(307261) 2002 MS4

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(307261) 2002 MS4
Synodic rotation period
14.251 h[8]: 5, 54 
7.33 h or 10.44 h (single-peaked)[9]: 158 [a]
0.100±0.025[7]: 8  or 0.098±0.004[10]: 2  (geometric)
0.039±0.005 (Bond)[10]: 23 
Temperature65 K[11]
B−V=0.69±0.02[12]: 6 
V−R=0.38±0.02
B−R=1.07±0.02
20.5[13]
3.56±0.03[8]: 62, 74 
3.63±0.05[7]: 8 
3.62[2][1]

(307261) 2002 MS4 (

2013 FY27 have a diameter close to 800 km (500 mi), which makes them the largest unnamed objects in the Solar System. 2002 MS4 is large enough that astronomers consider it a possible dwarf planet
.

The surface of 2002 MS4 is dark gray and is composed of water and

stellar occultations, which have revealed massive topographic features along the outline of its shape. These features include a mountain-like peak that is 25 km (16 mi) tall and a crater-like depression that is 320 km (200 mi) wide and 45 km (28 mi) deep. 2002 MS4's topographic features are among the tallest
and deepest known for Solar System bodies.

History

Discovery

2002 MS4 was discovered on 18 June 2002 by astronomers

Near Earth Asteroid Tracking program at Palomar.[14]: 100  This survey was responsible for the discovery of several other large objects beyond Neptune, which includes the dwarf planets Eris, Sedna, and Quaoar.[15]
: 214 

2002 MS4 was found through manual vetting of potential moving objects identified by the team's automatic image-searching software.

provisional designation of 2002 MS4.[16]

The 1.2-meter Samuel Oschin telescope that was used to discover 2002 MS4 at Palomar Observatory
Discovery images of 2002 MS4 from 18 June 2002

Further observations

Since receiving follow-up in August 2002, 2002 MS4 remained unobserved for more than nine months until it was recovered by Trujillo at Palomar Observatory on 29 May 2003, followed by observations by Wolf Bickel at Bergisch Gladbach Observatory in Germany in June 2003.[17] These recovery observations significantly reduced the uncertainty of 2002 MS4's orbit, allowing for further extrapolation of its position backwards in time for identification in precovery observations.[18] Seven precovery observations from Digitized Sky Survey plates were identified by astronomer Andrew Lowe in 2007; the earliest of these was taken on 8 April 1954 by Palomar Observatory.[18][19]: 42  As of 2023, 2002 MS4 has been observed for over 68 years, or about 25% of its orbital period.[2][1]

Numbering and naming

2002 MS4 received its permanent

Working Group for Small Bodies Nomenclature, 2002 MS4 is open for name suggestions that pertain to creation myths, as required for Kuiper belt objects in general.[21]
: 8 

Orbit and classification

2002 MS4 is a

aphelion.[5] It has an orbital inclination of nearly 18° with respect to the ecliptic.[5] 2002 MS4 last passed perihelion in April 1853, passed aphelion in February 1987, and will make its next perihelion passage in June 2123.[23][24][6]

2002 MS4 is located in the classical region of the Kuiper belt 37–48 AU from the Sun,[25]: 227  and is thus classified as a classical Kuiper belt object or cubewano.[3]: 53  2002 MS4's high orbital inclination qualifies it as a dynamically "hot" member of the classical Kuiper belt, which implies that it was gravitationally scattered out to its present location by Neptune's outward planetary migration in the Solar System's early history.[25]: 227, 229  2002 MS4's present orbit is far enough from Neptune (minimum orbit intersection distance 6.6 AU)[1] that it no longer experiences scattering from close encounters with the planet.[4][25]: 214 

A dynamical study in 2007 simulated 2002 MS4's orbital evolution over a 10-million-year timespan and found that it may be in an intermittent 18:11 mean-motion orbital resonance with Neptune,[25]: 218  which seems to cause irregular fluctations in 2002 MS4's orbital inclination and eccentricity.[25]: 225  Despite this, researchers do not consider 2002 MS4 to be in resonance with Neptune.[4][3]: 56 [10]: 2 

