2020 CD3 (2nd moon)
eta 4 04 2020 {444) antarctica midday-ish
2020 CD3 imaged in color by the Gemini Observatory
Theodore A. Pruyne
Kacper W. Wierzchoś [1]
Discovery date 15 February 2020
Designations
MPC designation 2020 CD3
Observation arc 15 days
Perihelion 0.9860 AU
Semi-major axis 1.0253 AU
Eccentricity 0.03838
Orbital period 1.04 yr (379.2 d)
Mean anomaly 39.719°
Mean motion 0° 56m 57.582s / day
Inclination 0.8447°
Longitude of ascending node 138.574°
Argument of perihelion 339.620°
Earth MOID 0.00175557 AU
Mean diameter 1.9–3.5 m (est.)[6]
2 m (est.)[7]
Absolute magnitude (H) 31.678±0.345[5]
31.8[2]
2020 CD3 is a tiny near-Earth asteroid and temporary satellite of Earth. It was discovered at the Mount Lemmon Observatory by astronomers Theodore Pruyne and Kacper Wierzchoś on 15 February 2020, as part of the Mount Lemmon Survey or Catalina Sky Survey. The asteroid's discovery was announced by the Minor Planet Center on 25 February 2020, after subsequent observations have confirmed that it is orbiting around Earth. It is the second temporary satellite of Earth discovered in situ, after 2006 RH120, which was discovered in 2006. Based on its preliminary orbit, 2020 CD3 may have been captured by Earth around 2016–2017, and is expected to remain in Earth orbit until April 2020.[9]
2020 CD3 has an absolute magnitude around 32, indicating that it is very small in size. Assuming that 2020 CD3 has a low albedo characteristic of dark, carbonaceous C-type asteroids, its diameter is probably around 1.9–3.5 metres (6–11 ft).[10][11] The JPL Small-Body Database classifies 2020 CD3 as an Earth-crossing Apollo asteroid, though the Minor Planet Center considers 2020 CD3 to be part of the Amor group of near-Earth asteroids orbiting beyond Earth.
Contents
Discovery[edit]
(looks like a rave in a coal mine, it could be anything)
Color composite image of 2020 CD3 obtained by the Gemini Observatory on 24 February 2020[6]
2020 CD3 was discovered on 15 February 2020, by astronomers Theodore Pruyne and Kacper Wierzchos at the Mount Lemmon Observatory. The discovery formed part of the Mount Lemmon Survey designed for discovering near-Earth objects, which is also part of the Catalina Sky Survey conducted at Tucson, Arizona.[1][6] 2020 CD3 was found as a faint, 20th magnitude object in the constellation of Virgo, located about 0.0019 AU (280,000 km; 180,000 mi) from Earth at the time.[12][9][a] The observed orbital motion of the object suggested that it may be gravitationally bound to Earth, which prompted further observations to secure and determine its motion.[4]
The object's discovery was reported to the Minor Planet Center's Near-Earth Object Confirmation Page (NEOCP), where a preliminary orbit was calculated from additional observations conducted at several observatories.[4] Follow-up observations of 2020 CD3 spanned six days since its discovery, and the object was formally announced in a Minor Planet Electronic Circular notice issued by the Minor Planet Center on 25 February 2020. No indication of perturbations by solar radiation pressure was observed, and 2020 CD3 could not be linked to any known artificial object.[1] Although the evidence implied that 2020 CD3 is most likely a dense, rocky asteroid, the possibility of the object being artificial has not yet been fully ruled out.[13][9]
As of February 2020, no precovery images of 2020 CD3 have been identified.[5] The discoverers of 2020 CD3 have suspected that it is possible that the object may have been imaged by other astronomical surveys prior to its discovery, but had not been identified due to its faintness and highly variable orbit.[13]
Nomenclature[edit]
