volcanic deposits, resulting in a fragmentary history. The deep-sea drilling enabled by the IODP’s JOIDES Resolution gives researchers access to a geologic record rarely preserved on land.

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Following a volcanic eruption, pyroclastic materials – pieces of rock and ash formed during the eruption – settle through the column to collect on the seafloor. There, clays and biological material, such as the shells of tiny marine organisms, rain down continuously, capping the volcanic rock deposits. This preserves a record of an individual eruption as a single layer. Layers build with time, with each successive volcanic creating a near-continuous chronologic record of the volcanic history of the region.

Expedition 398’s mission was to access this deep-sea record in order to document the extensive history of eruptions in each area of concentrated volcanic activity.

IODP Expedition 398

IODP Expedition 398 collected drill cores to better understand the volcanic history and recurrence interval of the Santorini, Christiana and Kolumbo volcanoes in this region. The JOIDES Resolution crew drilled 12 sites to a maximum depth of 2,950 feet (900 meters) below the seafloor. We recovered more than 11,000 feet (3,356 meters) of total core over 780 cores.

As technicians cut the core into 4½-foot (1½-meter) sections, scientists would gather to see what material had been recovered. After bringing the cores to surface pressure, the team would split them lengthwise, photograph them, analyze them for physical properties such as magnetic susceptibility, and describe the material. Core describers measure and record the geologic composition of each rocky unit contained within.

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Two researchers lean over a table holding long cylinders of seafloor sample cut in half
After the long, cylindrical cores are cut lengthwise, researchers pore over the layered sediment inside.
Erick Bravo/IODP

As the geochemistry lab lead, I took small samples of multiple layers of volcanic rock and ash to dissolve into solution and analyze for their trace element composition. During an eruption, magma crystallizes and mixes with elements in the water and rock it into contact with. The resulting chemical changes in the magma are unique to the conditions of that particular eruption. So once I figure out the chemical composition of the deposit samples, I can fingerprint their volcanic origin.

Our discovery: The Archaeos Tuff

During the expedition, our group of researchers discovered a thick, white pumice layer at multiple sites, in several different basins. Shipboard biostratigraphy dated each occurrence of the layer to the same age: between 510,000 and 530,000 years ago. Geochemical correlations suggested the composition was the same across drill holes as well.

Finding the same layer across these basins allows our research team to model how big the eruption that caused it might have been. We used seismic data collected during the expedition to determine that the bulk volume of the volcanic sediment is about 21 cubic miles (90 cubic kilometers), with thicknesses up to 490 feet (150 meters) in some places. In addition, we determined that this layer of volcanic rock was spread over 1,100 square miles (3,000 square kilometers) of this region in the southern Aegean Sea.

aerial view of ship on blue sea with islands in background
The JOIDES Resolution cruised the southern Aegean Sea, near the Kameni islands within the Santorini caldera, which were created by volcanic eruptions.
Ronge/IODP

Our team named this deposit the Archaeos Tuff, from the Greek word archea for ancient. The name reflects the rock’s Greek origin, as well as the fact that it was significantly older than much of the volcanic activity we know about on land.

Based on the Archaeos Tuff’s characteristics, we can understand the nature of the volcanic eruption that formed it. Its thickness and distribution over a wide area suggest that the Archaeos Tuff is the result of a single, high-intensity eruption. The numerous vesicles, or tiny holes, in the rock indicate that a large amount of gas was released at the same time as the liquid magma. These little gas bubbles paint a picture of a powerful eruption in which a great deal of volatile gas was released quite quickly.

Yet despite its evident size and ferocity, this eruption did not correlate with any previously known on-land deposits or large eruptions. The relative lack of on-land material suggests a mainly submarine eruption. Once we knew what we were looking for, our team was able to match our newly discovered deep-sea layer of volcanic sediment to a few small, previously uncorrelated on-land deposits on Santorini, Christiana and Anafi islands. The presence of these deposits indicates some breach of the sea surface during the eruption, which again fits with our picture of an energetic eruption.

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Further study of the Archaeos Tuff’s composition and age confirmed the unique nature of the rock deposit left by this eruption. Based on the data we collected, our team believes the Archaeos Tuff is the result of an eruption six times bigger than the Bronze Age Minoan eruption, leaving behind rock deposits 30 times thicker. The presence of such a large volcanic deposit tells us that the South Aegean Volcanic Arc is more capable of producing large submarine volcanic eruptions than scientists previously recognized.

