2015 YQ1

2015 YQ₁ (also written 2015 YQ1) is an Apollo asteroid that is a temporary horseshoe companion to the Earth, the twelfth known Earth horseshoe librator.^[6] It experienced a close encounter with the Earth on 2015 December 22 at 0.0037 AU.

2015 YQ₁

Discovery
Discovered by	Mount Lemmon Srvy.
Discovery site	Mount Lemmon Obs.
Discovery date	19 December 2015
Designations
Designation	2015 YQ1
Minor planet category	Apollo asteroid[1][2] Earth crosser
Orbital characteristics[2][3][4]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 6
Observation arc	3 days
Aphelion	1.40586 AU
Perihelion	0.59681 AU
Semi-major axis	1.00134 AU
Eccentricity	0.40398
Orbital period (sidereal)	1.00202 y (365.99 d)
Mean anomaly	317.067°
Inclination	2.4865°
Longitude of ascending node	88.89770°
Argument of perihelion	112.185°
Earth MOID	0.00052 AU
Physical characteristics
Dimensions	7–16 m[a][5]
Absolute magnitude (H)	28.1[2]

Discovery

2015 YQ₁ was discovered on 19 December 2015 by A. D. Grauer observing with the 1.5-m reflector telescope at the Mount Lemmon Survey.^[7] As of 9 March 2016, it has been observed 64 times with an observation arc of 3 days.^[2]

Orbit and orbital evolution

Animation of 2015 YQ1's orbit relative to Sun and Earth
  2015 YQ1 ·   Sun ·   Earth

2015 YQ₁ is currently an Apollo asteroid (Earth-crossing but with a period greater than a year). Its semi-major axis (currently 1.00134 AU) is similar to that of Earth (1.00074 AU), but it has a relatively high eccentricity (0.40398) and low orbital inclination (2.4865°). It alternates between being an Aten asteroid and being an Apollo asteroid. As of 9 March 2016, this object is the 17th known Earth co-orbital and the 12th known object following a horseshoe path with respect to our planet. Asteroid 2015 YQ₁ follows an asymmetrical horseshoe path with respect to our planet; the value of its relative mean longitude oscillates about 180°, but enclosing 0°; its orbital evolution is rather unstable.^[6]

Physical properties

With an absolute magnitude of 28.1 mag, it has a diameter in the range 7–16 meters (for an assumed albedo range of 0.04–0.20, respectively).^{[citation needed]}

See also

• 54509 YORP
• (419624) 2010 SO16
• 3753 Cruithne
• 2015 SO2
• 2015 XX169
• 2015 YA

Notes

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