After years of observation and weeks of rumor-mill rumblings, astronomers today unveiled their first image of the supermassive black hole at the center of our own Milky Way galaxy, Sagittarius A*.
Technically, the picture from the Event Horizon Telescope project doesn’t show light from the black hole itself. After all, a black hole is a gravitational singularity so dense that nothing, not even light, can escape its grip. Rather, the picture shows the “shadow” of a black hole, surrounded by the superheated, glowing gas that surrounds it.
And technically, the picture may not match what folks might see with their own eyes up close. Rather, the readings come from eight observatories around the world that combined their observations in radio wavelengths.
Nevertheless, the new view of Sagittarius A*, or Sgr A* for short (pronounced “sadge-ay-star”), serves to confirm in graphic terms what astronomers have long suspected: that our galaxy, like many others, has a supermassive black hole at its heart.
Today’s revelations follow up on the Event Horizon Telescope’s first-ever black hole image, which was released in 2019 and showed the supermassive black hole at the center of M87, an elliptical galaxy about 55 million light-years away.
Sgr A* is much closer — a mere 27,000 light-years from Earth, in the constellation Sagittarius. But there’s nothing to fear from this black hole: It’s relatively quiescent, in contrast to the galaxy-gobbling behemoths that are standard science-fiction fare.
Our galaxy’s black hole is thought to hold the mass of 4 million suns within an area that’s roughly as big around as Mercury’s orbit. Checking those dimensions against the image data serves as a test of relativity theory. Spoiler alert: Albert Einstein was right … again.
“We were stunned by how well the size of the ring agreed with predictions from Einstein’s theory of general relativity,” EHT project scientist Geoffrey Bower said in a news release. “These unprecedented observations have greatly improved our understanding of what happens at the very center of our galaxy and offer new insights on how these giant black holes interact with their surroundings.”
The EHT’s findings about Sgr A* are the subject of a special issue of The Astrophysical Journal Letters — and to whet your appetite for all that reading material, here are three videos that summarize the past, present and future of black hole imaging: