Wednesday, September 25, 2013

Dating our Galaxy's Dormant Volcano

The supermassive black hole at the centre of our Galaxy was 100 million times more powerful about two million years ago. Credit: R. Jay GaBany (Cosmotography.com), J. Bland-Hawthorn (U Sydney)

A dormant volcano - a supermassive black hole - lies at the heart of our Galaxy. Fresh evidence suggests that it last erupted two million years ago. Astronomers have long suspected such an outburst occurred, but this is the first time they've been able to date it. The evidence comes from a lacy filament of gas, mostly hydrogen, called the Magellanic Stream. This trails behind our Galaxy's two small companion galaxies, the Large and Small Magellanic Clouds. "For twenty years we've seen this odd glow from the Magellanic Stream," said Professor Joss Bland-Hawthorn, an ARC Federation Fellow at the University of Sydney, Australia, and a Fellow at the Australian Astronomical Observatory, who led a team studying this problem.

"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."

"It's been long suspected that our Galactic Centre might have sporadically flared up in the past. These observations are a highly suggestive 'smoking gun'," said Martin Rees, Astronomer Royal, who was one of the first people to suggest that black holes generate the power seen coming from quasars and galaxies with 'active' centres.

The team gives its arguments in a paper accepted for publication in The Astrophysical Journal. Professor Bland-Hawthorn will presented the work at the Galaxy Zoo meeting in Sydney, Australia, on 24 September.

The Galaxy's supermassive black hole has been known for decades. It's orbited by a swarm of stars whose paths let us measure the black hole's mass: four million times the mass of the Sun.

The region around the black hole, called Sagittarius A* ["A-star"], pours out radio waves, infrared, X-rays and gamma rays.

Flickers of radiation rise up when small clouds of gas fall onto the hot disk of matter that swirls around the black hole.

But evidence has been building of a real cataclysm in the past. Infrared and X-ray satellites have seen a powerful "wind" (outflow) of material from this central region. Antimatter boiling out has left its signature. And there are the "Fermi bubbles" - two huge hot bubbles of gas billowing out from the Galactic Centre, seen in gamma-rays and radio waves.

"All this points to a huge explosion at the centre of our Galaxy," said team member Dr Philip Maloney of the University of Colorado in Boulder, USA. "What astronomers call a Seyfert flare."

Scientists studying the Galactic Centre came together at a workshop at Stanford University in California earlier this year.

While at the workshop, Professor Bland-Hawthorn realised the Stream could be holding the memory of the Galactic Centre's past.

Struck by the fiery breath of Sagittarius A*, the Stream is emitting light, much as particles from the Sun hit our atmosphere and trigger the coloured glows of the aurorae - the Northern and Southern Lights.

In the Stream, ultraviolet light splits hydrogen atoms into protons and electrons. When those components recombine, the electrons give off "H-alpha" emission - a specific wavelength of light.

The brightest glow in the Stream comes from the region nearest the Galactic Centre.

Geometry, the amount of energy from the original flare from Sagittarius A*, the time the flare would take to travel to the Magellanic Stream, the rate at which the Stream would have cooled over time - "it all fits together, it all adds up," says team member Dr Greg Madsen of the University of Cambridge in the UK.

The Galaxy's stars don't produce enough ultraviolet to account for the glow. Nor could they have in the past, says Professor Bland-Hawthorn. "The Galactic Centre never formed stars at a high enough rate."

Will such an explosion happen again?

"There are lots of stars and gas clouds that could fall onto the hot disk around the black hole," says Professor Bland-Hawthorn.

"There's a gas cloud called G2 that we think will fall in next year. It's small, but we're looking forward to the fireworks!"

Credit: aao.gov.au

1 comment:

  1. Both, Newton & Einstein had rejected aether before introducing their laws & theories. Whereas aether has been shown to be existing and containing the secrets of light & time. Once aether is accepted space is again finite & absolute and filled up with aether, the electric dipoles, and it is aether through which forces of nature are transmitted as against the irrational action at a distance through fields without knowing the physicality of the fields, time is emergent & relative depending upon motion of the observer, and as humans perceive it, time is emergent and matter is not absolute but emergent. (This alternative paradigm reveals that there is very powerful God who has power on matter & time and everything existing in the finite space and existence of God is the prerequisite for the creation & existence of universe ).
    In brief the scenario is as under
    Aristotle:- Space- absolute & finite; time- absolute, matter-absolute, light/radiation- not properly known

    Newton:- Space, time & matter same as Aristotle; light a wave-motion with corpuscular theory

    Einstein:- Space- interconnected with time & emergent, Time-emergen & interconnected with space & relative, matter & Energy (light/radiation) is absolute & transmutable and light/radiation as wave-motion with no clue as to what is light/radiation physically.

    Final state of existence:- Space-absolute & finite, time- emergent & relative depending on the motion of the observer/body with respect to aether at rest frame of reference, matter-emergent & finite, light/radiation- a electromagnetic disturbance of electric dipoles of aether creating a wave motion and all forces of nature being
    electromagnetic forces which is being transmitted through aether, the electric dipoles.

    Following is the list of my published scientific articles in peer-reviewed journals & sites where these articles are available
    1. Experimental & Theoretical Evidences of Fallacy of Space-time Concept and Actual State of Existence of the Physical Universe
    2. Foundation of Theory of Everything: Non-living Things & Living Things (Revised version on World Science Database, General Science Journal, Vixra and Academia.edu in my profile)
    3.Michelson-Morley Experiment: A Misconceived & Misinterpreted Experiment
    4. Energy Theory of Matter & Cosmology (Revised version on World Science Database, General Science Journal, Vixra and Academia.edu in
    my profile)
    5. 'On the Electrodynamics of Moving Bodies' by Albert Einstein is Based on Trickeries (www.elixirjournal.org Feb.2012)
    6.Ultimate Proof of Energy Theory of Matter & Cosmology
    7. Theory of Origin & Phenomenon of Life
    These publications are available at the journal site of Indian Journal
    of Science & Technology (a peer-reviewed journal) www.indjst.org
    (March 2012,oct 2010, oct 2011,Aug 2010) and also on
    www.gsjournal.net, www.worldsci.org, viXra, Intellectual Archives,
    ResearchGate & Academia.edu in my profile.
    On the basis of above-mentioned articles an open challenge has been put forward to the adopted paradigm of physics. The standing (till date) open challenge could seen at
    http://www.worldsci.org/php/index.php?tab0=Abstracts&tab1=Display&id=6476&tab=2
    and
    http://www.gsjournal.net/Science-Journals/Essays/View/4018.

    ReplyDelete