A dormant volcano: the black hole at the heart of our galaxy is more explosive than we thought

A dormant volcano: the black hole at the heart of our galaxy is more explosive than we thought
The bright area in the lower left is the centre of the galaxy. Only the densest clouds of dust can be seen in this infrared image. Credit: Atlas / 2MASS / University of Massachusetts / California Institute of Technology

The supermassive black hole at the heart of our galaxy spat out an enormous flare of radiation 3.5 million years ago that would have been clearly visible from Earth.

In new research that will soon be published in the Astrophysical Journal my colleagues and I found that the flare left traces in a trail of gas called the Magellanic Stream that lies some 200,000 away and encircles the Milky Way.

The team includes Ralph Sutherland and Brent Groves at the Australian National University and ASTRO-3-D; Magda Guglielmo, Wen Hao Li and Andrew Curzons at the University of Sydney; Philip Maloney at the University of Colorado; Gerald Cecil at the University of Carolina; and Andrew J. Fox at the Space Telescope Science Institute in Baltimore.

The discovery changes our view of our galaxy's central black hole, which has appeared dormant throughout recorded human history. Astronomers are coming to realise that it has been hugely active, even explosive, in the relatively recent past in galactic terms (measured in millions of years).

This activity has been flickering on and off for billions of years. We don't understand why this activity is intermittent, but it has something to do with how material gets dumped onto the black hole. It might be like on a hot plate that sputter and explode chaotically, depending on their size.

Our situation on Earth resembles living near a largely like Mount Vesuvius that is known to have been explosively active in the past, with disastrous consequences for Pompeii.

Despite this, there's no need to be alarmed: as far as we can tell, we are safe here in orbit about a far from the centre of the Milky Way.

Radiation flashes out from the hot spinning gas around the supermassive black hole at the centre of the Milky Way, leaving traces in the Magellanic Stream. Credit: James Josephides / Swinburne University

Why is there a black hole at the centre of the galaxy?

If you look along the Milky Way in the direction of the constellation Sagittarius, you will see the dense agglomeration of stars around the centre of the galaxy. The galactic centre is marked by a very dense, very massive cluster of stars orbiting the .

Earlier this year, the ESO Gravity team found a star close to the black hole travelling at up to 10,000 km per second, a few percent of the speed of light. This let them weigh the black hole to a precision of 1%, arriving at a number of about 4 million times the Sun's mass.

As galactic supermassive go, this is a featherweight. For example, our neighbouring galaxy Andromeda also has a supermassive black hole, but it is 50 times heavier than ours.

Essentially all large galaxies have central massive black holes. We don't know exactly why this is so, but we know it's important and that the growth phases of these monsters are likely to have affected the galaxy as a whole.

Understanding the effect of interactions between black holes and host galaxies is one of the hottest topics in modern astrophysics.

A dormant volcano: the black hole at the heart of our galaxy is more explosive than we thought
An enhanced radio image of Centaurus A. The inset picture zooms in on the jets coming from the central black hole. Credit: CSIRO/ATNF; ATCA;ASTRON; Parkes;MPIfR; ESO/WFI/AAO (UKST); MPIfR/ESO/APEX; NASA/CXC/CfA

Some black holes are more active than others

But if we look out across the universe, we see only a few percent of galaxies appear to have "active" black holes. By active, we mean that gas and stars spiralling into the black hole form an extremely hot ring of gas.

This ring, called an accretion disc, gets so hot that it drives jets, winds and radiating beams of light out across the galaxy. The effects of these explosions are particularly impressive in more massive .

For decades, Australian radio telescopes have mapped out jet flows that are far larger than the visible galaxy in the middle.

The radio jets in the galaxy Centaurus A extend more than 10 degrees across the sky—that's the size of 20 full moons next to each other. This is remarkable given Centaurus A is 10 million light years away.

The beams of radiation from the black hole’s accretion disk flop around in different directions over thousands of years. Credit: Phil Hopkins / Caltech

The Milky Way explosion

Some 3 million years ago, our direct ancestor Australopithecus afarensis walked the Earth. They may well have looked up towards Sagittarius and seen cones of light shooting sideways from the Milky Way, brighter than any star in the night sky.

The lightshow would have appeared as static beams on a human timescale, only flickering on timescales of thousands of years. Today, the only visible remnant of that immensely powerful event is the cooling gas along the distant Magellanic Stream.

So how would life on Earth have fared if the explosive jet was directed straight at us? This is a valid question, because we believe that the spin axis of the accretion disc flops around wildly in lightweight supermassive black holes.

If the beam was pointing at the solar system, the jet would have to plough through the Milky Way disc, and it would take about 10 million years to reach us.

