REVIEW 1 cited by
The discovery and characterization of minimoon 2024 PT$_5$
T0 review · reviewed 2026-08-12 · deepseek-v4-flash
Pith's one-line read 2024 PT5 is a newly discovered ~5 m minimoon captured by Earth for about 60 days, with colors and density resembling lunar rock and S-type asteroids.
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
The colors place 2024 PT5 close to lunar rock samples and to Sv-type asteroids, two groups that are hard to tell apart with only four broadband measurements. Assuming an albedo of 0.21, the absolute magnitude of 28.6 implies a diameter near 5 meters. The orbit fit also detects a small nongravitational acceleration from sunlight, which gives an area-to-mass ratio of about 7e-5 m2/kg. Combining that with the diameter yields a density of roughly 3.9 g/cm3, within the range of rocky materials. A separate comparison with a model of near-Earth asteroid sources favors the inner Main Belt (88% probability) but does not exclude a lunar impact origin.
The paper's claims are mostly transparent about uncertainties, but the derived size and density depend on an assumed albedo and an assumed phase law for converting brightness to absolute magnitude, and the rotation period of about 2600 seconds is inferred from a short time series. The spectral match statement has a minor internal inconsistency between a figure caption and the reported chi-square values.
Extended reading notes
Core claim
2024 PT5 is a newly discovered minimoon, temporarily captured by the Earth-Moon system from 2024 September 29 to November 25 (~60 days, the shortest known capture, with no complete revolution), whose measured colors (g-r=0.58, r-i=0.29, i-z=-0.27) best match lunar rock samples and Sv-type asteroids, whose absolute magnitude 28.64±0.04 gives a diameter of 5.4±1.2 m for an assumed albedo of 0.21, and whose radiation-pressure-fitted area-to-mass ratio implies a density of 3.9±2.1 g/cm3, compatible with a rocky composition.
Load-bearing premise
The density result rests on the fitted area-to-mass ratio AMR=7.02±2.05e-5 m2/kg being a true radiation-pressure signal rather than an artifact of the assumed ~1-arcsec astrometric uncertainties or unmodeled systematic errors; the AMR is only a ~3.4-sigma detection and the density also scales with the assumed albedo (0.21) and the adopted phase function when converting photometry to H. If the astrometric error model or the albedo assumption is wrong, the derived diameter and density fail with it.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Assumptions & free parameters
free parameters (3)
- Visible geometric albedo pv =
0.21 (primary), 0.14 (lunar alternative), 0.1 (conservative)
- Phase coefficient G =
0.2
- Area-to-mass ratio (AMR) =
7.02e-5 ± 2.05e-5 m2/kg
assumptions (6)
- domain assumption The H-G phase function (Bowell et al. 1988) with G=0.2 is valid for 2024 PT5 at phase angle 84.4 deg.
- domain assumption The only non-gravitational force needed to fit the orbit is solar radiation pressure acting through a constant area-to-mass ratio.
- domain assumption The albedo of 2024 PT5 is represented by the S-complex value 0.21 (or lunar 0.14) from literature albedo distributions.
- domain assumption The single-epoch g,r,i,Z colors are representative of the surface reflectance without significant phase-reddening or rotational color variation.
- domain assumption The lightcurve amplitude maps to an axial ratio via b/a=10^(0.4A) with a≈c (prolate triaxial ellipsoid).
- domain assumption The NEOMOD3 model's source probabilities apply to this single object, and the NEO albedo model (Morbidelli et al. 2020) can be weighted by those probabilities.