The 18:11-resonant libration of 2002 MS4's nominal orbit, in a frame co-rotating with Neptune
Top and side views of 2002 MS4's orbit (white) with Pluto and other classical Kuiper belt objects for comparison

Observability

constellation Scutum in 2020, moving eastward (left) across the brightest areas of the Milky Way

In the night sky, 2002 MS4 is located near the

stellar occultations as there are numerous stars for it to pass in front of.[10]
: 9 

Occultations

2002 MS4 occultations observed in 2019–2022[7]: 5, 18B.4 
Date Star apparent
magnitude
(V-band)		 Positive
detections		 Negative
detections[c]		 Number of
telescope
locations[d]		 Continents
observed
09 Jul 2019 15.00 2 4 10 South America
26 Jul 2019 17.78 3 0 3 South America
26 Jul 2019 15.45 1 0 1 North America
19 Aug 2019 16.51 2 0 2 North America
26 Jul 2020 14.76 2 0 5 Africa
8 Aug 2020 14.62 61 40 116 Europe, Africa, Asia
24 Feb 2021 16.51 1 1 2 South America
14 Oct 2021 15.83 2 0 14 North America
10 Jun 2022 15.1 3 0 3 North America, Africa

Stellar occultations by 2002 MS4 occur when it passes in front of a star and blocks out its light, causing the star to dim for several seconds until 2002 MS4 emerges.[7]: 2  Observing stellar occultations by 2002 MS4 can provide precise measurements for its position, shape, and size.[7]: 1 [8]: 35  Due to parallax between Earth, 2002 MS4, and the occulted star, occultations by 2002 MS4 may only be observable to certain locations on Earth. For this reason, the 2002 MS4's orbital trajectory and ephemeris must be precisely known before occultation predictions can be reliably made.[7]: 2 [8]: 35 

To facilitate occultation predictions for 2002 MS4, astronomers of the European Research Council's Lucky Star project gathered astrometric observations of 2002 MS4 from 2009–2019 to reduce its orbital uncertainty and utilized the Gaia catalogues for high-precision positions of stars.[26][7]: 2  From 2019–2022, the Lucky Star project organized campaigns for astronomers worldwide to observe the predicted occultations by 2002 MS4, yielding nine successfully-observed occultations by the end of the period.[7]: 1, 3  The first successfully-observed occultation by 2002 MS4 took place in South America on 9 July 2019, which yielded two positive detections and four negative detections from the 10 participating telescope locations; the remaining four telescopes were affected by poor weather.[26][7]: 2, 18B.4  More successful observations of 2002 MS4's occultations took place on 26 July and 19 August 2019, which provided highly precise astrometry that helped refine later occultation predictions.[27][7]: 2 

On 8 August 2020, the Lucky Star project organized a large observing campaign for 2002 MS4, which would occult a relatively bright star of apparent magnitude 14.6 and be observable over densely-populated regions in multiple continents.[7]: 4  A total of 116 telescope locations from Europe, North Africa, and Western Asia participated in the campaign and yielded 61 positive detections and 40 negative detections, with the remaining 15 telescopes inhibited by poor weather or technical difficulties.[7]: 4, 18B.1–3  The observers of the occultation found no evidence of rings, cometary jets, or natural satellites around 2002 MS4.[7]: 9  This is the most extensive participation in a TNO occultation campaign as of 2023.[28]: 1347 [7]: 9  Thanks to the large amount of positive detections across various locations, the global shape outline and topography of 2002 MS4 could be seen clearly for the first time.[29][7]

  • Map showing the location of telescopes that participated in the 8 August 2020 occultation campaign. Telescopes within the path of 2002 MS4's shadow (region between the two solid blue curves) made positive detections (blue and red points), whereas telescopes outside the path made negative detections (green points).
    Map showing the location of telescopes that participated in the 8 August 2020 occultation campaign. Telescopes within the path of 2002 MS4's shadow (region between the two solid blue curves) made positive detections (blue and red points), whereas telescopes outside the path made negative detections (green points).
  • 2002 MS4's projected shape revealed by the many positive detection chords from the 8 August 2020 occultation (blue with red error bars). A massive topographic peak and depression is visible along 2002 MS4's limb in the northeast direction.
    2002 MS4's projected shape revealed by the many positive detection chords from the 8 August 2020 occultation (blue with red error bars). A massive topographic peak and depression is visible along 2002 MS4's limb in the northeast direction.

