2013 BS45

2013 BS₄₅
Discovery
Discovered by	James V. Scotti (Spacewatch)
Discovery date	20 January 2013
Designations
MPC designation	2013 BS45
Minor planet category	Aten; NEO; Earth crosser;
Orbital characteristics
	Epoch 13 January 2016 (JD 2457400.5)
	Uncertainty parameter 0
Observation arc	375 days (1.03 yr)
Aphelion	1.0758430 AU (160.94382 Gm)
Perihelion	0.9093608 AU (136.03844 Gm)
Semi-major axis	0.9926019 AU (148.49113 Gm)
Eccentricity	0.0838615
Orbital period (sidereal)	0.99 yr (361.2 d)
Mean anomaly	257.52229°
Mean motion	0° 59m 47.93s /day
Inclination	0.7726189°
Longitude of ascending node	83.40080°
Argument of perihelion	150.3038°
Earth MOID	0.0114221 AU (1.70872 Gm)
Jupiter MOID	3.89526 AU (582.723 Gm)
Physical characteristics
Dimensions	20–40 m[a]
Absolute magnitude (H)	25.9

2013 BS₄₅ (also written 2013 BS45) is a horseshoe companion to the Earth like 3753 Cruithne.^[6] Like Cruithne, it does not orbit the Earth in the normal sense and at times it is on the other side of the Sun, yet it still periodically comes nearer to the Earth in sort of halo orbit before again drifting away. While not a traditional natural satellite, it does not quite have normal heliocentric orbit either and these are sometimes called quasi-satellites or horseshoe orbits.

Discovery, orbit and physical properties

2013 BS₄₅ was discovered by James V. Scotti on 20 January 2013, observing for the Spacewatch project from Kitt Peak (KPNO).^[7]^[8] Its orbit is characterized by low eccentricity (0.084), low inclination (0.77º) and a semi-major axis of 0.993 AU;^[8] it is the most Earth-like among those of asteroids moving in Earth-like orbits.^[6] Upon discovery, it was classified as an Aten asteroid but also an Earth crosser by the Minor Planet Center. Its orbit is well determined; as of 26 August 2015, its orbit is based on 96 observations spanning a data-arc of 375 days.^[2] 2013 BS₄₅ has an absolute magnitude of 25.9 which gives a characteristic diameter of 30 m.^[5] Radar observations indicate that it may be a very rapid rotator with a period of just a few minutes.

Horseshoe companion to the Earth and orbital evolution

Recent calculations indicate that it follows a horseshoe orbit with respect to the Earth.^[6] Its orbital evolution is highly chaotic and its orbit is difficult to predict beyond a few thousand years.^[6] As for the available data, it had its closest encounter ever with Earth on 12 February 2013 at 0.013 AU, closer than in 1934, the previously closest approach at 0.014 AU. The next approach closer than 0.020 AU will take place on 2 September 2090 at 0.016 AU.^[2] Its orbit matches the expected properties of that of an object in the Arjuna class.^[9]

Origin

2013 BS₄₅ may have originated within the Venus-Earth-Mars region; alternatively, it may have come from the main asteroid belt like other Near-Earth Objects, then transitioned to an Amor-class asteroid before entering Earth's co-orbital region.^[6]

Notes

^{^} This is assuming an albedo of 0.20–0.04.

References

^ "List Of Aten Minor Planets". Minor Planet Center. Retrieved 27 August 2015.
^ ^a ^b ^c ^d ^e "2013 BS45". JPL Small-Body Database. Jet Propulsion Laboratory. SPK-ID: 3625129. Retrieved 3 April 2016.(last obs: 2014-01-30)
^ "2013 BS45 – Summary". AstDys-2, Asteroids – Dynamic Site. Retrieved 11 May 2013.
^ "2013 BS45 – Summary". NEODyS-2, Near Earth Objects – Dynamic Site. Retrieved 11 May 2013.
^ ^a ^b "Absolute-magnitude conversion table (H)". NASA. 27 August 2015. Archived from the original on 2 March 2001.
^ ^a ^b ^c ^d ^e de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl (July 2013). "A resonant family of dynamically cold small bodies in the near-Earth asteroid belt". Monthly Notices of the Royal Astronomical Society: Letters. 434 (1): L1–L5. arXiv:1305.2825. Bibcode:2013MNRAS.434L...1D. doi:10.1093/mnrasl/slt062.
^ Discovery MPEC
^ ^a ^b "2013 BS45". MPC (last obs: 2014-01-30.0). Retrieved 26 August 2015.
^ de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl (12 February 2015). "Geometric characterization of the Arjuna orbital domain". Astronomische Nachrichten. 336 (1): 5–22. arXiv:1410.4104. Bibcode:2015AN....336....5D. doi:10.1002/asna.201412133.

Further reading

A resonant family of dynamically cold small bodies in the near-Earth asteroid belt de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl (2013), Monthly Notices of the Royal Astronomical Society: Letters, Vol. 434, Issue 1, pp. L1-L5.
Geometric characterization of the Arjuna orbital domain de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl (2015), Astronomische Nachrichten, Vol. 336, Issue 1, pp. 5–22.