User:Nrco0e/Notes/Dimorphos

Dimorphos
	Dimorphos captured by the DART spacecraft, seconds before impact in September 2022
Discovery
Discovered by	Petr Pravec et al.
Discovery site	Ondřejov Observatory
Discovery date	20 November 2003
Designations
Designation	Didymos I
Pronunciation	/daɪˈmɔːrfəs/
Named after	Greek word for "having two forms"
Alternative names	S/2003 (65803) 1; Didymos B; Didymoon
Orbital characteristics
Semi-major axis	Pre-impact:; 1.187±0.017 km; Post-impact:; 1.152±0.018 km
Eccentricity	Pre-impact:; <0.03; Post-impact:; 0.0274±0.0015
Orbital period (sidereal)	Pre-impact:; 11.921493±0.000030 hr; (11h 55m 17.4s ± 0.1s); Post-impact:; 11.3675±0.0004 hr; (11h 22m 3.0s ± 1.4s)
Average orbital speed	Pre-impact:; 0.174 m/s; Post-impact:; 0.177 m/s
Inclination	170.7°±0.5° (to ecliptic)
Satellite of	65803 Didymos
Physical characteristics
Dimensions	Pre-impact:; 179 × 169 × 115 m; (± 1 × 4 × 1 m); Post-impact:; 192 × 148 × 118 m; (± 12 × 8 × 14 m)
Mean diameter	150.0±2.5 m (volume equivalent)
Surface area	7.47×104 m2
Volume	1.76×106 m3
Mass	≈ 4.3×109 kg (if same density as Didymos)
Mean density	<2.4±0.3 g/cm3 (assuming same as Didymos)
Synodic rotation period	Pre-impact:; synchronous; Post-impact:; chaotic
Albedo	0.15±0.02
Spectral type	S
Absolute magnitude (H)	21.4±0.2

Dimorphos (formal designation (65803) Didymos I; provisional designation S/2003 (65803) 1) is a small, 150-meter (490 ft) diameter moon of the near-Earth asteroid 65803 Didymos, with which it forms a binary system. Discovered on 20 November 2003 by Petr Pravec and collaborators, Dimorphos was the target of NASA's Double Asteroid Redirection Test (DART) mission, which deliberately collided a spacecraft with the moon on 26 September 2022 to alter its orbit around Didymos. Around the same time, the Italian Space Agency's LICIACube spacecraft flew by Dimorphos to image the DART impact. The impact reduced Dimorphos's orbital period by 33 minutes and ejected over 10 million kg (22 million lb) of dusty debris into space, which produced an expanding dust plume and a 70,000-kilometer (43,000 mi)-long tail of dust swept away by solar radiation pressure.^[3]^: 9–10

Before DART impacted Dimorphos, the moon had an oblate spheroid shape with a surface covered in boulders and few small craters. The surface features of Dimorphos suggest that the moon is a weakly-held rubble pile that formed less than 300,000 years ago, as a result of Didymos shedding its mass by its rapid rotation. Computer simulations and telescopic observations by researchers indicate that, as a result of Dimorphos's rubble pile structure, the DART impact globally resurfaced Dimorphos and deformed its shape into an elongated ellipsoid, rather than creating an impact crater. Simulations and observations also suggest that the DART impact caused Dimorphos's rotation to begin tumbling chaotically. The European Space Agency's Hera mission is planned to arrive at the Didymos system in 2026 to further study the effects of DART's impact on Dimorphos.

