As recorded in amateur
CCDs
Juan Lacruz, sep 2003
(Español)
The outburst of August 2003. 1
Useful information about 29/P. 6
Discovered on January
17th 1929 by Schwassmann
and Wachmann at Hamburg at magnitude 11, but rapidly faded to magnitude 16.
Later on, observations were pre-discovered of the comet at outburst to magnitude
12 in 1902.
Has been seen at 6
returns to perihelion (1908, 1925, 1941, 1957, 1974 & 1989) but, in reality,
its almost circular orbit - eccentricity 0.045 - means that its distance from
the Sun hardly varies. The comet has a perihelion distance of 5.77AU and a
period of 14.9 years; thus its orbit is almost circular outside that of Jupiter.
However, both the eccentricity and the period have decreased steadily over the
last century, the period from 16.44 years and the eccentricity from 0.15.
Studies of the light
curve over the years have shown that outbursts of the kind observed at discovery
are common. It occurs at least once a year, despite the fact that the comet is
at a heliocentric distance where most objects are inactive or barely active. The
magnitude is about 17 in quiescence, but has risen to 9.4 in the largest known
outburst. The mechanism of the outbursts is unknown, but their pattern is fairly
consistent with the formation of an intense stellar nucleus and a rise in
brightness over a few hours or days. The coma expands and forms spiral jets,
before fading slowly. The mechanism of the outbursts is currently
unknown.
This outburst was first
notified to Observadores_cometas
list by Ramón Naves on August 23rd 2003 and then notified to comets-ml list
by Diego Rodriguez on August 25th 2003 :
Hello.
29P in outburst on August 24.050 at
12.9 mag with well defined nucleus and spiral structure within
coma.
29P/Schwassmann-Wachmann 1
0029P C2003 08 24.05046 22 36 18.12
-03 34 40.0 12.9 N 213
0029P C2003 08 24.05153 22 36 18.10
-03 34 40.1 12.9 N 213
0029P C2003 08 24.96788 22 35 53.16
-03 36 16.7 13.0 N 458
0029P C2003 08 24.97252 22 35 53.04
-03 36 17.0 13.1 N 458
0029P C2003 08 25.11207 22 35 49.13
-03 36 32.5 13.0 N 442
0029P C2003 08 25.11402 22 35 49.07
-03 36 32.7 13.0 N 442
The observers have
measured the brightness in a 10”x10” arc seconds
diameter
Photometry with the USNO A2 catalog
(in R band)
Regards
Diego
Rodriguez
code 458
Ramon
Naves
Code 213
Albert Sanchez
Caso
Code 442
On September
the 4th the comet continued active so I decided to take a high
resolution (1.16 arc sec per pixel) series of pictures of it with the idea of
imaging the coma structure. The night of September the 5th I started a series of 60 sec. exposures,
I was able to take 13 frames before the sky became overcasted. Note that the
stars are elongated because the images have been stacked, using Astrometrica,
centering on the comet’s nucleus using the speed and position angle as
calculated from the orbital elements.
The above image
illustrates the current outburst the comet is undergoing, two jets are visible,
one at a PA of about 209 deg and another
at a PA of 152 (north is up, east is left).
No spiral structure is
apparent, however a few days ago it was detected by other observers, suggesting
that the outburst somehow has destroyed such structures, in the second picture
of the composite (The sequence) such spiral structure is quite
obvious.
To boost the contrast
of the jets it’s usual to apply a Larson-Sekanina filter which shows the
gradients of luminosity in both, radial and angular displacements. The filter
has been applied to the previous picture, the jets are readily
evident,
The jet to the south
west is curved to the south east, the other jet however seems straight, this
suggest that they are probably of a different composition.
A rotational gradient
process by Sebastian Hönig done on the same picture
The following picture
is a false colour rendition with an estimate of the coma size encircled, the
diameter exceeds 72 arc sec, note
that the comet’s nucleus is not the centre of the coma, there’s a noticeable
shift of the coma to north east, the north west side of the coma is less dense
than the rest.
(north up, east
left)
The coma profile shows
the asymmetry and allows a better estimation of the coma
size,
The decay to the right
(west) is quite sharp, the coma size in this section is about 60 pixels which
gives 96 arc. sec. diameter.
If we look at the
South-North section
(South is left) We can
see the slow raise from south to north and the sharp drop past the nucleus, some
field stars are apparent, the coma size can be estimated in 70 pixels or about
112”.
The following light
curves have been elaborated with the CCD data acquired by the Spanish amateurs
contributing to the mail list cometas-obs, available at :
http://astrosurf.com/cometas-obs/29P/web.htm
The magnitudes have
been measured in a standar photometric aperture of 10”X10” reducing in this way
the dispersion of the results. Here
you’ll find a description of the
10x10 method .
From the light curve we
can see a sudden increase in brightness starting the 22-23 august, in less than
two days the magnitude raises from 15.2 to 12.9, around 2 magnitudes, the
maximum is the day 24 when a slow decay, lasting around one week fades it back
to normal magnitude.
For comparison
purposes, the following picture shows the light curve of the outburst in August
2002, the raising edge is not well covered but we know that on July the
30th it was at 15.2 mag. We can see a similar relaxation in about one
week time.
The following composite shows the evolution in terms of mangitud and visual aspect, at the maximum the coma is very bright and concentrated, two days later we can appreciate spiral details developing in the coma, one week after the maximum the comet is fading and an extended coma can be seen with two jets developed, fifteen days after the maximum the comet is back to normal.
29/P great activity, (Diego
Rodriguez)
CometographySeichii Yoshida
Herbert Raab for Astrometrica and the excellent track
& stack facility.
Thanks to
:
All the amateurs
contributing with their CCD photometry to the Observadores de cometas
list.
Sebastian Hönig for
his rotational gradient process.
Gerald Rhemann for the
second picture of the composite.
