, provisional designation , is a dark

asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...

and synchronous

binary system A binary system is a system of two astronomical bodies of the same kind that are comparable in size. Definitions vary, but typically require the center of mass to be located outside of either object. (See animated examples.) The most common ki ...

, classified as

near-Earth object A near-Earth object (NEO) is any small Solar System body orbiting the Sun whose closest approach to the Sun ( perihelion) is less than 1.3 times the Earth–Sun distance (astronomical unit, AU). This definition applies to the object's orbit a ...

and potentially hazardous asteroid of the Amor group, approximately 3 kilometers in diameter. It was discovered on 19 August 1998, by astronomers of the

LINEAR In mathematics, the term ''linear'' is used in two distinct senses for two different properties: * linearity of a '' function'' (or '' mapping''); * linearity of a '' polynomial''. An example of a linear function is the function defined by f(x) ...

program at Lincoln Laboratory's Experimental Test Site near Socorro, New Mexico, in the United States. Its sub-kilometer

minor-planet moon A minor-planet moon is an astronomical object that orbits a minor planet as its natural satellite. , there are 457 minor planets known or suspected to have moons. Discoveries of minor-planet moons (and binary objects, in general) are important ...

was discovered by radar on 30 May 2013.

Classification and orbital characteristics

As an

Amor asteroid The Amor asteroids are a group of near-Earth asteroids named after the archetype object 1221 Amor . The orbital perihelion of these objects is close to, but greater than, the orbital aphelion of Earth (i.e., the objects do not cross Earth's orbit ...

, 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 longe ...

of 2.42 AU). Its orbit has an

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...

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 reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

of 13 ° with respect to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. Fr ...

. The ''Earth

minimum orbit intersection distance Minimum orbit intersection distance (MOID) is a measure used in astronomy to assess potential close approaches and collision risks between astronomical objects. It is defined as the distance between the closest points of the osculating orbits o ...

'' 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 An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

beyond the orbit of

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

(at 1.66 AU) which also makes it a

Mars-crosser A Mars-crossing asteroid (MCA, also Mars-crosser, MC) is an asteroid whose orbit crosses that of Mars. Some Mars-crossers numbered below 100000 are listed here. They include the two numbered Mars trojans 5261 Eureka and . Many databases, for i ...

. The

soot Soot ( ) is a mass of impure carbon particles resulting from the incomplete combustion of hydrocarbons. Soot is considered a hazardous substance with carcinogenic properties. Most broadly, the term includes all the particulate matter produced b ...

y surface of suggested that it might have previously been a

comet A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...

that experienced a close encounter with the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

. However, the Tisserand parameter 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 Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...

(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 Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

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 Arecibo (; ) is a Arecibo barrio-pueblo, city and Municipalities of Puerto Rico, municipality on the northern coast of Puerto Rico, on the shores of the Atlantic Ocean, located north of Utuado, Puerto Rico, Utuado and Ciales, Puerto Rico, Ciale ...

from June 6 to June 12. At its closest approach the asteroid had an

apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

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 system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...

observations on 29 May 2013 discovered that is orbited by a

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 on a specific question or field outside the scope of Earth. Astronomers observe astronomical objects, such as stars, planets, natural satellite, moons, comets and galaxy, galax ...

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

y substance, making it optically dark with a geometric

albedo Albedo ( ; ) is the fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...

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 C-type (carbonaceous ) asteroids are the most common variety, forming around 75% of known asteroids. They are volatile-rich and distinguished by a very low albedo because their composition includes a large amount of carbon, in addition to rocks ...

. 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 potentially hazardous asteroid ''(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 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 agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

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