Physical characteristics

History of diameter estimates for 2002 MS4
Year of
Publication		 Diameter
(km)		 Method Refs
2008 726.2+123.2
−122.9 		thermal
(Spitzer) 		[30]: 173 
2009 730+118
−120 		thermal
(Spitzer, remodeled) 		[31]: 291 
2012 934±47 thermal
(Herschel) 		[32]: 10 
2020 770±2 occultation
(9 Jul 2019) 		[26]
2022 <810±70 occultation
(26 Jul 2019) 		[33]
2023 796±24 occultation
(8 Aug 2020) 		[7][e]

Results from the extensively observed 8 August 2020 occultation show that 2002 MS4 has a shape close to that of an

2013 FY27 (diameters 729–807 km[35] and 659–820 km,[36] respectively) as the largest unnamed object in the Solar System
.

2002 MS4 was previously thought to have a larger diameter of 934 km (580 mi), according to infrared thermal emission measurements made by the Spitzer and Herschel space telescopes in 2006 and 2010.[32]: 4, 7, 10  This thermal emission-derived diameter disagrees with the occultation-derived diameter; if both the thermal emission measurements and occultation-derived diameter are correct, then 2002 MS4 would be emitting more thermal radiation than predicted if it were a non-rotating, simple airless body.[8]: 68, 70, 73  It is not yet clear why 2002 MS4 seems to be emitting excess thermal radiation; it could be possible that either there is an unknown satellite of 2002 MS4 contributing to the excess thermal emission,[7]: 9  or the predictions for 2002 MS4's thermal emission behavior are inaccurate.[8]: 73 

The mass and density of 2002 MS4 is unknown since it has no known moons, otherwise estimation of its mass would have been possible by

Kepler's third law.[8]: 35  Without a known mass and density, it is not possible to determine whether 2002 MS4's spheroidal shape is due to hydrostatic equilibrium, which would qualify it as a dwarf planet.[37]: 10  Inferring from its diameter and albedo, 2002 MS4 is probably not in hydrostatic equilibrium since it lies within the 400–1,000 km (250–620 mi) diameter range where TNOs are typically observed with very low densities, presumably due to having highly porous interior structures that have not gravitationally compressed into solid bodies.[38]: 1, 8  Otherwise, if 2002 MS4 is in hydrostatic equilibrium, then its density could be estimated from its oblateness and rotation period.[7]: 8  However, both of these properties are poorly known for 2002 MS4, so only its minimum and maximum possible densities could be estimated.[7]: 8  Assuming a Maclaurin spheroid as the equilibrium shape for 2002 MS4, the ranges of possible densities are 0.72–8.0 g/cm3 and 0.36–3.9 g/cm3 for possible rotation periods of 7.44 and 10.44 hours, respectively.[7]
: 8 

Surface

2002 MS4 has a gray or spectrally neutral surface color, meaning it reflects similar amounts of light for

New Horizons spacecraft, which indicates 2002 MS4 has a very dark and unevolved surface in contrast to the bright and volatile-rich dwarf planets like Pluto.[10]: 2, 18–19  New Horizons observations of 2002 MS4's phase curve indicate that the icy regolith grains on the object's surface are rough and irregularly shaped.[10]
: 19 

Topographic features

Projected shape of 2002 MS4 seen in the 8 August 2020 occultation
Plot of topographic elevation variations along 2002 MS4's limb

