Cupids

Amur group asteroid area highlighted in green

Cupids are a group of near-Earth asteroids whose orbits are completely outside the Earth’s orbit (their distance from the Sun at perihelion is greater than the aphelionic distance of the Earth, but less than 1.3 AU 1.017 AU <q <1.3 ae ) ^{[1 ]} . Thus, even at the closest point of their orbit, these asteroids are farther from the Sun than the Earth at the farthest point of their orbit. This group of asteroids was named after one of its most famous representatives, the asteroid (1221) Amur , which was discovered in early March 1932 ^[2] and named after the god of love Amur .

Asteroid (433) Eros gained fame due to the fact that he became the first asteroid to have an artificial satellite - the NEAR Shoemaker spacecraft . Subsequently, this spacecraft made the first ever landing on this asteroid ^[3] .

As of March 2013, 3653 asteroids of this group are known, of which 571 are assigned serial numbers, and sixty-five have their own names ^[4] .

Cupids, like other representatives of near-Earth asteroids, are relatively small. Only four cupids with a diameter of more than 10 km are known. The largest of these is (1036) Ganymede , whose diameter is almost 32 km ^[5] . The second largest cupid, asteroid (3552) Don Quixote , with a diameter of about 19 km, is one of the darkest known asteroids, with an albedo of about 3%. ^[6] .

Content

Existing Definitions

There are two definitions of cupids, each of which includes three criteria that an asteroid must satisfy in order to be considered to belong to a group of cupids. The main difference between these definitions lies in the fact that, in the first case, the asteroid’s orbit from the inside is limited by the average distance of the Earth to the Sun (1,000 AU), while secondly, the eccentricity of the Earth’s orbit is taken into account and the point aphelion of the earth's orbit (1.017 AU). Such disagreements lead to confusion, because the same asteroid in different databases can be assigned to two different groups, as, for example, this happened with the asteroid (65803) Didim . Such misunderstandings became possible due to the fact that in one database one definition is used ^[7] , and in the second another ^[8] . Because of this, the number of asteroids in different databases varies: in one case there are 3840 ^[9] , in the other - 3653 ^[4] .

Definition 1

The asteroid should approach the Earth at a distance of less than 0.3 a. e. In other words, it should come closer to the earth's orbit than any major planet. The planet closest to the Earth is Venus , which at moments of greatest confrontation approaches it to a distance of 0.27 a. e., and this value for convenience is rounded to 0.3 a. e. Since the orbit of Cupids is located outside the Earth’s orbit, the obtained distance is used to limit the distribution of asteroid orbits from the outer side of the Earth’s orbit and in total with the semimajor axis is 1.3 a. e. ( q <1.3 a.u. ). Beyond 1.3 a. e. there are bodies belonging already to the group of asteroids crossing the orbit of Mars . It is important to understand that since cupids have rather elongated orbits, almost all of them, one way or another, approaching the aphelion of their orbit, cross the orbit of Mars, although they do not belong to this group.

The asteroid’s orbit should be located outside the Earth’s orbit . Among the groups of near-Earth asteroids for cupids, there is a group of atira asteroids, which, on the contrary, are entirely inside the Earth’s orbit .

The asteroid’s orbit should not cross the Earth’s orbit . This is a key condition for cupids, because otherwise it will apply to either the atons or the Apollos . In other words, the asteroid should not come closer to the Sun than the average distance of the Earth to the Sun (1.0 AU). A more rigorous definition of this criterion is as follows: at any point along the asteroid’s orbit, the Earth’s orbit is closer to the Sun. It should be remembered that due to the eccentricity, the distance of the Earth to the Sun during the year varies from 0.983 a. e. up to 1.017 a. e. This circumstance makes it very difficult to identify asteroids.

All these three criteria can be reduced to one condition: the perihelion distance of the asteroid should be greater than the average distance of the Earth from the Sun ( semi-major axis ), but less than 1.3 a. e. ( 1.0 a.u. <q <1.3 a.u. ). Any asteroid whose orbit satisfies this condition can be considered part of the cupid group. This definition is used primarily in the center of minor planets .

Definition 2

The orbital period of an asteroid is more than one year. This is equivalent to the fact that its major axis is more than 1,000 a. e. ( a> 1,000 a.u. ).

The asteroid’s orbit does not cross the Earth’s orbit. The perihelion distance of the asteroid is greater than the aphelion distance of the Earth ( q> 1.017 AU ).

An asteroid is a near-Earth object , that is, its perihelion is less than 1.3 a. e. ( q <1.3 a.u. ).