Discovery

Radar images of Didymos and Dimorphos taken by the Arecibo Observatory in 2003

Eclipsing binary lightcurve, radar

Name

Designation, name

DART and LICIACube missions

Planning

DART mission was selected in 2015, planetary defense goals

Impact

Impact ejecta

Dust plume

Dust tail

Ejected boulders

Orbit

Origin

Surface

Composition

Geology

Five boulders (saxa) and six craters have been given names of traditional drums from several cultures. They are approximately 10 meters across or smaller:^[12]

Named features
Name	Pronunciation	Feature	Named after	Date approved^[12]
Atabaque Saxum	UK: /ætəˈbæki/ US: /ɑːtəˈbɑːki/	boulder	atabaque (Brazil)	25 Jan 2023
Bodhran Saxum	/ˈbɔːrɑːn/	boulder	bodhrán (Ireland)	25 Jan 2023
Caccavella Saxum	/kækəˈvɛlə/	boulder	caccavella a.k.a. putipù (Italy)	25 Jan 2023
Dhol Saxum	/ˈdɔːl/	boulder	dhol (India)	25 Jan 2023
Pūniu Saxum	/ˈpuːni.uː/	boulder	pūniu a.k.a kilu (Hawaii)	25 Jan 2023
Bala Crater	/ˈbælə/	crater	balafon (Guinea, Senegal, Mali)	14 Nov 2023
Bongo Crater	/ˈbɒŋɡoʊ/	crater	bongo (Cuba)	14 Nov 2023
Marimba Crater	/məˈrɪmbə/	crater	marimba (Central America)	14 Nov 2023
Msondo Crater	/ɛmˈsɒndoʊ/	crater	msondo (Tanzania)	14 Nov 2023
Naqqara Crater	/næˈkɑːrə/	crater	naqqara (naker) (Mid East and India)	14 Nov 2023
Tamboril Crater	/tæmbəˈrɪl/	crater	tamboril (Uruguay, Candombe)	14 Nov 2023

Left: DART impact site on Dimorphos. Clockwise: Caccavella, Bodhran, and Atabaque saxum.
Right: Composite map of Dimorphos with named features as of 14 November 2023.

Shape and structure

Rotation

Hera mission

Footnotes

^ Astronomers involved in the discovery of Dimorphos include P. Pravec, L. A. M. Benner, M. C. Nolan, P. Kusnirak, D. Pray, J. D. Giorgini, R. F. Jurgens, S.J. Ostro, J.-L. Margot, C. Magri, A. Grauer, and S. Larson. The discovery used lightcurve and radar observations from the Jet Propulsion Laboratory, Pasadena, CA; National Astronomy and Ionosphere Center / Arecibo Observatory, Arecibo, PR; and Ondrejov Observatory, Ondřejov, CZ.^[1]
^ ^a ^b For a circular orbit with negligible eccentricity, the mean orbital speed can be approximated by the time $T$ it takes to complete one revolution around its orbital circumference, with the radius being its semi-major axis $a$ : $v={2\pi a \over T}$ .
^ Naidu et al. (2024) give Didymos's rotational north pole direction in terms of ecliptic coordinates, where $λ$ is ecliptic longitude and $β$ is ecliptic latitude.^[4] $β$ is the angular offset from the ecliptic plane, whereas inclination or obliquity $i$ with respect to the ecliptic is the angular offset of Didymos's rotational north pole from the ecliptic north pole, at $β$ = +90° ; $i$ with respect to the ecliptic would be the complement of $β$ .^[6] Therefore, given $β$ = –80.7° , $i$ = 90° – (–80.7°) = 170.7° from the ecliptic. Naidu et al. (2024) assume that Dimorphos's orbit is coplanar to Didymos's equator, so Dimorphos's orbital inclination would be the same as Didymos's obliquity.
^ The dimensions 179 × 169 × 115 refer to the longest extent of Dimorphos's shape. If using a triaxial ellipsoid to approximate Dimorphos's shape, then the dimensions are 173 × 170 × 113.^[7]^: 12
^ Absolute magnitude of Dimorphos calculated from the addition of its magnitude difference to Didymos's absolute magnitude: 18.07 + 3.29 ≈ 21.4.^[1]

