[neo_followup] {MPML} C26FED2 = interesting object
Bill Gray
pluto at projectpluto.com
Tue Feb 18 22:09:04 EST 2020
Hi Sam,
I'd second the request that observations be passed on. I,
for one, have definitely not lost interest in this object.
Far from it.
MPC is quite possibly right about this object being junk.
The nominal AMR I get, with 36 of 37 observations, is
0.014 +/- 0.021 m^2/kg, which really doesn't tell you if it's
a rock or not. (It mostly just rules out it being, say, a loose
scrap of insulation.) If it's a rock, we can run the orbit back
a few orbits with some degree of confidence that the uncertainties
reflect reality. If it's junk, we really have almost no idea
where it was very far back. Junk does not (usually) fit the simple
SRP model over those time spans.
The answer will come from more data, and I do fear that that
flow of data may cease now that MPC has dropped the object from
NEOCP. We may have to follow this guy all the way down to V=24
to definitively get the AMR determined. (Though there will be some
hope of getting precovery observations, especially if it's a rock.)
I have an inquiry in to MPC about this, but haven't heard back
yet. They do, I expect, have some access to information that I
lack. Such as the ability to ask around NASA and ESA and JPL folks
and say, "Do you know anything about this?". They may have done
so and had someone reply, "Oh yeah, we know what that is."
-- Bill
On 2/18/20 7:36 PM, Sam Deen wrote:
> Hi Peter,
>
> Many thanks for the info. I had been assuming the uncertainties in all of the measurements, and probably in a handful of cases slightly underestimating them. To re-emphasize what I should have been clearer about in the original post: all of this is extremely preliminary, and prone to inaccuracy. I definitely wouldn't claim at this point that this object is certainly an artsat, it just seems to be generally leading towards being one.
>
> That said, if anyone has further observations of this object over the next few days, please send them here, publicly or privately! I'd like to get to the bottom of this object if at all possible, and there's still many lingering questions that I don't believe have been adequately answered by the time the MPC pulled it from the NEOCP.
>
> ~Sam
> On Tuesday, February 18, 2020, 4:39:05 PM MST, Peter Birtwhistle <peter at birtwhistle.org.uk> wrote:
>
>
> Hi Sam,
>
> At around mag +21 my four J95 positions are treated rather
> optimistically in the standard FindOrb sigma.txt file. Setting their
> Sigma's to 0.5" (which is still probably smaller than reality) and using
> 36 of the 37 available observations, I get an AMR of 0.009 +/- 0.023
> m^2/kg, which looks to me like rock is still very possible. I'm a little
> surprised it's already been pulled from the NEOCP as a "was not a minor
> planet".
>
> Peter
> J95
>
> On 18/02/2020 20:14, Sam Deen via Groups.Io wrote:
> > With the newest data, it's starting to look like C26FED2 might be an
> > artsat, due to an interesting reason.
> >
> > I've been trying to peer past the March (now April) perigee for a
> > while now, and something interesting has appeared with the most recent
> > observations.
> >
> > Currently, the nominal perigee distance (including free SRP parameter)
> > is 7200 +/- 5800 km. Furthermore, find_orb has started measuring the
> > size/mass ratio with a significance of >1 sigma, at 0.031 +/- 0.021
> > m^2/kg. However, with the perigee distance constrained, the size/mass
> > ratio becomes constrained as well.
> >
> > q=3800 (S22.91590 W84.36982) 0.023 +/- 0.015 m^2/kg
> > q=4000 (S26.15681 W54.32953) 0.023 +/- 0.015 m^2/kg
> > q=4200 (S29.53229 W167.13331) 0.024 +/- 0.014 m^2/kg
> > q=4400 (S33.03794 E95.82559) 0.024 +/- 0.014 m^2/kg
> > q=4600 (S36.68628 E9.64050) 0.025 +/- 0.014 m^2/kg
> > q=4800 (S40.49965 W68.35291) 0.025 +/- 0.014 m^2/kg
> > q=5000 (S44.51065 W139.79428) 0.026 +/- 0.014 m^2/kg
> > q=5200 (S48.76527 E154.22276) 0.027 +/- 0.014 m^2/kg
> > q=5400 (S53.33045 E93.06067) 0.027 +/- 0.014 m^2/kg
> > q=5600 (S58.30737 E36.38756) 0.027 +/- 0.014 m^2/kg
> > q=5800 (S63.86060 W15.62502) 0.028 +/- 0.014 m^2/kg
> > q=6000 (S70.28076 W61.49060) 0.028 +/- 0.014 m^2/kg
> > q=6200 (S78.02334 W92.00780) 0.029 +/- 0.014 m^2/kg
> > q=6300 (S81.65253 W79.61484) 0.029 +/- 0.014 m^2/kg
> > q=6350 (S80.24785 W46.75104) 0.029 +/- 0.014 m^2/kg
> > q=6371 (S77.71472 W35.97998) 0.029 +/- 0.014 m^2/kg
> > q=6400 0.029 +/- 0.014 m^2/kg
> > q=6600 0.030 +/- 0.014 m^2/kg
> > q=6800 0.030 +/- 0.014 m^2/kg
> > q=7000 0.031 +/- 0.014 m^2/kg
> >
> > Obviously the area/mass ratio is a fairly poorly constrained even for
> > objects observed over multiple months or years, but there seems to be
> > something to be said about the fact that higher, more reasonable
> > perigee solution it has, the more non-gravitational movement is
> > required. It's erratic enough that I wouldn't be certain it's
> > artificial at this point, but the fact that for it to be a rock, it
> > would have to come awfully, nearly impossibly, close to Earth.
