(meteorobs) 103P/Hartley 2 Meteor Outburst?

  • Subject: (meteorobs) 103P/Hartley 2 Meteor Outburst?
  • From: Skywayinc
  • Date: Mon, 27 Oct 1997 10:30:15 -0500 (EST)
The advisory for a possible meteor outburst from Peter Jennniskens of
NASA/Ames (California) for this weekend is certainly of some interest. . .
however, for those hoping for something even along the lines a display
similar to one of the principal annual showers, a few facts must be noted:

First. . . prior to December 1993, 103P/Hartley2 was traveling in an orbit
where its perihelion was located inside Earth's orbit. . . a distance of 0.95
AU from the Sun.

In late December 1993, this comet passed to within 0.37 AU of Jupiter.  This
caused its period to lengthen slightly from 6.26 to 6.39 years and placed its
perihelion outside the Earth's orbit at a distance of 1.031 AU from the Sun. 

Thus, the upcoming apparition will be the very first one for 103P/Hartley 2
traveling along this "new" orbit.  So. . . when the Earth makes its closest
approach to the comet's descending node and perihelion point next weekend (as
noted by Dr. D.K. Yeomans) we should assume that there is no chance of any
encounter of meteoric debris that has been shed from any previous apparition.
 In fact. . . for a meteor shower of any intensity to occur, we must hope
that there is a fair amount of cometary debris that is traveling well out
ahead of this comet. . . and well off its orbit and at least 0.04 AU toward
the Sun; a tall order even for a dusty and intrinsically large and bright
object (like a P/Halley or P/Swift-Tuttle!).  With a smaller, fainter object
like 103P/Hartley 2, this would likely be a difficult criteria to fulfill.

A more interesting set of circumstances will accompany this comet on its
return to the Sun in October 2010.  My findings indicate that 103P/Hartley 2
will pass to within only 0.11 AU of Earth (perigee October 22-23).
 Perihelion comes on October 28.  The Earth will arrive at the comet's
descending node on November 2, a mere 7 days after the comet (!); similarly,
the Earth will pass the perihelion point of the comet's orbit on November 3
-- again just 7 days after the comet!
Unfortunately, by 2010, the comet's perihelion distance will have increased
to 1.058 AU, meaning that the orbits of the Earth and comet will be separated
by nearly 0.07 AU (approximately 10 million kilometers).  Thus, although the
linear distance between Earth and comet is tantalizing, the gap separating
the respective orbits "could" negate any significant activity.

On another note, my findings also show that 103P/Hartley 2 in late October
2010 should briefly become an easy naked-eye object. . . perhaps in the 3.5
to 4.0 magnitude range. . . as it slides rapidly south and east through the
stars of Auriga and Gemini.  I have utilized the 1997 orbital elements for
103P/Hartley 2 which appear on page 189 of the 1997 Observer's Handbook of
the RASC to provide the following osculating elements for the 2010 return
(non-gravitational forces neglected):    

For 2000.0: 

                                          T = 2010 October 28.22 UT
        Argument of Perihelion = 181.21 Degrees
Longitude of Ascending Node = 219.57 Degrees
                                           i = 13.62 Degrees
                                           q = 1.058 a.u.
                                           e = 0.6951
                                           P = 6.49 years

-- Joe Rao
     Skyway, Inc.