U of A researcher makes stellar discovery
Elise Stolte, edmontonjournal.com
Published: Wednesday, November 04, 2009
EDMONTON - NIGHT SKY-GAZING
Meet Craig Heinke
When: Thursdays, 7-8 p.m.
Where: Roof-top observatory, U of A fine arts building
A University of Alberta professor is being credited with discovering the youngest neutron star yet known, the dense remnant of a supernova seen by an English astronomer in 1680.
The discovery gives scientists access to the complete life cycle of supernovae, exploding stars that scientists believe are responsible for creating the metals and elements essential to life on Earth today.
Craig Heinke and his University of Southampton research partner Wynn Ho studied a supernova at the centre of the Cassiopeia constellation, with images taken from the Chandra X-ray observatory, one of NASA's telescopes mounted on a satellite orbiting the Earth. Their findings were published in the international weekly journal Nature on Wednesday.
Although the neutron star produces a faint light, it can't be seen with a human eye because the light gets overwhelmed by surrounding stars. Instead, the orbiting observatory takes pictures using the star's X-ray radiation.
In those images, the neutron star can be seen as a tiny dot of light that doesn't change, year after year, as the rest of the gases in the supernova are hurled out into space around it.
Other scientists first spotted the point of light in 1999. They thought it was probably a neutron star and tested the frequencies of wavelength in the X-rays given off, but the models kept coming back with errors.
A neutron star should be between 22 and 28 kilometres across. Their models kept coming back as nine kilometres.
Heinke and Ho identified the problem. The other scientists were assuming the star was surrounded by either helium or hydrogen, like the sun in our solar system.
Those elements are so light, if they are present anywhere around they should be floating at the top and should be the only elements seen on a dense, spinning sphere.
Heinke and Ho ran the same equations, but assumed the dense interior of the star was surrounded by a light coating of carbon.
Suddenly, all the numbers fit. The new neutron star is so hot, Heinke says, the hydrogen and helium burn off and disappear. For Heinke and Ho, it was an "ah-ha" moment.
"It's not going to cure cancer or anything, but for intellectual interest ..." Heinke trails off, but it's clear on his face the find is pretty exciting. "We've never seen that on the surface of a neutron star," he says. "They're such exotic objects, so mysterious."
Heinke was in Grade 1 when he first fell in love with space, black holes and neutron stars. He left his former love, paleontology, and decided to be an astrophysicist, and says he never wavered.
He studies neutron stars because their density fascinates him. A new neutron star is born about every 50 to 100 years, he says. It's what's left after a large star dies and collapses in on itself, then explodes sending most of its mass billowing out like a cloud out into space.
The small, dense core left over is the neutron star. If you took the Earth and squished it into a block the size of a sugar cube, that's how dense that core would be.
Carl Sagan, one of Heinke's childhood heroes, coined the phrase that describes the importance of such star explosions, when he said on the Cosmos TV series: "We are star stuff."
In Big Bang theories, the early universe had only stars. It wasn't until those first generation stars exploded into supernovae that carbon, iron and other heavier elements were created. That's when planets could start forming. Studying neutron stars, and especially young stars, helps scientists understand that process.
Heinke, 33, grew up in Oregon and came to the University of Alberta about a year ago. He lives in downtown Edmonton with his wife, a chaplain at the Royal Alexandra Hospital. Heinke sometimes attends a unitarian church, he says, but sees his faith and astronomy as quite separate and takes a secular approach.
Even though you can't see Heinke's neutron star, you can see the Cassiopeia constellation. Find the Big Dipper, follow the line of the two stars that form the lip of the cup straight to the North Star, then keep going about the same distance again. That's Cassiopeia, about 11,000 light years away.
English astronomer John Flamsteed recorded the supernova explosion in 1680 when he was mapping the Cassiopeia star cluster. But he likely didn't know it. He saw a bright light and marked an extra star in his map where early and later maps show nothing. The supernova Heinke and Ho are studying would likely have been visible that year for several months.
estolte@thejournal.canwest.com
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