> >
> > At any rate, assuming nothing too funky happened around the April
> > approach, now there's a few more certain orbits before April:
> >
> > 2019/04/04 q = 7200 +/- 5800 km, e = 0.9927 +/- 0.0057
> > 2019/01/18 q = 120,000 +/- 110,000 km, e = 0.885 +/- 0.079
> > 2018/10/25 q = 360,000 +/- 360,000 km, e = 0.65 +/- 0.30 (at which
> > point it could have either entered Earth orbit, or been orbiting before.)
> >
> > ~Sam
> > On Monday, February 17, 2020, 12:53:42 AM MST, Sam Deen via Groups.Io
> > <planetaryscience=yahoo.com at groups.io <mailto:yahoo.com at groups.io>> wrote:
> >
> >
> > Here's an update on the analysis with ~1.5 days of observations:
> >
> > Regarding the orbital evolution:
> >
> > The following perihelia have definitely, no-question taken place:
> >
> > 2019/03/23 (q = 4,300 +/- 7,600 km, e = 0.999 +/- 0.016)
> > 2019/06/22 (q = 309,000 +/- 11,000 km, e = 0.632 +/- 0.017)
> > 2019/09/03 (q = 341,000 +/- 24,000 km, e = 0.636 +/- 0.014)
> > 2019/11/18 (q = 298,200 +/- 5,900 km, e = 0.7146 +/- 0.0073)
> > 2020/02/13 (q = 47,061 +/- 22 km, e = 0.959661 +/- 0.000064)
> > [ejected by April 2020]
> >
> > The object has definitely been orbiting us since the 2019/03/23
> > perigee at least, but unfortunately a close approach with the Moon
> > between then and the next perigee combined with the resultant
> > retroactive low perigee creates a gravitational keyhole that makes it
> > really difficult to figure out what happened before.
> >
> > I very much doubt any of the orbits having it launching from Earth are
> > true, since there's no way an object would be launched from the
> > surface directly to a barely-bound orbit without any kind of reports
> > on it. Not to mention that nothing above geosynchronous orbit was
> > launched in March 2019. Beresheet was launched on 22 February to the
> > Moon, but the projected orbit of this object doesn't really fit with a
> > Feb 22 launch at all. I could analyze its possible "launch" path, but
> > I expect it wouldn't be very helpful at all.
> >
> > Regarding the AMR and telling if it's an artsat or not:
> >
> > The AMR has been constrained to a somewhat nonsensical -0.016 +/-
> > 0.067 m^2/kg (read: <0.051 m^2/kg) which rules out it being one of
> > Bill's so-called ETBOs, but still leaves it firmly in the realm of
> > possible artsat bits. Also, although the object has only been observed
> > between elongations of ~128 and ~133 degrees, I suppose it's worth
> > mentioning that it hasn't displayed any massive differences in
> > brightness with phase or with time. The most consistent observer, L01,
> > recorded its brightness as varying by only 0.2 magnitudes over the 5
> > observations made of it on 02/16 over 15 minutes, and 0.4 magnitudes
> > over the 3 observations made of it on 02/17 over 20 minutes. Of course
> > depending on the exact exposure length, this seems to imply that
> > C26FED2 does not have a drastic, chaotic light curve like tumbling
> > artsats tend to have. Just as a disclaimer, though, all of this is
> > very preliminary and absolutely subject to being incorrect.
> >
> > Many thanks to all of the people who have gone to the effort of
> > observing this object in recent days! Hopefully a handful more over
> > the next few days should let us peer past the 2019/03/23 keyhole and
> > see if it's been here a while, or just got captured.