Cite this review
Pith. "Pith review of The discovery and characterization of minimoon 2024 PT$_5$." pith.science (2026). https://pith.science/paper/NZMVOTOF
@misc{pith2026241108029,
author = {Pith},
title = {Pith review of: The discovery and characterization of minimoon 2024 PT$_5$},
year = {2026},
howpublished = {\url{https://pith.science/paper/NZMVOTOF}},
note = {Machine review of arXiv:2411.08029}
}
abstract
Minimoons are asteroids that become temporarily captured by the Earth-Moon system. We present the discovery of 2024 PT$_5$, a minimoon discovered by the Asteroid Terrestrial-impact Last Alert System (ATLAS) Sutherland telescope on 2024 August 7. The minimoon with heliocentric semi-major axis, $a$$\sim$1.01 au, and perihelion, $q$$\sim$0.99 au, became captured by the Earth-Moon system on 2024 September 29 and left on 2024 November 25 UTC. Visible g, r, i, and Z spectrophotometry was obtained using Gemini North/Gemini Multi-Object Spectrograph (GMOS) on 2024 September 27. The color indices are g-r = 0.58$\pm$0.04, r-i = 0.29$\pm$0.04, i-Z = -0.27$\pm$0.06, and the spectrum best matches lunar rock samples followed by S-complex asteroids. Assuming an albedo of 0.21 and using our measured absolute magnitude of 28.64$\pm$0.04, 2024 PT$_5$ has a diameter of 5.4$\pm$1.2 m. We also detect variations in the lightcurve of 2024 PT$_5$ with a 0.28$\pm$0.07 magnitude amplitude and a double-peaked period of $\sim$2600$\pm$500 s. We improve the orbital solution of 2024 PT$_5$ with our astrometry and estimate the effect of radiation pressure on its deriving an area-to-mass ratio of 7.02$\pm$2.05$\times$10$^{-5}$ m$^2$/kg, implying a density of $\sim$3.9$\pm$2.1 g/cm$^3$, compatible with having a rocky composition. If we assume 2024 PT$_5$ is from the NEO population, its most likely sources are resonances in the inner Main Belt by comparing its orbit with the NEO population model, though this does not exclude a lunar origin.
Figures
Figures from the paper (4 more)
Forward citations
Cited by 1 Pith paper
-
On The Lunar Origin of Near-Earth Asteroid 2024 PT5
2024 PT5 is likely the second near-Earth object of lunar origin, identified by its Moon-like reflectance spectrum and natural, debris-free orbit.
Reference graph
Works this paper leans on
-
[1]
, " * write output.state after.block = add.period write newline
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-
[2]
write newline
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-
[3]
- [1] #1 = = ^ ^ ^ .\!\!^ d .\!\!^ h .\!\!^ m .\!\!^ s .\!\!^ @mss
thebibliography [1] 20pt to REFERENCES 6pt =0pt 10pt plus 3pt =0pt =0pt =1pt plus 1pt =0pt =0pt -12pt =13pt plus 1pt =20pt =13pt plus 1pt \@M =10000 =-1.0em =0pt =0pt 0pt =0pt =1.0em @enumiv\@empty 10000 10000 `\.\@m \@noitemerr \@latex@warning Empty `thebibliography' environment \@ifnextchar \@reference \@latexerr Missing key on reference command Each re...
2017
-
[4]
P., Farinella , P., Zappal\`a , V., & Cellino , A
