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Snapping Sagittarius A*: How scientists captured the first image of our galaxy’s black hole – RFI English

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Issued on: 22/05/2022 – 09:26

On May 12, scientists from the international research team called the Event Horizon Telescope (EHT) Collaboration unveiled the first image of Sagittarius A*, the supermassive black hole located at the centre of our Milky Way Galaxy.

This was the result of observations conducted using a global array of radio telescopes that form the EHT.

Dr Frederic Gueth, deputy director of the Grenoble-based Institut de Radioastronomie Millimetrique (IRAM), is one of the scientists involved in the project.

In an  interview with RFI’s Dhananjay Khadilkar, Gueth talked about the monumental effort involved in capturing this image, and its significance. 

Q1. What is a black hole and why is it located at the centre of our galaxy?

A black hole is one of those fascinating objects whose presence was predicted by Albert Einstein. It is so massive that nothing, not even light, can escape from it.

We cannot observe a black hole because nothing can get out of it. However, there is a trick to observing it. There is a black hole at the centre of every galaxy, not just the Milky Way.

The Sagittarius A* is four million times more massive than the Sun, which is already an incredibly massive object. It is located at 27,000 light years away.

Q2. How did you capture the image of Sagittarius A*?

We knew there was a black hole (at the centre of our galaxy) but we never had direct imaging of it.

All the proof we had of its existence was indirect. To observe the black hole, we used a network of radio telescopes that operate in the millimetre (wavelength) domain. 

We have 10 observatories all over the planet. All the observations from different sites were carried out simultaneously. We needed to have atomic clocks at all these sites to make sure the synchronisation was perfect.

The (observational) data was combined by using a very complicated mathematical process to create this image which is not an optical image.

We needed to observe at radio wavelengths for one simple reason. There is a lot of gas and dust in the interstellar medium, which absorbs light at optical wavelength. That’s why we cannot observe the vicinity of the black hole in the optical wavelength. 

Q3. Out of the ten telescopes that form the EHT array, two belong to IRAM. What are the features of these two telescopes?

One is an antenna of 30 metre diameter located in Sierra Nevada in Spain. The other instrument, called NOEMA or Northern Extended Millimeter Array, is an array of 12 antennas, each of which is 15 metre in diameter. It is located in the French Alps. These two instruments are extremely sensitive. 

Q4. Three years ago, the EHT Collaboration captured the first image of a black hole. Why is it important to capture images of black holes?

(Until these images were taken), all the proof we had about the existence of black holes was indirect. We observed orbits of stars around black holes. By calculating the speed of the stars, we would conclude that the mass of the central object must be so high that it has to be a black hole.

We have never had any direct imaging of black holes. It is therefore extremely satisfactory to do these observations so that we really know it exists. Moreover, we can also start to investigate the physics of the material surrounding the black holes.

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Facial Recognition—Now for Seals – Hakai Magazine

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Have you ever looked at a seal and thought, Is that the same seal I saw yesterday? Well, there could soon be an app for that based on new seal facial recognition technology. Known as SealNet, this seal face-finding system was developed by a team of undergraduate students from Colgate University in New York.

Taking inspiration from other technology adapted for recognizing primates and bears, Krista Ingram, a biologist at Colgate University, led the students in developing software that uses deep learning and a convolutional neural network to tell one seal face from another. SealNet is tailored to identify the harbor seal, a species with a penchant for posing on coasts in haulouts.

The team had to train their software to identify seal faces. “I give it a photograph, it finds the face, [and] clips it to a standard size,” says Ingram. But then she and her students would manually identify the nose, the mouth, and the center of the eyes.

For the project, team members snapped more than 2,000 pictures of seals around Casco Bay, Maine, during a two-year period. They tested the software using 406 different seals and found that SealNet could correctly identify the seals’ faces 85 percent of the time. The team has since expanded its database to include around 1,500 seal faces. As the number of seals logged in the database goes up, so too should the accuracy of the identification, Ingram says.

The developers of SealNet trained a neural network to tell harbor seals apart using photos of 406 different seals. Photo courtesy of Birenbaum et al.

As with all tech, however, SealNet is not infallible. The software saw seal faces in other body parts, vegetation, and even rocks. In one case, Ingram and her students did a double take at the uncanny resemblance between a rock and a seal face. “[The rock] did look like a seal face,” Ingram says. “The darker parts were about the same distance as the eyes … so you can understand why the software found a face.” Consequently, she says it’s always best to manually check that seal faces identified by the software belong to a real seal.

Like a weary seal hauling itself onto a beach for an involuntary photo shoot, the question of why this is all necessary raises itself. Ingram believes SealNet could be a useful, noninvasive tool for researchers.

Of the world’s pinnipeds—a group that includes seals, walruses, and sea lions—harbor seals are considered the most widely dispersed. Yet knowledge gaps do exist. Other techniques to track seals, such as tagging and aerial monitoring, have their limitations and can be highly invasive or expensive.

