Comet’s 29P/Schwassmann-Wachmann 1
Great activity
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Various series of astrometric and photometric
reductions on comet 29P Schwassmann - Wachmann 1 (29P/SW 1) are presented
at heliocentric distances of 5.1 (UA) . Even though the great distance
to the Sun this comet presents an unexpected and irregular activity. It’s
brightness has changed up to 4 magnitud orders during the detected outburts
in 2002. There’s no commonly accepted theory explaining this behaviour
as yet. In this work it is tried to show the cometary behaviour as observed
by amateur astronomers using a novelty photometric estimation method.
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Introduction
Nowadays we know comets are ice and rock particles, that from time to time
enter the solar system from some external region (probably the Oort’s cloud).
These bodies sometimes perform their travel periodicaly trapped by the
Sun. When comets reach the Sun’s neighborhood, the heat makes it’s components
to evaporate. The gas nucleus and the dust form long tails that can be
seen from Earth. These tails may extend as far as tenths of millions of
kilometers.
There’s a comet group trapped in eliptical orbits, most of them with low inclination to the ecliptic plane and moving in the direct sense. This comet group, named the Jupiter’s family, lies orbiting in between Jupiter and the Sun and they all have periods under 20 years. The discovery of comet 29P/Schwassmann-Wachmann 1.-
The orbit.-
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Magnitud estimation
General.-
The brightness determination has been one of the most important goals of the comet observers. The defy of doing reliable estimations has been enormous given that we are measuring non punctual sources moving over the background stars. Most of the magnitud estimations have been accomplished by photographic or visual methods. Nevertheless, in last years different methods for magnitud estimation are being used. · James Scotti coma’s substraction method (Spacewatch).m2 · Estimations by other professional astronomers using CCD attached to big telescopes (m2). David Jewitt ,Licandro and others. · Amateur estimations with CCD cameras. Various methods. · Amateur visual observations with little telescopes and binoculars (m1) The (m1) magnitud.
Nuclear magnitud (m2).
Magnitud estimation with the 10x10 method.
http://usuarios.lycos.es/obscometas/_10X10/inicio.htm Observation techniques.-
V02 Rafael Benavides Palencia. SC 23cm f/10Telescope V03 Carlos Labordena Barceló. SC 20-cm f/10Telescope V04 Carlos Segarra García. Newton 25cm f/5Telescope V09 Maciej Reszelski You can find theobserver’s technical data at: http://personals.ip.ictonline.es/+mcampas/lista-obs/datos.html Used Catalogs.
Photometry with the USNO catalog (in R band) · 57% of the stars have error lower than .2 tenths · 43% of the star have errors bigger that 0.2 tenths
The data gathered at the mail list "Cometas_Obs" are the following: 12 visual observations 30 CCD images The light curve has been represented as corrected magnitud for the distance to the Earth against the time. UIT the observational data it can be seen the different outbursts the comet has undergo during the year. The posible cyclic changes that can show a rotation period are masked,
but we can see instead the bchanges in more than one magnitud that are
probably related to outburts of CO2 ice deposits (carbon dioxide) and CH4
(methane) than the Sun heats gradually.
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Curva realizada por Julio Castellano
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The coma.
The comet’s coma is a matter halo sorrounding the
comet’s actual nucleus. The coma and the tail is all we really see from
Earth. The coma’s shape and size may vary for the smae comet during aparition.
The shape depends on the distance to the Sun and the relative quantities
of dust and gas production. For comets producing little dust, the coma
is generally spheric. Comets producing great amounts of dust, use to have
tails with parabolic shapes. This is due to different dust grain sizes.
The bigger grains are ejected along the comet’s orbit whereas the tiny
dust particles are ejected against the Sun by the pressure of radiation
of light. When there’s a distribution of dust particles sizes a tipical
tail with beautiful shape develops.
Coma’s diameter
In general the coma’s diameter is given as arc minutes (´) when
the coma grows it can be expressed as degrees. When the coma is elongated,
the measure stands for the shortest dimension. In the acompaning table
we show the 29P coma’s actual diameter, against the distance to the Earth,
based on the angular diameter as obtained from the CCD images. The images
used for the coma size estimation have always been obtained with the same
integration time (exposure) and the same values of the background have
been used to calculate the relative size. We can see a relation between
the comet’s brightness and the coma’s diameter. In continued followup we
always found coma sorrounding the nucleus changing in size from day to
day.
 Conclusion.-
· 278 CCD observations have been gathered, 12visuale and more than
30 CCD pictures of a great quality.
· The light curve is non typical for a standard comet and this probably speaks of a nucleus with gas deposits that provide the comet’s extra unexpected brightness. · There’s a correlation between the brightness
and the coma size.
It is important to note there are not many comets with such a big activity at a large heliocentric distances 6AU. In effect, another object from the external solar system is the asteroid Quiron, with orbit between Saturn and Uranus, a coma was detected around his nucleus in the year 1989. Acknowledgements.-
I’m gratefull to Julio Castellano for his cooperation with bthe graphics. The observations with astrometry, photometry and images can be obtained
at:
Diego Rodríguez
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