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Comet Lulin
http://www.visualastronomy.com/2009/01/comet-lulin.html
There's a new comet on the way, and this one could get quite interesting! This comet's name is Comet
Lulin, more formally known as Comet C/2007 N3. This potential naked eye comet could be a very
interesting one since it follows an unusual orbit. Comet Lulin is actually moving in the opposite direction
of the planets! It also occupies a very low-inclination orbit of about 1.6° from the ecliptic. On top of all
this, the comet is in a parabolic trajectory, which means it may have never interacted with the planets
and that this may be its first trip into the inner Solar system. As we will see below, this comet's strange
orbit will make for some odd behavior.
Since Comet Lulin will be moving opposite the motion of the Earth, it will
appear to approach us and move away especially fast. Beginning in
February 2009, Comet Lulin will rise at about midnight local time, and
will be about 6th or 7th magnitude. This won't be bright enough to go out
and look at it with the naked eye, but any telescope or binoculars should
allow you to see it.
By the middle of February 2009, Comet Lulin will be about 5th or 6th
magnitude. By this time, the comet may possibly be visible to observers
in "perfect" dark sky sites.
Comet Lulin's closest approach will be on February 24th, 2009 at a
distance of about 61 million kilometers. By now, Comet Lulin is predicted
to be 5th magnitude, which means it could be visible to the naked eye in
rural locations. The most interesting thing about closest approach,
however, is the comet's ridiculously high apparent velocity. Comet Lulin
will be speeding along at more than 5° per day! This means that in a
telescope or binoculars, one will actually be able to see the comet's
apparent motion against the background stars! This effect is a must-see,
and does not present itself often.
This object was initially described as an asteroidal object, when found by Quanzhi Ye (Sun Yatsen University, Guangzhou, China) on three images obtained by Chi-Sheng Lin (Institute of
Astronomy, National Central University, Jung-Li, Taiwan) on 2007 July 11. Lin had acquired the
images using the 41-cm Ritchey-Chretien and a CCD camera at Lulin Observatory (Nantou,
Taiwan). The magnitude was given as 18.9. Several confirming observations were obtained;
however, on July 17, J. Young (Table Mountain Observatory, California, USA) noted a coma 2-3"
across, with a bright central core.
Tip of the Day: (1) How sunrise to sunset is defined. Sunrise is time from just when the top of the
sun clears the horizon to sunset when the last bit of sun disappears.
(2) Astronomy Magazine Sept. 2002 issue defines the faintest naked eye star at 6.5 apparent
magnitude.
“Apparent Magnitude” was defined by Hipparachus in 150 BC. He devised a
magnitude scale based on:
However, he underestimated
the magnitudes. Therefore,
many very bright stars today
have negative magnitudes.
Magnitude
Constellation
1
(Orion)
2
Big Dipper
6
Star
Betelgeuse
various
stars just barely seen
Magnitude Difference is based on the idea that the difference between the
magnitude of a first magnitude star to a 6th magnitude star is a factor of 100.
Thus a 1st mag star is 100 times brighter than a 6th mag star. This represents a
range of 5 so that 2.512 = the fifth root of 100. Thus the table hierarchy is the
following.
Absolute Magnitude is defined
Magnitude Difference of 1 is 2.512:1, 2 is
2.5122:1 or 6.31:1, 3 is 2.5123 =
15.85:1 etc.
as how bright a star would appear
if it were of certain apparent
magnitude but only 10 parsecs
distance.
From: www.astronomynotes.com by Nick Strobel