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Q and A: She discovered the black hole at the center of our galaxy. This week, she finally saw it – Phys.org

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Credit: EHT Collaboration, CC BY-SA

This week, the world got its first-ever look at Sagittarius A*, the supermassive black hole in the center of our galaxy. The image of a hazy golden ring of superheated gas and bending light was captured by the Event Horizon Telescope, a network of eight radio observatories scattered across the globe.

Feryal Özel, a University of Arizona astronomer and founding member of the EHT consortium, said that seeing the black hole’s image was like finally meeting in real life a person you’ve only interacted with online.

For Andrea Ghez, an astrophysicist at UCLA, the encounter was perhaps more like a biographer meeting her subject after decades of pursuit.

In 2020, Ghez was awarded the Nobel Prize in physics for her role in the discovery of a supermassive object at the core of the Milky Way. That object is now known to be Sagittarius A*, or Sgr A* for short.

Ghez studies the center of our galaxy and the orbits of thousands of stars encircling the dense object at its very heart. Though she wasn’t involved with the EHT project, she said its “impressive” achievements—including its 2019 unveiling of the black hole anchoring a distant galaxy known as Messier 87—offer intriguing new possibilities for the study of the cosmos.

The Los Angeles Times spoke to her about black holes, cosmic surprises and what Einstein has to do with the GPS app on your phone. The interview has been edited for length and clarity.

How does it feel to finally lay eyes on the thing you’ve spent your career studying?

It’s super exciting. We live in a really interesting moment where technology is advancing so rapidly in so many arenas and giving us new insights into these incredibly exotic objects.

Does it look different than you anticipated?

No, actually. It’s remarkably similar. You should see this ring at roughly two and a half times the Schwarzschild radius (the radius of the event horizon, the boundary around a black hole beyond which no light or matter can escape). That’s the prediction of where gravity should bend, and that’s exactly where you see it. That’s impressive.

How much have technological capabilities changed for researchers since you started studying black holes?

Huge, huge advances. I often say we’re surfing on a wave of technological development. Everything that we do really can be described as technology-enabled discovery.

One of the things that I love about working in these areas where the technology is evolving really quickly is that it affords you the opportunity to see the universe in a way you haven’t been able to see before. And so often that reveals unexpected discoveries.

We’re really lucky that we’re living at this moment where technology is evolving so quickly that you can really rewrite the textbooks. The Event Horizon Telescope is a similar story.

What unanswered questions about the universe excite you most?

I have a couple favorites right now. The one that I’m super excited about is our ability to test how gravity works near the using star orbits, and also as a probe of dark matter at the center of the galaxy. Both of those things should imprint on the orbits.

A simple way that I like to think about it is: The first time around, these orbits tell you the shape. And then after that you get to probe more detailed questions because you kind of know where in space the star is.

For example, S0-2 (which is my favorite star in the galaxy, and probably in the universe) goes around every 16 years. Now we are on the second passage, and that’s giving us the opportunity to test Einstein’s theories in ways that are different than what the Event Horizon Telescope is probing, as well to constrain the amount of dark matter that you might expect at the center of the galaxy. There are things that we don’t understand about the early results, and to me that’s always the most exciting part of a measurement—when things don’t make sense.

What’s your approach in those moments?

You have to have complete integrity with your process. Things may not make sense because you’re making a mistake, which is the uninteresting result, or they may not make sense because there’s something new to be discovered. That moment when you’re not sure is super interesting and exciting.

We’ve just discovered these objects at the center of the galaxy that seem to stretch out as they get close to the black hole, then become more compact. They’re called tidal interactions. If you think of the movie “Interstellar” with that big giant tidal wave, this would be like a big tidal wave that just lifts off the planet. If we’re seeing stars having those kinds of interactions, it means that the star has to be, I don’t know, a hundred times larger than anything we predicted to exist in this region. So that makes you scratch your head.

Does the new image of Sgr A* reinforce your finding that, for now, Einstein’s theory of general relativity seems to do the best job of explaining how gravity operates throughout the universe?

Yes. Absolutely. Black holes kind of represent the breakdown of our understanding of how gravity works. We don’t know how to make gravity and quantum mechanics work together. And you need those two things to work together to explain what a black hole is, because a black hole is strong gravity plus an infinitesimally small object.

Wait, what? I thought black holes were huge

No. The image is of the phenomena that happens around the black hole. The black hole has no finite size, but there is this abstract size of the event horizon, which is the last point that light can escape. And then the gravitational interaction with local light gets concentrated in this ring that’s two-and-a-half times bigger that the event horizon.

Anyway, we know that represent the breakdown of our knowledge. That’s why everyone keeps testing Einstein’s ideas about gravity there, because at some point you expect to see what you might call the expanded version of gravity, in the same way that Einstein was the expanded version of Newton’s version.

Is it fair to say that Newton’s laws do a decent job of explaining how gravity works here on our little planet, but we need Einstein once we head out into the universe?

Yes, except for what we take for granted today: our cellphones. The fact that we can find ourselves so well on Google or Waze or your favorite traffic app is because GPS systems position your phone with respect to satellites going around the Earth. Those systems have to use Einstein’s version of gravity. So, yes. We could use Newton until we cared about things like this.


Explore further

Seeing Milky Way’s new black hole is ‘only the beginning’: US researcher


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Here’s how Helene and other storms dumped a whopping 40 trillion gallons of rain on the South

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More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.

That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.

“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”

The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.

Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.

Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.

Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.

Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.

Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.

“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”

The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.

North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.

Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”

Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.

Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.

For Dello, the “fingerprints of climate change” were clear.

“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”

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Follow AP’s climate coverage at https://apnews.com/hub/climate

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Follow Seth Borenstein on Twitter at @borenbears

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Associated Press climate and environmental coverage receives support from several private foundations. See more about AP’s climate initiative here. The AP is solely responsible for all content.

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‘Big Sam’: Paleontologists unearth giant skull of Pachyrhinosaurus in Alberta

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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.

On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.

They call it “Big Sam.”

The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.

It didn’t die alone.

“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.

She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”

“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.

The head alone, she said, is about the size of a baby elephant.

The discovery was a long time coming.

The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.

“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.

When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”

“It contains about 100 to 300 bones per square metre,” she said.

Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.

About a year ago, they found the second adult: Big Sam.

Bamforth said both dinosaurs are believed to have been the elders in the herd.

“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.

“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”

The genders of the two adults are unknown.

Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.

The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.

She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.

“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.

“It’s pretty exciting.”

This report by The Canadian Press was first published Sept. 25, 2024.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.

Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.

Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.

The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.

The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.

It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.

Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.

Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.

Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.

Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.

Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.

The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”

The Canadian Press. All rights reserved.

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