By coincidence, the Atacama Massive Millimeter/submillimeter Array (ALMA) was taking observations of Sgr A* for EHT when that X-ray flare occurred — filling an necessary information hole. The analysis was published today (Sept. 22) in Astronomy & Astrophysics.
“What is actually new and fascinating is that such flares had been to this point solely clearly current in X-ray and infrared observations of Sagittarius A*,” stated lead writer Maciek Wielgus of the Max Planck Institute for Radio Astronomy in Bonn, Germany, in a press release. “Right here, we see for the primary time a really sturdy indication that orbiting scorching spots are additionally current in radio observations.”
Mysteries abound
Black holes are objects the place gravity is so sturdy that nothing, not even gentle can escape. The event horizon, or “floor” of the black hole, marks this boundary of no return. Astronomers can only theorize as to what goes on past this level.
However the area outdoors the event horizon isn’t freed from mysteries both.
Scientists don’t absolutely grasp what causes flares such because the one Chandra detected. One idea factors to interactions between materials within the black hole’s accretion disk and the magnetic discipline surrounding the black hole. Within the case of Sgr A*, the researchers assume the magnetic discipline acts a barrier, stopping the black hole from devouring as a lot materials because it in any other case would. This magnetic blockage causes gasoline and dust to clump up in sure areas across the black hole.
Finally, this built-up stress causes one of many magnetic discipline strains to briefly break, permitting the black hole to gorge itself. The breakage additionally releases vitality into the encompassing materials, forming a scorching bubble of plasma.
Initially, these scorching spots would possibly primarily emit X-rays, Wielgus informed Astronomy. “Perhaps it wants a little bit of time to chill down to point out up at low frequencies equivalent to millimeter [radio] wavelengths.” It was these latter wavelengths that ALMA was in a position to detect.
On common, a scorching spot usually lasts for a single orbit earlier than being sheared aside by the black hole. On this case, the clump of gasoline was zipping across the Milky Way’s black hole at some 30 p.c the velocity of sunshine. At these mind-bending speeds, it was in a position to full a lap in about 70 minutes, and it was torn aside some 35 minutes later.
Whereas the brand new observations help a magnetic origin for these energetic flares, they provide only a glimpse on the true form of Sgr A*’s magnetic discipline. Like with M87*, extra information from EHT telescopes might present a extra full view of our galaxy’s central black hole.
“Hopefully, one day,” Wielgus stated within the ESO press launch, “we shall be comfy saying that we ‘know’ what’s going on in Sgr A*.”
