<html><head></head><body><div class="ydpb823fbacyahoo-style-wrap" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:13px;"><div></div><div>With the newest data, it's starting to look like C26FED2 might be an artsat, due to an interesting reason.</div><div><br></div><div dir="ltr" data-setdir="false">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.</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">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.</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false"><div>q=3800 (S22.91590 W84.36982) 0.023 +/- 0.015 m^2/kg<br>q=4000 (S26.15681 W54.32953) 0.023 +/- 0.015 m^2/kg<br>q=4200 (S29.53229 W167.13331) 0.024 +/- 0.014 m^2/kg<br>q=4400 (S33.03794 E95.82559) 0.024 +/- 0.014 m^2/kg<br>q=4600 (S36.68628 E9.64050) 0.025 +/- 0.014 m^2/kg <br>q=4800 (S40.49965 W68.35291) 0.025 +/- 0.014 m^2/kg<br>q=5000 (S44.51065 W139.79428) 0.026 +/- 0.014 m^2/kg <br>q=5200 (S48.76527 E154.22276) 0.027 +/- 0.014 m^2/kg<br>q=5400 (S53.33045 E93.06067) 0.027 +/- 0.014 m^2/kg<br>q=5600 (S58.30737 E36.38756) 0.027 +/- 0.014 m^2/kg<br>q=5800 (S63.86060 W15.62502) 0.028 +/- 0.014 m^2/kg<br>q=6000 (S70.28076 W61.49060) 0.028 +/- 0.014 m^2/kg<br>q=6200 (S78.02334 W92.00780) 0.029 +/- 0.014 m^2/kg<br>q=6300 (S81.65253 W79.61484) 0.029 +/- 0.014 m^2/kg<br>q=6350 (S80.24785 W46.75104) 0.029 +/- 0.014 m^2/kg<br>q=6371 (S77.71472 W35.97998) 0.029 +/- 0.014 m^2/kg<br>q=6400 0.029 +/- 0.014 m^2/kg<br>q=6600 0.030 +/- 0.014 m^2/kg<br>q=6800 0.030 +/- 0.014 m^2/kg<br>q=7000 0.031 +/- 0.014 m^2/kg</div><div><br></div><div dir="ltr" data-setdir="false">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.</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">At any rate, assuming nothing too funky happened around the April approach, now there's a few more certain orbits before April:</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">2019/04/04 q = 7200 +/- 5800 km, e = 0.9927 +/- 0.0057</div><div dir="ltr" data-setdir="false">2019/01/18 q = 120,000 +/- 110,000 km, e = 0.885 +/- 0.079</div><div dir="ltr" data-setdir="false">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.)<br></div></div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">~Sam<br></div></div><div id="yahoo_quoted_2340788865" class="yahoo_quoted">
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On Monday, February 17, 2020, 12:53:42 AM MST, Sam Deen via Groups.Io <planetaryscience=yahoo.com@groups.io> wrote:
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<div dir="ltr">Here's an update on the analysis with ~1.5 days of observations:</div><div dir="ltr"><br clear="none"></div><div dir="ltr">Regarding the orbital evolution:</div><div dir="ltr"><br clear="none"></div><div dir="ltr">The following perihelia have definitely, no-question taken place:<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">2019/03/23 (q = 4,300 +/- 7,600 km, e = 0.999 +/- 0.016)<br clear="none"></div><div dir="ltr">2019/06/22 (q = 309,000 +/- 11,000 km, e = 0.632 +/- 0.017)<br clear="none"></div><div dir="ltr">2019/09/03 (q = 341,000 +/- 24,000 km, e = 0.636 +/- 0.014)<br clear="none"></div><div dir="ltr">2019/11/18 (q = 298,200 +/- 5,900 km, e = 0.7146 +/- 0.0073)<br clear="none"></div><div dir="ltr">2020/02/13 (q = 47,061 +/- 22 km, e = 0.959661 +/- 0.000064)</div><div dir="ltr">[ejected by April 2020]<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">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.</div><div dir="ltr"><br clear="none"></div><div dir="ltr">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.<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">Regarding the AMR and telling if it's an artsat or not:</div><div dir="ltr"><br clear="none"></div><div dir="ltr">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.<br clear="none"></div><div dir="ltr"><br clear="none"></div><div dir="ltr">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.</div><div dir="ltr"><br clear="none"></div><div dir="ltr">~Sam<br clear="none"></div>