Binzel , R. P., Farinella , P., Zappal\`a , V., & Cellino , A. 1989, in Asteroids II, ed. R. P. Binzel , T. Gehrels , & M. S. Matthews , 416--441
work page 1989
-
[5]
Binzel , R. P., Rivkin , A. S., Stuart , J. S., et al. 2004, , 170, 259, 10.1016/j.icarus.2004.04.004
-
[6]
T., Ghosal , M., & Jedicke , R
Bolin , B. T., Ghosal , M., & Jedicke , R. 2024, , 527, 1633, 10.1093/mnras/stad3227
-
[7]
Bolin , B. T., Noll , K. S., Caiazzo , I., Fremling , C., & Binzel , R. P. 2023, , 400, 115562, 10.1016/j.icarus.2023.115562
arXiv 2023
-
[8]
Bolin , B. T., Weaver , H. A., Fernandez , Y. R., et al. 2018, , 852, L2, 10.3847/2041-8213/aaa0c9
Show all 70 references
-
[9]
T., Fremling , C., Holt , T
Bolin , B. T., Fremling , C., Holt , T. R., et al. 2020, , 900, L45, 10.3847/2041-8213/abae69
2020 doi
-
[10]
T., Fernandez , Y
Bolin , B. T., Fernandez , Y. R., Lisse , C. M., et al. 2021, , 161, 116, 10.3847/1538-3881/abd94b
2021 doi
-
[11]
T., Ahumada , T., van Dokkum , P., et al
Bolin , B. T., Ahumada , T., van Dokkum , P., et al. 2022, , 517, L49, 10.1093/mnrasl/slac089
2022 doi
-
[12]
1988, Asteroids II, 399
Bowell , E., Hapke , B., Domingue , D., et al. 1988, Asteroids II, 399
1988
-
[13]
A., Connors , M., et al
Brasser , R., Innanen , K. A., Connors , M., et al. 2004, , 171, 102, 10.1016/j.icarus.2004.04.019
2004 doi
-
[14]
J., & Binzel , R
Bus , S. J., & Binzel , R. P. 2002, Icarus, 158, 146, 10.1006/icar.2002.6856
2002
-
[15]
2007, , 467, 777, 10.1051/0004-6361:20066514
Casali , M., Adamson , A., Alves de Oliveira , C., et al. 2007, , 467, 777, 10.1051/0004-6361:20066514
2007 doi
-
[16]
C., Magnier , E
Chambers , K. C., Magnier , E. A., Metcalfe , N., et al. 2016, ArXiv e-prints. 1612.05560
2016 arXiv
-
[17]
W., Binzel , R
Delbo , M., Harris , A. W., Binzel , R. P., Pravec , P., & Davies , J. K. 2003, , 166, 116, 10.1016/j.icarus.2003.07.002
2003 doi
-
[18]
E., Binzel , R
DeMeo , F. E., Binzel , R. P., Slivan , S. M., & Bus , S. J. 2009, , 202, 160, 10.1016/j.icarus.2009.02.005
2009 doi
- [19]
-
[20]
2024, Minor Planet Electronic Circulars, 2024-P170
Denneau , L., Siverd , R., Tonry , J., et al. 2024, Minor Planet Electronic Circulars, 2024-P170
2024
-
[21]
M., et al
Farnocchia , D., Reddy , V., Bauer , J. M., et al. 2022, , 3, 156, 10.3847/PSJ/ac7224
2022 doi
-
[22]
2017, , 285, 83, 10.1016/j.icarus.2016.12.022
Fedorets , G., Granvik , M., & Jedicke , R. 2017, , 285, 83, 10.1016/j.icarus.2016.12.022
2017 doi
-
[23]
2020, , 160, 277, 10.3847/1538-3881/abc3bc
Fedorets , G., Micheli , M., Jedicke , R., et al. 2020, , 160, 277, 10.3847/1538-3881/abc3bc
2020 doi
-
[24]
E., et al
Fukugita , M., Ichikawa , T., Gunn , J. E., et al. 1996, , 111, 1748, 10.1086/117915
1996 doi
-
[25]
Gaia Collaboration , Prusti , T., de Bruijne , J. H. J., et al. 2016, , 595, A1, 10.1051/0004-6361/201629272
2016 doi
-
[26]
Gaia Collaboration , Brown , A. G. A., Vallenari , A., et al. 2018, , 616, A1, 10.1051/0004-6361/201833051
2018 doi
-
[27]
J., Burns , J
Gladman , B. J., Burns , J. A., Duncan , M. J., & Levison , H. F. 1995, , 118, 302, 10.1006/icar.1995.1193
1995
-
[28]