References

^ ^a ^b ^c ^d Cite error: The named reference johnston was invoked but never defined (see the help page).
^ "IAU approves name of target of first NASA and ESA planetary defence missions". iau.org (Press release). International Astronomical Union. 23 June 2020. Retrieved 1 July 2020.
^ ^a ^b ^c ^d ^e Chabot, Nancy L.; Rivkin, Andrew S.; Cheng, Andrew F.; Barnouin, Olivier S.; Fahnestock, Eugene G.; Richardson, Derek C.; et al. (February 2024). "Achievement of the Planetary Defense Investigations of the Double Asteroid Redirection Test (DART) Mission". The Planetary Science Journal. 5 (2): 24. Bibcode:2024PSJ.....5...49C. doi:10.3847/PSJ/ad16e6. 49.
^ ^a ^b ^c ^d Cite error: The named reference Naidu2024 was invoked but never defined (see the help page).
^ ^a ^b Scheirich, Peter; Pravec, Petr; Meyer, Alex J.; Agrusa, Harrison F.; Richardson, Derek C.; Chesley, Steven R.; et al. (January 2024). "Dimorphos Orbit Determination from Mutual Events Photometry". The Planetary Science Journal. 5 (1): 12. Bibcode:2024PSJ.....5...17S. doi:10.3847/PSJ/ad12cf. 17.
^ "Coordinate transformations". Astronomy and Astrophysics. European Southern Observatory. January 1998. Archived from the original on 17 June 2021. Retrieved 17 June 2022.
^ ^a ^b Daly, R. Terik; Ernst, Carolyn M.; Barnouin, Olivier S.; Gaskell, Robert W.; Nair, Hari; Agrusa, Harrison; et al. (January 2024). "An Updated Shape Model of Dimorphos from DART Data". The Planetary Science Journal. 5 (1): 19. Bibcode:2024PSJ.....5...24D. doi:10.3847/PSJ/ad0b07. 24.
^ ^a ^b ^c Daly, R. Terik; Ernst, Carolyn M.; Barnouin, Olivier S.; Chabot, Nancy L.; Rivkin, Andrew S.; Cheng, Andrew F.; et al. (April 2023). "Successful Kinetic Impact into an Asteroid for Planetary Defense". Nature. 616 (7957): 443–447. arXiv:2303.02248. Bibcode:2023Natur.616..443D. doi:10.1038/s41586-023-05810-5. PMC 10115643. PMID 36858073.
^ Raducan, S. D.; Jutzi, M.; Cheng, A. F.; Zhang, Y.; Barnouin, O.; Collins, G. S.; et al. (February 2024). "Physical properties of asteroid Dimorphos as derived from the DART impact". Nature Astronomy: 21. doi:10.1038/s41550-024-02200-3.
^ Cite error: The named reference Agrusa2021 was invoked but never defined (see the help page).
^ Cite error: The named reference Nakano2022 was invoked but never defined (see the help page).
^ ^a ^b "Planetary Names". planetarynames.wr.usgs.gov.

External links

Media related to Nrco0e/Notes/Dimorphos at Wikimedia Commons

[2] Astronomers involved in the discovery of Dimorphos include P. Pravec, L. A. M. Benner, M. C. Nolan, P. Kusnirak, D. Pray, J. D. Giorgini, R. F. Jurgens, S.J. Ostro, J.-L. Margot, C. Magri, A. Grauer, and S. Larson. The discovery used lightcurve and radar observations from the Jet Propulsion Laboratory, Pasadena, CA; National Astronomy and Ionosphere Center / Arecibo Observatory, Arecibo, PR; and Ondrejov Observatory, Ondřejov, CZ.^[1]

[orbitspeed-7] For a circular orbit with negligible eccentricity, the mean orbital speed can be approximated by the time $T$ it takes to complete one revolution around its orbital circumference, with the radius being its semi-major axis $a$ : $v={2\pi a \over T}$ .

