View source for Astronomy:(469219) 2016 HO3

{{DISPLAYTITLE:{{mp|(469219) 2016 HO|3}}}}
{{Infobox planet
 | minorplanet     = yes
 | name            = {{mp|(469219) 2016 HO|3}}
 | background      = #FFC2E0
 | image           = 2016 HO3 orbit_Jan2018.png
 | image_size      = 255
 | caption         = Orbit of {{mp|2016 HO|3}} in the inner Solar System
 | discovery_ref   = &thinsp;<ref name="jpldata" /><ref name="MPC-object" />
 | discoverer      = [[Astronomy:Pan-STARRS|Pan-STARRS]]
 | discovery_site  = [[Astronomy:Haleakala Observatory|Haleakala Obs.]]
 | discovered      = 27 April 2016
 | mpc_name        = (469219) {{mp|2016 HO|3}}
 | alt_names       = {{mp|2016 HO|3}}
 | pronounced      = 
 | named_after     = <!-- xafter<br />{{small|(desciption)}}-->
 | mp_category     = [[Astronomy:Near-Earth object|NEO]]{{·}}[[Astronomy:Apollo asteroid|Apollo]]&thinsp;<ref name="jpldata" /><ref name="MPC-object" /><br />{{nowrap|Earth [[Astronomy:Quasi-satellite|quasi-satellite]]&thinsp;<ref name="de-la-Fuente-Marcos-2016" /><ref name="NASA-news" />}}
 | orbit_ref       = &thinsp;<ref name="jpldata" />
 | epoch           = 4 September 2017 ([[Astronomy:Julian day|JD]] 2458000.5)
 | uncertainty     = 0
 | observation_arc = 13.20 yr (4,820 days)
 | aphelion        = 1.1055 [[Astronomy:Astronomical unit|AU]]
 | perihelion      = 0.8973 AU
 | semimajor       = 1.0014 AU
 | eccentricity    = 0.1040<br>(~530 wrt Earth){{efn|name=geocentric}}
 | period          = 1.00 [[Astronomy:Julian year|yr]] (366 days)
 | mean_anomaly    = 331.49[[Degree (angle)|°]]
 | mean_motion     = {{Deg2DMS|0.9836|sup=ms}} / day
 | inclination     = 7.7741°
 | asc_node        = 66.407°
 | arg_peri        = 306.93°
 | moid            = 0.0348 AU{{·}}13.6 [[Astronomy:Lunar distance|LD]]
 | dimensions      = 0.041 km {{small|(calculated)}}<ref name="lcdb" /><br />0.04–0.10 km<ref name="NASA-news" />
 | rotation        = {{val|0.467|0.008}} [[Hour|h]]{{refn|group=lower-alpha|name=lcdb-Reddy-2018}}
 | albedo          = 0.20 {{small|(assumed)}}<ref name="lcdb" />
 | spectral_type   = [[Astronomy:S-type asteroid|S]] {{small|(assumed)}}<ref name="lcdb" />
 | abs_magnitude   = 24.2<ref name="jpldata" />{{·}}24.3<ref name="lcdb" />
}}

'''{{mp|(469219) 2016 HO|3}}''' is a micro-[[Astronomy:Asteroid|asteroid]], [[Astronomy:List of fast rotators (minor planets)|fast rotator]] and [[Astronomy:Near-Earth object|near-Earth object]] of the [[Astronomy:Apollo asteroid|Apollo group]], approximately 41 meters in diameter. It is currently the smallest, closest, and most stable (known) [[Astronomy:Quasi-satellite|quasi-satellite]] of Earth. The asteroid was discovered by [[Astronomy:Pan-STARRS|Pan-STARRS]] at [[Astronomy:Haleakala Observatory|Haleakala Observatory]] on 27 April 2016.<ref name="MPC-object" />

== Orbit and classification ==

{{mp|2016 HO|3}} orbits the Sun at a distance of 0.9–1.1&nbsp;[[Astronomy:Astronomical unit|AU]] once every 366 days. Its orbit has an [[Astronomy:Orbital eccentricity|eccentricity]] of 0.10 and an [[Astronomy:Orbital inclination|inclination]] of 8[[Degree (angle)|°]] with respect to the [[Astronomy:Ecliptic|ecliptic]].<ref name="jpldata" /> It has an Earth minimum orbital intersection distance of {{convert |0.0348 |AU |km |abbr=on |lk=on |sigfig=3}} which translates into 13.6 [[Astronomy:Lunar distance|lunar distances]].<ref name="jpldata" />

=== Quasi-satellite of Earth ===

As it orbits the Sun, {{mp|2016 HO|3}} appears to circle around Earth as well. The object is beyond the [[Astronomy:Hill sphere|Hill sphere]] of Earth and the Sun exerts a much stronger pull on it than Earth does. Although it is too distant to be considered a true [[Astronomy:Natural satellite|natural satellite]] of Earth, it is the best and most stable example to date of a [[Astronomy:Near-Earth object|near-Earth companion]], or [[Astronomy:Quasi-satellite|quasi-satellite]].<ref name="de-la-Fuente-Marcos-2016" />

