NASA's Hubble Space Telescope is further probing the remnants of a massive space explosion visible from Earth 3.5 million years ago.
Embedded in the center of our galaxy, the Milky Way, a supermassive black hole known as Sagittarius A* (Sgr A*) had unleashed a massive amount of energy. New research shows that the energy was so pervasive that it illuminated gas associated with two satellite galaxies of our own: the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC).
"The flash was so powerful that it lit up the [gas] stream like a Christmas tree. It was a cataclysmic event," Andrew Fox, the principal investigator of the study and an astronomer at the Space Telescope Science Institute (STScI) in Baltimore, said in a NASA statement.
This shows us that different regions of the galaxy are linked — what happens in the galactic center makes a difference to what happens out in the Magellanic Stream," Fox added, referring to the massive, ribbon-like gas structure that trails the Magellanic Clouds. "We're learning about how the black hole impacts the galaxy and its environment."
The black hole's activity likely came from a large hydrogen cloud, about 100,000 times the mass of the sun, falling onto material circling near the black hole. Ultraviolet radiation from the subsequent explosion penetrated far above and below our galaxy's plane, stripping atoms of their electrons in the Magellanic Stream.
To learn more about the ancient explosion, the powerful ultraviolet eyes of Hubble peered at quasars (cores of active galaxies) in the background of the Magellanic Stream. This allowed the telescope's spectrograph to see the signatures of "excited" (ionized) atoms in ultraviolet light. Researchers also looked at 10 quasars behind the Leading Arm, which is a gaseous feature just ahead of the LMC and SMC in the galaxies' orbits around the Milky Way.