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2010 KH

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  • Andrea Milani
    The object 2010 KH has been observed only by WISE and currently has a disgusting orbit: semimajor axis = 3.2 +- 3 AU. In fact, it might not even be a NEO.
    Message 1 of 6 , Jun 28, 2010
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      The object 2010 KH has been observed only by WISE and currently has a
      disgusting orbit: semimajor axis = 3.2 +- 3 AU. In fact, it might not
      even be a NEO. However, by using the available data, we have found Virtual
      impactors, including one in 2015, of course with a very low impact
      probability (the asteroid could be almost anywhere, thus we cannot exclude
      that it could be on top of us at some time in the near future).

      Now this situation is very unpleasant. This object possibly does not even
      exist as a NEO, on the other hand the nominal solution is a NEO with
      absolute magnitude 18.2. Our way to handle this would be to proclaim
      that it has not been discovered, and refuse to give credit to WISE and to
      NASA for such a terrible job. However, as you well know, this kind of
      decision is not in our hands.

      Our job is to report objects which might be impacting the Earth. It is not
      part of our style to adopt scare tactics to push astronomers to observe
      asteroids with Virtual Impactors; however, with very simple arithmetics,
      it can be deduced from our risk page that in case this asteroid was to
      impact the Earth in 2015, the impact energy is estimated at 8,000
      megatons. Thus we are assuming that, whenever an asteroid has a Virtual
      Impactor, the astronomers, be they professionals or amateurs, are
      available to make an effort to follow up. It should be especially the
      responsibility of the person/organization who is credited with the
      discovery, because if in fact an asteroid is lost while still having VIs,
      the risk for our planet has not in fact been decreased. In this case, the
      responsibility should belong mostly to the WISE team, and ultimately to
      NASA.

      We are aware that the observation of this object is not easy, now there is
      full moon and the uncertainty is growing rapidly; the magnitude, although
      not low, is feasible for several observatories. However, we ask that an
      effort is done to recover this object.

      Yours

      Andrea Milani


      ================================================
      Andrea Milani Comparetti
      Dipartimento di Matematica
      Piazzale B. Pontecorvo 5
      56127 PISA ITALY

      tel. +39-050-2213254 fax +39-050-2213224
      cellular phone +39-349-4482751
      E-mail: milani@...
      WWW: http://adams.dm.unipi.it/~milani/
      ================================================
    • rstoss@catanga.org
      ... V 20.4, -15° decl. and 70deg from the moon. Isn t PS1 able to scan the uncertainty area? Should be peanuts for them. And they are not affected by the
      Message 2 of 6 , Jun 28, 2010
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        > The object 2010 KH has been observed only by WISE and currently has a
        > disgusting orbit: semimajor axis = 3.2 +- 3 AU. In fact, it might not
        > even be a NEO. However, by using the available data, we have found Virtual
        > impactors, including one in 2015, of course with a very low impact
        > probability (the asteroid could be almost anywhere, thus we cannot exclude
        > that it could be on top of us at some time in the near future).
        >
        > We are aware that the observation of this object is not easy, now there is
        > full moon and the uncertainty is growing rapidly; the magnitude, although
        > not low, is feasible for several observatories. However, we ask that an
        > effort is done to recover this object.
        V 20.4, -15° decl. and 70deg from the moon.
        Isn't PS1 able to scan the uncertainty area? Should be peanuts for them.
        And they are not affected by the Arizona monsoon either.
         
        R.
         
      • Dave Tholen
        ... I don t think that a plus-or-minus value is a very good way to describe a quantity that has a decidedly non-Gaussian distribution. One might be led to
        Message 3 of 6 , Jun 28, 2010
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          > The object 2010 KH has been observed only by WISE and currently has a
          > disgusting orbit: semimajor axis = 3.2 +- 3 AU.

          I don't think that a plus-or-minus value is a very good way to describe a
          quantity that has a decidedly non-Gaussian distribution. One might be led
          to believe that the semimajor axis could be as small as 0.2 AU at the
          one-sigma level, when the semimajor axis is probably no smaller than
          0.85 AU. At the other end, one might be led to believe that the semimajor
          axis has a 12.2 AU upper limit at the three-sigma level, when it is
          probably unconstrained at the high end; I found a solution that satisfies
          the observations with a semimajor axis of 953 AU. In fact, we have a
          double-solution in this case. It's either an Aten with perihelion
          distance between 0.57 and 0.60 AU and an aphelion distance between
          1.10 and 1.23 AU, or it's an Apollo/Amor/Mars crosser with a perihelion
          distance between 0.94 and 1.45 AU and an aphelion distance greater than
          1.84 AU.