"Since {{mp|2016 HO|3}} loops around our planet, but never ventures very far away as we both go around the Sun, we refer to it as a quasi-satellite of Earth", said Paul Chodas, manager of [[Organization:NASA|NASA]]'s Center for Near-Earth Object (NEO) Studies at the [[Organization:Jet Propulsion Laboratory|Jet Propulsion Laboratory]] in Pasadena, California.<ref name="NASA-news" />

{{quote|"One other asteroid – {{mpl|2003 YN|107}} – followed a similar orbital pattern for a while over 10 years ago, but it has since departed our vicinity. This new asteroid is much more locked onto us. Our calculations indicate {{mp|2016 HO|3}} has been a stable quasi-satellite of Earth for almost a century, and it will continue to follow this pattern as Earth's companion for centuries to come." — <ref name="NASA-news" />}}

In its yearly trek around the Sun, asteroid {{mp|2016 HO|3}} spends about half of the time closer to the Sun than Earth is (that is, the asteroid is inside the [[Astronomy:Earth's orbit|Earth's orbit]]) and passes ahead of our planet, and about half of the time farther away (crosses outside Earth's orbit), causing it to fall behind. Its orbit is also tilted a little, causing it to bob up and then down once each year through Earth's orbital plane. In effect, this small asteroid is caught in a game of leap frog with Earth that will last for hundreds of years.<ref name="NASA-news" />

The asteroid's orbit also undergoes a slow, back-and-forth twist over multiple decades. "The asteroid's loops around Earth drift a little ahead or behind from year to year, but when they drift too far forward or backward, Earth's [[Physics:Gravity|gravity]] is just strong enough to reverse the drift and hold onto the asteroid so that it never wanders farther away than about 100 times the distance of the moon", said Chodas. "The same effect also prevents the asteroid from approaching much closer than about 38 times [[Astronomy:Lunar distance|the distance of the moon]]. In effect, this small asteroid is caught in a little dance with Earth."<ref name="NASA-news" />As of now, it has by far the most stable quasi-satellite of Earth discovered, in terms of orbit.

== Physical characteristics ==

The size of {{mp|2016 HO|3}} has not yet been firmly established, but it is likely about {{convert |40|–|100|m|ft|abbr=on}}.<ref name="NASA-news" /> Based on an assumed standard [[Astronomy:Astronomical albedo|albedo]] for stony [[Astronomy:S-type asteroid|S-type asteroid]]s of 0.20 and an [[Astronomy:Absolute magnitude|absolute magnitude]] of 24.3, it measures {{convert|41|m|ft|sp=us}} in diameter.<ref name="lcdb" />

Photometric observations in April 2017 revealed that {{mp|2016 HO|3}} is a [[Astronomy:List of fast rotators (minor planets)|fast rotator]]. [[Astronomy:Lightcurve|Lightcurve]] analysis gave a [[Rotation period|rotation period]] of {{convert |0.467|±|0.008 |hour|minute|abbr=off}} and a brightness variation of {{val|0.80|0.05}}  [[Astronomy:Magnitude|magnitude]] ({{small|U=2}}).<ref name="lcdb" />{{refn|group=lower-alpha|name=lcdb-Reddy-2018}}

== Discovery and naming ==

Asteroid {{mp|2016 HO|3}} was first spotted on 27 April 2016, by the [[Astronomy:Pan-STARRS|Pan-STARRS]]&nbsp;1 asteroid survey telescope on [[Earth:Haleakalā|Haleakalā]], Hawaii, operated by the [[Organization:University of Hawaii|University of Hawaii]]'s Institute for Astronomy and funded by NASA's [[Astronomy:Planetary Defense Coordination Office|Planetary Defense Coordination Office]].<ref name="NASA-news" /> As of 2018, the object has not been named.<ref name="MPC-object" />

== Gallery ==
<gallery mode="packed">
Asteroid-2016HO3-20160427.jpg|Asteroid {{mp|2016 HO|3}} is a constant companion of the Earth.
Asteroid2016HO3-SunEarthOrbit.webm|Asteroid {{mp|2016 HO|3}} orbiting the Sun and Earth (animation; [[:File:Asteroid2016HO3-SunEarthOrbit.webm|file]]).
</gallery>

