The electromagnetic counterpart to the Galactic center supermassive black hole, Sgr A*, has been observed in the near-infrared for over 20 years and is known to be highly variable. We report new Keck Telescope observations showing that Sgr A* reached much brighter flux levels in 2019 than ever measured at near-infrared wavelengths. In the K$^\prime$ band, Sgr A* reached flux levels of $\sim6$ mJy, twice the level of the previously observed peak flux from $>13,000$ measurements over 130 nights with the VLT and Keck Telescopes. We also observe a factor of 75 change in flux over a 2-hour time span with no obvious color changes between 1.6 $\mu$m and 2.1 $\mu$m.
Even though the black hole at the center of the Milky Way is a monster, it’s still rather quiet. Called Sagittarius A*, it’s about 4.6 million times more massive than our Sun. Usually, it’s a brooding behemoth. But scientists observing Sgr. A* with the Keck Telescope just watched as its brightness bloomed to over 75 times normal for a few hours.
Astronomers have been watching the black hole at the center of our galaxy for 20 years, and in May, they saw something they’d never seen before.
Our time-dependent Seyfert flare models adequately explain the observations and indicate the Seyfert flare event took place T_o = 3.5 +/- 1 Myr ago.
In 2013, astrophysicist Joss Bland-Hawthorn of the University of Sydney and the ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) and colleagues estimated that the event occurred between 1 and 3 million years ago.
Now, more observations taken using the Hubble Space Telescope – and therefore a bigger dataset – have provided even more compelling evidence for the event. And the team has been able to narrow down a timeframe for both when the event occurred, as well as its duration.
Thus it is likely that the Stream emission arose from a `Seyfert flare‘ that was active 1-3 Myr ago, consistent with the cosmic ray lifetime in the Fermi bubbles. Sgr A* activity today is greatly suppressed (70-80 dB) relative to the Seyfert outburst…
The key the astronomers found was actually discovered 20 years old, in the form of a strange glow that astronomers had noticed in the Magellanic Stream. The Magellanic Stream is composed of large clouds of gas – mostly hydrogen – that stretch for light years in the wake of the Milky Way’s two companion Galaxies, the Large and Small Magellanic Clouds. The Stream is about 2 billion years old.
„We didn’t understand the cause. Then suddenly we realised it must be the mark, the fossil record, of a huge outburst of energy from the centre of our Galaxy,“ remarked researcher Joss Bland-Hawthorn in a press release.
ESO’s exquisitely sensitive GRAVITY instrument has added further evidence to the long-standing assumption that a supermassive black hole lurks in the centre of the Milky Way. New observations show clumps of gas swirling around at about 30% of the speed of light on a circular orbit just outside a four million solar mass black hole — the first time material has been observed orbiting close to the point of no return, and the most detailed observations yet of material orbiting this close to a black hole.
The artist impression of the ejection mechanism by the supermassive black hole. Credit: James Josephides (Swinburne Astronomy Productions)
“My favorite part of this discovery is thinking about where this star came from and where it’s going,” said Ji. “It was born in one of the craziest places in the universe, near a supermassive black hole with lots of other nearby star friends; but it’s going to leave our galaxy and die all alone, out in the middle of nowhere. Quite a fall from grace.”
Five million years ago, when humanity’s ancestors were just learning to walk upright, a star was ejected from Sagittarius A*, the supermassive black hole at the center of the Milky Way Galaxy, at a staggering 3.7 million mph. This month, a group of researchers spotted the superfast star traveling relatively close to Earth.