Ingram points to site fidelity as an aspect of seal behavior that SealNet could shed more light on. The team’s trials indicated that some harbor seals return to the same haulout sites year after year. Other seals, however, such as two animals the team nicknamed Clove and Petal, appeared at two different sites together. Increasing scientists’ understanding of how seals move around could strengthen arguments for protecting specific areas, says Anders Galatius, an ecologist at Aarhus University in Denmark who was not involved in the project.

Galatius, who is responsible for monitoring Denmark’s seal populations, says the software “shows a lot of promise.” If the identification rates are improved, it could be paired with another photo identification method that identifies seals by distinctive markings on their pelage, he says.

In the future, after further testing, Ingram hopes to develop an app based on SealNet. The app, she says, could possibly allow citizen scientists to contribute to logging seal faces. The program could also be adapted for other pinnipeds and possibly even for cetaceans.

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NASA launches nanosatellite in preparation for lunar 'Gateway' station – Yahoo News Canada

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The rocket carrying the Capstone satellite lifts off. (NASA)

Nasa has launched a tiny CubeSat this week to test and orbit which will soon be used by Gateway, a lunar space station.

It’s all part of the space agency’s plan to put a woman on the moon by 2025.

The Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment (Capstone) mission launched from New Zealand on Tuesday.

Jim Reuter, associate administrator for the Space Technology Mission Directorate, said: “Capstone is an example of how working with commercial partners is key for Nasa’s ambitious plans to explore the moon and beyond.

“We’re thrilled with a successful start to the mission and looking forward to what Capstone will do once it arrives at the Moon.”

Read more: Astronomers find closest black hole to Earth

The satellite is currently in low-Earth orbit, and it will take the spacecraft about four months to reach its targeted lunar orbit.

Capstone is attached to Rocket Lab’s Lunar Photon, an interplanetary third stage that will send it on its way to deep space.

Over the next six days, Photon’s engine will periodically ignite to accelerate it beyond low-Earth orbit, where Photon will release the CubeSat on a trajectory to the moon.

Capstone will then use its own propulsion and the sun’s gravity to navigate the rest of the way to the Moon.

The gravity-driven track will dramatically reduce the amount of fuel the CubeSat needs to get to the Moon.

Read more: There might once have been life on the moon

Bradley Cheetham, principal investigator for CAPSTONE and chief executive officer of Advanced Space, “Our team is now preparing for separation and initial acquisition for the spacecraft in six days.

“We have already learned a tremendous amount getting to this point, and we are passionate about the importance of returning humans to the Moon, this time to stay!”

At the moon, Capstone will enter an elongated orbit called a near rectilinear halo orbit, or NRHO.

Once in the NRHO, Capstone will fly within 1,000 miles of the moon’s north pole on its near pass and 43,500 miles from the south pole at its farthest.

It will repeat the cycle every six-and-a-half days and maintain this orbit for at least six months to study dynamics.

“Capstone is a pathfinder in many ways, and it will demonstrate several technology capabilities during its mission timeframe while navigating a never-before-flown orbit around the Moon,” said Elwood Agasid, project manager for Capstone at Nasa’s Ames Research Center in California’s Silicon Valley.

“Capstone is laying a foundation for Artemis, Gateway, and commercial support for future lunar operations.”

Nasa estimates the cost of the whole Artemis mission at $28bn.

It would be the first time people have walked on the moon since the last Apollo moon mission in 1972.

Just 12 people have walked on the moon – all men.

Nasa flew six manned missions to the surface of the moon, beginning with Neil Armstrong and Buzz Aldrin in July 1969, up to Gene Cernan and Jack Schmitt in December 1972.

The mission will use Nasa’s powerful new rocket, the Space Launch System (SLS), and the Orion spacecraft.

Watch: NASA launch paves way for moon orbit station

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The year’s biggest and brightest supermoon will appear in July & here’s when you’ll … – Curiocity

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Summer is here and with it? Sunshine – and some serious moonshine (of the visible variety, of course). This upcoming month, look up in anticipation of the biggest and brightest event of the year, the July Buck supermoon – which will hover over North America on July 13th.

Appearing 7% larger and lower in the sky, this particular event will be one well worth keeping an eye on when it rises above the horizon.

This will be the closest we’ll get to our celestial neighbour in 2022 (357,418 km) and while North America won’t get to see it when it reaches peak illumination at 2:38 pm ETC., it’ll still look pretty dang impressive after the sunsets.

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Not sure when the moon rises in your area? Here’s the earliest that you’ll be able to see the moon in various cities across the continent according to the Farmer’s Almanac.

  • Seattle, Washington  – 9:50 pm PDT
  • Vancouver, British Columbia – 10:02 pm PDT
  • Calgary, Alberta – 10:35 pm MST
  • Edmonton, Alberta – 10:49 pm MST
  • Toronto, Ontario – 9:34 pm MST
  • Montreal, Quebec – 9:18 pm MST

Until then, cross your fingers for a clear sky, friends! It’s going to be incredible.

Happy viewing.

JULY BUCK SUPERMOON 

When: Wednesday, July 13th

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