Hal,

You might find that P/2010 H2 (almost the namesake of A2) to be a rewarding
object to image at very high resolution.

P/2010 H2 has some parallels with 'A2' in that the object was not known
prior to the appearance of the comet. On April 15, t brightened by >7 mags
in <14 hr and that after that time the magnitude has remained largely
constant. The main mass of material ejected has remained close to the
photocenter indicative of relatively slow expansion velocities (<20 m/s).
We may actually be witnessing (for the first time) the formation of a new
Hilda-type comet but it is not clear what the trigger mechanism was in this
particular case.

Richard Miles
BAA

----- Original Message -----
From: "hal.weaver" <hal.weaver@...>
To: <comets-ml@yahoogroups.com>
Sent: Friday, April 23, 2010 2:24 PM
Subject: [comets-ml] Re: questions about P/210 A2 (LINEAR)


I second Mike Kelley's comments about what's happening to the particulate
trail of P/A2. Note, however, that solar radiation pressure (i.e., photon
absorption and emission, not solar wind interactions) is responsible for
pushing small grains into the tail.

Hubble is continuing to follow the temporal evolution; the most recent
observations were this past Monday (4/19). The geometry is getting poorer
over time (P/A2 is farther from the Earth and the solar phase angle is
increasing), but we still clearly see the residual nucleus at the Eastern
end and some structure in the tail/trail. The Hubble observations will
continue into June, when the asteroid/comet enters the Hubble solar
avoidance zone.

Cheers,

Hal Weaver

--- In comets-ml@yahoogroups.com, Bernd Häusler <bernhard.haeusler@...>
wrote:
>
> Hi Mike,
>
> thanks a lot for your answer, that's very interesting. Now I understand,
> the
> small dust is pushed away long time ago by the solar wind and the large
> grains are remaining in the old ejection cloud.
>
> I think it's worth to observe the cloud furthermore to record the
> structure,
> before it will be invisible for a while.
> Really hope to see the structure again later in next opposition.
>
> Best Regards and clear sky
> Bernd
>
>
> -----Ursprüngliche Nachricht-----
> Von: comets-ml@yahoogroups.com [mailto:comets-ml@yahoogroups.com] Im
> Auftrag
> von Michael S Kelley
> Gesendet: Mittwoch, 21. April 2010 17:00 in Rimpar
> An: comets-ml@yahoogroups.com
> Betreff: Re: [comets-ml] questions about P/210 A2 (LINEAR)
>
> Hi Bernhard,
>
> That the position angle and size are roughly consistent over many months
> suggests the dust is primarily composed of large grains. By large I
> mean roughly millimeter sized, maybe larger. The dust grains are moving
> together in very similar orbits around the Sun. The bright end of the
> "comet" may be explained with a cloud of grains that are even larger
> than the tail grains. Typically larger grains have lower ejection
> velocities. Thus they haven't drifted as far from the parent asteroid
> as have the smaller tail dust grains. Also, millimeter and centimeter
> sized dust are not strongly influenced by radiation pressure, so the
> direction of the Sun is less important than the ejection velocities.
> I'm not sure if this will explain the position angle of the tail, but it
> is something we can look into.
>
> In contrast, the small dust typical of comet tails have large ejection
> velocities and are greatly affected by solar radiation pressure,
> therefore they quickly leave the vicinity of the parent nucleus. The
> tiny dust ejected in the collision/comet activity is long gone.
>
> Cheers,
> Mike Kelley
>
> --
> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> Dr. Michael S Kelley
> Department of Astronomy
> University of Maryland
> College Park, MD 20742-2421
> Office phone: 301-405-3796
>
> On 4/20/2010 2:48 PM, Bernd Häusler wrote:
> >
> >
> > Hello,
> >
> > since January 2010 I observe P/2010 A2 (LINEAR) on eight nights
> > meanwhile.
> > The results of the measurements as follows:
> >
> > Date mag (10x10 box) "tail" PA SN.ang.
> > ----------------------------------------------------------
> > 2010-01-13 17.58 1'48" 280 308
> > 2010-02-07 2'41" 278 280
> > 2010-03-04 19.70 42" 278 276
> > 2010-03-06 19.10 1'37" 278 276
> > 2010-03-11 19.33 37" 280 276
> > 2010-04-01 19.69 1'03" 286 277
> > 2010-04-07 19.90 47" 290 278
> > 2010-04-17 18.34 43" 288 279
> >
> > The measurement are influenced from different sky conditions, off
> > course.
> > But generally I can say, that the structure is very constant since three
> > months of observing.
> >
> > So I have some questions now:
> >
> > 1. If the object is the result of an asteroid collision, which forces
> > are
> > holding the structure so constant?
> > 2. From beginning on, the brightest part of the structure is situated on
> the
> > Eastern part. The "tail" has a direction roughly to the Sun (SN.ang.
> > from
> > Horizons). Is this coincidental?
> > 3. Has anybody new informations of the development of the structure,
> perhaps
> > from bigger observatories than mine?
> >
> > For any answer I would be very happy.
> > Here are the corresponding informations from my web with images and
> > animations:
> >
> > http://www.amication.de/Bernhards_Comet_Project/p2010a2.htm
>
> > <http://www.amication.de/Bernhards_Comet_Project/p2010a2.htm>
> >
> > Thanks and clear skies
> > Bernhard Haeusler
> > B82 Maidbronn
> >
> >
>
>
> ------------------------------------
>
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