Alinda asteroid

The Alinda asteroids are a dynamical group of asteroids with a semi-major axis of about 2.5 AU and an orbital eccentricity approximately between 0.4 and 0.65.[1] The namesake is 887 Alinda, discovered by Max Wolf in 1918.

These objects are held in this region by the 1:3 orbital resonance with Jupiter (2.502 AU), which results in their being close to a 4:1 resonance with Earth (2.520 AU). An object in this resonance has its orbital eccentricity steadily increased by gravitational interactions with Jupiter until it eventually has a close encounter with an inner planet that breaks the resonance.

Some Alindas have perihelia very close to Earth's orbit, resulting in a series of close encounters at almost exactly four-year intervals, due to the 4:1 near resonance.

One consequence of this is that if an Alinda asteroid happens to be in an unfavorable position for viewing at the time of its close approach to Earth (for instance, at a small elongation from the Sun), then this situation can persist for decades. Indeed, as of 2010, the Alinda asteroid 1915 Quetzálcoatl had been observed only once since 1985.

Another consequence is that some of these asteroids make repeated relatively close approaches to Earth, making them good subjects for study by Earth-based radar. Examples are 4179 Toutatis and 6489 Golevka, as well as 2019 MO, which impacted Earth in June 2019.

Dynamic age

The 3:1 resonance with Jupiter causes a repeating growth in the eccentricity of the asteroid's orbit. Dynamically young members have an eccentricity ranging from about 0.30 to 0.34 staying mostly in the asteroid belt ranging 1.7–3.4 AU from the Sun.[2] Older members such as 8709 Kadlu have an eccentricities between 0.465 and 0.475 and cross the orbit of Mars. (8709 Kadlu makes approaches close enough to Jupiter, Mars, and Earth to be gravitationally nudged.)[3] The oldest members with eccentricities between 0.57 and 0.75 cross the orbit of Earth.[2] 3360 Syrinx is the most eccentric of the Alinda group with an eccentricity of 0.7 and the orbit has a dynamically short life expectancy.

List of members

DesignationaeRefs
887 Alinda2.484220.56356JPL · MPC
1429 Pemba2.551850.33858JPL · MPC
1550 Tito2.546730.30984JPL · MPC
1607 Mavis2.547830.30741JPL · MPC
1915 Quetzálcoatl2.542070.57170JPL · MPC
2608 Seneca2.50350.57620JPL · MPC
3360 Syrinx2.468030.74295JPL · MPC
3628 Božněmcová2.536910.30052JPL · MPC
3806 Tremaine2.540580.31301JPL · MPC
4179 Toutatis2.510050.63423JPL · MPC
5847 Wakiya2.544420.30086JPL · MPC
5864 Montgolfier2.558660.32007JPL · MPC
6318 Cronkite2.510020.46522JPL · MPC
(6322) 1991 CQ2.516280.47349JPL · MPC
6489 Golevka2.507680.60382JPL · MPC
(6491) 1991 OA2.509590.58946JPL · MPC
7092 Cadmus2.524930.70202JPL · MPC
7345 Happer2.450470.32467JPL · MPC
(7568) 1988 VJ22.527390.33216JPL · MPC
(7569) 1989 BK2.549500.30348JPL · MPC
7638 Gladman2.536340.31606JPL · MPC
(8201) 1994 AH22.533620.70851JPL · MPC
8709 Kadlu2.534970.48432JPL · MPC
(9047) 1991 QF2.524790.31661JPL · MPC

See also

References

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