Forget the hype about the film Pearl Harbor. This summer's biggest blast could well be a first-of-its-kind movie featuring a neutron star. An international team this week released unique footage of Scorpius X-1 gobbling gas from a companion star and then spitting out gigantic blobs like so many watermelon seeds. The new flick should help astronomers understand the narrow jets formed by neutron stars and black holes in our galaxy and beyond.
The jets have turned up everywhere in the past decade, from nearby neutron stars to black holes in distant galaxies. Seen up close, the seemingly smooth jets break up into a hail of plasma gunfire that races down the length of the jet at nearly the speed of light. Astronomers believe the trigger is pulled when hot gas reaches a tremendous pressure inside the star or black hole. If they are right, a burst of x-rays from near the star should precede each new blob like the muzzle flash of a gun barrel.
But testing the idea is difficult. Blobs cool rapidly and become invisible to x-ray telescopes; it takes many optical and radio telescopes working together around the globe to follow them down the jet. Coordinating such an operation is a logistical and political nightmare that had prevented any team from watching the birth and evolution of a single blob--until now.
For 56 hours in June 1999, Scorpius X-1 was continuously observed by a worldwide network of radio telescopes, called the Very Long Baseline Array (VLBA), and by additional radio telescopes in Australia, China, Japan, and South Africa. Two optical observatories and the orbiting Rossi X-ray Timing Explorer also tuned in.
The stellar movie--described in a paper published in the 20 May issue of Astrophysical Journal Letters--reveals the predicted x-ray flash, followed by two pairs of blobs exploding in opposite directions at 95% of the speed of light. After a few hours, the blobs catch up with cooler material left over from previous eruptions. Soon another blob takes off. "This is the first time anyone has ever watched the whole cycle," says lead author Ed Fomalont, an astronomer at the National Radio Astronomy Observatory in Socorro, New Mexico.
"This is what the VLBA was set up to do, and by combining it with x-ray and optical observations they have pushed it to the max," says astrophysicist Roger Blandford of the California Institute of Technology in Pasadena. The next step is to figure out what causes the explosions.
The full-length movie; site includes a "guided tour" version