The 8 August 2020 occultation revealed massive topographic features along 2002 MS4's northeastern outline, or limb, which notably includes a crater-like depression 322 ± 39 km (200 ± 24 mi) wide and 45.1 ± 1.5 km (28.02 ± 0.93 mi) deep, and a 25+4
−5 km (15.5+2.5
−3.1 mi)-tall peak near the rim of the depression.[7]: 7  Another depression feature about 10 km (6.2 mi) wide and 11 km (6.8 mi) deep was detected by a single telescope from Varages, France during the occultation; this depression feature partially occulted the star as 2002 MS4 emerged, which resulted in the star brightening gradually instead of instantly.[7]: 7  The elevations of these observed topographic features lie beyond the maximum elevation of 6–7 km (3.7–4.3 mi) expected for an icy body of 2002 MS4's size, signifying that the object may have experienced a large impact in its past.[7]: 6, 9  It would be possible for 2002 MS4 to support its massive topographic features if its material strength increases toward its core.[7]: 6  Topographic features on other TNOs have been previously observed through occultation, such as (208996) 2003 AZ84 which has a depression feature at least 8 km (5 mi) deep.[41][42]

The topographic peak on 2002 MS4 has a height comparable to Mars's tallest mountain, Olympus Mons, and the central mound of the Rheasilvia crater on asteroid Vesta.[42][43] If 2002 MS4's topographic peak is a mountain, then it would qualify as one of the tallest known mountains in the Solar System.[42] It is possible that this topographic peak may actually be an unknown 213 km (132 mi)-diameter satellite that was passing in front or behind 2002 MS4 during the occultation, but this scenario is unlikely according to Bruno Sicardy, one of the occultation team members.[7]: 9, 25 [42] A satellite of this size would not be large enough to explain 2002 MS4's excess thermal emission.[7]: 25 

If 2002 MS4's massive depression is a crater, then it would be the first observation of a massive crater on a TNO.

Mimas has a depth of up to 10–12 km (6.2–7.5 mi)[44]: 424  and Vesta's Rheasilvia crater has a depth of up to 25 km (16 mi).[43]

Rotation and light curve

The

rotation period of 2002 MS4 is uncertain and its rotational axial tilt is unknown. It is difficult to measure 2002 MS4's rotation period photometrically with telescopes on Earth since the object is obscured in a dense field of background stars.[9]: 118 [7]: 7  Due to 2002 MS4's spheroidal shape and possible surface albedo variations, its light curve only exhibits very small fluctuations in brightness (amplitude 0.05–0.12 mag[8]: 85 ) over time as it rotates.[7]: 7 [8]: 73  The first attempts at measuring 2002 MS4's rotation were made with the Sierra Nevada Observatory's 1.5-meter telescope in August 2005, but it did not observe the object long enough to identify any periodicities in its light curve.[9]: 31, 92  Subsequent observations by the Galileo National Telescope in June–July 2011 took advantage of 2002 MS4 passing in front of a dark nebula, which enabled it to determine possible periods of either 7.33 hours or 10.44 hours.[9]: 94  On the other hand, observations by the Canada–France–Hawaii Telescope in July–August 2013 measured a rotation period of 14.251 hours, with other less probable rotation period aliases of 8.932 and 5.881 hours.[8]
: 43, 53, 74 

Exploration

New Horizons

The

New Horizons spacecraft observed 2002 MS4 during 2016–2019, as part of its extended Kuiper belt mission after its successful Pluto flyby in 2015.[10]: 8  2002 MS4 was 15.3 AU (2.29 billion km; 1.42 billion mi) away from the spacecraft when it began observations on 13 July 2016, and was 12.0 AU (1.80 billion km; 1.12 billion mi) away from the spacecraft when it ended observations in 1 September 2019.[10]: 8  New Horizons had the unique vantage point of observing 2002 MS4 and other TNOs while it was inside the Kuiper belt, which allowed the spacecraft to observe these objects at high phase angles (>2°) that are not observable from Earth.[10]: 1  By observing how 2002 MS4's brightness changes as a function of phase angle, the object's phase curve could be determined, which can reveal the light scattering properties of 2002 MS4's surface regolith.[10]: 1  In addition to significantly improving the knowledge of 2002 MS4's phase curve, the observations by New Horizons also significantly improved the precision of 2002 MS4's orbit.[45]

  • 2002 MS4 imaged by the New Horizons spacecraft in July 2016, from a distance of 15.3 AU (2.3 billion km; 1.4 billion mi)
    2002 MS4 imaged by the
    New Horizons
     spacecraft in July 2016, from a distance of 15.3 AU (2.3 billion km; 1.4 billion mi)
  • New Horizons trajectory through the Kuiper belt, with positions of nearby KBOs including 2002 MS4 labeled
    New Horizons trajectory through the Kuiper belt, with positions of nearby KBOs including 2002 MS4 labeled

