- 3403 - BLACKHOLES - all eyes on our galactic center? Several next-generation telescopes will be headed to space in the coming years, like the James Webb Space Telescope (JWST) that was launched from the European Spaceport in French Guiana last month, January , 2021. By 2027, when the ELT begins to gather light, the JWST will be joined by Hubble’s successor , the Nancy Grace Roman Space Telescope (RST).
--------------------- 3403 - BLACKHOLES - all eyes on our galactic center?
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- It all began with the discovery of Sagittarius A*, a persistent radio source located at the Galactic Center of the Milky Way that turned out to be a supermassive blackhole. This discovery was accompanied by the realization that blackholes exist at the heart of most galaxies, which account for their energetic nature and the hypervelocity jets extending from their center.
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- Since then, scientists have been trying to get a better look at Sag A* and its surroundings to learn more about the role blackholes play in the formation and evolution of our galaxy.
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- This has been the goal of the “GRAVITY collaboration“, an international team of astronomers and astrophysicists that have been studying the core of the Milky Way for the past thirty years.
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- Using the Very Large Telescope Interferometer (VLTI), this team obtained the deepest and sharpest images to date of the region around Sag A*. These observations led to the most precise measurement yet of the blackhole’s mass and revealed a never-before-seen star that orbits close to it.
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- The GRAVITY collaboration is made of scientists from (MPE), (LESIA), (CNRS), (CENTRA), (MPIA), (ESO). The collaboration takes its name from the GRAVITY adaptive optics instrument that they developed for the VLTI.
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- This unique instrument combines the light of all four 27 foot telescopes at the Very Large Telescope’s (VLT) located at the Paranal Observatory in Chile, a technique known as interferometry.
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- Astronomers are measuring the blackhole at the center of the Milky Way, Sagittarius A*. How massive is it exactly? Does it rotate? Do stars around it behave exactly as we expect from Einstein’s general theory of relativity?
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- The best way to answer these questions is to follow stars on orbits close to the supermassive blackhole.
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- The collaboration team also employed a machine-learning technique called “Information Field Theory“. This consisted of modeling how the real light sources would appear, how GRAVITY would observe them, then comparing the simulated results to the actual observations. This allowed them to acquire highly-accurate measurements of Sag A* and images of Galactic Center that were 20 times sharper than any made by the individual VLT telescopes alone.
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- The team also used data from two former VLT instruments (NACO and SINFONI) and measurements from the Keck Observatory and NOIRLab’s Gemini Observatory in the US. During their observation period, which ran from March to July 2021, the team used these instruments to make precise measurements of the stars that orbit Sag A* as they made their closest approach.
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- Images obtained by the GRAVITY instrument on the VLTI between March and July 2021, showing stars orbiting very close to Sgr A*, the supermassive blackhole at the heart of the Milky Way.
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- This included S29, which holds the record for making the closest and speediest approach around Sag A* ever observed. This star made its nearest pass in late May 2021, passing within 8 billion miles, or 90 times the distance between the Earth and Sun (90 AU), and achieving a velocity of 5430 miles per second.
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- In addition, they found a new star (S300) that was previously undetected, demonstrating the power and effectiveness of their observations.
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- T he VLTI gives us this incredible spatial resolution. Astronomers were stunned by their amount of detail, and by the action and number of stars they reveal around the blackhole.
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- Following stars on close orbits around Sagittarius A* allows astronomers to precisely probe the gravitational field around the closest massive blackhole to Earth, to test General Relativity, and to determine the properties of the blackhole.
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- Originally proposed by Albert Einstein in 1916, General Relativity provides a geometric explanation of gravitation and its effect on space-time. Since then, scientists have sought opportunities to test this theory under the most extreme conditions, which SMBHs provide.
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- These latest observations, combined with the team’s previous data, confirmed that the stars follow paths predicted by General Relativity perfectly. From this, the team was able to constrain the mass of Sag A* to 4.3 million Solar masses, the most precise estimate of the blackhole’s mass yet.
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- The precise nature of the images and measurements allowed the collaboration team to fine-tune the distance to Sagittarius A* to 27,000 light-years from Earth.
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- The team aims to eventually find stars that orbit so close to Sag A* that they are subject to the gravitational effects caused by the blackhole’s rotation. The ESO is also busy constructing the Extremely Large Telescope (ELT) in the Atacama Desert in northern Chile. Once it is complete ,scheduled for 2027, the ELT will be the most powerful observatory in the world and allow for the most precise measurements of these stars’ velocities.
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- It will be joined by the Giant Magellan Telescope (GMT), which is scheduled for completion by 2025.
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- Several next-generation telescopes will be headed to space in the coming years, like the James Webb Space Telescope (JWST) that was launched from the European Spaceport in French Guiana last month, January , 2021.
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- By 2027, when the ELT begins to gather light, the JWST will be joined by Hubble’s successor , the Nancy Grace Roman Space Telescope (RST).
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- It’s little wonder why astrophysicists are looking to the coming years with such great excitement! We have so many new instruments to learn here we came from. All eyes on our galactic center?
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January11, 2022 BLACKHOLES - all eyes on our galactic center? 3386
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--------------------- --- Tuesday, January 11, 2022 ---------------------------
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