- By Pallab Ghosh
- Science correspondent
Scientists have captured shock waves from the orbit of supermassive black holes at the center of distant galaxies as they begin to merge.
This may be the first direct evidence of giant black holes destroying space and time as they orbit each other.
The theory is that this is how galaxies grow. Now, astronomers will soon be able to watch what happened.
These distortions are happening all the time, throughout the Universe.
One of the discovery groups is the European Pulsar Timing Array Consortium (EPTA), led by Prof Michael Kramer of the Max Planck Institute for Radio Astronomy in Bonn.
He told BBC News that the discovery has the potential to change astronomers’ ideas about the cosmos forever.
“It could tell us if Einstein’s theory of gravity was wrong; it could tell us what dark matter and dark energy, the mysterious stuff that makes up most of the Universe, really are; and it could give us a new window into new. theories of physics.”
Further study may provide new insights into the role supermassive black holes play in the evolution of all galaxies.
Dr Rebecca Bowler, of Manchester University, told BBC News that researchers believe there are supermassive black holes at the center of all galaxies and that they are growing over billions of years. But for now everything has been theoretical.
“We know that massive black holes exist, we just don’t know how they got there. One possibility is that smaller black holes have merged, but there is little observational evidence for this.
“But with these new observations we can see such a merger for the first time. And it will tell us directly how the most massive black holes form,” he said.
The observations were made by studying signals from dead stars called pulsars. They rotate and send out bursts of radio signals at extremely precise intervals.
But the researchers, who include astronomers from the Lovell Telescope at Jodrell Bank in Cheshire and from Birmingham University, have found that these signals reach Earth slightly faster or slower than they should. And they say that the distortion of time is consistent with the gravitational waves created by the merging of supermassive black holes throughout the Universe.
Dr Stanislav Babak from Laboratory APC at CNRS, France, said that gravitational waves carry information about “some of the Universe’s best-kept secrets”.
The newly discovered gravitational waves are different from those seen until now. Those early waves were caused by smaller, star-sized black holes collapsing into each other.
The type described in the latest research are thought to be from black holes hundreds of millions of times larger, spinning around each other as they approach.
Their gravitational upheaval is so powerful that it destroys time and space – a process that can continue for billions of years until the supermassive black holes finally merge.
Gravitational waves detected by scientists before can be considered short-lived hums, while the new ones are more like the background hum that surrounds us all the time.
Their next step is to take more readings and combine the observations. As further progress is made, another goal is to discover individual pairs of supermassive black holes – assuming they are the source.
It’s possible that gravitational waves could also be the cause of other exciting phenomena, such as the very first black hole ever created, or strange structures called cosmic strings, both of which can be thought of as the seeds from which the Universe grew.
What are gravitational waves?
Gravity is a constant force in our daily lives. If you drop a cup, it falls and breaks on the ground every time you do it. But in space gravity will not remain the same. This can change if there is a sudden and catastrophic event – such as the collision of black holes.
The event was so pervasive that space and time itself were disrupted and ripples were sent throughout the Universe – just as happens when a pebble falls into a lake.
In the case of gravitational waves, everything in the Universe – the stars, planets and even us – is water. Everything gets squeezed and stretched and then squeezed and compressed slightly as the waves pass us. And like in a lake, the ripples quickly diminish and disappear.
Gravitational waves from merging star-sized black holes were detected directly for the first time in 2015. A highly sensitive laser system measured the ripples produced in the final moments before the collision.
For the type of ripples that come from a pulsating supermassive black hole, the pulsar approach captures ripples produced billions of years before the final merger.
It is like a steady stream of pebbles thrown into a lake. And since mergers occur throughout the galaxy, the signal can be seen as a cacophony.
EPTA combined the results with a consortium in India (InPTA) and published their study results in the journal Astronomy and Astrophysics.
Three other separate, competing research groups, from North America (NANOGrav), Australia (PPTA) and China (CPTA), published similar assessments, causing great excitement throughout the physics and astronomy community .
Scientists must first confirm their observations. None of the research teams had data that passed the gold standard of less than a one in a million chance of error, which is usually required for definitive proof – even when combined, the results of the different teams were certainly compelling.
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