Third Gravitational Wave Detected

From the ABC:

Third gravitational wave detection puts new spin on black holes

For the third time, physicists have detected a gravitational wave: a tiny ripple in the fabric of space-time.

Like the two previous detections, it comes from two colliding black holes, but this pair is much further away and may have been spinning in different directions.

Key points

  • Third confirmed gravitational wave detected on January 4, 2017
  • Wave produced by two black holes 3 billion light-years away — twice the distance of previous discoveries
  • Search is now on to find gravitational waves from other sources

The discovery, reported today in the journal Physical Review Letters, has important implications for our understanding of black holes, dark matter and the early Universe.

It was made on January 4 this year, when an international research team picked up the infinitesimal wobble produced by two black holes, 3 billion light-years away, spiralling towards each other and eventually merging to form a bigger black hole 50 times the mass of the Sun.

Study co-author Professor Susan Scott said the signal offered fresh and intriguing insights.

“The black holes are not necessarily lined up,” said Professor Scott, of the Australian National University, one of several Australian universities involved in the research.

In a binary system like this, the two black holes each rotate on their own axis, as well as circling each other in space.

According to Professor Scott, the new findings offer the first evidence that those individual spins might not always be aligned.

She said the discovery was “a very significant advancement” because it provided some insight into how double black hole systems evolved.

“It’s also interesting because black holes of the types of masses that we’ve found could actually be black holes from the very early Universe and contribute significantly to the dark matter in the Universe,” she said.

The gravitational wave was detected using the LIGO observatories 3,000 kilometres apart in Livingston, Louisiana and Hanford, Washington.

Each instrument uses laser beams to constantly measure the lengths of two perpendicular 4km pipes, with stunning accuracy; tiny, fleeting changes in length can reveal a passing gravitational wave.

In 2015 the same 1,000-strong team of scientists detected gravitational waves from black holes 1.3 billion and 1.4 billion light-years away. Those historic discoveries were confirmed and reported in 2016.

At 3 billion light-years, the new discovery is more than twice as distant.

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