"Men occasionally stumble over the truth, but most of them pick themselves up and hurry off as if nothing had happened." -- Sir Winston Churchill
NASA's Swift Looks To Comets For A Cool View.
ScienceDaily (Dec. 3, 2008) — NASA's Swift Gamma-ray Explorer satellite rocketed into space in 2004 on a mission to study some of the highest-energy events in the universe. The spacecraft has detected more than 380 gamma-ray bursts, fleeting flares that likely signal the birth of a black hole in the distant universe. In that time, Swift also has observed 80 exploding stars and studied six comets.Comets are dirty snowballs? I wonder why they haven't melted in the sun during the past million years. It looks more like a unicorn than a snowball.
Comets? ... Comets are "dirty snowballs" made of frozen gases mixed with dust.
X-rays come from superhot plasmas.Eureka!!!
What do cold comets have in common with exploding stars or the birth of black holes?Good question. I suspect either plasma or else absolutely nothing.
"It was a big surprise in 1996 when the NASA-European ROSAT mission showed that comet Hyakutake was emitting X-rays," says Dennis Bodewits, a NASA Postdoctural Fellow at the Goddard Space Flight Center in Greenbelt, Md. "After that discovery, astronomers searched through ROSAT archives. It turns out that most comets emit X-rays when they come within about three times Earth's distance from the sun."Hmmm, they emit x-rays but they don't melt. Sounds like the snowballs I know. A database full of comets observed and every time they emit x-rays it's a surprise? When will it stop being a surprise?
Bodewits is working with the Swift team at NASA's Goddard Space Flight Center in Greenbelt, Md., to study comets using data from the spacecraft's Ultraviolet/Optical Telescope (UVOT) and X-Ray Telescope (XRT). "Swift is an excellent platform for studying dynamic processes in comets," he says.Plasma? What's that all about? Ah nevermind, just forget it. Let's talk about gravity some more.
Ultraviolet wavelengths let astronomers identify the chemical composition of the comet's atmosphere, observe the structure of dust emission, and identify the rotation of the comet's icy nucleus. X-rays reveal the structure of the comet's gas and the state of the solar wind, a stream of charged particles that flows from the sun at speeds upwards of 900,000 mph.
Swift's UVOT captured a striking sequence that shows unresolved blobs of dust trailing from a crumbling comet.Dust or plasma? Must be dust.