A ‘massive blast’ of radiation caused the Milky Way to explode 3m years ago


7 Oct 2019388 Views

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The researchers say their findings change the understanding of the galaxy that houses Earth. Image: James Josephides/ASTRO 3D/PA Media

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Astronomers say that high-energy radiation sliced through the galaxy, making the Milky Way a ‘much more dynamic place’ than was previously thought.

The Milky Way was ripped apart in an explosion caused by a gigantic flare emerging from its centre more than 3m years ago, astronomers say.

New research suggests this colossal beam of energy sprung from the heart of the galaxy and punched out into deep space before hitting the Magellanic Stream – a long trail of gas extending from nearby galaxies called the Large and Small Magellanic Cloud.

The high-energy radiation, which scientists call a Seyfert flare, created two enormous ionisation cones that sliced through the Milky Way. The researchers say their findings change the understanding of the galaxy that houses Earth.

Lisa Kewley, director of Australia’s ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), a project involving international astronomers studying the mysteries of the universe, said: “A massive blast of energy and radiation came right out of the galactic centre and into the surrounding material.

“This shows that the centre of the Milky Way is a much more dynamic place than we had previously thought.”

The team first described the evidence of this explosion in 2013, when they identified Sagittarius A* – a massive black hole at the centre of the Milky Way around 4.2m times bigger than the sun – as the cause of the explosion. Their latest work, published in the Astrophysical Journal, reinforces previous findings.

‘These results dramatically change our understanding of the Milky Way … We are the witness to the awakening of the sleeping beauty’
– MAGDA GUGLIELMO

Black holes are places where matter is compressed by gravity to a point where the normal laws of physics break down, bending and distorting space and time. By definition, they cannot be seen in the conventional sense, making them hard to study. Their presence is inferred from radiation emitted as gas and debris swirl around them.

In 1996, astronomers became aware of a strange glow radiating from the Magellanic Stream. Scientists began to hunt for a cause and Sagittarius A* became the prime suspect.

Based on a recent analysis of the data gathered by the Hubble Space Telescope, the researchers calculated the massive explosion took place 3.5m years ago. They believe the blast lasted for around 300,000 years.

Magda Guglielmo, from the University of Sydney and one of the study authors, said: “These results dramatically change our understanding of the Milky Way.

“We always thought about our galaxy as an inactive galaxy, with a not-so-bright centre. These new results instead open the possibility of a complete reinterpretation of its evolution and nature.

“The flare event that occurred 3m years ago was so powerful that it had consequences on the surrounding of our galaxy. We are the witness to the awakening of the sleeping beauty.”

– PA Media