• MPC Preparation (Info)


    The following Minor Planet Electronic Circular may be linked-to from your own Web pages, but must not otherwise be redistributed electronically.

    A form allowing access to any MPEC is at the bottom of this page.

    Read MPEC 1993-Y04 Read MPEC 1993-Y06

    M.P.E.C. 1993-Y05                                Issued 1993 Dec. 25, 13:59 UT
         The Minor Planet Electronic Circulars contain information on unusual
             minor planets and routine data on comets.  They are published
       on behalf of Commission 20 of the International Astronomical Union by the
              Minor Planet Center, Smithsonian Astrophysical Observatory,
                              Cambridge, MA 02138, U.S.A.
                                   EDITORIAL NOTICE
         In response to several requests, we propose to issue in these
    Circulars monthly lists of the unusual minor planets that are reasonably
    observable.  These will be listings of the objects in order of
    increasing right ascension from the sun for the "ten-day date" closest
    to each new moon.  Numbered and other multiple-opposition objects will
    be included, together with objects from the current opposition and from
    earlier single oppositions for which perturbations were included in
    the orbit solution.  Minor planets will generally be included if they are
    brighter than magnitude 21 and their elongations from the sun are greater
    than 90 degrees.  At smaller elongations, the brightness limit will be
    changed by 0.1 mag/deg to a limit of magnitude 18 and elongation 60 degrees
    for numbered objects and magnitude 15 and elongation 30 degrees for unnumbered
    objects.  Because of their extreme interest and the difficulty of securing
    adequate observations, the magnitude limit will be ignored for unnumbered
    objects with perihelia greater than 7 AU and down to a 30-degree elongation.
         The various columns will give the number and/or provisional
    designation or name, together with the number of observed oppositions or
    the observed arclength in days for unnumbered minor planets.  Reference
    will be given to the orbital elements, either in Efemeridy Malykh Planet
    (EMP) for a specified year (last two digits), the five-digit (or four-digit)
    number of the Minor Planet Circulars, or (for very recent orbits) the
    three-character coding for these Minor Planet Electronic Circulars.
    After the right ascension and declination (J2000.0) in the usual units,
    five columns (Geo., Hel., El., Ph. and V) will give the geocentric and
    heliocentric distances (in AU), the solar elongation and phase angle (in deg)
    and the visual magnitude.
         In some instances there will be an asterisk following the reference.
    This will generally indicate unusual numbered objects that are on the
    critical list, although the opportunity will also be taken to indicate
    other objects for which observations are particularly desirable, with
    the reasons given in notes at the end.
         The appearance of the word "precovered" on MPEC 1993-Y03 necessitates
    an explanation.  In the case of an unnumbered minor planet, the "discovery"
    refers to the detection that allowed a provisional designation to be given,
    generally to the first observation on the first of two or more nights.
    It is possible that an "independent discovery" will be made at the same
    opposition.  It can also happen that one or more "prediscovery",
    chronologically earlier images will be detected at that opposition by an
    observer aware of the discovery.  Sometimes it will not immediately be
    appreciated, or it may initially be unclear, that there is an independent
    discovery of a particular object at the same opposition, in which case
    a second designation may be applied to the same object; if and when the
    objects are proven to be the same, there is a "double designation".  An
    "identification" refers to the recognition that the same object has been
    given provisional designations at different oppositions.  In such a case,
    a "principal discovery" and "principal designation" will be defined,
    generally to the chronologically earliest opposition for which there was
    an orbit determination that allowed the identification to be established.
    The principal discovery is the one of relevance when the minor planet
    is deemed to have a reliable enough orbit solution that the object can
    be numbered.  Each supporting designation will generally then be of a
    "rediscovery" of the object.  When a single-opposition object is found from
    a deliberate search on an exposure deliberately made for the object at a
    future opposition, there is said to be a "recovery", a term that can
    also apply to a multiple-opposition object found far from its expected
    place.  The term "precovery" refers to the same act on an exposure that was
    not deliberately made for the object, the exposure generally being at
    an earlier opposition.  It can be noted that, in the case of a comet,
    a "recovery" generally applies to the first deliberate detection at the
    first of each sequence of oppositions that observations again become
    possible--generally as the object next approaches perihelion--and the
    comet receives a new provisional designation.  If a comet is observed at all
    of its oppositions (or most oppositions, including one near aphelion), the
    term recovery and a provisional designation are not applied.  A new
    permanent designation is given to a comet at each perihelion passage when
    observations are made, whether or not a recovery is involved.
    Brian G. Marsden                                              M.P.E.C. 1993-Y05

    Read MPEC 1993-Y04 Read MPEC 1993-Y06

    MPEC number:

    Enter an MPEC number in one of the following forms:

    • 1997-B01 (the full form)
    • J97B01 (the packed version of the full form)
    • B01 (the abbreviated form)