is a

near-Earth object A near-Earth object (NEO) is any small Solar System body whose orbit brings it into proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun (perihelion) is less than 1.3 astronomical units (AU). ...

and Apollo asteroid, approximately in diameter. It was the most dangerous

potentially hazardous asteroid A potentially hazardous object (PHO) is a near-Earth object – either an asteroid or a comet – with an orbit that can make close approaches to the Earth and is large enough to cause significant regional damage in the event of impact. They are ...

on Sentry Risk Table upon its discovery by the Mount Lemmon Survey in December 2014. At the time, the asteroid had a cumulative 1 in 83000 chance of impacting Earth on 4–5 June between the years 2048 and 2084. After the object's

observation arc In observational astronomy, the observation arc (or arc length) of a Solar System body is the time period between its earliest and latest observations, used for tracing the body's path. It is usually given in days or years. The term is mostly use ...

had been extended to 35 days, it was removed from the Sentry Risk Table on 15 January 2015. Since then the asteroid's orbit has been secured. Although it has an Earth minimum orbit intersection distance of less than one lunar distance, there are no projected close encounters with Earth in the foreseeable future, with its closest passage to occur in May 2046, still millions of kilometers away.

Discovery

On 1 September 2014, the asteroid passed about from Earth, but remained undetected as at that time the asteroid had an

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

of 25 and was roughly 25 ° from the Sun. It was discovered on 11 December 2014, by the Mount Lemmon Survey at an apparent magnitude of 20 using the Steward Observatory's reflecting telescope at

Mount Lemmon Observatory Mount Lemmon Observatory (MLO), also known as the Mount Lemmon Infrared Observatory, is an astronomical observatory located on Mount Lemmon in the Santa Catalina Mountains approximately northeast of Tucson, Arizona (US). The site in the Coronad ...

near Tucson, Arizona, and received the

provisional designation Provisional designation in astronomy is the naming convention applied to astronomical objects immediately following their discovery. The provisional designation is usually superseded by a permanent designation once a reliable orbit has been calcu ...

Palermo Scale rating

With an

of only 19 days, it had a cumulative Palermo Scale rating of –2.85 and was briefly the 9th most dangerous asteroid known. It was calculated that on 4 June 2065, there was a 1 in 270,000 chance of impact and on 4 June 2076, there was a 1 in 137,000 chance of impact. On 15 January 2015, the asteroid was recovered by Cerro Paranal Observatory which extended the observation arc to 35 days, and was subsequently removed from the Sentry Risk Table using JPL solution 9.

Orbit and classification

, and last observed in November 2016, the asteroid has a better constrained orbit with an observation arc of 713 days and an

uncertainty parameter The uncertainty parameter ''U'' is introduced by the Minor Planet Center (MPC) to quantify the uncertainty of a perturbed orbital solution for a minor planet. The parameter is a logarithmic scale from 0 to 9 that measures the anticipated longit ...

of 2, which ranges from 0 (good) to 9 (highly uncertain). It has an apparent magnitude of 25.82, and orbits the Sun at a distance of 0.77–2.5 AU once every 2 years and 2 months (777 days;

semi-major axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the long ...

of 1.65 AU). Its orbit has an eccentricity of 0.53 and an

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...

of 8 ° with respect to the ecliptic. The

has a minimum orbit intersection distance with Earth of , or less than the distance to the Moon. Its closest encounter with Earth will occur on 29 May 2046, at a nominal distance of . With an

absolute magnitude Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse Logarithmic scale, logarithmic Magnitude (astronomy), astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent mag ...

of 21, the asteroid is approximately in diameter.

Notes

References

External links

List of the Potentially Hazardous Asteroids (PHAs)
Minor Planet Center

Minor Planet Center * * * {{DEFAULTSORT:2014 XL7 # Minor planet object articles (unnumbered) Discoveries by MLS # # 20140901 20141211