Identifying the Archaeos Tuff expands what we know about volcanic processes in the south Aegean Sea. It suggests a greater propensity for hazardous submarine volcanism than previously realized – and that officials need to reevaluate volcanic hazards to the surrounding population.The Conversation

Molly Colleen McCanta, Associate Professor of Petrology and Planetary Geoscience, University of Tennessee

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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The Conversation

The Boeing Starliner has returned to Earth without its crew – a former astronaut details what that means for NASA, Boeing and the astronauts still up in space

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theconversation.com – Michael E. Fossum, Vice President, Texas A&M – 2024-09-07 10:41:12

The Boeing Starliner, shown as it approached the International Station.
NASA via AP

Michael E. Fossum, Texas A&M University

Boeing’s crew transport space capsule, the Starliner, returned to Earth without its two-person crew right after midnight Eastern time on Sept. 7, 2024. Its remotely piloted return marked the end of a fraught test flight to the International Space Station which left two astronauts, Butch Wilmore and Sunita “Suni” Williams, on the station for months longer than intended after thruster failures led NASA to deem the capsule unsafe to pilot back.

Wilmore and Williams will stay on the International Space Station until February 2025, when they’ll return to Earth on a SpaceX Dragon capsule.

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U.S. asked former commander of the International Space Station Michael Fossum about NASA’s decision to return the craft uncrewed, the future of the Starliner program and its crew’s extended stay at the space station.

What does this decision mean for NASA?

NASA awarded contracts to both Boeing and SpaceX in 2014 to provide crew transport vehicles to the International Space Station via the Commercial Crew Program. At the start of the program, most bets were on Boeing to take the , because of its extensive aerospace experience.

However, SpaceX moved very quickly with its new rocket, the Falcon 9, and its cargo ship, Dragon. While they suffered some early failures during testing, they aggressively built, tested and learned from each failure. In 2020, SpaceX successfully launched its first test crew to the International Space Station.

Meanwhile, Boeing struggled through some setbacks. The outcome of this first test flight is a huge disappointment for Boeing and NASA. But NASA leadership has expressed its support for Boeing, and many experts, me, believe it remains in the agency’s best interest to have more than one American crew launch system to support continued human space operations.

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NASA is also continuing its exchange partnership with Russia. This partnership provides the agency with multiple ways to get crew members to and from the space station.

As space station operations continue, NASA and its partners have enough options to get people to and from the station that they’ll always have the essential crew on the station – even if there are launch disruptions for any one of the capable crewed vehicles. Having Starliner as an option will help with that redundancy.

The ISS, a cylindrical craft with solar panels on each side.
NASA has a few options to get astronauts up to the International Space Station.
Roscosmos State Space Corporation via AP

What does this decision mean for Boeing?

I do think Boeing’s reputation is going to ultimately suffer. The company is going head-to-head with SpaceX. Now, the SpaceX Dragon crew spacecraft has several flights under its belt. It has proven a reliable way to get to and from the space station.

It’s important to remember that this was a test flight for Starliner. Of course, the program managers want each test flight to perfectly, but you can’t anticipate every potential problem through ground testing. Unsurprisingly, some problems cropped up – you expect them in a test flight.

The space environment is unforgiving. A small problem can become catastrophic in zero gravity. It’s hard to replicate these situations on the ground.

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The technology SpaceX and Boeing use is also radically different from the kind of capsule technology used in the early days of the Mercury, Gemini and Apollo programs.

NASA has evolved and made strategic moves to advance its mission over the past two decades. The agency has leaned into its legacy of thinking outside the box. It was an innovative move to break from tradition and leverage commercial competitors to advance the program. NASA gave the companies a set of requirements and left it up to them to figure out how they would meet them.

What does this decision mean for Starliner’s crew?

I know Butch Wilmore and Suni Williams as rock-solid professionals, and I believe their first are about completing their mission safely. They are both highly experienced astronauts with previous long-duration space station experience. I’m sure they are taking this in stride.

Prior to joining NASA, Williams was a Naval aviator and Wilmore a combat veteran, so these two know how to face risk and accomplish their missions. This kind of unfavorable outcome is always a possibility in a test mission. I am sure they are leaning forward with a positive attitude and using their bonus time in space to advance science, technology and space exploration.

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Their families shoulder the bigger impact. They were prepared to welcome the crew home in less than two weeks and now must adjust to unexpectedly being apart for eight months.

Right now, NASA is dealing with a ripple effect, with more astronauts than expected on the space station. More people means more consumables – like food and clothing – required. The space station has supported a large crew for short periods in the past, but with nine crew members on board today, the systems have to work harder to purify recycled drinking water, generate oxygen and remove carbon dioxide from their atmosphere.

Wilmore and Williams are also consuming food, and they didn’t arrive with the clothes and other personal supplies they needed for an eight-month stay, so NASA has already started increasing those deliveries on cargo ships.

