is a bright sub-kilometer

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

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 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 which is large enough to cause significant regional damage in the event of impact. Th ...

of the

Apollo group Apollo Education Group, Inc. is an American corporation based in the South Phoenix area of Phoenix, Arizona, with an additional corporate office in Chicago, Illinois. It is privately-owned by a consortium of investors including The Vistria Grou ...

, approximately in diameter. It was discovered on 30 January 2004 by astronomers of the

Lincoln Near-Earth Asteroid Research The Lincoln Near-Earth Asteroid Research (LINEAR) project is a collaboration of the United States Air Force, NASA, and the Massachusetts Institute of Technology's Lincoln Laboratory for the systematic detection and tracking of near-Earth object ...

at Lincoln Laboratory's Experimental Test Site near Socorro, New Mexico. Its

moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

was discovered during the asteroid's close approach to the Earth in January 2015.

2015 Earth approach

On 26 January 2015 at 16:20

UTC Coordinated Universal Time (UTC) is the primary time standard globally used to regulate clocks and time. It establishes a reference for the current time, forming the basis for civil time and time zones. UTC facilitates international communica ...

, passed , or 3.1 lunar distances, from Earth. The asteroid briefly peaked around

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), ...

9 and was near the

celestial equator The celestial equator is the great circle of the imaginary celestial sphere on the same plane as the equator of Earth. By extension, it is also a plane of reference in the equatorial coordinate system. Due to Earth's axial tilt, the celestial ...

. The asteroid was visible in

telescope A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...

s with objectives of or larger; high-end

binoculars Binoculars or field glasses are two refracting telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes (binocular vision) when viewing distant objects. Most binoculars are sized to be held ...

under a dark sky may also have worked. Near closest approach the asteroid was moving about 2.5 degrees per hour (2.5

arcsecond A minute of arc, arcminute (abbreviated as arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of a degree. Since one degree is of a turn, or complete rotation, one arcminute is of a tu ...

s per second). The asteroid came to

opposition Opposition may refer to: Arts and media * ''Opposition'' (Altars EP), 2011 EP by Christian metalcore band Altars * The Opposition (band), a London post-punk band * ''The Opposition with Jordan Klepper'', a late-night television series on Comedy ...

(furthest elongation in the sky from the Sun) on 27 January 2015 at 04:37 UTC. Around 5:00 UTC, the asteroid was near M44 (the

Beehive Cluster The Beehive Cluster (also known as Praesepe (Latin for "manger", "cot" or "crib"), M44, NGC 2632, or Cr 189), is an open cluster in the constellation Cancer. One of the nearest open clusters to Earth, it contains a larger population of stars tha ...

). The 26 January 2015 approach of 3.1 lunar distances was the closest approach of for at least the next 200 years. For comparison, , about twice the size of , passed , or 1.3 lunar distances, from Earth on 31 October 2015.

Satellite

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 ...

orbiting was first detected by ground-based telescopes by Joe Pollock and

Petr Pravec Petr Pravec (born September 17, 1967) is a Czech astronomer and a discoverer of minor planets, born in Třinec, Czech Republic. Pravec is a prolific discoverer of binary asteroids, expert in photometric observations and rotational lightcurves ...

. Observations by the

Goldstone Deep Space Communications Complex The Goldstone Deep Space Communications Complex (GDSCC), commonly called the Goldstone Observatory, is a satellite ground station located in Fort Irwin in the U.S. state of California. Operated by NASA's Jet Propulsion Laboratory (JPL), its ...

and

Green Bank Telescope The Robert C. Byrd Green Bank Telescope (GBT) in Green Bank, West Virginia, US is the world's largest fully steerable radio telescope, surpassing the Effelsberg 100-m Radio Telescope in Germany. The Green Bank site was part of the National Rad ...

confirmed that it is a

binary asteroid A binary asteroid is a system of two asteroids orbiting their common barycenter. The binary nature of 243 Ida was discovered when the Galileo spacecraft flew by the asteroid in 1993. Since then numerous binary asteroids and several triple a ...

with a secondary roughly across. The secondary is estimated to orbit at least from the primary. About 16% of asteroids over in diameter are thought to be binaries.

Numbering and naming

This

minor planet According to the International Astronomical Union (IAU), a minor planet is an astronomical object in direct orbit around the Sun that is exclusively classified as neither a planet nor a comet. Before 2006, the IAU officially used the term ''minor ...

was numbered on 27 March 2013 (). As of 2020, it has not been named.

Gallery

File:Animation of 2004 BL86 orbit.gif, Animation of 2004 BL86's orbit
File:Asteroid2004BL86-20150119.png, safely passes Earth on 26 January 2015 File:Asteroid-2004BL86-EarthCloseApproach-20150126.png, Trajectory of during Earth close approach File:2004BL86XiPup2.jpg, (

star trail A star trail is a type of photograph that uses long exposure times to capture '' diurnal circles'', the apparent motion of stars in the night sky due to Earth's rotation. A star-trail photograph shows individual stars as streaks across the ...

on left) near Xi Puppis

Notes

References

External links

Asteroids with Satellites
Robert Johnston, johnstonsarchive.net
PSI Scientists Study Surface Composition of Asteroid 2004 BL86 During Close Flyby of Earth
''

Planetary Science Institute The Planetary Science Institute (PSI) is a 501(c)(3) non-profit research institute based in Tucson, Arizona, focusing on planetary science. , its director is Dr. Mark V. Sykes. PSI, along with Space Science Institute (SSI) Southwest Researc ...

'', 27 January 2015
Asteroid Lightcurve Database (LCDB)
query form

) * * * {{DEFAULTSORT:2004 BL86 357439 357439 357439 357439 357439 357439 20150126 20040130