Friday, October 26, 2007

17P/Holmes - Naked eye comet

Session name: 20071025.2105

A photograph of comet 17P/Holmes where a bright central nucleus outshines the surrounding ionized gases, the coma. The nucleus and the coma form the head of a comet. This comet lacks any tail.

Observed the bright 17P/Holmes, my guesstimate is magnitude 2.3 ~ 2.5. It is less bright than Mirfak, brighter than delta Per, cheating towards Mirfak. Comparing to the few other brighter stars that beat the clouds, only Mirfak and Capella were brighter. So bright it shone through the cirrus and cirrostratus clouds. With naked eye, the comet's size is visibly greater than nearby stars though no tail observed. In 7x50 binoculars it is obvious in brightness and dimension. In 22x60 binoculars, the nucleus resolves clearly off center from a round coma.

Effect pronounced because of the clouds?

Discovered in 1892, Comet Holmes takes 7.3 years to revolve about the Sun. No one can say for certain how long this brightness will last - a few days, weeks, or months. Either way get out soon and take it in as early as possible.

What makes it glow so brightly? Most likely cause is the result of an eruption, heated gases from within escaping violently through the comet's crust. Think in terms of volcano, common activity with Solar System objects. A comet's crust and surface consist of loose accumulation of ice and rock so it becomes susceptible as it approaches the Sun and heats. When the gases expire or cool down the volcanic-like activity ceases and the comet goes on its merry way.

The session was not without frustration. I chose to observe from Artists' Gate, the south Central park entrance used to refer to as The Statues. I really couldn't find a spot without interference from the street lamps and I didn't want to venture too far into the park in this area alone. Many places are off the beaten path. I ended up on the rock smaller in stature than Drip Rock. I left the SD card of one camera in the computer at home and the other camera simply misbehaved with the dreaded remote control. In the end I was able to capture a few photos and scratch a sketch or two.

A young guy, Jesus, who drives the Hansom Cab driver, stopped by. He reminded me that we've met before and that he hadn't picked up a scope yet. He asked some questions about the wonders of the sky. With naked eye and mounted Tak bins, we observed 17P/Holmes, rising Mars, and the Moon. We spoke of how rising stars appear to twinkle with rainbow effect as we look through more atmosphere due to our our angle. Castor was a shining example.

View of the sky from a tucked away spot on the rock inside of Artists' Gate. The sky improved and was clear for a period of time but the cameras were not cooperative. Naked eye limiting magnitude from this area under these conditions was around magnitude 3.5

Skychart of area around alpha Perseus and the Fishhook.

Marked up version of skychart of area around alpha Perseus and the Fishhook.

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