Thursday, April 25, 2024

Asteroid hunters name space rock for Distinguished Professor Roy Kerr

A pair of University of Canterbury astronomers have named an asteroid they discovered in honour of University of Canterbury Distinguished Professor Roy Kerr.

Professor Kerr was renowned for his influential work in astrophysics resulting from his solving Einstein’s equation of relativity relating to rotating black holes – which are now called ‘Kerr Black Holes’.

Long-serving members of UC Science, Adjunct Senior Fellows of the School of Physical & Chemical Sciences Alan Gilmore and Pam Kilmartin have been observers at the University of Canterbury Mount John Observatory since 1980.

As Fellows of the Royal Astronomical Society of New Zealand, they track Near Earth Objects (NEOs) such as asteroids and comets that may be a long-term threat to Earth. Together they have discovered 41 minor planets, a comet and a nova.

“The naming of an asteroid is an honour in the way that naming a geographical feature after someone is an honour,” Gilmore says. 

The asteroid they named recently for Canterbury Distinguished Professor Roy Kerr – ‘Asteroid (5718) Roykerr’ – is around 3km in diameter. It is in the Main Belt of asteroids, averaging 2.21 AU, 332million-km distance from the Sun. It does one orbit in 3.3 years. They discovered it in August 1983 using a telescope at the University of Canterbury’s Mount John Observatory.

Together, the married astronomers have been studying the skies for more than 50 years.

From the University of Canterbury’s Mount John Observatory, near Takapō Lake Tekapo, they have produced several thousand observations and discovered more than 40 asteroids, mostly in the main belt between Mars and Jupiter.

Despite retiring in 2014, the couple still spend nights studying NEOs.

“Our near-Earth object programme contributes to the knowledge of asteroids that might in the long-term be a threat to the Earth. The work is broadly described as ‘planetary defence’. We follow-up discoveries of near-Earth asteroids that are mostly found by NASA-funded searches with telescopes in Arizona and Hawaii. Because Aotearoa New Zealand is several hours behind those places in the night, we can often ensure that new fast-moving objects are not lost,” Gilmore explains.

“Our southern location enables triangulation with the northern observatories to get a first estimate of a new object’s distance. We also observe objects that have been discovered in past years and are returning to Earth’s vicinity. As most of these objects are small – mostly tens to hundreds of metres in size – they are faint and can be seen only when they are relatively nearby.”

The naming of Distinguished Professor Kerr’s asteroid was recently announced in the Newsletter of the Royal Astronomical Society of New Zealand WGSBN Bulletin Volume 2, #8.

The naming citation reads: “Roy Patrick Kerr (b. 1934) is a New Zealand mathematician. He was awarded the 2016 Crafoord Prize, as well as many other awards, for his 1963 discovery of the solution of Einstein’s equation which exactly describes a rotating black hole. This work revolutionized both physics and astronomy.”

In 2019, international astronomers captured the first image of a black hole, heralding a revolution in our understanding of the universe’s most enigmatic objects, and proving Canterbury Distinguished Professor Kerr’s 1963 solution correct.

Professor Kerr was awarded the British Royal Society’s Hughes Medal in 1984 and the Rutherford Medal from the New Zealand Royal Society in 1993. He was made a Companion of the New Zealand Order of Merit in 2011, and was awarded the 2013 Albert Einstein medal by the Albert Einstein Society in Switzerland.

The University of Canterbury awarded the rare honour of the title Canterbury Distinguished Professor to Professor Roy Kerr who also received the prestigious Crafoord Prize in Sweden in 2016. Canterbury Distinguished Professor is the highest academic title that can be awarded by UC and has been conferred only twice before in the University’s history. Title recipients are Nobel Prize winners or equivalent, such as the Crafoord Prize.

One of the world’s foremost theoretical physicists famous for his work on black holes, Stephen Hawking, described Kerr’s discovery in his celebrated book, A Brief History of Time.

Professor Hawking wrote: “In 1963, Roy Kerr, a New Zealander, found a set of solutions of the equations of general relativity that described rotating black holes. These ‘Kerr’ black holes rotate at a constant rate, their size and shape depending only on their mass and rate of rotation. If the rotation is zero, the black hole is perfectly round and the solution is identical to the Schwarzschild solution. If the rotation is non-zero, the black hole bulges outward near its equator (just as the Earth or the Sun bulge due to their rotation), and the faster it rotates, the more it bulges. So … it was conjectured that any rotating body that collapsed to form a black hole would eventually settle down to a stationary state described by the Kerr solution. In 1970 a colleague and fellow research student of mine at Cambridge, Brandon Carter, took the first step toward proving this conjecture. He showed that, provided a stationary rotating black hole had an axis of symmetry, like a spinning top, its size and shape would depend only on its mass and rate of rotation. Then, in 1971, I proved that any stationary rotating black hole would indeed have such an axis of symmetry. Finally, in 1973, David Robinson at Kings College, London, used Carter’s and my results to show that the conjecture had been correct: such a black hole had indeed to be the Kerr solution.”

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