Pear Tree Observatory

Comet 67P/Churyumov-Gerasimenko holds the distinction of being the first comet to be orbited by a spacecraft as well as the first to have a probe soft land on its surface. After a 10 year trip the Rosetta spacecraft entered orbit and on November 12, 2014 dropped its lander (Philae) on to the nucleus. The primary purpose of the mission was to characterize the comet and its behaviour during its perihelion passage on 13 August 2015. The comet, with its attendants, is now heading back out into deep space and will return to visit the inner solar system in 2023.

This image is a stack of fifteen 120 second exposures with the images registered to the comet. The image is very noisy as the Moon was very close and there was some faint wispy clouds overhead.
 

FYI, the comet symbol on the chart is not an indicator of the tail orientation. Also, notice the obvious difference between the comet’s predicted position in the chart versus the actual position in the image stack.

No doubt, you will hear a lot about this comet in the coming year.  Although the press is incorrectly using ISON as it’s name, the designation is only to identify the location of the discovery organization.  The official  ‘name’  is C/2012 S1.  If it was named, it would be Comet Nevski-Novichonok, after its discoverers. But whatever you call it, this comet has the potential to be the brightest comet that anyone alive has ever seen.  The operative word is POTENTIAL.  Forecasting the brightness of comets is notoriously difficult.  Remember the 1973 Comet Kohoutek or the more recent Comet Elenin?

Here is what astronomers know:

• The comet will come very close to the sun.  Perihelion on the 28th of November has the comet coming as close as 680,000 miles above the surface of the sun.  Close to the sun means more energy to form a tail or it means enough energy to destroy the comet.
• The comet will come fairly close to the Earth.  Perigee on the 26th of December has the comet coming as close as 39,000,000 miles from the Earth.
• The currently calculated orbit is parabolic implying this is an Oort cloud comet on it’s first pass through the solar system.  If true, this means the comet may have a lot of volatile components to form a long, bright tail.  It also means there is no way to predict if the comet is strong enough to survive the pass.

 

These images were taken on the 3rd of January and I measured the brightness at a 16.7 magnitude. As usual, North is to the right and East is up. The comet shows a East to West motion.

At the time the comet was above the ecliptic, outside the orbit of Jupiter, and on the same side of the Sun as the Earth. It will not drop below the ecliptic until November when it is still inbound and between the orbits of Earth and Venus.

Discovered by Robert McNaught on May 20, 2005, this comet’s 7.1 year period brought it back to a September 12th perihelion.  The comet is now outbound, about to cross the orbit of Mars and viewable in the constellation Andromeda.

This image was taken on the evening of September 13th.  It is a stack of 45 sixty second exposures all aligned to the comet.  This is one of the few images of comets that I have taken that shows some structure in the tail.