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. 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, which results in their being close to a 4:1 resonance with Earth. 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, 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. Older members such as 8709 Kadlu have an eccentricities between 0.465 and 0.475 and cross the orbit of Mars. The oldest members with eccentricities between 0.57 and 0.75 cross the orbit of Earth. 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 Alinda2.484220.56356
1429 Pemba2.551850.33858
1550 Tito2.546730.30984
1607 Mavis2.547830.30741
1915 Quetzálcoatl2.542070.57170
2608 Seneca2.50350.57620
3360 Syrinx2.468030.74295
3628 Božněmcová2.536910.30052
3806 Tremaine2.540580.31301
4179 Toutatis2.510050.63423
5847 Wakiya2.544420.30086
5864 Montgolfier2.558660.32007
6318 Cronkite2.510020.46522
1991 CQ2.516280.47349
6489 Golevka2.507680.60382
1991 OA2.509590.58946
7092 Cadmus2.524930.70202
7345 Happer2.450470.32467
2.527390.33216
1989 BK2.549500.30348
7638 Gladman2.536340.31606
2.533620.70851
8709 Kadlu2.534970.48432
1991 QF2.524790.31661