48 AUSTRALIAN SKY & TELESCOPE February | March 2019
COMETS by David SeargentHistorical records are helping to overcome mistaken cometary identities.
Mysteries of the sungrazers
A
lthough February and March
2019 do not hold any promise
for comets within the visual
range of small telescopes (at the time
of writing), these months have in times
past seen some of the brightest comets
ever recorded — members of (or, in
some instances, suspected members of)
the famous Kreutz group of sungrazing
objects.
Long ago, in February 1106, a comet
blazed in full daylight “one foot and
a half” from the Sun and a few days
later extended a magnificent tail across
the sky. Nearer our own time, a great
Kreutz sungrazer again became visible
in full daylight during the closing
days of February 1843 and, during the
following month, its brilliant tail of
up to 50 degrees in length graced the
evening skies. Then, in February 1880,
yet another great comet (following an
orbit almost identical to that of 1843)
became visible after sunset. Although
not as brilliant as the 1843 one, C/1880
C1 (as it is now officially known) seems
to have possessed an even longer tail —
some 75 degrees long according to thewell-known astronomer David Gill who
observed it from South Africa.
Following extensive investigations
of this fascinating group of comets
by Professor Z. Sekanina, it is now
thought that both of these 19th century
comets — together with the majority
of the myriad tiny sungrazers found
in images from the SOHO space-based
solar observatory since the mid-1990s
— were fragments of the comet of 1106
following a series of (unobserved)
disruptions after its very close
encounter with the Sun.
Several other large members of the
group have been seen at various times of
the year, the most recent having been the
spectacular ‘Christmas Comet’ C/2011
W3 (Lovejoy) discovered by Aussie Terry
Lovejoy, and of which many readers will
no doubt have fond memories. They are
all thought to have originated with the
disruption of a large comet sometime
in the past, although not all of them
relate directly to the one seen in 1106.
Sekanina’s research suggests that the
progenitor of the group might have been
a comet noted briefly in a single Chinesechronicle for 214 BC — ironically, a
rather obscure object!
In addition to the well-established
February/March sungrazers mentioned
above, a bright comet observed in
March 1668 and another in late
February and early March of 1702 may
also have belonged to the group.Tales from the sea
Then there is the mysterious account
of a long-tailed comet in the evening
skies of February 1666. The story behind
this report is interesting. It comes
from Robert Knox, a sea captain, who,
together with his father of the same
name, ran aground in Ceylon (Sri
Lanka) on November 19, 1659 and were
taken captive by the King of Kandy
to be held at the monarch’s pleasure
(apparently indefinitely). The captives
were, however, allowed considerable
freedom and, after 19 years, Knox and
one of the captured members of the
crew escaped, arriving back in England
in 1680 (Knox senior having died some
years earlier). Back in England, Knox
set about writing of his adventures and ESO/GUILLAUME BLANCHARDComet C/2011 W3 (Lovejoy),
a sungrazer, was discovered
by Aussie Terry Lovejoy on
November 27, 2011. This
image was taken less than
four weeks later, on December
22, at the European Southern
Observatory’s Paranal site.