          > In fact, it might not even be a NEO.

          Indeed; there are lots of Mars crosser solutions, but they all have
          aphelion distances beyond Jupiter. Possible, but less common.

          > However, by using the available data, we have found Virtual
          > impactors, including one in 2015, of course with a very low impact
          > probability (the asteroid could be almost anywhere, thus we cannot exclude
          > that it could be on top of us at some time in the near future).
          >
          > Now this situation is very unpleasant. This object possibly does not even
          > exist as a NEO, on the other hand the nominal solution is a NEO with
          > absolute magnitude 18.2.

          My best-fitting orbit has it as Mars crosser, though I rejected three
          observations (or rather my automatic outlier rejection software rejected
          them). My overall best-fitting orbit has an absolute magnitude of 18.0,
          but the best-fitting orbit with an Earth-crossing solution has an absolute
          magnitude of 20.4.

          > Our way to handle this would be to proclaim
          > that it has not been discovered, and refuse to give credit to WISE and to
          > NASA for such a terrible job. However, as you well know, this kind of
          > decision is not in our hands.

          Let's not mix the politics of discovery credit with the issue at hand.
          It's a can of worms to draw a dividing line between "terrible job" and
          "good job", if that's the criterion you're advocating for assigning
          discovery credit. We recently looked at the NEO discoveries in 2008
          and 2009 and found that about 60 percent of them will have ephemeris
          uncertainties in excess of 3 degrees at their next apparition, with
          only about 2 percent of them getting bright enough to be recovered by
          the existing surveys. That means to find the others, some larger
          aperture telescope is going to have to do a LOT of hunting with smaller
          fields of view. One could easily conclude that the 60 percent constitutes
          a "terrible job" and therefore "haven't been discovered". See why it's a
          can of worms?

          > Our job is to report objects which might be impacting the Earth.

          But if you look at short-arc orbit solutions for newly-discovered objects
          with ordinary motion that are almost certainly main-belt asteroids, you'll
          probably find a lot of Earth-crossing solutions, with some smaller fraction
          being virtual impactors. As a general rule, you don't look at those,
          however. Are you looking at this one only because it was MPECed with an
          Amor-class orbit?

          > It is not
          > part of our style to adopt scare tactics to push astronomers to observe
          > asteroids with Virtual Impactors; however, with very simple arithmetics,
          > it can be deduced from our risk page that in case this asteroid was to
          > impact the Earth in 2015, the impact energy is estimated at 8,000
          > megatons. Thus we are assuming that, whenever an asteroid has a Virtual
          > Impactor, the astronomers, be they professionals or amateurs, are
          > available to make an effort to follow up. It should be especially the
          > responsibility of the person/organization who is credited with the
          > discovery, because if in fact an asteroid is lost while still having VIs,
          > the risk for our planet has not in fact been decreased. In this case, the
          > responsibility should belong mostly to the WISE team, and ultimately to
          > NASA.

          As you know, WISE does not do targeted observations. Are you advocating
          that they don't bother looking for NEOs in the WISE data because they are
          unable to do the necessary follow-up? What about the NEOs that fade
          below the ability of the groundbased discoverers to follow-up? Are you
          arguing that they failed in their responsibility?

          > We are aware that the observation of this object is not easy, now there is
          > full moon and the uncertainty is growing rapidly; the magnitude, although
          > not low, is feasible for several observatories. However, we ask that an
          > effort is done to recover this object.

          I have the ephemeris uncertainty as 5.3 by 1.3 degrees right now (one-sigma),
          with an apparent magnitude of 21.4, subject to the usual uncertainty of
          converting a thermal flux into a visual magnitude. NeoDys shows a rhombus-
          shaped uncertainty region only about 3 degrees wide (three-sigma). The
          difference is partly because it's a double-solution. The Aten solutions
          produce ephemeris positions that are east and spatially separated from
          those for the Apollo/Amor/Mars crossing solutions. The NeoDys prediction
          is pretty much centered on the Mars crossing solutions, but encompasses
          the Apollo and Amor solutions at the eastern end of the clump, but excludes
          the Aten clump much farther toward the east. Right now it would take us
          three Megaprime fields to recover the object, one centered on the Aten
          clump and two adjacent ones on the Apollo/Amor/Mars crosser clump. However,
          Megaprime doesn't go back on the telescope until July 6, by which time the
          problem will be twice as bad. Fortunately, it should be getting brighter,
          possibly bright enough for the groundbased surveys to recover later in the
          year, by which time it would be hopeless with a smaller-field telescope.
          However, for now, attempts at recovery shouldn't ignore the Aten clump.
          If anybody wants a KNOBS plot, let me know (site, date, time). I make
          that offer with some trepidation, because we hand generate them one at a
          time. It would be easy to become swamped, even by one site wanting a
          plot for every day of the next lunation.
        • Bill J Gray
          Dave Tholen wrote: ...In fact, we have a double-solution in this case. It s either an Aten with perihelion distance between 0.57 and 0.60 AU and an aphelion
          Message 4 of 6 , Jun 28, 2010
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            Dave Tholen wrote:

