Which Black Hole Was Photographed First
The first black hole ever directly imaged is the supermassive black hole in galaxy Messier 87, known as M87*. The Event Horizon Telescope collaboration released the image in April 2019, showing a bright ring of emission around a dark central shadow. The black hole has a mass of about 6.5 billion solar masses and lies roughly 55 million light-years from Earth. The image was produced using very-long-baseline interferometry linking radio telescopes across multiple continents, including sites in the United States, Europe, Mexico, and Antarctica. For background on the project and its partners, see the Event Horizon Telescope overview at https://eventhorizontelescope.org/. The M87* result remains the most widely cited black hole image in astronomy and science communication.
Follow-up observations and analyses have refined the M87* image and related data. Researchers have examined polarization of the light around the black hole to map magnetic fields near the event horizon. The collaboration has also published models comparing the observed ring diameter and brightness asymmetry with predictions from general relativity. These studies support the interpretation that the central object is a Kerr black hole consistent with Einstein's theory. The Event Horizon Telescope continues to expand its global array and data processing capabilities to improve resolution and sensitivity for future imaging campaigns.
Which Black Hole Was Photographed in Our Galaxy
The first image of the black hole at the center of the Milky Way, called Sagittarius A* or Sgr A*, was released by the Event Horizon Telescope on May 12, 2022. Sgr A* has a mass of about 4 million solar masses and is located roughly 27,000 light-years from Earth in the direction of the constellation Sagittarius. The image shows a ring-like structure similar to M87*, but the source is much smaller and varies on shorter timescales because of its lower mass and faster orbital dynamics near the innermost stable circular orbit. The data were collected during coordinated observing runs that required precise atomic-clock timing and atmospheric correction at millimeter wavelengths. For more detail on the Sgr A* results and methodology, see the Event Horizon Telescope publication summary at https://eventhorizontelescope.org/. The image provides a direct view of the immediate environment of a supermassive black hole in our own galaxy.
Since the Sgr A* image, the collaboration has released polarized-light data and additional analysis of the accretion flow and jet-launching region near the Galactic Center. Researchers have compared the size and shape of the emission ring with magnetohydrodynamic simulations to constrain the black hole spin and viewing angle. The results support a picture in which Sgr A* is a rapidly rotating black hole surrounded by a hot, magnetized plasma orbiting close to the event horizon. The Event Horizon Telescope has also coordinated with other facilities, including space-based X-ray observatories, to study variability and high-energy counterparts. These multiwavelength efforts help contextualize the radio images within the broader astrophysical environment of the Milky Way's central black hole.
How Black Hole Images Are Produced and Verified
Producing a black hole image requires combining signals from widely separated radio telescopes to create a virtual Earth-sized aperture. The Event Horizon Telescope uses atomic clocks and precise time-stamping to correlate data from sites including the Atacama Large Millimeter Array, the South Pole Telescope, and the IRAM 30-meter telescope on Pico Veleta. The correlated data are then processed with imaging algorithms that reconstruct a picture of the sky brightness at millimeter wavelengths, accounting for atmospheric and instrumental effects. For a description of the imaging pipeline and challenges, see the Event Horizon Telescope methods page at https://eventhorizontelescope.org/. The resulting images are tested against simulations and independent imaging teams to ensure robustness before publication.
Verification of black hole images involves comparing the observed ring diameter, asymmetry, and polarization patterns with general-relativistic magnetohydrodynamic simulations. The