Event Horizon Telescope

The Event Horizon Telescope (EHT) is a special group of telescopes around the world that work together like one big telescope. These telescopes are called radio telescopes, and they look at objects in space using radio waves. By combining data from many telescopes, the EHT can see very small details, even as small as the edge of a black hole.

The EHT project began in 2009 after many years of research and development. Scientists from over 300 groups in more than 20 countries work together on this project. They study black holes, especially the ones at the centers of galaxies.

In 2019, the EHT made history by publishing the first ever image of a black hole. This black hole is in a galaxy called Messier 87. The telescope took this picture using waves that are very small, just 1.3 millimeters long. Later, in 2021, they showed an image that showed more details about the black hole. Then, in 2022, they revealed the first image of the huge black hole at the center of our own galaxy, the Milky Way, called Sagittarius A*. The EHT continues to improve, adding more telescopes and looking at even smaller waves to see space in amazing detail.

Telescope array

A schematic diagram of the VLBI mechanism of EHT. Each antenna, spread out over vast distances, has an extremely precise atomic clock. Analogue signals collected by the antenna are converted to digital signals and stored on hard drives together with the time signals provided by the atomic clock. The hard drives are then shipped to a central location to be synchronized. An astronomical observation image is obtained by processing the data gathered from multiple locations.

The Event Horizon Telescope is made up of many radio telescopes around the world that work together. By using a special method called very-long-baseline interferometry (VLBI), these telescopes can act like one giant telescope, as big as the whole Earth. This helps scientists see very small details in space.

Since 2006, more telescopes have joined this global network each year. The first picture of the huge black hole at the center of our Milky Way galaxy, called Sagittarius A*, was made from data collected in April 2017. Because of winter conditions at the South Pole, the data from that area could not be sent until December 2017.

The information collected is carried by airplanes to special labs where it is processed by powerful computers. The 2020 observations were delayed until March 2021 because of weather, the spread of a disease, and how the stars move.

Published images

Messier 87*

A series of images descriptive of the level of magnification achieved by the EHT (akin to seeing, from the Earth's surface, an object the size of a tennis ball on the Moon); starts at top-left image and moves counter−clockwise to finish at top-right corner

In 2019, scientists using the Event Horizon Telescope shared the first ever picture of a black hole. The image showed the huge black hole at the center of a galaxy called Messier 87, known as M87*. This picture helped test ideas about space and time from a famous scientist, Albert Einstein. The picture matched what we expect to see near a black hole, with a dark area where light cannot escape.

The picture also helped scientists learn more about M87*. They figured out that this black hole has a mass of about 6.5 billion times that of our Sun. The picture showed details very close to the black hole, helping us understand more about how black holes work.

3C 279

In 2020, the telescope showed pictures of an object called 3C 279. These pictures were very detailed and showed movement in a stream of particles coming from the black hole, which looks faster than the speed of light but is actually an effect of how we see it from Earth.

Image of M87* generated from data gathered by the Event Horizon Telescope

Centaurus A

In 2021, the telescope captured detailed pictures of the stream of particles from another black hole in a galaxy called Centaurus A. These pictures were much sharper than before and helped scientists study how particles move around black holes.

Sagittarius A*

Sagittarius A*, first image released in 2022

Sagittarius A* in polarised light, image released in 2024

In 2022, the telescope showed the first picture of the black hole at the center of our own Milky Way galaxy, called Sagittarius A*. Even though this black hole is much smaller and farther away than M87*, it looked surprisingly similar close up. This tells us that the rules about space and time work the same way for both black holes.

In 2024, scientists released another picture of Sagittarius A* that showed how light behaves around the black hole, giving more clues about what’s happening there.

J1924-2914

EHT image of the archetypal blazar 3C 279 showing a relativistic jet down to the AGN core surrounding the supermassive black hole.

In 2022, the telescope and other observatories took pictures of a faraway object called J1924-2914. These pictures showed twists in streams of particles and helped scientists learn about magnetic fields around black holes.

NRAO 530

In 2023, the telescope looked at another faraway object called NRAO 530. This object has a huge black hole, and the pictures showed details of streams of particles coming from it. The pictures helped scientists understand more about how magnetic fields behave in these streams.

Collaborating institutes

The Event Horizon Telescope works with 13 groups of scientists and researchers around the world. These include universities and observatories such as the University of Arizona, University of Chicago, Goethe University Frankfurt, and the Smithsonian Astrophysical Observatory.

These institutes work together to combine data from telescopes around the globe, allowing the EHT to study very distant and tiny objects in space.

Funding

The Event Horizon Telescope project gets money from many different places around the world. Some of these include the United States National Science Foundation, the European Research Council, and the Max Planck Society.

Other groups that help fund the project are the National Science and Technology Council of Taiwan, the Consejo Nacional de Ciencia y Technologia, Mexico, and the John Templeton Foundation. Companies like Western Digital and Xilinx also give support.