> >
> > ~Sam
> > On Sunday, February 16, 2020, 10:35:30 AM MST, Sam Deen via Groups.Io
> > <planetaryscience=yahoo.com at groups.io <mailto:yahoo.com at groups.io>> wrote:
> >
> >
> > My bad... noticed far too late that a large AMR makes an object empty
> > trash baggy, and not more like a solid object. Ignore my comments on
> > the current AMR estimate, they were definitely far too premature to
> > say much of anything.
> >
> > On Sunday, February 16, 2020, 8:11:17 AM MST, Bill J. Gray
> > <pluto at projectpluto.com <mailto:pluto at projectpluto.com>> wrote:
> >
> >
> > On 2/16/20 1:20 AM, Sam Deen wrote:
> > > I'm leaning on rock, personally.
> >
> > I expect to remain in the "insufficient data" camp for
> > quite a while. It's unlikely that we'll get enough
> > astrometry to tell.
> >
> > > The current orbit gives an Area/mass ratio of 2.8 +/- 8.0 m^2/kg,
> > which obviously is very far from conclusive,
> >
> > Extremely inconclusive. The object could have the effectively
> > zero AMR of a rock. Or it could have the 5.6 m^2/kg of an empty
> > trash bag object, and the residuals would be the same. Or
> > anywhere in between and still fit the available data.
> >
> > We're up to 19 observations as I write this, which has
> > brought the AMR to 0.13 +/- 0.51. If it's artificial, an
> > AMR of, say, 0.02 would probably be in the right ballpark
> > for a piece of junk this size. I don't think it's an ETBO,
> > because something that light would have a tough time staying
> > in orbit around us; solar radiation pressure would push
> > it out into an heliocentric orbit... actually, then into
> > interstellar space; ETBOs are that light.
> >
> > but seems to point towards the object not being artificial. For
> > comparisons, here are a few AMRs according to Bill's distant artsat
> > pseudo-mpec catalog:
> >
> > Yes, but we also have, for example, ZTF00V9 = ZTF00Vv
> > = ZTF00Y5 = ZTF00Yq, with an area/mass ratio of 107 +/- 3
> > m^2/kg :
> >
> > https://www.projectpluto.com/pluto/mpecs/ztf00v9.htm#etbo
> >
> > and many in between. I've learned, mostly over the last
> > couple of years, that artsats come with a fairly bewildering
> > range of area/mass ratios. (I'd previously assumed such high
> > AMRs must be bogus, and that I had bad data or data for
> > two or three different objects, or that it was maneuvering.
> > Once I started looking for ETBOs, I realized they were
> > everywhere. One, 'Multijunk', has been a "discovery" on
> > NEOCP at least two dozen times.)
> >
> > > Im not sure how to use find_orb to force-fit test AMR values,
> >
> > You can apply a constraint of, say, "A=0.005", much as
> > you would constrain "e=1" if you thought it was a comet or
> > "a=5.2,e=0" for a circular Jupiter Trojan orbit.
> >
> > but I suppose that even with a poorly-defined orbit, being able to
> > demonstrate its AMR is over 0.05 m^2/kg would make it most likely not
> > an artsat in my opinion at least.
> >
> > If you find, say, AMR = 0.020 +/- 0.001, _then_ you've
> > got evidence it's an artsat, with the uncertainty in the
> > value significantly less than the value itself. Proving
> > something is _not_ an artsat is a lot harder. Tell me
> > you've got AMR = 0.001 +/- 0.010, and I'll just say that
> > an AMR of 0.01 would fit within that uncertainty, so it
> > _could_ be an artsat, roughly as likely as being a rock.
> >
> > Getting an accurate AMR for a rock has happened... in
> > fact, for 2006 RH120 (only confirmed temporarily captured
> > rock), we got AMR = (98.5 +/- 2)E-5 m^2/kg. That object,
> > however, did three orbits over most of a year, and we got
> > a radar observation on it. Unless we get far more precovery
> > data than I expect, astrometry isn't going to tell us if
> > this is a rock or not. Radar data might -- for example,
> > with 2018 AV2, we not only measured a high AMR; Arecibo
> > got a stronger radar echo from it than would be expected
> > for a rock. Or spectroscopy, as happened initially with
> > J002E3 (it had the spectral signature of titanium dioxide
> > paint). Or infrared data; if the albedo is near 100%,
> > you start to think about an object with white TiO2 paint.