Proposed

2002 MS4 has been considered as a possible exploration target for future missions to the Kuiper belt and beyond, such as NASA's Interstellar Probe concept.[46] A 2019 study by Amanda Zangari and collaborators identified several possible trajectories to 2002 MS4 for a spacecraft that would be launched in 2025–2040.[47] For a spacecraft launched in 2027–2031, a single gravity assist from Jupiter could bring a spacecraft to 2002 MS4 over a minimum duration of 9.1–12.8 years, depending on the excess launch energy of the spacecraft.[47]: 922  Another trajectory using a single Jupiter gravity assist for a 2040 launch date could bring a spacecraft to 2002 MS4 over a minimum duration of 13 years.[47]: 922  A 2038–2040 launch trajectory using a single Saturn gravity assist could bring a spacecraft to 2002 MS4 over a minimum duration of 16.7 years,[47]: 925  while a 2038–2040 launch trajectory using two gravity assists from Jupiter and Saturn could bring a spacecraft to 2002 MS4 over a minimum duration of 18.6–19.5 years.[47]: 923 

See also

Notes

  1. triaxial ellipsoid on the other hand, then it would produce a double-peaked light curve, where the object's true rotation period is double the single-peaked period since it spans two peaks and two troughs in its light curve.[9]
    : 77 
  2. Solar System Barycenter (SSB) as the frame of reference.[5] Due to planetary perturbations, the Sun revolves around the SSB at non-negligible distances, so heliocentric-frame orbital elements and distances can vary in short timescales as shown in JPL-Horizons.[22]
  3. ^ Telescopes that were affected by poor weather or technical problems are not counted as negative detections.
  4. ^ Telescopes that are located in the same place or are located very close together are considered single locations.
  5. ^ Rommel et al. previously reported a diameter of 800±24 km in a 2021 conference talk about their preliminary 8 August 2020 occultation results.[29] This preliminary diameter estimate has been superseded by the more recent estimate of 796±24 km in their paper published in 2023.[7]
  6. ^ Pluto has an over-1,000 km (620 mi)-wide ice-covered basin named Sputnik Planitia, although it is unclear whether it originated from an impact.

