Comets
Details of the
brighter comets visible in 2010
Comets are usually small objects, the solid cores only a few kilometres across. They usually
have highly eccentric orbits, taking some far out from the Sun.
They are thought to be like dirty "snowballs", that is they are a conglomerate of rock dust and
frozen gases like water, ammonia and other volatiles. When a comet approaches the Sun it
warms up and the volatiles start to evaporate, so that the comet becomes surrounded by a large
halo, or coma, of vapour and dust. The coma can be pushed out as an elongated tail by the
solar wind.
The coma of a comet may be tens of thousands of kilometres across so that, visually, the comet
is a small, diffuse object. Because the amount of gassing which will
occur is very hard to predict, magnitude predictions for comets can be quite unreliable.
They may be much fainter than expected, or sometimes brighter, especially if there is an
outburst of vapour. The magnitudes given are for the whole object, but since the comet is not
a star like point, the apparent brightness is lower, making the comet more difficult to
see than a star of the same magnitude.
The material left behind in the comet's tail will continue to orbit the Sun and some may
eventually enter and burn up in the Earth's atmosphere resulting in a
meteor shower.
Information will be provided on these pages about bright comets predicted to occur during the
year. As comet discoveries are continually being made, it is always possible an unpredicted
comet will become visible.
General information on comets is available at
Gary Kronk's comet pages.
Ephemeris details of a large number of comets are available at the
IAU Minor Planet Centre. Users of the site can generate their own ephemerides for
a any of a large number of comets and download orbital elements.
The majority of the orbital information presented on this site is based on elements from
the IAU Minor Planet Centre.
Brighter comets visible during 2010
Listed are comets which may reach a magnitude brighter than 10 during 2010. For those which
may be visible from southern latitudes click on the links for further details including charts
and ephemerides.
Brighter than magnitude 10 from the beginning of February to the beginning of May,
brightest magnitude 9.3 late March.
Visible from NZ throughout, a morning object at first,
but becoming visible all night by late April.
Brighter than magnitude 10 from late March to mid May,
brightest magnitude 9.6 for most of April.
It is low in NZ skies, especially the South Island, and does not rise at all after about
April 20 even in the extreme north.
C/2009 R1 should be brighter than magnitude 10 from mid May to mid August. It is too close
too the Sun to observe when brightest, magnitude 4.5, in July.
It will be visible, but low, in NZ skies in before sunrise in May and briefly after sunset
in August.
Tempel should be brighter than magnitude 10 from the beginning of May to the end of September.
It is brightest in the second half of July, reaching magnitude 8.1
The comet will be well place for viewing in the southern hemisphere, at first as a morning
object, but during the evening as well by mid August.
Encke will be too far north and then too close to the Sun to observe from NZ until mid August.
It is brightest, magnitude 5 early August.
In mid August it will be magnitude 6.5, fading to 10 by early September. It will be
low in the early evening sky.
Brighter than magnitude 10 from late August to the end of the year,
brightest magnitude 4.5 October 25 when very low in NZ.
It is very low, or does not rise, in NZ until mid October. Then a morning object at
first but rises before sunset by mid December.
C/2009 O2 (Catalina)
Catalina is expected to reach magnitude 8.9 in late March but will be unobservable as it will
be a low day time object in NZ.
The comet has a period of about 4000 years, its perihelion distance is 0.69 AU, its
aphelion distance 500 AU.
141P/Machholz
This comet will be brighter than magnitude 10 between May 17 and June 10. Throughout this
time it will be only a few degrees from the Sun and so unobservable.
The period of the comet is 5.25 years, with a perihelion distance of 0.76 AU and aphelion
distance 5.28 AU.