Upon discovery, the asteroid was given the temporary internal designation C26FED2.[4][3] After follow up observations confirming the object, it was then given the provisional designation 2020 CD3 by the Minor Planet Center on 25 February 2020.[1] The provisional designation signifies the object's discovery date and year. The object has not yet been issued a permanent minor planet number by the Minor Planet Center due to its short observation arc of several days.[14]
Orbit[edit]
The heliocentric orbit of 2020 CD3 appears similar to that of Earth's, having a nearly circular shape and low orbital inclination with respect to the ecliptic plane.[15] 2020 CD3's nominal average orbital distance from the Sun is 1.025 AU, slightly farther than that of Earth's. The orbital period of 2020 CD3 is 1.04 years, or about 379 days. With a low orbital eccentricity of 0.038, 2020 CD3's distance from the Sun varies from 0.986 AU at perihelion to 1.065 AU at aphelion. 2020 CD3's perihelion distance is smaller than Earth's aphelion distance of 1.017 AU, hence it is classified as an Earth-crossing Apollo asteroid by the JPL Small-Body Database.[5] The Minor Planet Center also classifies 2020 CD3 as an Amor asteroid since it orbits beyond Earth, albeit only slightly.[2]
2020 CD3's nominal minimum orbital intersection distance (MOID) from Earth is approximately 0.0017 AU (250,000 km; 160,000 mi) according to the JPL Small-Body Database. Accounting for gravitational perturbations and changes in 2020 CD3's heliocentric orbit, the object can approach Earth at a much closer distance than its nominal Earth MOID, especially during its temporary capture.[5][13]
Trajectory and orbits of 2020 CD3 around Earth, from 2015–2020.[b]
(click image to see spin view)
Because the heliocentric orbit of 2020 CD3 is similar to that of Earth's, its motion relative to Earth is low, allowing for it to slowly approach the planet and get captured.[15] Nominal orbit solutions for 2020 CD3 suggest that it was captured by Earth around 2016–2017, and is expected to leave Earth orbit by April 2020 according to simulations of its orbit.[16][9] 2020 CD3 had likely been captured when it passed through Earth's L1 Lagrange point 1.5 million km (0.93 million mi) from the planet, where the object's heliocentric orbital period becomes equal to that of Earth's.[16][17] The geocentric orbit of 2020 CD3 is chaotic due to the combined effects of tidal forces from the Sun and Earth as well as repeated close encounters with the Moon.[15][13] The Moon gravitationally perturbs 2020 CD3's geocentric orbit, causing it to be unstable. Over the course of 2020 CD3's orbit around Earth, repeated close encounters with the Moon will eventually lead to ejection from its geocentric orbit as the Moon's perturbations can transfer enough momentum for 2020 CD3 to escape Earth's gravitational influence.[18][15]
2020 CD3's orbit around Earth is highly variable and eccentric.[11][15] 2020 CD3's distance from Earth usually ranges from 0.2 lunar distances (77,000 km or 48,000 mi) at perigee and 4.5 lunar distances (1.73 million km or 1.07 million mi) at apogee.[13] According to the JPL Small-Body Database, 2020 CD3 has approached Earth as close as 13,023 km (8,092 mi) on 4 April 2019.[5][c] The orbital period of 2020 CD3 around Earth is estimated to be around 47 days,[11] though this estimate is largely uncertain due to the chaotic dynamics of 2020 CD3's orbit.[13]
Because 2020 CD3 has been captured into a temporary orbit around Earth, it is considered to be a temporarily captured object or a temporary satellite of Earth.[1][16] 2020 CD3 has also been widely referred to in the media as a "mini-moon" of Earth, due to its small size.[6][10][11][19] 2020 CD3 is the second known temporary captured object discovered in situ around Earth, with the first being 2006 RH120, which was discovered in 2006.[19] Other objects have also been suspected to have once been temporarily captured, including the small near-Eath asteroid 1991 VG and the bolide DN160822_03.[20][21] Objects that get temporarily captured by Earth are thought to be common, though larger objects over 0.6 m (2 ft) in diameter are believed to be less likely to be captured by Earth and detected by modern telescopes.[19]