[pole-9] Naidu et al. (2024) give Didymos's rotational north pole direction in terms of ecliptic coordinates, where $λ$ is ecliptic longitude and $β$ is ecliptic latitude.^[4] $β$ is the angular offset from the ecliptic plane, whereas inclination or obliquity $i$ with respect to the ecliptic is the angular offset of Didymos's rotational north pole from the ecliptic north pole, at $β$ = +90° ; $i$ with respect to the ecliptic would be the complement of $β$ .^[6] Therefore, given $β$ = –80.7° , $i$ = 90° – (–80.7°) = 170.7° from the ecliptic. Naidu et al. (2024) assume that Dimorphos's orbit is coplanar to Didymos's equator, so Dimorphos's orbital inclination would be the same as Didymos's obliquity.

[dimensions-11] The dimensions 179 × 169 × 115 refer to the longest extent of Dimorphos's shape. If using a triaxial ellipsoid to approximate Dimorphos's shape, then the dimensions are 173 × 170 × 113.^[7]^: 12

[magdiff-16] Absolute magnitude of Dimorphos calculated from the addition of its magnitude difference to Didymos's absolute magnitude: 18.07 + 3.29 ≈ 21.4.^[1]

[johnston-1] Cite error: The named reference johnston was invoked but never defined (see the help page).

[IAU-20200623-3] "IAU approves name of target of first NASA and ESA planetary defence missions". iau.org (Press release). International Astronomical Union. 23 June 2020. Retrieved 1 July 2020.

[Chabot2024-4] Chabot, Nancy L.; Rivkin, Andrew S.; Cheng, Andrew F.; Barnouin, Olivier S.; Fahnestock, Eugene G.; Richardson, Derek C.; et al. (February 2024). "Achievement of the Planetary Defense Investigations of the Double Asteroid Redirection Test (DART) Mission". The Planetary Science Journal. 5 (2): 24. Bibcode:2024PSJ.....5...49C. doi:10.3847/PSJ/ad16e6. 49.

[Naidu2024-5] Cite error: The named reference Naidu2024 was invoked but never defined (see the help page).

[Scheirich2024-6] Scheirich, Peter; Pravec, Petr; Meyer, Alex J.; Agrusa, Harrison F.; Richardson, Derek C.; Chesley, Steven R.; et al. (January 2024). "Dimorphos Orbit Determination from Mutual Events Photometry". The Planetary Science Journal. 5 (1): 12. Bibcode:2024PSJ.....5...17S. doi:10.3847/PSJ/ad12cf. 17.

[coordstransform-8] "Coordinate transformations". Astronomy and Astrophysics. European Southern Observatory. January 1998. Archived from the original on 17 June 2021. Retrieved 17 June 2022.

[Daly2024-10] Daly, R. Terik; Ernst, Carolyn M.; Barnouin, Olivier S.; Gaskell, Robert W.; Nair, Hari; Agrusa, Harrison; et al. (January 2024). "An Updated Shape Model of Dimorphos from DART Data". The Planetary Science Journal. 5 (1): 19. Bibcode:2024PSJ.....5...24D. doi:10.3847/PSJ/ad0b07. 24.

[Daly2023-12] Daly, R. Terik; Ernst, Carolyn M.; Barnouin, Olivier S.; Chabot, Nancy L.; Rivkin, Andrew S.; Cheng, Andrew F.; et al. (April 2023). "Successful Kinetic Impact into an Asteroid for Planetary Defense". Nature. 616 (7957): 443–447. arXiv:2303.02248. Bibcode:2023Natur.616..443D. doi:10.1038/s41586-023-05810-5. PMC 10115643. PMID 36858073.

[Raducan2024-13] Raducan, S. D.; Jutzi, M.; Cheng, A. F.; Zhang, Y.; Barnouin, O.; Collins, G. S.; et al. (February 2024). "Physical properties of asteroid Dimorphos as derived from the DART impact". Nature Astronomy: 21. doi:10.1038/s41550-024-02200-3.

[Agrusa2021-14] Cite error: The named reference Agrusa2021 was invoked but never defined (see the help page).

[Nakano2022-15] Cite error: The named reference Nakano2022 was invoked but never defined (see the help page).

[features-17] "Planetary Names". planetarynames.wr.usgs.gov.

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