So it's possible that a more ancient explosion could have produced a powerful jet that is yet to reach us.

But we need not worry—at its peak, the intensity of the jet when it reaches us is unlikely to exceed the most energetic solar flares. These are known to knock out satellites, and pose a threat to space-walking astronauts, but our own atmosphere largely protects us on Earth.


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Not long ago, the center of the Milky Way exploded

Journal information: Astrophysical Journal

Provided by The Conversation

This article is republished from The Conversation under a Creative Commons license. Read the original article.The Conversation

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Oct 08, 2019
The discovery changes our view of our galaxy's central black hole, which has appeared dormant throughout recorded human history. Astronomers are coming to realise that it has been hugely active, even explosive, in the relatively recent past in galactic terms (measured in millions of years).

But not to LaViolette, who has predicted this for decades in his Continuous Creation Model, and suffered ridicule as a result of sustained ignorance throughout the community bent on the more sexy Black Hole math fantasy. So if his prediction is correct, why not examine why he made it? His SQK physics explains countless observations, observations that confound conventional cosmologists, who contort their explanations into increasingly logical nonsense.

Oct 08, 2019
For decades, Australian radio telescopes have mapped out jet flows that are far larger than the visible galaxy in the middle.

The radio jets in the galaxy Centaurus A extend more than 10 degrees across the sky—that's the size of 20 full moons next to each other. This is remarkable given Centaurus A is 10 million light years away.

So logically, the source of the jets cannot be from accretion. But logic is not a common trait among cosmologists.

Oct 08, 2019
But we need not worry—at its peak, the intensity of the jet when it reaches us is unlikely to exceed the most energetic solar flares.

If the superwave of radiation from the core dims our star by the facilitating the invasion of interstellar dust into our inner solar system, climate change may make life on earth impossible for such a large population. So don't worry. Be happy!

Oct 08, 2019

So logically, the source of the jets cannot be from accretion. But logic is not a common trait among cosmologists.


According to whom?

Oct 09, 2019
crappy clickbait headline
bad enough but understandable

sure the editor who wrote the silly headline
hasn't cracked a real science textbook
since he graduated with an English Majors Degree
back in the seventies, most likely

the importance of his job is to divert viewer eyeballs to the advertisers
they pay the bills & salaries

my suspicion is that the article posted above?
was re-writen by a hack
no better educated in the sciences than the editor

i would urge everyone to look at the original published article
then read the original peer-reviewed paper

it is important that all the errors in this version of the article be understood
cause the looneyticks like tux
will use these poorly written popular articles
as an excuse to spread their lying steershit
to unsuspecting & gullible readers

Oct 09, 2019
Dint we do this last week? Were we not done?

Oct 09, 2019
Just more anti-science from phys.org...

Oct 09, 2019
since the article posted above
is a non-scientist's rewrite
of another writer's published magazine article
based on someone else's interviews of the researchers?

this site admins chose to use the mangled version of the scientific work
as bait to draw in pro & anti science viewers

"mmh tasty..."
BANG!!

like shooting fish in a barrel

Oct 09, 2019
Just more anti-science from phys.org...


What are you talking about now, dumbo?

Oct 09, 2019
"The black hole just imploded" - line from the latest episode of 'The Flash' tv show. Just how STUPID do these writers think we are? Correction - just how STUPID are the people who write this junk???

Oct 09, 2019
This activity has been flickering on and off for billions of years. We don't understand why this activity is intermittent, but it has something to do with how material gets dumped onto the black hole. It might be like water droplets on a hot plate that sputter and explode chaotically, depending on their size.

Science, according to The Conversation, with the appropriate analogy for their ignorant audience. Not even a hint as to why they claim "This activity has been flickering on and off for billions of years".

Oct 09, 2019
"In new research that will soon be published in the Astrophysical Journal my colleagues and I found that the flare left traces in a trail of gas called the Magellanic Stream that lies some 200,000 light years away and encircles the Milky Way. "

"The lightshow would have appeared as static beams on a human timescale, only flickering on timescales of thousands of years. Today, the only visible remnant of that immensely powerful event is the cooling gas along the distant Magellanic Stream."

Antigoracle, I'm assuming when they publish their research soon it will contain data to back up the "flickering"

Oct 09, 2019
jimbob, it will not matter to any of the woomongers
they are innumerate
as well as incompetent
at reading scientific papers
or comprehending the data

copy & paste out of context is the best they can do

hoping for a reasoned response from the lunatic trolls?
will just leave you frustrated
at their buffoonery

that is why i treat them with contemptuous derision
they deserve no better

Oct 10, 2019
Is rrwillsj a human? It can't seem to formulate a well-structured paragraph?

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