, provisional designation , is a dark

asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

and synchronous binary system, classified as

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

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 ...

of the

Amor group Amor Group was Scotland's largest independent business technology company before being acquired by Lockheed Martin in September 2013. The business was formed after a £28 million management buyout of Glasgow based Real Time Engineering Ltd. an ...

, approximately 3 kilometers in diameter. It was discovered on 19 August 1998, by astronomers of the

LINEAR Linearity is the property of a mathematical relationship (''function'') that can be graphically represented as a straight line. Linearity is closely related to '' proportionality''. Examples in physics include rectilinear motion, the linear r ...

program at

Lincoln Laboratory's Experimental Test Site The MIT Lincoln Laboratory, located in Lexington, Massachusetts, is a United States Department of Defense federally funded research and development center chartered to apply advanced technology to problems of national security. Research and dev ...

near Socorro, New Mexico, in the United States. Its sub-kilometer minor-planet moon was discovered by radar on 30 May 2013.

Classification and orbital characteristics

As an Amor asteroid the orbit of is entirely beyond Earth's orbit. The asteroid orbits the Sun at a distance of 1.0–3.8 AU once every 3 years and 9 months (1,378 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 2.42 AU). Its orbit has an eccentricity of 0.57 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 13 ° with respect to the ecliptic. The ''Earth minimum orbit intersection distance'' with the orbit of the asteroid is , which translates into 13.4 lunar distances. As with many members of the Amor group, this asteroid has an aphelion beyond the orbit of

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury (planet), Mercury. In the English language, Mars is named for the Mars (mythology), Roman god of war. Mars is a terr ...

(at 1.66 AU) which also makes it a Mars-crosser. The sooty surface of suggested that it might have previously been a

comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ar ...

that experienced a close encounter with the Sun. However, the

Tisserand parameter Tisserand's parameter (or Tisserand's invariant) is a value calculated from several orbital elements (semi-major axis, orbital eccentricity and inclination) of a relatively small object and a larger " perturbing body". It is used to distinguish dif ...

with respect to

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but ...

(T_J=3.2) does not make it obvious whether was ever a comet, since cometary T_J values are typically below 3.

Earth approach

On 31 May 2013, approached within (15 lunar distances) of

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

at 20:59 UT (4:59 pm EDT). This was the closest approach the asteroid will make to Earth for at least the next two centuries. It is a very strong radar target for Goldstone from May 30 to June 9 and will be one for Arecibo from June 6 to June 12. At its closest approach 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 11 and therefore required a small telescope to be seen. Integrating the orbital solution shows the asteroid passed from Earth on 8 June 1975 with an apparent magnitude of about 13.9. The next notable close approach will be 27 May 2221, when the asteroid will pass Earth at a distance of .

Satellite

Goldstone

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

observations on 29 May 2013 discovered that is orbited by a minor-planet moon approximately 600–800 meters in diameter. In radar images, the satellite appears brighter than because it is rotating significantly more slowly, which compresses the radar return of the satellite along the Doppler axis. This makes the satellite appear narrow and bright compared to . The satellite orbits the primary every 32 hours with a maximum separation of . Once the satellite's orbit is well determined,

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, natural satellite, moons, comets and galaxy, g ...

s and astrophysicists will be able to determine the mass and density of .

Physical characteristics

Surface, albedo and composition

The surface of is covered with a sooty substance, making it optically dark with a geometric

albedo Albedo (; ) is the measure of the diffuse reflection of sunlight, solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body ...

of 0.06, meaning it absorbs 94% of the light that hits it, which is indicative for a carbonaceous surface of a C-type asteroid. The asteroid is covered with craters and is dark, red, and primitive.

Diameter

With a diameter between 2.7 and 3.2 kilometers, is one of largest known

''(see PHA-list)''. Conversely, the ''Collaborative Asteroid Lightcurve Link'' assumes a standard albedo for stony asteroids of 0.20 and calculates a diameter of 1.08 kilometers based on 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 17.2.

Gallery

File:Asteroid 1998 QE2 May 31, 2013 orbit.jpg, Orbit of on 31 May 2013 File:Orbit-Asteroid-285263-1998QE2-20130602b.jpg, and 2 June 2013

Notes

References

External links

NASA Radar Reveals Asteroid Has Its Own Moon
at

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

Animation of binary asteroid 1998 QE2 derived from radar data

(15 June 2013)
Asteroid Lightcurve Database (LCDB)
query form

)

Robert Johnston, johnstonsarchive.net * * * {{DEFAULTSORT:1998 QE2 285263 285263 285263 285263 285263 20130531 19980819