Saturday, October 01, 2005

Way Too Cool: Tales of Stellar Corpses

I went to the second lecture of the Cosmic Frontiers series at the University of Toronto's Convocation Hall, last night. The Cosmic Frontier series of lectures are to celebrate 100 years of Astronomy at the University of Toronto, and there are two more lectures left of the series. Last night's speaker was David Helfand of Columbia University, and he spoke, more or less, for the general audience, although a casual acquaintance of Astronomy and Astrophysics wouldn't hurt to get the most from his talk. His talk focused on our current understanding of neutron stars, and how they are acting as a bridge between the world at the cosmic scale, where gravity holds sway, and the world of the quantum, where the bizarre occurs. The abstract of his lecture summarizes the lecture quite well:

On an early August evening in 1181 AD, Chinese astrologers were shocked to find a brilliant new star in the sky, outshining all the others. They recorded it as a "sign of ill-omen". Modern astronomers, studying the site of this apparition are considerably more sanguine. The explosion witnessed by the Chinese has left behind a dense, spinning neutron star whose temperature may hold the key to understanding the atomic nucleus. The lecture will show how observing this stellar corpse 10,000 light years away reveals new insights into that structure of matter at its smallest scale.

The photograph of Professor Helfand used to promote this lecture is one from his younger days -- in it, the long hair, bearded astronomer, is standing in front of blackboard, that has an image of a supernova inserted on it. In the black and white program, the photo looks for all the world, like Jesus, with a halo of light behind him. Professor Helfand turned out to be an older version of the young man in that photo. His hair is white -- he's partially bald, with his hair drawn back in a ponytail -- and he's put on a little weight -- chubby, not fat. He has transitioned from what may have been a revolutionary Jesus, to a grandfatherly Santa Claus, who loves to tell stories. Don't get me wrong, Helfand is still quite active in his field. He's an animated, engaging speaker -- witty and quite quick on his feet. He was a pleasure to listen to, as he was to observe.

Way Too Cool. Helfand began by putting his area of study in context -- both in a historical sense, and in the grander subject of Astronomy and Astrophysics. One very effective way of demonstrating the need to look at the universe in more than just the visible spectrum, is to relate it to sound. We can't see what we can't see without the aid of technology. With technology, we've been able to peer into the wider spectrum, from gamma rays to radio. Imagine if the 10 octaves we can hear, represented the entire spectrum, then slowly take away octaves to leave only what we can see within the visible range -- Beethoven's Ninth Symphony [Quicktime] would sound quite different.

Tales of Stellar Corpses. Helfand uses radio and x-rays to peer into the universe. He observes neutron stars -- the remnants of stars that have gone supernova. Neutron stars are made up neutrons -- the nucleus of atoms -- that are densely packed. Typically, you will find the mass of 1.5 of our Sun, locked up in a star with a radius 60,000 times smaller than the Sun's. Something so extreme, exhibits some extreme behaviour. Neutron stars rotate -- or spin -- at extreme velocities -- several times a second; and have intense magnetic fields -- 10 million times stronger than that of the Earth. Since they are entirely made up of neutrons, they are analogous to atoms -- a macro analogy for the micro. Within neutron stars, conditions are so extreme, that it is believed that neutrons breakdown to their constituent quarks. Imagine a plasma of quarks roiling in the depths of a neutron star, unable to escape. It's like having the results of a collisions in a particle accelerator trapped for eternity. Too bad be can't study them directly. Neutron stars degenerated from normal stars -- and from there, continues to degenerate, losing energy and cooling -- leaving just a lifeless hulk of material.

Helfand quipped that this process, from the universe beginning in the big bang, forming fundamental particles, then atoms of hydrogen and helium, to galaxies, stars, etc., which eventually die, collapsing and going back to the grave as fundamental particles, is kinda like undergrads: they come in as slimeballs, and undergo this process by which they gain a level of enlightenment, and by the time they leave, they sometimes return back to being slimeballs. He further commented on historical Astronomy. In ancient times, the rest of the world looked up, saw the night sky, and noticed things happening: from the Asians to the American Natives. They recorded what they saw. The Europeans on the other hand, were in denial. The heavens were static and unchanging -- and if they saw something happening, they refused to recognize it. So tight was the grip that the church had on European society. It truly was the dark ages. This Helfand commented, isn't much different from America today, where it seems like intellectual thought is being be suppressed.

Keeping his audience engaged was not a problem. Helfand injected timely, and smart humour throughout his talk. Quite enjoyable. So far, the Cosmic Frontier series have had two great lectures. There are two more to go, and if this is a trend, I'm definitely looking forward to the others.

For related reading, check out:
  • Magnetic Fields of Neutron Stars: an Overview [PDF] -- Andreas Reisenegger

  • Experimental signatures of gravitational wave bursters [PDF] -- Florian Dubath, Stefano Foffa, Maria Alice Gasparini, Michele Maggiore, Riccardo Sturani

  • Neutron star crust matter [PDF] -- Nicolas Chamel

  • Recent Progress In Neutron Star Theory -- Henning Heiselberg, Vijay Pandharipande

  • Gravitational Wave Astronomy: A Facilities Overview [PDF] -- Barry C. Barish

  • Strange Quark Matter in Stars: A General Overview [PDF] -- J. Schaffner-Bielich

  • Neutron Stars [PDF] -- Gordon Baym, Frederick K. Lamb

  • Neutron Stars and X-Ray Binaries -- Images from the Chandra X-Ray Observatory

  • X-ray Wide Field View, Crab Nebula
    X-Ray Wide Field View of the Crab Nebula. [Chandra X-Ray Observatory]

    1 comment:

    1. The presentation from this lecture is now available online -- click here! [PDF]


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