2013, Earth's Temporarily-Captured Natural Satellites - The First Step towards Utilization of Asteroid Resources , ed
Granvik , M., Jedicke , R., Bolin , B., Chyba , M., & Patterson , G. 2013, Earth's Temporarily-Captured Natural Satellites - The First Step towards Utilization of Asteroid Resources , ed. V. Badescu , 151--167
2013
-
[29]
2017, , 598, A52, 10.1051/0004-6361/201629252
Granvik , M., Morbidelli , A., Vokrouhlick \'y , D., et al. 2017, , 598, A52, 10.1051/0004-6361/201629252
2017 doi
-
[30]
2012, , 218, 262, 10.1016/j.icarus.2011.12.003
Granvik , M., Vaubaillon , J., & Jedicke , R. 2012, , 218, 262, 10.1016/j.icarus.2011.12.003
2012 doi
-
[31]
2018, , 312, 181, 10.1016/j.icarus.2018.04.018
Granvik , M., Morbidelli , A., Jedicke , R., et al. 2018, , 312, 181, 10.1016/j.icarus.2018.04.018
2018 doi
-
[32]
2018, , 299, 84, 10.1016/j.icarus.2017.07.007
Hanu s , J., Delbo , M., Al \' -Lagoa , V., et al. 2018, , 299, 84, 10.1016/j.icarus.2017.07.007
2018 doi
-
[33]
2016, , 592, A34, 10.1051/0004-6361/201628666
Hanu s , J., Delbo , M., Vokrouhlick \'y , D., et al. 2016, , 592, A34, 10.1051/0004-6361/201628666
2016 doi
-
[34]
C., Warren , S
Hewett , P. C., Warren , S. J., Leggett , S. K., & Hodgkin , S. T. 2006, , 367, 454, 10.1111/j.1365-2966.2005.09969.x
2006
-
[35]
T., Irwin , M
Hodgkin , S. T., Irwin , M. J., Hewett , P. C., & Warren , S. J. 2009, , 394, 675, 10.1111/j.1365-2966.2008.14387.x
2009
-
[36]
M., J rgensen , I., Allington-Smith , J
Hook , I. M., J rgensen , I., Allington-Smith , J. R., et al. 2004, , 116, 425, 10.1086/383624
2004 doi
-
[37]
J., Pieters , C
Isaacson , P. J., Pieters , C. M., Besse , S., et al. 2011, Journal of Geophysical Research (Planets), 116, E00G11, 10.1029/2010JE003731
2011 doi
-
[38]
2001, , 122, 2749, 10.1086/323452
Ivezi \'c , Z ., Tabachnik , S., Rafikov , R., et al. 2001, , 122, 2749, 10.1086/323452
2001 doi
-
[39]
H., Juri \'c , M., et al
Ivezi \'c , Z ., Lupton , R. H., Juri \'c , M., et al. 2002, , 124, 2943, 10.1086/344077
2002 doi
-
[40]
T., Bottke , W
Jedicke , R., Bolin , B. T., Bottke , W. F., et al. 2018, Frontiers in Astronomy and Space Sciences, 5, 13, 10.3389/fspas.2018.00013
2018
- [41]
-
[42]
2024, Nature Astronomy, 8, 819, 10.1038/s41550-024-02258-z
Jiao , Y., Cheng , B., Huang , Y., et al. 2024, Nature Astronomy, 8, 819, 10.1038/s41550-024-02258-z
2024 doi
-
[43]
H., et al
Juri \'c , M., Ivezi \'c , Z ., Lupton , R. H., et al. 2002, , 124, 1776, 10.1086/341950
2002 doi
-
[44]
S., Macke , R
Kiefer , W. S., Macke , R. J., Britt , D. T., Irving , A. J., & Consolmagno , G. J. 2012, , 39, L07201, 10.1029/2012GL051319
2012 doi
-
[45]
2008, LPI Contributions, 1405, 8297
Kwiatkowski , T., Kryszczynska , A., Polinska , M., et al. 2008, LPI Contributions, 1405, 8297
2008
-
[46]
2023, Research Notes of the American Astronomical Society, 7, 214, 10.3847/2515-5172/ad0044
Labrie , K., Simpson , C., Cardenes , R., et al. 2023, Research Notes of the American Astronomical Society, 7, 214, 10.3847/2515-5172/ad0044
2023 doi
-
[47]