All these three criteria can be reduced to one condition: the semi-major axis of the asteroid should be greater than the average distance of the Earth from the Sun ( a> 1.0 AU ), and its perihelion distance should be greater than the aphelion distance of the Earth, but less than 1.3 a . e. ( 1.017 a.u. <q <1.3 a.u. ) ^[10] . Any asteroid whose orbit satisfies this condition can be considered part of the cupid group. This definition is used primarily in the Jet Propulsion Laboratory database ^[1] and in Russian sources ^[11] .

Subgroups

The asteroids of the Amur group can be divided into four subgroups, depending on their average distance from the Sun :

The most famous representative of the Amur group is the asteroid (433) Eros

Cupids I is a relatively small subgroup of cupids, to which less than 1/5 of all known asteroids of this group belong, including (433) Eros . They are located between the orbits of the Earth and Mars (major axis 1.017 - 1.523 AU) and are characterized by more weakly elongated orbits, in comparison with other subgroups of cupids.

Low values of eccentricity lead to the fact that some asteroids of this subgroup never even leave the area between the orbits of the Earth and Mars, form a peculiar belt of near-Earth asteroids in it. However, there are enough available eccentricity values so that some asteroids of this subgroup, such as, for example, the same (433) Eros, penetrate far in the aphelion far beyond the orbit of Mars.

Cupids II is a rather large subgroup of cupids, which includes about 1/3 of all known asteroids of this group, including (1221) Cupids . They are located between the orbits of Mars and asteroids of the inner part of the main belt (semi-major axis are 1.523 - 2.12 AU) and are characterized by moderately elongated orbits (eccentricity 0.17 - 0.52). Thus, they cross the orbit of Mars from the outside , and the asteroid belt from the inside .

Cupids III is the largest subgroup of cupids, to which more than half of all known asteroids of this group belong. They are located inside the main belt (major axis 2.12 - 3.57 AU) and are characterized by rather elongated orbits (eccentricity 0.4 - 0.6). Such large eccentricities lead to the fact that about a third of the asteroids of this subgroup, such as, for example, (719) Albert and (1036) Ganymede , have orbits that extend beyond the main belt and come close to the orbit of Jupiter, at a distance of up to 1 a . e., and some even cross its orbit , for example, (5370) Taranis .

Since cupids of this subgroup are located within the main belt, they also belong to subgroups of the asteroid belt. For example, the asteroid (887) Alinda , who also heads the family of the same name , is in orbital resonance with Jupiter 1: 3 and with the Earth 4: 1 .

Cupids IV is the smallest subgroup of cupids, from which only 14 representatives are known. They are located outside the main belt (the major axis are more than 3.57 AU) and are characterized by a very strongly elongated orbit (from 0.65 to 0.75). All asteroids of this subgroup cross the orbit of Jupiter . Although their orbits have a very high eccentricity, they are still not as elongated as the orbits of most damocloids and comets , whose orbits have an eccentricity of about 0.9. Of all 14 asteroids of this subgroup, only one has its own name - asteroid (3552) Don Quixote , and only two - serial numbers in the catalog, - (85490) 1997 SE ₅ .

Another asteroid of this subgroup, 2007 VA ₈₅ , is interesting in that it rotates around the Sun in the opposite direction, compared with most bodies in the Solar System ( 2007 VA _{85 is} 132 ° inclined to the ecliptic plane ^[12] .

Intersection of Cupids with Earth Orbit

According to the first, simpler definition adopted at the center of small planets, cupids can not only approach the Earth’s orbit, but also go inside its orbit up to 1,000 a. e. Thus, such asteroids, along with Apollo or Atons, cross the Earth's orbit ( external grabber ) and can pose a real danger to the Earth.

According to the second, more precise definition adopted in Russian science, cupids do not cross the Earth’s orbit. Nevertheless, they often pose a certain danger to it, because their orbits are located in close proximity not only from the Earth, but also from Mars, and both planets are able to influence the orbits of these bodies, changing them in an unpredictable way, including bringing them to the intersection paths with the Earth’s orbit - in this case they move into a group of Apollos and Atons - and their danger to our planet rises sharply.

Potentially Dangerous Asteroids

Most of the potentially dangerous asteroids crossing the Earth’s orbit belong either to the atons or to the Apollos, but about 1/10 of them are cupids. To be considered potentially dangerous, an asteroid must be able to approach the Earth closer than 0.05 a. e. The most famous examples of such bodies are the asteroids (2061) Ansa , (3908) Nyukta and (3671) Dionysus .

