Event Horizon Telescope facts for kids
Quick facts for kids Event Horizon Telescope |
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| Established | 2009 |
The Event Horizon Telescope (EHT) is like a giant, Earth-sized telescope! It's actually a network of many radio telescopes spread out all over the world. This amazing project combines data from these telescopes to create a "virtual" telescope. It's powerful enough to see tiny details, like the edge of a supermassive black hole.
The EHT's main goals are to observe two of the biggest black holes we can see from Earth. One is at the center of a huge galaxy called Messier 87. The other is Sagittarius A*, which is the supermassive black hole right at the center of our own Milky Way galaxy.
This international team started in 2009 after many years of planning and technical work. Scientists had to figure out what a black hole would look like and how to use telescopes to see it. They also needed to improve radio telescope technology. Now, the EHT team has over 300 members from 60 different groups in more than 20 countries!
The EHT made history on April 10, 2019, when it released the very first image of a black hole. This image showed the black hole in the Messier 87 galaxy. Later, in March 2021, they showed a new image of the same black hole using "polarized light," which helps us understand the strong forces around it. On May 12, 2022, astronomers shared the first image of our Milky Way's central black hole, Sagittarius A*. The team plans to make the "virtual" telescope even better by adding more telescopes and observing at different wavelengths.
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How Does the EHT Work?
The EHT uses many radio observatories around the world. They all work together to create one giant, super-sensitive telescope. This method is called very-long-baseline interferometry (VLBI). Imagine many separate radio antennas, hundreds or thousands of kilometers apart. They all act like one huge telescope, as big as Earth itself! This makes it possible to see incredibly small details in space.
The project also involves creating special receivers that can pick up very faint radio signals. They use super-accurate clocks to time the signals, which is key for VLBI. They also need fast ways to record and send all the data. New telescope sites are always being added to the network.
Since 2006, the EHT has been adding more observatories. For example, the first image of Sagittarius A* was expected from data collected in April 2017. But because planes can't fly to the South Pole Telescope during the Antarctic winter (April to October), the data couldn't be processed until December 2017, when it finally arrived!
All the collected data is stored on hard drives. These drives are then flown by regular cargo planes (sometimes called a "sneakernet") to two main centers: the MIT Haystack Observatory in the US and the Max Planck Institute for Radio Astronomy in Germany. There, powerful grid computers with about 800 CPUs work together to combine and analyze the data.
Because of the COVID-19 pandemic, bad weather, and how planets move, the EHT couldn't do observations in 2020. They had to wait until March 2021.
Amazing Black Hole Images
The Messier 87* Black Hole
The Event Horizon Telescope team announced their first big discovery on April 10, 2019. They showed the world the first direct image of a black hole! This image was of the supermassive black hole at the center of the Messier 87 galaxy, which scientists call M87*. The scientific details were published in six different papers.
This image was a great way to test Albert Einstein's general theory of relativity in extreme conditions. Einstein's theory predicts that a black hole would have a dark, shadow-like area. This is because its gravity is so strong that it bends and traps light. The image we saw perfectly matched this prediction! Scientists said the image was "consistent with expectations for the shadow of a spinning Kerr black hole as predicted by general relativity."
The image also helped scientists measure M87*'s mass and size. They found the black hole's mass is about 6.5 billion times the mass of our Sun. Its event horizon (the point of no return) is about 40 billion kilometers wide. This is about 2.5 times smaller than the shadow it casts in the image. The EHT also found that this black hole spins clockwise when seen from Earth.
Creating these images from all the radio telescope data is a huge math problem! Four different teams worked independently to make images to make sure the results were reliable. They used special computer programs, including one called CLEAN, and another called CHIRP.
In March 2021, a new image of the M87 black hole was released. This one showed how the black hole looks in polarized light. This was the first time astronomers could measure polarization so close to a black hole's edge. The lines on the photo show the direction of the polarization, which tells us about the magnetic field around the black hole's shadow.