Lomb , N. R. 1976, , 39, 447, 10.1007/BF00648343
1976 doi
-
[48]
J., Britt , D
Macke , R. J., Britt , D. T., & Consolmagno , G. J. 2011, , 46, 311, 10.1111/j.1945-5100.2010.01155.x
2011
-
[49]
2008, , 47, 4981, 10.1364/AO.47.004981
Matthews , G. 2008, , 47, 4981, 10.1364/AO.47.004981
2008 doi
-
[50]
J., & Elliott , G
Micheli , M., Tholen , D. J., & Elliott , G. T. 2012, , 17, 446, 10.1016/j.newast.2011.11.008
2012 doi
-
[51]
2013, , 226, 251, 10.1016/j.icarus.2013.05.032
---. 2013, , 226, 251, 10.1016/j.icarus.2013.05.032
2013 doi
-
[52]
L., Farnocchia , D., et al
Mommert , M., Hora , J. L., Farnocchia , D., et al. 2014, , 786, 148, 10.1088/0004-637X/786/2/148
2014 doi
-
[53]
Morais , M. H. M., & Morbidelli , A. 2002, , 160, 1, 10.1006/icar.2002.6937
2002
-
[54]
2020, , 340, 113631, 10.1016/j.icarus.2020.113631
Morbidelli , A., Delbo , M., Granvik , M., et al. 2020, , 340, 113631, 10.1016/j.icarus.2020.113631
2020
-
[55]
P., Micheli , M., Farnocchia , D., et al
Naidu , S. P., Micheli , M., Farnocchia , D., et al. 2021, , 913, L6, 10.3847/2041-8213/abf836
2021 doi
-
[56]
F., et al
Nesvorn \'y , D., Deienno , R., Bottke , W. F., et al. 2023, , 166, 55, 10.3847/1538-3881/ace040
2023 doi
-
[57]
2024, , 417, 116110, 10.1016/j.icarus.2024.116110
Nesvorn \'y , D., Vokrouhlick \'y , D., Shelly , F., et al. 2024, , 417, 116110, 10.1016/j.icarus.2024.116110
2024
-
[58]
Ofek, E. O. 2012, The Astrophysical Journal, 749, 10
2012
-
[59]
2012, Astrometrica: Astrometric data reduction of CCD images
Raab , H. 2012, Astrometrica: Astrometric data reduction of CCD images . 1203.012
2012
-
[60]
Russell , H. N. 1916, , 43, 173, 10.1086/142244
1916 doi
-
[61]
Sharkey , B. N. L., Reddy , V., Malhotra , R., et al. 2021, Communications Earth and Environment, 2, 231, 10.1038/s43247-021-00303-7
2021 doi
-
[62]
2012, , 218, 571, 10.1016/j.icarus.2011.10.008
Solontoi , M., Ivezi \'c , Z ., Juri \'c , M., et al. 2012, , 218, 571, 10.1016/j.icarus.2011.10.008
2012 doi
-
[63]
Stellingwerf , R. F. 1978, , 224, 953, 10.1086/156444
1978 doi
-
[64]
A., Trilling , D
Thomas , C. A., Trilling , D. E., Emery , J. P., et al. 2011, , 142, 85, 10.1088/0004-6256/142/3/85
2011 doi
-
[65]
L., Stubbs , C
Tonry , J. L., Stubbs , C. W., Lykke , K. R., et al. 2012, , 750, 99, 10.1088/0004-637X/750/2/99
2012 doi
-
[66]
L., Denneau , L., Heinze , A
Tonry , J. L., Denneau , L., Heinze , A. N., et al. 2018, , 130, 064505, 10.1088/1538-3873/aabadf
2018 doi
-
[67]
2015, , 261, 34, 10.1016/j.icarus.2015.08.007
Vere s , P., Jedicke , R., Fitzsimmons , A., et al. 2015, , 261, 34, 10.1016/j.icarus.2015.08.007
2015 doi
-
[68]
R., & Chamberlin , A
Vere s , P., Farnocchia , D., Chesley , S. R., & Chamberlin , A. B. 2017, , 296, 139, 10.1016/j.icarus.2017.05.021
2017 doi
-
[69]
Williams , G. V. 2024, Minor Planet Electronic Circulars, 2024-V67
2024
-
[70]
M., Fulchignoni , M., & Lupishko , D
Zappala , V., Cellino , A., Barucci , A. M., Fulchignoni , M., & Lupishko , D. F. 1990, , 231, 548
1990
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