What does this decision mean for the future?

Human spaceflight is excruciatingly hard and relentlessly unforgiving. A million things must go right to have a successful mission. It’s impossible to fully understand the performance of systems in a microgravity environment until they’re tested in space.

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NASA has had numerous failures and near-misses in the quest to put Americans on the Moon. They lost the Apollo 1 crew in a fire during a preflight test. They launched the first space shuttle in 1981, and dealt with problems throughout that program’s 30-year life, including the terrible losses of Challenger and Columbia.

After having no other U.S. options for over 30 years, three different human spacecraft programs are now underway. In addition to the SpaceX Crew Dragon and the Boeing Starliner, NASA’s Orion spacecraft for the Artemis II mission, is planned to fly four astronauts around the Moon in the next of years.

These programs have had setbacks and bumps along the way – and there will be more – but I haven’t been this excited about human spaceflight since I was an 11-year-old cheering for Apollo and dreaming about putting the first human footprints on Mars.The Conversation

Michael E. Fossum, Vice President, Texas A&M University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Space travel comes with risk − and SpaceX’s Polaris Dawn mission will push the envelope further than any private mission has before

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theconversation.com – Chris Impey, Distinguished Professor of Astronomy, University of Arizona – 2024-09-06 07:30:06

Spacewalks are among the more dangerous activities associated with human spaceflight.

Ignatiev/E+ via Getty Images

Chris Impey, University of Arizona

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is an unnatural for humans. We can’t survive unprotected in a pure vacuum for more than two minutes. Getting to space involves being strapped to a barely contained chemical explosion.

Since 1961, fewer than 700 people have been into space. Private space companies such as SpaceX and Blue Origin hope to boost that number to many thousands, and SpaceX is already taking bookings for flights to Earth orbit.

I’m an astronomer who has written extensively about space travel, including a book about our future off-Earth. I think a lot about the risks and rewards of exploring space.

As the commercial space industry takes off, there will be accidents and people will die. Polaris Dawn, planned to launch early in September 2024, will be a high-risk mission using only civilian astronauts. So, now is a good time to assess the risks and rewards of leaving the Earth.

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Space travel is dangerous

Most Americans vividly recall the disasters that led to the loss of 14 astronauts’ lives. Two of the five space shuttles disintegrated, Challenger in 1986 soon after launch and Columbia in 2003 on reentry.

The Challenger and Columbia accidents are two of the most prominent examples of the risk that comes with human spaceflight.

In total, 30 astronauts and cosmonauts have died while for or during space missions.

There have also been dozens of close calls. Two astronauts are currently staying on the International Space Station for an extra six months because NASA declared their Boeing Starliner vehicle unsafe for the return journey. Starliner has had many problems during its development, including flammable tape, stuck valves and inadequate parachute systems. But a critical thruster malfunction is what caused NASA to abandon it as a return vehicle.

It’s not always safe on the ground, either. In addition to the three Apollo 1 astronauts who died in a 1967 launch pad fire, about 120 people died in the launchpad explosion of an unmanned rocket in Russia in 1960, and hundreds died in 1996 when a Chinese rocket veered off course and crashed into a nearby village.

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The fatality rate of people traveling in space is about 3%. That sounds low, but it’s higher than extreme sports such as BASE jumping or jumping off a cliff wearing a wingsuit. The only recreations that rival the risk of space travel are solo free-climbing and climbing above 19,685 feet (6,000 meters) in the Himalayas.

Civilians in space

The 2020s have kicked off the era of civilian astronauts. After the death of Christa McAuliffe in the Challenger disaster, NASA stopped sending civilians into space. But for commercial space companies, it’s part of the business model.

The first all-civilian crew to reach orbit rode a SpaceX Dragon spacecraft in 2021, the Inspiration 4 mission. Since 2020, 69 private astronauts have gone to space, although only 46 reached the Kármán line – the formal definition of the edge of space.

The commercial space industry’s safety record is not perfect. No civilian has died in space, but one pilot died and another was seriously injured in a test flight of Virgin Galactic’s SpaceShipTwo craft in 2014. This accident followed three deaths and three injuries in an explosion during a prelaunch test of the SpaceShipTwo rocket in 2007.

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SpaceX, the largest commercial space company with 13,000 employees and a market value of US$180 billion, has seen no fatalities in flight, but it has recorded one death and hundreds of injuries in the workplace.

The Polaris Dawn mission was planned to launch Aug. 27, 2024, though a helium leak and bad weather has delayed it. It will push the envelope of risk for civilians in space. This SpaceX flight will reach an altitude of 435 miles (700 kilometers), higher than any astronauts since Apollo.

