[meteorite-list] Jan. 16 May Be Last Best Chance to Search for Comet ISON's Remains

[Ron Baalke]

http://www.universetoday.com/107542/jan-16-may-be-last-best-chance-to-search-for-comet-isons-remains/

Jan. 16 May Be Last Best Chance to Search for Comet ISON's Remains
by Bob King 
Universe Today
December 30, 2013

[Graphic]
Comet ISON revolves around the sun in steeply inclined orbit. Earth will 
pass through the plane of that orbit on Jan. 16. As we look "up" toward 
the comet, ISON's dust stacks up along our line of sight and could appear 
temporarily brighter. Credit: solarsystemscope.com with annotations and 
additions by Bob King

Is there any hope of detecting what's left of Comet ISON after the sun 
proved too much for its delicate constitution? German amateur astronomer 
Uwe Pilz suggest there remains a possibility that a photographic search 
might turn up a vestige of the comet when Earth crosses its orbital plane 
on January 16, 2014.

On and around that date, we'll be staring straight across the sheet of 
debris left in the comet's path. Whatever bits of dust and grit it left 
behind will be "visually compressed" and perhaps detectable in time exposure 
photos using wide-field telescopes. To understand why ISON would appear 
brighter, consider the bright band of the Milky Way. It stands apart from 
the helter-skelter scatter of stars for the same reason; when we look 
in its direction, we peer into the galaxy's flattened disk where the stars 
are most concentrated. They stack up to create a brighter band slicing 
across the sky. Similarly, dust shed by Comet ISON will be "stacked up" 
from Earth's perspective on the 16th.

This isn't the first time a comet has leapt in brightness at an orbital 
plane crossing. You might recall that Comet C/2011 L4 PanSTARRS temporarily 
brightened and assumed a striking linear shape when Earth passed through 
its orbital plane on May 27.

Pilz, a longtime contributor to the online Comets Mailing List for dedicated 
comet observers, has made a series of simulations of Comet ISON for mid-January 
using his own comet tail program. He bases his calculations on presumed 
larger particle sizes 1 mm-10 mm - not the more common 0.3-10 micrometer 
fragments normally shed by comets. The assumption here is that ISON has 
remained virtually invisible since perihelion because it broke up into 
a smaller number of larger-than-usual pieces that don't reflect light 
nearly as efficiently as larger amounts of smaller dust particles.

The images look bizarre at first glance but totally make sense given the 
unique perspective. Notice that the debris stream becomes thinner as we 
approach orbital crossing; any potential dust blobs appear exactly edge-on 
similar to the way Saturn's rings narrow to a "line" when Earth passes 
through the ring plane.

Besides the fact that not a single Earth-bound telescope has succeeded 
to date in photographing any of ISON's debris, amateurs who attempt to 
fire one last volley the comet's way will face one additional barrier 
- the moon. A full moon the same day as orbital crossing will make a difficult 
task that much more challenging. Digital photography can get around moonlight 
in many circumstances, but when it comes to the faintest of the faint, 
the last thing you want in your sky is the high-riding January moon. One 
night past full, a narrow window of darkness opens up and widens with 
each passing night.

Will anyone take up the challenge?

UPDATE Dec. 30 10 a.m. (CST):  We may have our very first photo of Comet 
ISON from the ground! Astrophotographer Hisayoshi Kato made a deep image 
of the comet's location in Draco on December 29 using a 180mm f/2.8 telephoto 
lens near the Mauna Loa Observatory in Hawaii at 11,000 feet. He stacked 
5 exposures totaling 110 minutes to record what could be the ISON's debris 
cloud. It's incredibly diffuse and faint and about the same brightness 
as the Integrated Flux Nebula, dust clouds threading the galaxy that glow 
not by the light of a nearby star(s) but instead from the integrated flux 
of all the stars in the Milky Way. We're talking as dim as it gets. What 
the photo recorded is only a tentative identification -  followup observations 
are planned to confirm whether the object is real or an artifact from 
image processing.  Stay tuned.


[Image]
The sausage-like glow running from upper left to lower right in this negative 
image may the dusty remains of Comet ISON as photographed on Dec. 29 from 
Hawaii. The blue dot shows the predicted position of the comet; the green 
type gives the names of stars. Click to enlarge. Credit: Hisayoshi Kato