Astronomers detect eerie echo coming from the Milky Way’s supermassive black hole

By William On Jun 21, 2023

Scientists have detected an eerie echo emanating from a supermassive black hole four million times more massive than the sun at the center of our galaxy.

The sound, which hits highs and lows, marks a very intense period of activity when gas and dust were swallowed up about 200 years ago when the dark abyss came to life after being dormant.

Researchers at the Astronomical Strasbourg Observatory in France captured massive amounts of radiation emitted by Sagittarius A* (Sgr A*) in light reflected from clouds in the Galactic Center – the middle part of our galaxy.

These findings explain why galactic molecular clouds near Sgr A*, 25,640 light-years from Earth, appear brighter than usual.

The sound was detected from Sagittarius A* (Sgr A*), a supermassive black hole at the center of our galaxy

Corresponding author Dr Frederic Marin of the University of Strasbourg in France said: ‘It reveals the past awakening of this giant object.’

“These results may further limit the activity of the galactic center in the past.”

When a black hole is “asleep,” the dark abyss does not emit high levels of X-rays, which is how such black holes are typically detected.

Astronomers captured a remarkable image of Sgr A* in 2022, showing what appears to be a glowing red and orange donut hanging in the darkness of space.

Previously, stars could be seen circling something invisible, compact and very massive in the center of the Milky Way.

This strongly suggested the object was a black hole, and last year’s image provides the first direct visual evidence.

While it’s impossible to see the black hole itself because it’s completely dark, glowing gas around it reveals a telltale signature: a dark central region (called a shadow) surrounded by a bright ring-like structure.

The new view captures light that is bent by the black hole’s powerful gravity.

Astronomers captured a remarkable image of Sgr A* in 2022, showing what appears to be a glowing red and orange colored donut hanging in the darkness of space

The sound, which hits highs and lows, marks a very intense period of activity when gas and dust were swallowed up about 200 years ago when the dark abyss came to life after being dormant. A curved beam of light in the lower left is the captured echo

The latest work shows that the black hole is no longer a sleeping giant.

Corresponding author Dr Frederic Marin of the University of Strasbourg in France said: ‘It reveals the past awakening of this giant object.’

“Our work presents the missing piece of evidence that X-rays from the giant molecular clouds result from the reflection of an intense, but short-lived solar flare produced in or near Sagittarius A*.

“These results may further limit the activity of the galactic center in the past.”

And Sgr A* is one of the few black holes in the universe where scientists can observe the flow of matter nearby.

Because the region absorbs all surrounding light, it’s hard to see, and scientists have spent decades looking for hints of black hole activity.

“To get a sense of the increase in X-ray intensity as the black hole emerged from its resting state, it’s like a single glowworm hidden in a forest suddenly becoming as bright as the sun,” says Dr. said Marian.

The international team combined data from the space telescope IXPE (Imaging X-ray Polarimetry Explorer) and the Chandra X-ray Observatory.

“The polarization angle is consistent with Sgr A* being the primary source of the emission,” said Dr Martin.

“The degree of polarization implies that about 200 years ago the X-ray brightness of Sgr A* was briefly comparable to that of a Seyfert galaxy.”

These are galaxies with very active centers with strong bursts of radiation.

Like a compass, the polarized X-ray light points directly at the source – Sgr A*.

The scientists are continuing their work on Sgr A* to try to determine the physical mechanisms a black hole needs to transition from a resting state to an active state.

SAGITTARIUS A* — THE SUPERMASSIVE BLACK HOLE AT THE CENTER OF THE GALAXY

The galactic center of the Milky Way is dominated by one resident, the supermassive black hole known as Sagittarius A*.

Supermassive black holes are incredibly dense regions at the center of galaxies with masses that can be billions of times greater than that of the sun.

They act as intense sources of gravity that suck up dust and gas around them.

Evidence of a black hole at the center of our galaxy was first presented by physicist Karl Jansky in 1931, when he discovered radio waves emanating from the region.

Eminent yet invisible, Sgr A* has the mass equivalent to some four million suns.

Only 26,000 light-years from Earth, Sgr A* is one of the few black holes in the universe where we can see the flow of matter up close.

Less than one percent of the material that initially fell under the influence of the black hole’s gravity reaches the event horizon, or “point of no return,” because much of it is ejected.

As a result, the X-ray emission from material near Sgr A* is remarkably weak, like that from most giant black holes in galaxies in the nearby Universe.

The captured material must lose heat and angular momentum before it can plunge into the black hole. This loss can occur due to the ejection of matter.