Name (subgroup)	Semimajor axis $a{\text{ (a. e.)}}$ ${\ displaystyle a {\ text {(ae)}}}$	Perihelion $q{\text{ (a. e.)}}$ ${\ displaystyle q {\ text {(ae)}}}$	Aphelion $Q{\text{ (a. e.)}}$ ${\ displaystyle Q {\ text {(ae)}}}$	Eccentricity $e$ ${\ displaystyle e}$	Incline $i$ ${\ displaystyle i}$
(433) Eros (I)	1.46	1.13	1.78	0.22	10.80
(719) Albert (III)	2.63	1.18	4.08	0.55	11.60
(887) Alinda (III)	2.48	1,07	3.88	0.57	9.40
(1036) Ganymede (III)	2.66	1.24	4.09	0.53	26.70
(1221) Cupid (II)	1.92	1.08	2.75	0.44	11.90
(1580) Betulia (III)	2.20	1.12	3.27	0.49	52.10
(1627) Ivar (II)	1.86	1.12	2.60	0.40	8.40
(1915) Quetzalcoatl (III)	2.54	1.09	3.99	0.57	20.40
(1916) Northwind (III)	2.27	1.25	3.29	0.45	12.90
(1917) Cuillot (III)	2.15	1,07	3.23	0.50	23.90
(1943) Anteros (I)	1.43	1.06	1.80	0.26	8.70
(1980) Tescatlipoca (II)	1.71	1.09	2,33	0.36	26.90
(2059) Babiokivari (III)	2.64	1.24	4.05	0.53	11.00
(2061) Ansa (III)	2.26	1.05	3.48	0.54	3.80
(2202) Pele (III)	2.29	1.12	3.46	0.51	8.70
(2368) Beltrovata (II)	2.10	1.23	2.98	0.41	5.20
(2608) Seneca (III)	2.51	1,07	3.96	0.57	14.80
(3102) Croc (III)	2.15	1.19	3.12	0.45	8.40
(3122) Florence (II)	1.77	1,02	2,52	0.42	22,20
(3199) Nefertiti (II)	1,57	1.13	2.02	0.28	33.00
(3271) St. (II)	2.10	1.27	2.93	0.40	25.00
(3288) Seleucus (II)	2.03	1.10	2.96	0.46	5.90
(3352) Macauliffe (II)	1.88	1.19	2.57	0.37	4.80
(3551) Beliefs (II)	2.09	1,07	3.11	0.49	9.50
(3552) Don Quixote (IV)	4.22	1.21	7.23	0.71	31.00
(3553) Measure (II)	1.64	1.12	2.17	0.32	36.80
(3691) Trouble (II)	1.77	1.27	2.28	0.28	20.40
(3757) Anagolai (II)	1.83	1,02	2.65	0.45	3.87
(3908) Nyukta (II)	1.93	1,04	2.81	0.46	2.20
(4055) Magellan (II)	1.82	1.23	2.41	0.33	23.20
(4401) Aditi (III)	2.58	1.12	4.04	0.56	26.70
(4487) Pocahontas (II)	1.73	1.22	2.24	0.30	16.40
(4503) Cleobulus (III)	2.71	1.29	4.12	0.52	2.50
(4587) Rice (III)	2.65	1.30	4.01	0.51	24.60
(4947) Ninkashi (I)	1.37	1.14	1.60	0.17	15.70
(4954) Eric (II)	2.00	1.10	2.90	0.45	17.40
(4957) Brusmurray (II)	1,57	1.22	1.91	0.22	35.00
(5324) Lyapunov (III)	2.96	1.14	4.78	0.61	19.50
(5332) Davidagillar (III)	2.16	1.18	3.15	0.46	25.50
(5370) Taranis (III)	3.33	1.22	5.45	0.63	19.10
(5620) Jasonwiler (III)	2.16	1.24	3.07	0.42	7.90
(5653) Camarillo (II)	1.79	1.25	2.34	0.30	6.90
(5751) Zao (II)	2.10	1.21	2.99	0.42	16.10
(5797) Beat (II)	1.89	1.05	2.73	0.44	4.20
(5863) Tara (III)	2.22	1.09	3.35	0.51	19.50
(5869) Tanit (II)	1.81	1.23	2,39	0.32	17.90
(5879) Almeria (II)	1.62	1.15	2.09	0.29	21.60
(6050) Miwablock (III)	2.20	1.24	3.16	0.44	6.40
(6456) Golombek (III)	2.19	1.29	3.09	0.41	8.21
(6569) Ondaje (II)	1,63	1.27	1.99	0.22	22.60
(7088) Ishtar (II)	1.98	1.21	2.75	0.39	8.30
(7336) Sounders (III)	2,31	1.20	3.41	0.48	7.20
(7358) Ojo (III)	2.20	1.09	3.30	0.50	4.70
(7480) Norvan (II)	1,57	1,07	2.06	0.32	9.50
(8013) Gordonmoor (III)	2.20	1.25	3.15	0.43	7.60
(8034) Akka (II)	1.83	1.08	2.58	0.41	2.00
(8709) Kadlu (III)	2,53	1.30	3.77	0.49	3.50
(9172) Abhram (III)	2.71	1.21	4.21	0.55	7.80
(9950) ESA (III)	2.44	1.15	3.74	0.53	14.60
(11284) Belen (II)	1.74	1.15	2,33	0.34	2.00
(13553) Masaakikoyama (III))	2.19	1.18	3.20	0.46	5.90
(15817) Lucanothezi (I)	1.32	1.17	1.48	0.12	13.90
(16064) Davidharvey (III)	2.85	1.17	4,53	0.59	4.50
(16912) Rhiannon (II)	1.75	1.27	2.23	0.27	24.50
(18106) Blum (III)	2.44	1.19	3.70	0.51	4.20
(20460) Robwightley (II)	1.88	1.10	2.65	0.41	33.90
(21088) Chelyabinsk (II)	1.71	1.29	2.11	0.24	38.46
(96189) Pygmalion (II)	1.82	1.26	2.38	0.31	14.00
(154991) Vinciguerra (II)	1.70	1.15	2.25	0.32	5.60
(162011) Connomaru (III)	2.83	1.13	4,52	0.60	4.60
(164215) Doloreshill (II)	2.11	1.27	2.95	0.40	4.90
(189011) Ogmy (I)	1.50	1.15	1.85	0.23	18.70