References

  1. ^ a b c d e f g "(307261) = 2002 MS4". Minor Planet Center. Retrieved 13 September 2021.
  2. ^ a b c d e "JPL Small-Body Database Lookup: 307261 (2002 MS4)" (2022-07-04 last obs.). Jet Propulsion Laboratory. Retrieved 10 December 2023.
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  4. ^ a b c Buie, Marc W. "Orbit Fit and Astrometric record for 307261". Southwest Research Institute. Archived from the original on 27 June 2021. Retrieved 13 September 2021.
  5. ^
    Barycenter
    . Ephemeris Type: Elements and Center: @0)
  6. ^ a b "JPL Horizons On-Line Ephemeris for 307261 (2002 MS4) from 2123-Jan-01 to 2124-Jan-01". JPL Horizons On-Line Ephemeris System. Jet Propulsion Laboratory. Retrieved 28 June 2022. (Perihelion occurs when deldot changes from negative to positive. Uncertainty in time of perihelion is 1-sigma from JPL Small-Body Database.)
  7. ^
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  8. ^
    hdl:1828/15363. Archived
    (PDF) from the original on 9 September 2023. Retrieved 9 September 2023.
  9. ^
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  10. ^
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  11. ^ a b c d e Cook, J. C.; Brunetto, R.; De Souza Feliciano, A. C.; Emery, J.; Holler, B.; Parker, A. H.; et al. (June 2023). Hapke Modeling of Several KBOs from JWST Observations (ePoster) (PDF). Asteroids, Comets, Meteors Conference 2023. Lunar and Planetary Institute. Archived (PDF) from the original on 10 December 2023.
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  13. ^ a b "(307261) 2002MS4 Ephemerides". Asteroids Dynamic Site. Department of Mathematics, University of Pisa, Italy. Retrieved 19 November 2019.
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  16. ^
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  17. ^ "MPEC 2003-M44 : 2002 KW14, 2002 MS4". Minor Planet Electronic Circular. Minor Planet Center. 29 May 2003. Retrieved 20 June 2022.
  18. ^ a b c Lowe, Andrew. "(307261) 2002 MS4 Precovery Images". andrew-lowe.ca. Retrieved 20 June 2022.
  19. ^ "M.P.S. 231732" (PDF). Minor Planet Circulars Supplement (231732). Minor Planet Center: 42. 30 December 2007. Retrieved 19 November 2019.
  20. ^ "M.P.C. 77416" (PDF). Minor Planet Circulars (77416). Minor Planet Center: 292. 10 December 2011. Retrieved 20 June 2022.
  21. ^ a b "Rules and Guidelines for Naming Non-Cometary Small Solar-System Bodies" (PDF). IAU Working Group for Small Bodies Nomenclature. 20 December 2021. p. 10. Retrieved 20 June 2022.
  22. ^ "JPL Horizons On-Line Ephemeris for 307261 (2002 MS4) at epochs JD 2450000.5–2460000.5". JPL Horizons On-Line Ephemeris System. Jet Propulsion Laboratory. Retrieved 28 June 2022. Solution using the Sun. Ephemeris Type: Elements and Center: @sun)
  23. ^ "JPL Horizons On-Line Ephemeris for 307261 (2002 MS4) from 1853-Jan-01 to 1854-Jan-01". JPL Horizons On-Line Ephemeris System. Jet Propulsion Laboratory. Retrieved 28 June 2022. (Perihelion occurs when deldot changes from negative to positive. Uncertainty in time of perihelion is 1-sigma from JPL Small-Body Database.)
  24. ^ "JPL Horizons On-Line Ephemeris for 307261 (2002 MS4) from 1987-Jan-01 to 1988-Jan-01". JPL Horizons On-Line Ephemeris System. Jet Propulsion Laboratory. Retrieved 10 December 2022. (Perihelion occurs when deldot changes from negative to positive. Uncertainty in time of perihelion is 1-sigma from JPL Small-Body Database.)
  25. ^
    S2CID 122671996
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  26. ^
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  27. ^ "2002 MS4 08/08/2020". ERC Lucky Star project. Retrieved 6 September 2021.
  28. doi:10.1093/mnras/stac1595
    .
  29. ^
    doi:10.5194/epsc2021-440
    . EPSC2021-440. Retrieved 13 September 2021.
  30. S2CID 578439
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  31. S2CID 53543791
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  32. ^
    S2CID 54222700
    . A94.
  33. doi:10.3847/2515-5172/ac5f3b
    . 59.
  34. doi:10.1017/S1743921316002970
    . A29A.
  35. S2CID 118513049
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  36. S2CID 119522310
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  37. ISBN 9780977574032
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  38. S2CID 126574999
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  39. S2CID 32008426
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  40. ^ a b Cook, J. C.; Brunetto, R.; De Souza Feliciano, A. C.; Emery, J.; Holler, B.; Parker, A. H.; et al. (June 2023). Hapke Modeling of Several KBOs from JWST Observations (PDF). Asteroids, Comets, Meteors Conference 2023. Lunar and Planetary Institute. Archived (PDF) from the original on 10 December 2023.
  41. S2CID 119098862
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  42. ^ a b c d O'Callaghan, Jonathan (29 August 2023). "Massive crater found on distant world far beyond Neptune". New Scientist. Retrieved 17 September 2023.
  43. ^ a b Schenk, P.; Marchi, S.; O'Brien, D. P.; Buczkowski, D. L.; Jaumann, R.; Yingst, A.; et al. (March 2012). Mega-Impacts into Planetary Bodies: Global Effects of the Giant Rheasilvia Impact Basin on Vesta (PDF). 43rd Lunar and Planetary Science Conference. Lunar and Planetary Institute. Archived (PDF) from the original on 22 October 2015.
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  45. ^ Lakdawalla, Emily (24 January 2018). "New Horizons prepares for encounter with 2014 MU69". The Planetary Society. Retrieved 13 November 2019.
  46. doi:10.5194/epsc2020-276
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External links
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