Astronomers using images from the the Swift satellite taken over the past two months have taken a closer look at comet ISON, which many are predicting to the one of the best and brightest comet ever.
ISON will be visible in the western sky later this year on its trek around the sun.
The Swift satellite images were take with the craft’s Ultraviolet/Optical Telescope (UVOT).
Swift’s mission isn’t to hunt and observe comets however. The craft was designed to aid in the detection of Gamma-ray bursts. These bursts are the most powerful explosions in the Universe and occur about once per day. Scientist are using the data from Swift to help the find out what causes them. You can follow Swift using apps on your smartphone, or look at real-time Gamma-ray bursts here.
It is interesting how images from a craft designed for a completely different purpose can help further our understand of objects like ISON. Using data from Swift, scientists have determined that the comet’s water, dust production and the size of its nucleus make ISON one of the “dirty snowball” type comets.
“Dirty snowballs” are comets that emit gas and dust as they pass near enough to the sun so that the ice sublimates (the transition of a substance directly from the solid phase to the gas phase without passing through an intermediate liquid phase). In other words “poof” your a gas. The dust or other particles clumped together with the solid material shoot out away from the sun’s heat. The tail of a comet is the reflection of sun light off the dust and vapor. So the more vapor and dust the better the show.
Data from Swift revealed that ISON is losing about 112,000 pounds (51,000 kg) of dust, or about two-thirds the mass of an unfueled space shuttle, every minute. The data also showed that ISON was shedding about 130 pounds (60 kg) of water every minute, or about four times the amount flowing out of a residential sprinkler system.
These facts led scientist to state that: “[t]he mismatch we detect between the amount of dust and water produced tells us that ISON’s water sublimation is not yet powering its jets because the comet is still too far from the sun. Other more volatile materials, such as carbon dioxide or carbon monoxide ice, evaporate at greater distances and are now fueling ISON’s activity.”
Comparing the amount of gas needed for a normal comet to blow off dust at the rate observed for ISON, the scientists estimate that the nucleus is roughly 3 miles (5 km) across, a typical size for a comet.
Based on orbital calculations, astronomers think this is ISON’s first-ever trip through the inner solar system. Before beginning its long fall toward the sun, the comet resided in the Oort cloud, a vast shell of perhaps a trillion icy bodies that extends from the outer reaches of the planetary system to about a third of the distance to the star nearest the sun.
I just hope it is better than Pan-STARRS 😦
– Ex astris, scientia –
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