In 2023, the EHT released even sharper images of the M87 black hole. These new images were made using the same 2017 data but with a new computer program called PRIMO.
The 3C 279 Black Hole
In April 2020, the EHT shared the first very detailed images of a type of galaxy called a blazar, named 3C 279. These images were taken in April 2017. They showed bright parts of a jet shooting out from the black hole. These parts seemed to move faster than the speed of light! This "superluminal motion" happens because the jet is moving almost at the speed of light and is pointed nearly directly towards us.
The Centaurus A Black Hole
In July 2021, the EHT released very detailed images of the jet coming from the supermassive black hole in the center of Centaurus A. This black hole is about 55 million times the mass of our Sun. It's not big enough for us to see its "photon sphere" (the area where light gets trapped). However, its jet is super interesting because it stays very narrow even as it shoots out far beyond its home galaxy. The images were 16 times sharper than previous ones.
The Sagittarius A* Black Hole
On May 12, 2022, the EHT team showed the world an image of Sagittarius A*. This is the supermassive black hole at the very center of our own Milky Way galaxy. This black hole is about 27,000 light-years away from Earth. It is thousands of times smaller than the M87* black hole.
A scientist named Sera Markoff said, "We have two completely different types of galaxies and two very different black hole masses, but close to the edge of these black holes they look amazingly similar." This tells us that Einstein's General Relativity theory works for these objects up close. Any differences we see further away are likely due to the different materials around the black holes.
On March 22, 2024, the EHT team released a new image of Sagittarius A* in polarized light, just like they did for M87*.
The J1924-2914 Black Hole
In August 2022, the EHT, along with other telescope networks, took pictures of a distant blazar called J1924-2914. These were the most detailed images ever taken of polarized light from a quasar. The pictures show a jet that is bent like a spiral. The polarization of the light suggests that the magnetic field in the jet is shaped like a donut. This object is also used to help calibrate observations of Sagittarius A*.
The NRAO 530 Black Hole
In February 2023, the EHT reported on observations of a quasar called NRAO 530. This quasar is a very bright object that changes its brightness a lot. It has a supermassive black hole, but its exact mass is still unknown. It could be anywhere from 300 million to 2 billion times the mass of our Sun.
The EHT observed NRAO 530 from April 5-7, 2017. It was used to help calibrate the observations of Sagittarius A*. At its distance, NRAO 530 is the farthest object the EHT has ever imaged! The team created the first images of this object, showing both its total brightness and its polarized light. The images show a bright spot at the southern end of the jet, which is thought to be the core. This spot is polarized, meaning its light waves vibrate in a specific direction. This suggests that the jet's energy is mostly from its magnetic field. The jet extends about 60 microarcseconds and shows a helical (spiral) structure of the magnetic field.
Who Works on the EHT?
The EHT project involves 13 main research groups:
- The Academia Sinica Institute of Astronomy and Astrophysics
- The University of Arizona
- The University of Chicago
- The East Asian Observatory
- Goethe University Frankfurt
- Smithsonian Astrophysical Observatory (part of the Center for Astrophysics – Harvard & Smithsonian)
- Institut de radioastronomie millimétrique (IRAM)
- Large Millimeter Telescope Alfonso Serrano
- Max Planck Institute for Radio Astronomy
- MIT Haystack Observatory
- National Astronomical Observatory of Japan
- Perimeter Institute for Theoretical Physics
- Radboud University
How is the EHT Funded?
The EHT team gets money from many different places, including:
- The National Science Foundation in the United States
- The European Research Council
- The Ministry of Science and Technology of Taiwan
- The Max Planck Society
- The Consejo Nacional de Ciencia y Technologia in Mexico
- The John Templeton Foundation
- The Gordon and Betty Moore Foundation
- The Japan Society for the Promotion of Science
- The Natural Sciences and Engineering Research Council of Canada
- Academia Sinica
- The Smithsonian Institution
Companies like Western Digital and Xilinx also donate to the project.