Future approaches[edit]
After 2020 CD3 leaves Earth orbit, it will continue orbiting the Sun until 2044, when it will approach Earth from a nominal distance of 0.0245 AU (3.67 million km; 2.28 million mi). Accounting for uncertainties in its orbit, the minimum approach distance from Earth is expected to be 0.0237 AU (3.55 million km; 2.20 million mi).[22] Assuming that 2020 CD3's orbit does not change after the 2044 close approach, the next encounter would be around 2061, when it is expected to approach Earth from a nominal distance of 0.0375 AU (5.61 million km; 3.49 million mi). However, uncertainties in the 2061 approach distance are greater; 2020 CD3's minimum approach distance could be 0.0131 AU (1.96 million km; 1.22 million mi).[22]
The possibility of 2020 CD3 impacting Earth has been considered by the Jet Propulsion Laboratory's Sentry risk table.[7] Being only a few meters in size, an impact by 2020 CD3 would pose no significant threat to Earth as it would most likely fragment and disintegrate upon atmospheric entry.[9] Because of the minimal impact hazard of 2020 CD3, it is given a Torino Scale rating of 0 and a cumulative Palermo Scale rating of –5.22.[7] Over a period of 100 years from the present, the cumulative impact probability of 2020 CD3 is estimated to be 0.022%. Within this time frame, the date with the highest probability of impact is probably 14 September 2061, which is estimated to have an impact probability of 0.0073% and a negligible Palermo Scale rating of –5.55.[7]
Physical characteristics[edit]
2020 CD3 is estimated to have an absolute magnitude (H) around 31.7, indicating that it is very small in size.[5] The rotation period and albedo of 2020 CD3 have not been measured due to the limited number of observations.[13] Assuming that the albedo of 2020 CD3 is similar to those of dark, carbonaceous C-type asteroids, the diameter of 2020 CD3 is around 1.9–3.5 m (6–11 ft), comparable to in size to that of a small car.[11][16] The JPL Sentry risk table estimates 2020 CD3 to have a mass of 4,900 kg (10,800 lb), based on the assumption that the asteroid has a diameter of 2 m (6.6 ft).[7]
See also[edit]
1991 VG – near-Earth asteroid temporarily captured by Earth after its discovery in 1991
2006 RH120 – the first temporary Earth satellite discovered in situ 2006
Notes[edit]
^ The celestial coordinates of 2020 CD3 at the time of discovery were 13h 03m 33.11s +09° 10′ 43.1″.[1] See Virgo for constellation coordinates.
^ 2020 CD3's 4 April 2019 close approach distance from Earth listed as 8.70549616524421×10−5 AU on the JPL Small-Body Database.[5]
References[edit]
^ Jump up to:a b c d e f g h i "MPEC 2020-D104 : 2020 CD3: Temporarily Captured Object". Minor Planet Electronic Circular. Minor Planet Center. 25 February 2020. Retrieved 25 February 2020.
^ Jump up to:a b c d e "2020 CD3". Minor Planet Center. International Astronomical Union. Retrieved 25 February 2020.
^ Jump up to:a b "2020 CD3". NEO Exchange. Las Cumbres Observatory. 15 February 2020. Retrieved 25 February 2020.
^ Jump up to:a b c d ""Pseudo-MPEC" for C26FED2". Project Pluto. 24 February 2020. Retrieved 25 February 2020.
^ Jump up to:a b c d e f g h i j k "JPL Small-Body Database Browser: 2020 CD3"(2020-03-01 last obs.). Jet Propulsion Laboratory. Retrieved 25 February2020.
^ Jump up to:a b c d "Gemini Telescope Images "Minimoon" Orbiting Earth — in Color!". National Optical-Infrared Astronomy Research Laboratory(Press release). National Science Foundation. 27 February 2020. Retrieved 28 February 2020.
