Researchers studying supermassive black holes have detected a mysterious flare emitted from the Milky Way’s supermassive black hole Sagittarius A*. The black hole at the heart of our galaxy is relatively quiet and has an inactive nucleus, which is why this odd fluctuation in brightness confused the team.
Sgr A* grew 75 times brighter as it was spewing out a mysterious flashing burst of energy, and then declined to its normal brightness levels. This is the first time researchers caught such a change in brightness in this particular supermassive black hole, studied in near-infrared wavelengths.
“I was pretty surprised at first and then very excited,” astronomer Tuan Do of the University of California Los Angeles told ScienceAlert. “The black hole was so bright I at first mistook it for the star S0-2, because I had never seen Sgr A* that bright. Over the next few frames, though, it was clear the source was variable and had to be the black hole. I knew almost right away there was probably something interesting going on with the black hole.”
The team published their findings regarding the Milky Way’s supermassive black hole in The Astrophysical Journal Letters. The study is currently available on a preprint website arXiv.
Do’s team used the WM Keck Observatory in Hawaii to catch the mysterious energy burst that Sgr A* emitted. They observed the brightening process over four nights with its peak being reached on May 13. The team captured a time lapse of the mysterious flash which summarizes two hours of observations into a couple of seconds. They observed the radiation which abruptly grew, manifesting as a mysterious light flash.
When the radiation is observed using the infrared range, it shows as brightness. The light flickers at all times, but when the brightness grows to such a range that the telescopes have picked it up, scientists know that something has approached this otherwise inactive black hole, and was grabbed up by its colossal gravity.
The team doesn’t yet know what has caused the Milky Way’s supermassive black hole to emit the bright flare, but there are two possibilities. The first possibility suggests that it’s the G2 object believed to be a gas cloud that approached the black hole within 36 light-hours of it in 2014. Another possibility suggests that it could be the star S0-2 which is on a looping 16-year elliptical orbit around Sgr A*. As ScienceAlert reported, its closest approach to the black hole was last year, when it approached within 17 light-hours of the black hole.
“One of the possibilities,” Do told ScienceAlert, “is that the star S0-2, when it passed close to the black hole last year, changed the way gas flows into the black hole, and so more gas is falling on it, leading it to become more variable.”