Complicated Cosmic Dance

Video highlights from Cosmos: Possible Worlds

First described by Einstein over a century ago, frame dragging theory is a rather complicated concept which basically suggests space is elastic. What it loosely means is when space is effected, so is time.

First described by Einstein over a century ago, frame dragging theory is a rather complicated concept which basically suggests space is elastic. What it loosely means is when space is effected, so is time.

NASA have proved the effect with satellite Gravity Probe B and physicists have attempted to explain  it by comparing the theory to a fast-flowing river and a straw floating down it. Hopefully a paper straw and not plastic but then again, a paper straw would become waterlogged and sink.

So to put it simply, let’s just say frame dragging is kind of hard to explain.

Be that as it may, frame dragging theory has just been proven by Australian radio astronomers who have uncovered further proof that the spinning and whirling of a celestial body affects space and time.

It is akin to a whisk going through a bowl of pancake batter – except the whisk is an incredibly dense object, and the batter is the very fabric of spacetime itself. A slow spinning cosmic dance.

This particular mixing bowl is a binary radio pulsar system called PSR J1141-6545 that consists of a neutron star and white dwarf.

The pulsar, which is a neutron star about the size of Sydney but 400,000 times heavier, has a ‘day’ of about half a second. It zips around its white dwarf primary (about the size of Earth but about 300,000 times more massive) approximately every five hours.

The very patient astronomers spent nearly two decades observing the pulsar and its white dwarf companion and noticed that the pair’s point of closest approach  was tumbling or shifting very, very slightly more than it should have been – by less than 2 arc seconds per year in fact.

To put you in the picture, the full Moon takes up about half a degree of arc or 30 arc minutes in the sky. There are sixty arc seconds in a degree – so less than two of those in a year – from 10,000 light years away. We are talking tiny changes here.

“It is a very subtle effect,” says Ramesh Bhat, an astrophysicist at Curtin University in Western Australia one of the co-authors of the paper published in the prestigious journal Science. 

“The rapidly spinning white dwarf drags space-time around with it, making the pulsar’s orbital plane tilt as it is dragged along. This tilting is what we observed through our patient mapping of the pulsar’s orbit,” says co-discover Matthew Bailes of Swinburne University.

The observations were made at the 50-year-old workhorse of Australian radio Astronomy, the 64m dish at Parkes – which features in the eponymous Aussie movie, The Dish.

Don't miss the return of award-winning Cosmos: Possible Worlds, World Premiere 7.30pm AEDT/NZDT on March 9, National Geographic, Foxtel, Fetch and Sky TV 

Lead Image: Artist’s depiction of ‘frame-dragging’: two spinning stars twisting space and time. Image provided by Mark Myers, OzGrav ARC Centre of Excellence.

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