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2008 CM false alarm

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  • Jean Meeus
    MPE 2008-C12, of February 2, announded the discovery of an object that received the designation 2008 CM and having an extraordinary orbit, with a revolution
    Message 1 of 5 , Feb 4, 2008
      MPE 2008-C12, of February 2, announded the discovery of an object
      that received the designation 2008 CM and having an extraordinary
      orbit, with a revolution period of only 0.37 year (the smallest
      known for an asteroid), a = 0.514 AU, and an *aphelion* distance
      Q = 0.88, so that the object would be a new interior asteroid.

      However, the observations were made over a span of 17 hours only,
      so the orbit was rather uncertain.

      And now MPE 2008-C23, of February 4, gives new orbital elements based
      on an arc of 2 days. The orbit's semimajor axis now appears to be 1.5885
      AU. The corresponding period of revolution is 2 years, and the object is
      actually an asteroid of the Apollo type.

      Jean Meeus
    • Alan W Harris
      Thanks for that note. I realized after my earlier post that the 17-hour arc was likely insufficient for a definitive orbit. This region around 60-90 deg.
      Message 2 of 5 , Feb 4, 2008
        Thanks for that note. I realized after my earlier post that the 17-hour
        arc was likely insufficient for a definitive orbit. This region around
        60-90 deg. solar elongation (the so-called "sweet spots") is notorious for
        ambiguoous solutions, and in particular for dual solutions well separated
        in chi-squared space such that when you land in one solution minimum it
        seems well determined, until you explore more broadly and find one or more
        equally good solution minima far removed in orbital element space.

        Cheers,

        Alan

        At 12:14 AM 2/4/2008, Jean Meeus wrote:
        >MPE 2008-C12, of February 2, announded the discovery of an object
        >that received the designation 2008 CM and having an extraordinary
        >orbit, with a revolution period of only 0.37 year (the smallest
        >known for an asteroid), a = 0.514 AU, and an *aphelion* distance
        >Q = 0.88, so that the object would be a new interior asteroid.
        >
        >However, the observations were made over a span of 17 hours only,
        >so the orbit was rather uncertain.
        >
        >And now MPE 2008-C23, of February 4, gives new orbital elements based
        >on an arc of 2 days. The orbit's semimajor axis now appears to be 1.5885
        >AU. The corresponding period of revolution is 2 years, and the object is
        >actually an asteroid of the Apollo type.
        >
        >Jean Meeus
        >
        >
        >
        >~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        >
        >Posts to this list or information found within may be freely used, with
        >the stipulation that MPML and the originating author are cited as the
        >source of the information.
        >Yahoo! Groups Links
        >
        >
        >
        *******************************************************************
        Alan W. Harris
        Senior Research Scientist
        Space Science Institute
        4603 Orange Knoll Ave. Phone: 818-790-8291
        La Canada, CA 91011-3364 email: awharris@...
        *******************************************************************
      • Brian Skiff
        ... I will say, however, that this is zone is especially good just from the observer-at-the-telescope viewpoint, since the daily motions of asteroids are quite
        Message 3 of 5 , Feb 4, 2008
          >> ...60-90 deg. solar elongation (the so-called "sweet spots") is notorious


          I will say, however, that this is zone is especially good just
          from the observer-at-the-telescope viewpoint, since the daily motions
          of asteroids are quite distinctive even if the orbits are not.
          The main-belters concentrate at something like 3/8-deg per day
          with little scatter, then there's a big gap in daily motion on the
          higher side, followed by NEOs, which are all going at closely
          1.0-deg/day. There's a nice paper by Rob Whiteley and Dave Tholen
          describing this that was in Icarus some years ago (~2000?) in
          reagrd to Arjunas and IEOs. Andrea Milani, too, published a review
          about this around the same time. (Sorry, don't have the citations
          handy just now.)


          \Brian
        • Dave Tholen
          ... Still too early to quote a semimajor axis to 0.0001 AU. The observations can be satisfied with semimajor axes anywhere from 1.32 to 2.09 AU. The
          Message 4 of 5 , Feb 4, 2008
            > And now MPE 2008-C23, of February 4, gives new orbital elements based
            > on an arc of 2 days. The orbit's semimajor axis now appears to be 1.5885
            > AU. The corresponding period of revolution is 2 years, and the object is
            > actually an asteroid of the Apollo type.

