Talk:(278361) 2007 JJ43

Absolute magnitude

Change in absolute magnitude reflect new measurement of apparent magnitude: 19.3 in June 2010 vs. 20.6 in June 2008. The orbit and distance did not change significantly in the recent update. —Preceding unsigned comment added by 207.191.220.250 (talk) 20:46, 13 September 2010 (UTC)

Object now has absolute magnitude of 3.7 according to the Minor Planet Centers list of Transneptunian Objects. This is no longer among the ten brightest. —Preceding unsigned comment added by 75.160.128.140 (talk) 19:50, 16 May 2011 (UTC)

According to [1], abs. magn. is now 3.2, so it might be among the 10 brightest again. --Roentgenium111 (talk) 15:04, 16 February 2012 (UTC)

Szabo's size

@Hevron1998: The conference presentation PDF referenced here does not indicate where this diameter (670) comes from. The arXiv version of the paper that this presentation references, Pushing the limits: K2 observations of the trans-Neptunian objects 2002 GV31 and (278361) 2007 JJ43, gives a value of 610, but it is just derived from an assumed albedo (.13) and the JPL absolute magnitude (3.9). Does anybody have access to the actual Astrophysical Journal article to see where the 670 number comes from? Tbayboy (talk) 18:29, 28 November 2015 (UTC)

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Anomalous size estimates?

I might be sounding like a bit of a stuck record, given recent comments and edits on other TNOs, plus also what others have said above, but: How have the three listed size estimates been arrived at? After all, the usual state of affairs is that, with a fixed brightness and colour profile, a lower albedo estimate matches a larger object size - not a smaller one, which is what appears to be the case in this article. Are the lower albedos also matched to rather higher magnitudes (ie, a dimmer appearance) or something? After all, the largest size, and highest estimated diameter, shown here is also with the highest magnitude out of the 3.2, 3.7 and 3.9 mentioned; in other words, it's the lowest estimate of the object's brightness.

If 3.9mag and 13% albedo makes for a 610km diameter, a 3.2mag observation (1.91x brighter on a linear scale) and 8% assumed albedo (= same brightness from 1.625 more light falling on the object surface) should make for a much larger 1073km diameter (610 x square root of 3.096x more light when normalised to 100% albedo) - somewhere in the range of Sedna, Quaoar or Tethys, larger than Ceres, and a firm shoo-in for being confidently called a dwarf planet. If we split the responsibility for reducing size to 538km between magnitude and albedo, we'd be looking at something like 4.04 and 14.7% respectively. If we want to reduce the albedo to less than 10%, the magnitude will have to increase considerably, and vice-versa. 146.199.60.87 (talk) 18:35, 13 August 2019 (UTC)

Update: The plot thickens. The Johnson Archive page doesn't even GIVE a magnitude, only an albedo and colour... sometimes (I guess we just have to take their diameter estimates on trust?). The cite given for Brown's estimate was both a) horrendously out of date (8 years old, and I've only been able to improve it by 3 so far), b) wholly incorrect (it said 694km at the time, not 554km, and the mag/albedo were similarly wrong; "now", ie 2014, it's 617km). So that's not really given the above question any answers.

I'm going to see if I can get a fresher version of the Brown page, because I'm sure it's out there, just the URL being used by the Internet Archive is broken (nothing but "crawl time errors" for the last five years of captures), but his list generally seems to just be fairly crude guesses at the best of time, with no sourcing any better than the usually hilariously terrible JPL or MPC figures, and there's a decent chance it'll just repeat the figure from the 2015 paper - which at this point should probably be considered the most reliable and effectively the gold standard, as it actually uses some kind of quotable research, and if it includes anything like e.g. Herschel or Spitzer space telescope data it'll be pretty much the best we have. 146.199.60.87 (talk) 19:02, 13 August 2019 (UTC)

Absolute magnitudes and colors should only be taken from specialized photometric literature, not from some websites. Please, also take into account that magnitudes can refers to different spectral bands: most often V but sometimes R or B. Ruslik_Zero 10:50, 14 August 2019 (UTC)