== See also ==
{{Div col|colwidth=10em}}
* [[Astronomy:Arjuna asteroid|Arjuna asteroid]]
* [[Astronomy:Natural satellite|Natural satellite]]
* [[Astronomy:Quasi-satellite|Quasi-satellite]]
* [[Astronomy:3753 Cruithne|3753 Cruithne]]
* [[Astronomy:6Q0B44E|6Q0B44E]]
* {{mpl|2001 GO|2}}
* {{mpl|2002 AA|29}}
* {{mpl|2003 YN|107}}
* {{mpl|2006 JY|26}}
* {{mpl|2006 RH|120}}
* {{mpl|2012 FC|71}}
* {{mpl|2013 BS|45}}
* {{mpl|(419624) 2010 SO|16}}
* {{mpl|(436724) 2011 UW|158}}
{{Div col end}}

== Notes ==
{{notelist|refs=

{{refn|group=lower-alpha|name=lcdb-Reddy-2018|1=Exceptional rotation period of {{convert|0.467|±|0.008|hour|minute|abbr=off}} with a brightness amplitude of {{val|0.80|0.05}} mag, quality code = 2, (Reddy 2018).<ref name="lcdb" />  Not yet listed on ADS (Nov 2017). Summary figures at the [[Astronomy:Light curve#Asteroid lightcurve database|LCDB]].<ref name="lcdb" />}}

{{efn|name=geocentric|1=Computed with [https://ssd.jpl.nasa.gov/horizons.cgi?find_body=1&body_group=sb&sstr=2016HO3 JPL Horizons] using a geocentric solution. Ephemeris Type: Orbital Elements / Center: 500 / Time Span: 2017-Sep-04 (to match infobox epoch)}}

}} <!-- end of notelist -->

== References ==
{{NASA}}
{{reflist|refs=

<ref name="jpldata">{{cite web
  |type       = 2017-05-28 last obs.
  |title      = JPL Small-Body Database Browser: 469219 (2016 HO3)
  |url        = http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2469219
  |publisher  = [[Organization:Jet Propulsion Laboratory|Jet Propulsion Laboratory]]
  |accessdate = 19 November 2017}}</ref>

<ref name="MPC-object">{{cite web
  |title      = (469219) = 2016 HO3
  |website    = [[Organization:Minor Planet Center|Minor Planet Center]]
  |publisher  = IAU
  |url        = http://www.minorplanetcenter.net/db_search/show_object?object_id=469219
  |accessdate = 19 November 2017}}</ref>

<ref name="lcdb">{{cite web
  |title      = LCDB Data for (469219)
  |publisher  = Asteroid Lightcurve Database (LCDB)
  |url        = http://www.minorplanet.info/PHP/GenerateALCDEFPage_Local.php?AstInfo=469219%7C
  |website    = MinorPlanet.Info — ALCDEF Query
  |accessdate = 19 November 2017}}</ref>

<ref name="NASA-news">{{cite web
  |last1      = Agle  |first1=DC
  |last2      = Brown |first2=Dwayne
  |last3      = Cantillo |first3=Laurie
  |title      = Small Asteroid Is Earth's Constant Companion
  |date       = 15 June 2016
  |publisher  = Jet Propulsion Laboratory
  |url        = https://www.jpl.nasa.gov/news/news.php?feature=6537
  |accessdate = 19 November 2017}}</ref>

<ref name="de-la-Fuente-Marcos-2016">{{Cite journal
  |first1     = C. |last1 = de la Fuente Marcos
  |first2     = R. |last2 = de la Fuente Marcos
  |date       = November 2016
  |title      = Asteroid (469219) 2016 HO3, the smallest and closest Earth quasi-satellite
  |url        = https://arxiv.org/pdf/1608.01518.pdf
  |journal    = Monthly Notices of the Royal Astronomical Society
  |volume     = 462
  |issue      = 4
  |pages      = 3441–3456
  |bibcode    = 2016MNRAS.462.3441D
  |doi        = 10.1093/mnras/stw1972
  |arxiv      = 1608.01518
  |access-date= 19 November 2017}}</ref>

}} <!-- end of reflist -->

==External links==
* [http://newton.dm.unipi.it/neodys2/index.php?pc=1.1.0&n=2016+HO3 {{mp|2016 HO|3}}] at NeoDyS-2
* [https://www.youtube.com/watch?v=zMJc7gmychk Asteroid 2016 HO3 - Earth's Constant Companion] NASA Jet Propulsion Laboratory, Jun 23, 2016
* [http://www.minorplanet.info/PHP/lcdbsummaryquery.php Asteroid Lightcurve Database (LCDB)], query form ([http://www.minorplanet.info/lightcurvedatabase.html info])
* [http://www.minorplanetcenter.net/iau/lists/NumberedMPs465001.html Discovery Circumstances: Numbered Minor Planets (465001)-(470000)] – Minor Planet Center
* {{JPL small body}}

{{2016 in space}}
{{Small Solar System bodies}}

{{DEFAULTSORT:469219}}
[[Category:Apollo asteroids]]
[[Category:Earth co-orbital asteroids]]
[[Category:Earth-crosser asteroids]]

{{Sourceattribution|(469219) 2016 HO3|1}}