Sungrazing comets question

[Josh Wilson]

From what I can tell, in all the pictures in S&T magazines, Comet ISON is supposed to go around the sun and "graze the sun", hence the term "sungrazer". They appear to go around the Sun opposite of us and swing around and get flung back in to the cold depths of space. Say a comet is a sungrazer but it's going to get flung around to where its tail will cross paths with Earth. Will it be visible crossing the Sun's surface with a filter? What would it look like if even possible? If there is such an event, I'd love to know when so I can mark my calender!

Josh

[Dave]

Hi Josh,

The comets that will be visible later this year do not transit directly across the Sun's face, so they will not be visible when they "graze" the Sun.

Apparently Halley's Comet passed directly in front of the Sun in 1910. However, despite many professional observatories attempting to view it, Halley's nucleus was far too small to be resolved at that distance. The Earth also went through Halley's tail during that apparition as well.

Dave

[Cath]

[michael.h.f.wilkinson]

The core of a comet is at most a few tens of km across. If it passes between us and the sun at say 0.5 AU, its angular size would be 0.03 arcsec across (assuming a 10km nucleus). Even the Hubble cannot resolve that (0.1 arsec, but not 0.03 arcsec). If the comet passes closer to the sun, matters get worse.

[Josh Wilson]

The core of a comet is at most a few tens of km across. If it passes between us and the sun at say 0.5 AU, its angular size would be 0.03 arcsec across (assuming a 10km nucleus). Even the Hubble cannot resolve that (0.1 arsec, but not 0.03 arcsec). If the comet passes closer to the sun, matters get worse.

Well that's quite depressing... In the video that Cath posted, thanks for that btw, The orbit was exactly as I described (opposite us and will appear to transit the sun) and I thought I might actually get to observe it. . Even if the Hubble could resolve it at that close a distance, the ONLY thing that they didn't put on the HST was a solar filter.