^ Jump up to:a b c d e f "2020 CD3 -- Earth Impact Risk Summary". Center for Near Earth Object Studies. Jet Propulsion Laboratory. Retrieved 3 March 2020.
^ "2020CD3". Near Earth Objects – Dynamic Site. Department of Mathematics, University of Pisa, Italy. Retrieved 25 February 2020.
^ Jump up to:a b c d e King, Bob (2 March 2020). "Earth Has A Mini-Moon — But Not for Long!". Sky & Telescope. Retrieved 3 March 2020.
^ Jump up to:a b Byrd, Deborah (26 February 2020). "Looks like Earth has a new natural moon". EarthSky. Retrieved 26 February 2020.
^ Jump up to:a b c d e Crane, Leah (26 February 2020). "Earth has acquired a brand new moon that's about the size of a car". New Scientist. Retrieved 27 February 2020.
^ "2020 CD3 Ephemerides". Near Earth Objects – Dynamic Site(Ephemerides at discovery). Department of Mathematics, University of Pisa, Italy. Retrieved 28 February 2020.
^ Jump up to:a b c d e f g Howell, Elizabeth (28 February 2020). "How scientists found Earth's new minimoon and why it won't stay here forever". Space.com. Retrieved 29 February 2020.
^ "How Are Minor Planets Named?". Minor Planet Center. International Astronomical Union. Retrieved 29 February 2020.
^ Jump up to:a b c d e Plait, Phil (27 February 2020). "The Earth has a new minimoon! But not for long..." Bad Astronomy. Syfy Wire. Retrieved 29 February2020.
^ Jump up to:a b c d Gough, Evan (27 February 2020). "Astronomers Discover a Tiny New Temporary Moon for the Earth. Welcome to the Family 2020 CD3". Universe Today. Retrieved 29 February 2020.
^ Cornish, Neil J. "The Lagrangian Points" (PDF). Department of Physics. Montana State University. Archived from the original (PDF) on 7 September 2015. Retrieved 29 February 2020.
^ Baoyin, He-Xi; Chen, Chen; Li, Jun-Feng (June 2010). "Capturing Near Earth Objects". Research in Astronomy and Astrophysics: Letters. 10(6): 587–598. arXiv:1108.4767. Bibcode:2010RAA....10..587B. doi:10.1088/1674-4527/10/6/008.
^ Jump up to:a b c Boyle, Rebecca (27 February 2020). "A New Mini-Moon Was Found Orbiting Earth. There Will Be More". The New York Times. Retrieved 29 February 2020.
^ Tancredi, G. (September 1997). "An Asteroid in a Earth-like Orbit". Celestial Mechanics and Dynamical Astronomy. 69 (1/2): 119–132. Bibcode:1997CeMDA..69..119T. doi:10.1023/A:1008378316299.
^ Gohd, Chelsea (2 December 2019). "Scientists Spot Rare Minimoon Fireball Over Australia". Space.com. Retrieved 29 February 2020.
^ Jump up to:a b "2020CD3 Close Approaches". Near Earth Objects – Dynamic Site. Department of Mathematics, University of Pisa, Italy. Retrieved 1 March2020.
External links[edit]
Wikimedia Commons has media related to 2020 CD3.
Earth Has A Mini-Moon — But Not for Long! by Bob King, Sky & Telescope, 2 March 2020
A New Mini-Moon Was Found Orbiting Earth. There Will Be More. by Rebecca Boyle, The New York Times, 27 Feb 2020
Gemini Telescope Images "Minimoon" Orbiting Earth — in Color!, OIR Laboratory press release, 27 Feb 2020
Looks like Earth has a new natural moon by Deborah Byrd, EarthSky, 26 Feb 2020
MPEC 2020-D104 : 2020 CD3: Temporarily Captured Object, Minor Planet Center announcement, 25 Feb 2020
2020 CD3 at NeoDyS-2, Near Earth Objects—Dynamic Site
Ephemeris · Obs prediction · Orbital info · MOID · Proper elements · Obs info · Close · Physical info · NEOCC
