An artist’s impression of the Milky Way’s supermassive black hole Sagittarius A*.

Scientists spot echo emitted by Sagittarius A* 200 years ago

Some 200 years ago, the supermassive black hole at the center of our galaxy Sagittarius A* woke up from a long period of hibernation.


About 200 years ago, Sagittarius A*, the supermassive black hole at the heart of our Milky Way, awakened from a long hibernation. This black hole, boasting a mass four million times that of the Sun, had its past awakening reported in the journal Nature by a team led by Frédéric Marin, a CNRS researcher at France’s Strasbourg Astronomical Observatory (CNRS/University of Strasbourg).

Sagittarius A* echo

For one year in the early 19th century, the black hole devoured cosmic objects within its reach before slipping back into dormancy. Given the immense distance separating us from the black hole, Earth felt no effects – about two billion times the distance from Earth to the Sun.


Bright Echoes from a Past Awakening

An observed X-ray echo, emitted roughly 200 years ago, indicates the original intensity was a million times stronger than the black hole’s current emission. This intensity surge is akin to a single firefly in a forest suddenly radiating the brightness of the Sun, as per a CNRS release. These findings shed light on why the galactic molecular clouds near Sagittarius A* glow brighter than expected – they’re reflecting X-rays emitted by the black hole two centuries ago.

Polarized X-ray Light and Sagittarius A*

NASA’s IXPE (Imaging X-ray Polarimetry Explorer) satellite was instrumental in this research. For the first time, it detected the polarization of this X-ray light with exceptional precision and pinpointed its source, a previously unachievable feat.

Polarized X-ray light serves as a compass, leading directly to its source, the virtually extinct Sagittarius A*. As the scientific journey continues, researchers are eager to unravel the physical mechanisms that transition a black hole from dormancy to activity.


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Written by Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

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