Four astronauts wearing white suits and helmets stand in front of a rocket on a launchpad.

The Polaris Dawn crew during their launch-day rehearsal.

Polaris Program/John Kraus, CC BY-NC-ND

The Polaris Dawn’s four-person civilian crew will a hefty dose of radiation, getting as much in a few hours as they would in 20 years on the Earth. NASA is doing research to understand the extent of the risks from radiation.

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The mission will also include a spacewalk – the first for nongovernment astronauts. It will use spacesuits never tested in space. Since the spacecraft they’re using – the SpaceX Dragon – has no airlock, the inside of the capsule will be exposed to the vacuum of space, with all the crew members wearing spacesuits.

Russian cosmonaut Alexei Leonov nearly died during the first spacewalk in 1965, and other spacewalks have led to temporary blindness, near drowning and nearly being lost in space forever. A spacesuit is like a miniature spacecraft, and it has to withstand rapid temperature changes of hundreds of degrees when moving in and out of direct sunlight. Even a small tear or puncture can be fatal.

But while space travel comes with dangers, it also has rewards. Since Polaris Dawn will travel higher than any previous mission that did not go to the Moon, the crew will be able to do research on high-radiation environments. They will investigate the effects of spaceflight on the human body and evaluate how future deep-space travelers might diagnose and treat themselves.

A less tangible but potentially profound benefit is the overview effect – many astronauts a feeling of awe from experiencing the Earth from space.

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Space boom

Space is booming – hopefully just metaphorically and not literally. SpaceX makes money by launching Starlink satellites and ferrying supplies and people to the International Space Station, with estimated revenues of $15 billion this year. Blue Origin sells rocket engines and has contracts with NASA.

Both companies sell rides into space to high-net-worth individuals, but that’s a small fraction of their revenues. Space tourism is not available to the masses yet. Virgin Galactic offers a short, suborbital ride for $450,000, but getting to Earth orbit will cost you $55 million.

The space tourism market was $750 million in 2023, and that’s projected to grow to $5.2 billion over the next decade. Reusable rockets have made the cost of launching a spacecraft 10 times cheaper than it was a decade ago.

For space to take off with a demographic broader than multimillionaires and thrill-seekers, it needs to be safe – both in perception and in reality. Many space entrepreneurs expect space travel to follow aviation’s arc, which also started by attracting rich people and thrill-seekers.

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Since 1930, improvements in technology and safety features have lowered the number of fatal accidents in the aviation industry per million miles flown by a factor of 3,000. A more realistic target may be to make space travel as safe as driving. That’s a more lenient target, since driving is more dangerous than flying. Your annual odds of dying in a car crash are 1 in 5,000, compared with annual odds of 1 in 11 million of dying in a plane crash.

In the United States, the government has kept regulations light on the commercial space industry to encourage entrepreneurs.

Elon Musk’s dreams of millions of passengers and a on Mars may not become reality. But if the cost of a jaunt to Earth’s orbit comes down to the cost of a high-end cruise, many people could experience the thrill of weightlessness and of seeing the Earth as a beautiful planet from above.The Conversation

Chris Impey, University Distinguished Professor of Astronomy, University of Arizona

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Tiny, compact galaxies are masters of disguise in the distant universe − searching for the secrets behind the Little Red Dots

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theconversation.com – Fabio Pacucci, Astrophysicist, Smithsonian Institution – 2024-09-06 07:36:33

Supermassive black holes grow by pulling in matter around them.

M. Kornmesser/ESO via AP

Fabio Pacucci, Smithsonian Institution

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Astronomers exploring the faraway universe with the James Webb Space Telescope, NASA’s most powerful telescope, have found a class of galaxies that challenges even the most skillful creatures in mimicry – like the mimic octopus. This creature can impersonate other marine animals to avoid predators. Need to be a flatfish? No problem. A sea snake? Easy.

When astronomers analyzed the first Webb images of the remote parts of the universe, they spotted a never-before-seen group of galaxies. These galaxies – some hundreds of them and called the Little Red Dots – are very red and compact, and visible only during about 1 billion years of cosmic history. Like the mimic octopus, the Little Red Dots puzzle astronomers, because they look like different astrophysical objects. They’re either massively heavy galaxies or modestly sized ones, each containing a supermassive black hole at its core.

However, one thing is certain. The typical Little Red Dot is small, with a radius of only 2% of that of the Milky Way galaxy. Some are even smaller.

As an astrophysicist who studies faraway galaxies and black holes, I am interested in understanding the nature of these little galaxies. What powers their light and what are they, really?

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Many galaxies, indicated as small, bright dots, shown against a dark backdrop.

The universe is full of countless galaxies, and the Webb telescope has helped astronomers study some of them.

NASA, ESA, CSA, STScI

The mimicking contest

Astronomers analyze the light our telescopes from faraway galaxies to assess their physical properties, such as the number of they contain. We can use the properties of their light to study the Little Red Dots and figure out whether they’re made up of lots of stars or whether they have a black hole inside them.

Light that reaches our telescopes ranges in wavelength from long radio waves to energetic gamma rays. Astronomers break the light down into the different frequencies and visualize them with a chart, called a spectrum.

Sometimes, the spectrum contains emission lines, which are ranges of frequencies where more intense light emission occurs. In this case, we can use the spectrum’s shape to predict whether the galaxy is harboring a supermassive black hole and estimate its mass.

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Similarly, studying X-ray emisson from the galaxy can reveal a supermassive black hole’s presence.

As the ultimate masters of disguise, the Little Red Dots appear as different astrophysical objects, depending on whether astronomers choose to study them using X-rays, emission lines or something else.

The information astronomers have collected so far from the Little Red Dots’ spectra and emission lines has led to two diverging models explaining their nature. These objects are either extremely dense galaxies containing billions of stars or they host a supermassive black hole.

The two hypotheses

In the stars-only hypothesis, the Little Red Dots contain massive amounts of stars – up to 100 billion stars. That’s approximately the same number of stars as in the Milky Way – a much larger galaxy.

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Imagine standing alone in a huge, empty room. This vast, quiet represents the region of the universe in the vicinity of our solar system where stars are sparsely scattered. Now, picture that same room, but packed with the entire population of China.

This packed room is what the core of the densest Little Red Dots would feel like. These astrophysical objects may be the densest stellar environments in the entire universe. Astronomers aren’t even sure whether such stellar can physically exist.

Then, there is the black hole hypothesis. The majority of Little Red Dots display clear signs of the presence of a supermassive black hole in their center. Astronomers can tell whether there’s a black hole in the galaxy by looking at large emission lines in their spectra, created by gas around the black hole swirling at high speed.

Astronomers actually estimate these black holes are too massive, with the size of their compact host galaxies.

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Black holes typically have a mass of about 0.1% of the stellar mass of their host galaxies. But some of these Little Red Dots harbor a black hole almost as massive as their entire galaxy. Astronomers call these overmassive black holes, because their existence defies the conventional ratio typically observed in galaxies.

Animation illustrating the James Webb Space Telescope’s discovery of overmassive black holes in the distant Universe. Credit: Timothy Rauch.

There’s another catch, though. Unlike ordinary black holes, those presumably present in the Little Red Dots don’t show any sign of X-ray emission. Even in the deepest, high-energy images available, where astronomers should be able to easily observe these black holes, there’s no trace of them.

Few solutions and plenty of hopes

So are these astrophysical curiosities massive galaxies with far too many stars? Or do they host supermassive black holes at their center that are too massive and don’t emit enough X-rays? What a puzzle.

With more observations and theoretical modeling, astronomers are starting to up with some possible . Maybe the Little Red Dots are composed only of stars, but these stars are so dense and compact that they mimic the emission lines typically seen from a black hole.

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Or maybe supermassive – even overmassive – black holes lurk at the cores of these Little Red Dots. If that’s the case, two models can explain the lack of X-ray emissions.

First, vast amounts of gas could float around the black hole, which would block part of the high-energy radiation emitted from the black hole’s center. Second, the black hole could be pulling in gas much faster than usual. This would produce a different spectrum with fewer X-rays than astronomers usually see.

The fact that the black holes are too big, or overmassive, might not be a problem for our understanding of the universe, but rather the best indication of how the first black holes in the universe were born. In fact, if the first black holes that ever formed were very massive – about 100,000 times the mass of the Sun – theoretical models suggest that their ratio of black hole mass to the mass of the host galaxy could stay high for a long time after formation.

So how can astronomers discover the true nature of these little specks of light that are shining at the beginning of time? As in the case of our master of disguise – the octopus – the secret resides in observing their behavior.

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Using the Webb telescope and more powerful X-ray telescopes to take additional observations will eventually uncover a feature that astronomers can attribute to only one of the two scenarios.

For example, if astronomers clearly detected X-ray or radio emission, or infrared light emitted from around where the black hole might be, they’d know the black hole hypothesis is the right one.

Just like how our marine friend can pretend to be a starfish, eventually it will move its tentacles and reveal its true nature.The Conversation

Fabio Pacucci, Astrophysicist, Smithsonian Institution

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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