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On Sunday, February 16, 2020, 10:35:30 AM MST, Sam Deen via Groups.Io <planetaryscience=yahoo.com@groups.io> wrote:
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<div>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.</div><div><br clear="none"></div>
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On Sunday, February 16, 2020, 8:11:17 AM MST, Bill J. Gray <pluto@projectpluto.com> wrote:
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<div><div dir="ltr">On 2/16/20 1:20 AM, Sam Deen wrote:<br clear="none">> I'm leaning on rock, personally.<br clear="none"><br clear="none"> I expect to remain in the "insufficient data" camp for<br clear="none">quite a while. It's unlikely that we'll get enough<br clear="none">astrometry to tell.<br clear="none"><br clear="none">> The current orbit gives an Area/mass ratio of 2.8 +/- 8.0 m^2/kg, which obviously is very far from conclusive, <br clear="none"><br clear="none"> Extremely inconclusive. The object could have the effectively<br clear="none">zero AMR of a rock. Or it could have the 5.6 m^2/kg of an empty<br clear="none">trash bag object, and the residuals would be the same. Or<br clear="none">anywhere in between and still fit the available data.<br clear="none"><br clear="none"> We're up to 19 observations as I write this, which has<br clear="none">brought the AMR to 0.13 +/- 0.51. If it's artificial, an<br clear="none">AMR of, say, 0.02 would probably be in the right ballpark<br clear="none">for a piece of junk this size. I don't think it's an ETBO,<br clear="none">because something that light would have a tough time staying<br clear="none">in orbit around us; solar radiation pressure would push<br clear="none">it out into an heliocentric orbit... actually, then into<br clear="none">interstellar space; ETBOs are that light.<br clear="none"><br clear="none">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:<br clear="none"><br clear="none"> Yes, but we also have, for example, ZTF00V9 = ZTF00Vv<br clear="none">= ZTF00Y5 = ZTF00Yq, with an area/mass ratio of 107 +/- 3<br clear="none">m^2/kg :<br clear="none"><br clear="none"><a rel="nofollow" shape="rect" target="_blank" href="https://www.projectpluto.com/pluto/mpecs/ztf00v9.htm#etbo">https://www.projectpluto.com/pluto/mpecs/ztf00v9.htm#etbo</a><br clear="none"><br clear="none"> and many in between. I've learned, mostly over the last<br clear="none">couple of years, that artsats come with a fairly bewildering<br clear="none">range of area/mass ratios. (I'd previously assumed such high<br clear="none">AMRs must be bogus, and that I had bad data or data for<br clear="none">two or three different objects, or that it was maneuvering.<br clear="none">Once I started looking for ETBOs, I realized they were<br clear="none">everywhere. One, 'Multijunk', has been a "discovery" on<br clear="none">NEOCP at least two dozen times.)<br clear="none"><br clear="none">> Im not sure how to use find_orb to force-fit test AMR values,<br clear="none"><br clear="none"> You can apply a constraint of, say, "A=0.005", much as<br clear="none">you would constrain "e=1" if you thought it was a comet or<br clear="none">"a=5.2,e=0" for a circular Jupiter Trojan orbit.<br clear="none"><br clear="none"> 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.<br clear="none"><br clear="none"> If you find, say, AMR = 0.020 +/- 0.001, _then_ you've<br clear="none">got evidence it's an artsat, with the uncertainty in the<br clear="none">value significantly less than the value itself. Proving<br clear="none">something is _not_ an artsat is a lot harder. Tell me<br clear="none">you've got AMR = 0.001 +/- 0.010, and I'll just say that<br clear="none">an AMR of 0.01 would fit within that uncertainty, so it<br clear="none">_could_ be an artsat, roughly as likely as being a rock.