            Still too early to quote a semimajor axis to 0.0001 AU. The observations
            can be satisfied with semimajor axes anywhere from 1.32 to 2.09 AU. The
            perihelion distance is fairly well known, lying between 0.90 and 0.95 AU.
          • Alain Maury
            It just goes to say that before saying anything about the 6 orbital elements of a given object, one should always look at the element number 0, i.e. the length
            Message 5 of 5 , Feb 4, 2008
              It just goes to say that before saying anything about the 6 orbital elements
              of a given object, one should always look at the element number 0, i.e. the
              length of the arc. It allows not to announce a collision with the Earth (it
              is late, and I don't remember the denomination of that asteroid which was
              like this one, with a very preliminary orbit, but with a delta getting to 0
              in a few days, I am pretty sure Alan Harris still remembers it), a new type
              of object, not to stress about anything like impact probabilities, etc...
              Unfortunately it is not systematically given in the MPECs. :

              Orbital elements:
              2008 CM Earth MOID = 0.1317
              AU
              Epoch 2007 Oct. 27.0 TT = JDT 2454400.5 MPC
              M 277.69942 (2000.0) P Q
              n 2.67164189 Peri. 331.75901 +0.46021835 +0.88150995
              a 0.5143798 Node 325.34090 -0.77561968 +0.34136769
              e 0.7045807 Incl. 10.69545 -0.43198748 +0.32620288
              P 0.37 H 18.1 G 0.15 U 9

              whereas :
              Orbital elements:
              2008 CO Earth MOID = 0.1275
              AU
              Epoch 2008 Jan. 15.0 TT = JDT 2454480.5 MPC
              M 259.97455 (2000.0) P Q
              n 0.77603545 Peri. 269.51139 -0.65507700 +0.74956725
              a 1.1727758 Node 319.03641 -0.62271584 -0.60681469
              e 0.0828740 Incl. 8.33117 -0.42790082 -0.26443312
              P 1.27 H 22.9 G 0.15
              >From 17 observations 2008 Feb. 2-2. E-assumed.

              So I believe it should be always included, and written in bold characters :)
              Alain



              > -----Original Message-----
              > From: mpml@yahoogroups.com [mailto:mpml@yahoogroups.com]On Behalf Of
              > Alan W Harris
              > Sent: lundi 4 fevrier 2008 16:42
              > To: Jean Meeus; MPML
              > Subject: Re: {MPML} 2008 CM false alarm
              >
              >
              > Thanks for that note. I realized after my earlier post that the 17-hour
              > arc was likely insufficient for a definitive orbit. This region around
              > 60-90 deg. solar elongation (the so-called "sweet spots") is
              > notorious for
              > ambiguoous solutions, and in particular for dual solutions well separated
              > in chi-squared space such that when you land in one solution minimum it
              > seems well determined, until you explore more broadly and find
              > one or more
              > equally good solution minima far removed in orbital element space.
              >
              > Cheers,
              >
              > Alan
              >
              > At 12:14 AM 2/4/2008, Jean Meeus wrote:
              > >MPE 2008-C12, of February 2, announded the discovery of an object
              > >that received the designation 2008 CM and having an extraordinary
              > >orbit, with a revolution period of only 0.37 year (the smallest
              > >known for an asteroid), a = 0.514 AU, and an *aphelion* distance
              > >Q = 0.88, so that the object would be a new interior asteroid.
              > >
              > >However, the observations were made over a span of 17 hours only,
              > >so the orbit was rather uncertain.
              > >
              > >And now MPE 2008-C23, of February 4, gives new orbital elements based
              > >on an arc of 2 days. The orbit's semimajor axis now appears to be 1.5885
              > >AU. The corresponding period of revolution is 2 years, and the object is
              > >actually an asteroid of the Apollo type.
              > >
              > >Jean Meeus
              > >
              > >
              > >
              > >~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
              > >
              > >Posts to this list or information found within may be freely used, with
              > >the stipulation that MPML and the originating author are cited as the
              > >source of the information.
              > >Yahoo! Groups Links
              > >
              > >
              > >
              > *******************************************************************
              > Alan W. Harris
              > Senior Research Scientist
              > Space Science Institute
              > 4603 Orange Knoll Ave. Phone: 818-790-8291
              > La Canada, CA 91011-3364 email: awharris@...
              > *******************************************************************
              >
              >
              >
              > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
              >
              > Posts to this list or information found within may be freely
              > used, with the stipulation that MPML and the originating author
              > are cited as the source of the information.
              > Yahoo! Groups Links
              >
              >
              >
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