Notes

↑ ¹ ² NASA JPL Small-Body Database. Amor (neopr.) . Date of treatment November 16, 2008. Archived March 10, 2013. (eng.)
↑ Discovery Circumstances: Numbered Minor Planets (1) - (5000) (neopr.) . Minor Planet Center. Date of treatment October 25, 2010. Archived November 24, 2012.
↑ Near Earth Asteroid Rendezvous (neopr.) . Archived March 20, 2012. (eng.)
↑ ¹ ² List of Amor asteroids generated by the JPL Small-Body Database Search Engine Retrieved 2013-03-05
↑ JPL Small-Body Database Browser: 1036 Ganymed. (Neopr.) Date of treatment October 26, 2008. Archived March 20, 2012.
↑ JPL Small-Body Database Browser: 3552 Don Quixote (Neopr.) Date of treatment October 26, 2008. Archived March 20, 2012.
↑ NASA JPL Database of Small Bodies in the Solar System (65803 )
↑ MPC Small Body Solar System Database (65803 )
↑ List objects with orbit type Amor (unspecified) . Minor Planet Center. Date of treatment April 5, 2013. Archived October 19, 2012.
↑ NEO Groups
↑ Shustov B.M., Rykhlova L.V. Asteroid-comet hazard: yesterday, today, tomorrow / Ed. Shustova B.M., Rykhlova L.V. - M .: FIZMATLIT, 2010 .-- P. 51 .-- 384 p. - ISBN 978-5-9221-1241-3 .
↑ NASA's JPL Small Body Solar System Database (2007 VA85 )

Links

Amor Asteroids. COSMOS - The SAO Encyclopedia of Astronomy

[JPLaten-1] ¹ ² NASA JPL Small-Body Database. Amor (neopr.) . Date of treatment November 16, 2008. Archived March 10, 2013. (eng.)

[2] Discovery Circumstances: Numbered Minor Planets (1) - (5000) (neopr.) . Minor Planet Center. Date of treatment October 25, 2010. Archived November 24, 2012.

[NEAR-3] Near Earth Asteroid Rendezvous (neopr.) . Archived March 20, 2012. (eng.)

[AmorsJPL-4] ¹ ² List of Amor asteroids generated by the JPL Small-Body Database Search Engine Retrieved 2013-03-05

[ganymed-5] JPL Small-Body Database Browser: 1036 Ganymed. (Neopr.) Date of treatment October 26, 2008. Archived March 20, 2012.

[quixote-6] JPL Small-Body Database Browser: 3552 Don Quixote (Neopr.) Date of treatment October 26, 2008. Archived March 20, 2012.

[7] NASA JPL Database of Small Bodies in the Solar System (65803 )

[8] MPC Small Body Solar System Database (65803 )

[9] List objects with orbit type Amor (unspecified) . Minor Planet Center. Date of treatment April 5, 2013. Archived October 19, 2012.

[10] NEO Groups

[11] Shustov B.M., Rykhlova L.V. Asteroid-comet hazard: yesterday, today, tomorrow / Ed. Shustova B.M., Rykhlova L.V. - M .: FIZMATLIT, 2010 .-- P. 51 .-- 384 p. - ISBN 978-5-9221-1241-3 .

[12] NASA's JPL Small Body Solar System Database (2007 VA85 )