<br clear="none"><br clear="none"> Getting an accurate AMR for a rock has happened... in<br clear="none">fact, for 2006 RH120 (only confirmed temporarily captured<br clear="none">rock), we got AMR = (98.5 +/- 2)E-5 m^2/kg. That object,<br clear="none">however, did three orbits over most of a year, and we got<br clear="none">a radar observation on it. Unless we get far more precovery<br clear="none">data than I expect, astrometry isn't going to tell us if<br clear="none">this is a rock or not. Radar data might -- for example,<br clear="none">with 2018 AV2, we not only measured a high AMR; Arecibo<br clear="none">got a stronger radar echo from it than would be expected<br clear="none">for a rock. Or spectroscopy, as happened initially with<br clear="none">J002E3 (it had the spectral signature of titanium dioxide<br clear="none">paint). Or infrared data; if the albedo is near 100%,<br clear="none">you start to think about an object with white TiO2 paint.<br clear="none"><br clear="none">> <br clear="none">> 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.<br clear="none"><br clear="none"> It would, but with e > 1. (In Settings, you can<br clear="none">choose the reference object. The default 'automatic'<br clear="none">setting gets you a geocentric orbit if the object is<br clear="none">within the earth's sphere of influence, a selenocentric<br clear="none">orbit if it's with the moon's sphere of influence, etc.<br clear="none">But you can, for example, insist on a Neptune-centric<br clear="none">orbit for an object that is nowhere near Neptune.)<br clear="none"><br clear="none"> 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<br clear="none">> right now, and was almost surely orbiting us since the November perigee.<br clear="none"><br clear="none"> I think there may have been some previous perigees, but<br clear="none">yeah, we don't have enough data yet to say.<br clear="none"><br clear="none">> <br clear="none">> In regards to ephemerides:<br clear="none">> <br clear="none">> 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.<br clear="none">> <br clear="none">> 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!<br clear="none">> <br clear="none">> ~Sam<br clear="none">> On Saturday, February 15, 2020, 5:59:52 PM MST, Bill Gray <<a rel="nofollow" shape="rect" ymailto="mailto:pluto@projectpluto.com" target="_blank" href="mailto:pluto@projectpluto.com">pluto@projectpluto.com</a>> wrote:<br clear="none">> <br clear="none">> <br clear="none">> With follow-up from (L01) Višnjan, it's confirmed that this<br clear="none">> is a temporarily captured object. Whether it's natural or junk<br clear="none">> is unknown. I _really_ hope someone gets more data for it. If<br clear="none">> it's a temporarily captured rock, that's a Really Big Deal.<br clear="none">> <br clear="none">> -- Bill<br clear="none">> <br clear="none">> On 2/15/20 1:09 PM, Bill Gray wrote:<br clear="none">> > Hi folks,<br clear="none">> ><br clear="none">> > This object might just be a satellite. If so, it's a<br clear="none">> > somewhat unusual one, in a very elongated orbit. It may be<br clear="none">> > lunar ejecta passing by us, perhaps even a temporarily captured<br clear="none">> > object a la 2006 RH120 = 6R10DB9. Or it could be heliocentric<br clear="none">> > junk passing by us, similar to J002E3 or 2018 AV2. Further<br clear="none">> > observations would be a really excellent idea.<br clear="none">> ><br clear="none">> > Thanks! -- Bill<br clear="none">> <br clear="none">> -- <br clear="none">> neo_followup mailing list<br clear="none">> <a rel="nofollow" shape="rect" ymailto="mailto:neo_followup@projectpluto.com" target="_blank" href="mailto:neo_followup@projectpluto.com">neo_followup@projectpluto.com</a> <mailto:<a rel="nofollow" shape="rect" ymailto="mailto:neo_followup@projectpluto.com" target="_blank" href="mailto:neo_followup@projectpluto.com">neo_followup@projectpluto.com</a>><div class="yiv6296859307ydp627e79d5yqt6511982399" id="yiv6296859307ydp627e79d5yqtfd62922"><br clear="none">> <a rel="nofollow" shape="rect" target="_blank" href="http://projectpluto.com/mailman/listinfo/neo_followup_projectpluto.com">http://projectpluto.com/mailman/listinfo/neo_followup_projectpluto.com</a></div><br clear="none"><br clear="none"><br clear="none"><br clear="none"></div></div></div>
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