> >
> > >
> > > Additionally, the aphelion of this thing is seriously impressively
> > large. Its aphelion is recorded at 0.0148 +/- 0.0005 AU, which is
> > larger than the radius of Earth's hill sphere at ~0.010004 AU. I
> > assume find_orb wouldn't be giving a geocentric orbit if it was
> > orbiting faster than escape velocity, though.
> >
> > It would, but with e > 1. (In Settings, you can
> > choose the reference object. The default 'automatic'
> > setting gets you a geocentric orbit if the object is
> > within the earth's sphere of influence, a selenocentric
> > orbit if it's with the moon's sphere of influence, etc.
> > But you can, for example, insist on a Neptune-centric
> > orbit for an object that is nowhere near Neptune.)
> >
> > Running the orbit forwards shows it won't be staying in geocentric
> > orbit for long, at least nominally. The radial velocity will reach its
> > minimum around April 7, at which point I assume the gravitational hold
> > of the sun will start to take over, and it will move back into
> > heliocentric orbit. Running the orbit backwards nominally says it's
> > been in orbit since February 13 2018, putting it as having orbited us
> > for around 2 years by now. Of course, that's massively premature to
> > conclude with only half a day's worth of observations. All I can say
> > for sure is that it's orbiting us
> > > right now, and was almost surely orbiting us since the November perigee.
> >
> > I think there may have been some previous perigees, but
> > yeah, we don't have enough data yet to say.
> >
> > >
> > > In regards to ephemerides:
> > >
> > > C26FED2 would have been above magnitude 23 since February 10,
> > although with a low enough elongation that would have made detection
> > improbable. The first time it really would have been detectable was on
> > February 13 when it peaked around magnitude ~16-17 at an elongation of
> > 124 degrees. It has been slowly dimming ever since, and will remain
> > above magnitude 23 until February 26.
> > >
> > > I would give it good chances of at least a couple other
> > observatories spotting it over the coming days. It's a shame the
> > orbital period is so long, though. Once it stops being visible on
> > February 26, it won't be coming back.. So, the next few days are all
> > we have to figure out more about this weird object. Hopefully some
> > larger scopes will get pointed at it in that time!
> > >
> > > ~Sam
> > > On Saturday, February 15, 2020, 5:59:52 PM MST, Bill Gray
> > <pluto at projectpluto.com <mailto:pluto at projectpluto.com> <mailto:pluto at projectpluto.com <mailto:pluto at projectpluto.com>>> wrote:
> > >
> > >
> > > With follow-up from (L01) Višnjan, it's confirmed that this
> > > is a temporarily captured object. Whether it's natural or junk
> > > is unknown. I _really_ hope someone gets more data for it. If
> > > it's a temporarily captured rock, that's a Really Big Deal.
> > >
> > > -- Bill
> > >
> > > On 2/15/20 1:09 PM, Bill Gray wrote:
> > > > Hi folks,
> > > >
> > > > This object might just be a satellite. If so, it's a
> > > > somewhat unusual one, in a very elongated orbit. It may be
> > > > lunar ejecta passing by us, perhaps even a temporarily captured
> > > > object a la 2006 RH120 = 6R10DB9. Or it could be heliocentric
> > > > junk passing by us, similar to J002E3 or 2018 AV2. Further
> > > > observations would be a really excellent idea.
> > > >
> > > > Thanks! -- Bill
> > >
> > > --
> > > neo_followup mailing list
> > > neo_followup at projectpluto.com <mailto:neo_followup at projectpluto.com> <mailto:neo_followup at projectpluto.com <mailto:neo_followup at projectpluto.com>>
> > <mailto:neo_followup at projectpluto.com <mailto:neo_followup at projectpluto.com>
> > <mailto:neo_followup at projectpluto.com <mailto:neo_followup at projectpluto.com>>>
> >
> > > http://projectpluto.com/mailman/listinfo/neo_followup_projectpluto.com
> >
> >
> >
> >
> >
>
>
> -=-=-=-=-=-=-=-=-=-=-=-
> Groups.io Links: You receive all messages sent to this group.
>
> View/Reply Online (#35370): https://groups.io/g/mpml/message/35370
> Mute This Topic: https://groups.io/mt/71319863/2027585
> -=-=-
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> 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.
> -=-=-
> Group Owner: mpml+owner at groups.io <mailto:owner at groups.io>
> Unsubscribe: https://groups.io/g/mpml/unsub [planetaryscience at yahoo.com <mailto:planetaryscience at yahoo.com>]
>
> -=-=-=-=-=-=-=-=-=-=-=-
>
More information about the neo_followup
mailing list