            "...In fact, we have a double-solution in this case. It's
            either an Aten with perihelion distance between 0.57 and 0.60
            AU and an aphelion distance between 1.10 and 1.23 AU, or it's
            an Apollo/Amor/Mars crosser with a perihelion distance between
            0.94 and 1.45 AU and an aphelion distance greater than 1.84 AU."

            It looks to me as if the closer (and more likely) solution
            involves the elongation growing after the original observations on
            16-19 May, but coming back down around 90 degrees in the next few
            days, with the object about a magnitude brighter than it was back
            then. If so, WISE ought to catch it again (nominally, on
            Wednesday).

            In which case, we could say that yes, WISE _does_ sometimes
            do follow-up.

            -- Bill
          • Dave Tholen
            ... I responded to point out that the object has a double solution, and Bill Gray noted that the Aten solution would be at a solar elongation of 90 deg in
            Message 5 of 6 , Sep 6, 2010
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              Readers may recall the following from earlier this summer:

              > The object 2010 KH has been observed only by WISE and currently has a
              > disgusting orbit: semimajor axis = 3.2 +- 3 AU. In fact, it might not
              > even be a NEO. However, by using the available data, we have found Virtual
              > impactors, including one in 2015, of course with a very low impact
              > probability (the asteroid could be almost anywhere, thus we cannot exclude
              > that it could be on top of us at some time in the near future).
              >
              > Now this situation is very unpleasant. This object possibly does not even
              > exist as a NEO, on the other hand the nominal solution is a NEO with
              > absolute magnitude 18.2. Our way to handle this would be to proclaim
              > that it has not been discovered, and refuse to give credit to WISE and to
              > NASA for such a terrible job. However, as you well know, this kind of
              > decision is not in our hands.

              I responded to point out that the object has a double solution,
              and Bill Gray noted that the Aten solution would be at a solar
              elongation of 90 deg in early July. WISE didn't see the object
              at that time, so there was some motivation to rule out the Aten
              possibility.

              However, WISE did see the object again in early August, and the
              orbit is now definitely Amor with a=2.759, e=0.553, and i=14.57.
              It's no longer on the risk page.

              Just luck that the orbit turned out to permit WISE to do its own
              follow-up, because it definitely can't do targeted follow-up, but
              it seems appropriate to note that the "terrible job" has been
              turned into a "great job". Presumably the matter of appropriate
              discovery credit is no longer an issue.
            • Bill J Gray
              Hi Dave, I d meant to post about this earlier in the month. I was happy to see the new data, especially since the nominal Amor solution just barely stayed at
              Message 6 of 6 , Sep 6, 2010
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                Hi Dave,

                I'd meant to post about this earlier in the month. I was
                happy to see the new data, especially since the nominal
                Amor solution just barely stayed at elongations greater than
                90 degrees, and seemed unlikely to get recovered.

                The Aten solution (the one that would have been "potentially
                dangerous") would have crossed completely over the 90 degree
                elongation line, and it seems to me that it definitely
                would have been found by WISE in early July. So in a way,
                you could say that WISE first eliminated the Aten solution
                (by failing to recover 2010 KH in early July), and then
                confirmed the "real" solution with the August recovery.

                Of course, much of this is pure luck; most objects don't
                have this sort of convenient "coming back for a second pass
                through elongation 90 degrees" trick, and WISE will get them
                once and do no follow-up. However, NEO follow-up wasn't really
                WISE's primary remit anyway. I'd say WISE is doing what it's
                supposed to do (full-sky survey in infrared, catching some
                minor planets and comets in the process) quite well. The sort
                of follow-up Andrea Milani (and I) would very much like to see
                ought to be done by something completely different.

                -- Bill
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