3122 Florence is a stony trinary

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. ...

of the Amor group. It is classified as 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

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 ...

. It measures approximately 5 kilometers in

diameter In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid for ...

. It orbits the Sun at a distance of 1.0–2.5 AU once every 2 years and 4 months (859 days); the 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-center, in geometry * Eccentricity (graph theory) of a v ...

of 0.42 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 22 ° with respect to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic again ...

. Florence has

two moons Two Moons (1847–1917), or ''Ishaynishus'' (Cheyenne language, Cheyenne: ''Éše'he Ôhnéšesêstse''), was one of the Cheyenne chiefs who took part in the Battle of the Little Bighorn and other battles against the United States Army. Life Two ...

. Florence was discovered on 2 March 1981 by American astronomer Schelte J. "Bobby" Bus at

Siding Spring Observatory Siding Spring Observatory near Coonabarabran, New South Wales, Australia, part of the Research School of Astronomy & Astrophysics (RSAA) at the Australian National University (ANU), incorporates the Anglo-Australian Telescope along with a coll ...

. Its provisional designation was . It was named in honor of

Florence Nightingale Florence Nightingale (; 12 May 1820 – 13 August 1910) was an English Reform movement, social reformer, statistician and the founder of modern nursing. Nightingale came to prominence while serving as a manager and trainer of nurses during t ...

, the founder of modern nursing; the naming citation was published on 6 April 1993 (). Florence is classified as a

potentially hazardous object 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 ar ...

because its

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 of ...

indicates that it has the potential to make close approaches to the Earth, and because measurements of its

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 ...

suggest that it is large enough to create serious damage were it to impact.

Moons

Radar observations during the 2017 flyby have shown that Florence has two moons. The inner of the two moons is estimated to have a diameter of 180 to 240 meters, the outer moon is between 300 and 360 meters across. Each moon is somewhat elongated, and both are

tidally locked Tidal locking between a pair of co-orbiting astronomical body, astronomical bodies occurs when one of the objects reaches a state where there is no longer any net change in its rotation rate over the course of a complete orbit. In the case where ...

to the main body. They probably formed as loose material spun away from the main body as its rotation accelerated due to the

YORP effect Yorp or YORP may refer to one of the following: * 54509 YORP, an Earth co-orbital asteroid *Yarkovsky–O'Keefe–Radzievskii–Paddack effect, a second-order variation on the Yarkovsky effect *Yorps, friendly one-eyed Martians from the Commander Ke ...

. The inner moon's period orbiting Florence appears to be approximately 7 hours, while the outer moon completes a revolution in about 21 to 23 hours. The inner moon of Florence has the shortest orbital period of any of the moons of the 60 near-Earth asteroids known to have moons. Florence is only the third known trinary asteroid in the near-Earth asteroid population, after and .

2017 close approach

from Earth, approximately eighteen times the average distance of the Moon. As seen from Earth, it brightened to

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 ...

8.5, and was visible in small telescopes for several nights as it moved south to north through the constellations

Piscis Austrinus Piscis Austrinus is a constellation in the southern celestial hemisphere. The name is Latin for "the southern fish", in contrast with the larger constellation Pisces, which represents a pair of fish. Before the 20th century, it was also known as ...

Capricornus Capricornus is one of the constellations of the zodiac. Its name is Latin for "horned goat" or "goat horn" or "having horns like a goat's", and it is commonly represented in the form of a sea goat: a mythical creature that is half goat, half fi ...

Aquarius Aquarius may refer to: Astrology * Aquarius (astrology), an astrological sign * Age of Aquarius, a time period in the cycle of astrological ages Astronomy * Aquarius (constellation) * Aquarius in Chinese astronomy Arts and entertainme ...

, and

Delphinus Delphinus (Pronounced or ) is a small constellation in the Northern Celestial Hemisphere, close to the celestial equator. Its name is the Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-Europea ...

. This was the asteroid's closest approach since 1890 and the closest until after 2500. Its previous flyby was on 29 August 1930, at a distance of 0.05239 AU and the next one will be on 2 September 2057, at 0.049952 AU. File:3122Florence (1981 ET3).gif, Animation: 2017-08-30 21:48:46 to 22:53:00 UTC File:Florence3122spon.jpg, 3122 Florence passing the Earth in 2017 File:3122 Florence 2017 flyby3.png, Orbit of Florence File:3122 Florence 2017 flyby.png, Daily motion of 3122 Florence as seen from earth near 1 September 2017 flyby.

Radar imagery

During the flyby, scientists studied Florence using the

Arecibo Observatory The Arecibo Observatory, also known as the National Astronomy and Ionosphere Center (NAIC) and formerly known as the Arecibo Ionosphere Observatory, is an observatory in Barrio Esperanza, Arecibo, Puerto Rico owned by the US National Science F ...

and 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 main ...

, and discovered that it has two moons. ; Goldstone Radar Florence.aug29.collage.5runs.p5usec.7.7Hz.jpg, Aug 29 Florence Goldstone September 1.gif, Sep 1 ; Arecibo Radar Florence Arecibo September 2.gif, Sep 2 Florence Arecibo September 2 (high-res).gif, Sep 2 Florence Arecibo September 3.gif, Sep 3 Florence Arecibo September 4.gif, Sep 4 Florence Arecibo September 5.gif, Sep 5

Notes

References

External links

*
(3122) Florence
Asteroids with Satellites Database—Johnston's Archive
Asteroid Florence found to have 2 moons
Eddie Irizarry, 2 September 2017
Lightcurve plot
Brian D. Warner, Center for Solar System Studies, Spring 2016
Asteroid Lightcurve Database (LCDB)
query form

)
Dictionary of Minor Planet Names
Google books

– Observatoire de Genève, Raoul Behrend * * * {{DEFAULTSORT:Florence 003122 Discoveries by Schelte J. Bus Named minor planets 003122 3122 Florence 003122 003122 Near-Earth objects in 2017 19810302