View source for Astronomy:(514107) 2015 BZ509

{{DISPLAYTITLE:{{mp|(514107) 2015 BZ|509}}}}
{{Infobox planet
 | minorplanet     = yes
 | name            = {{mp|(514107) 2015 BZ|509}}
 | background      = #FFE0C2
 | image           = 2015 BZ509-orbit.png
 | image_size      = 280
 | caption         = Retrograde orbit with 100 day motion markers
 | discovery_ref   = &thinsp;<ref name="MPC-object" />
 | discovered      = 26 November 2014
 | discoverer      = [[Astronomy:Pan-STARRS|Pan-STARRS]] 1
 | discovery_site  = [[Astronomy:Haleakala Observatory|Haleakala Obs.]]
 | mpc_name        = (514107) {{mp|2015 BZ|509}}
 | alt_names       = {{mp|2015 BZ|509}}
 | pronounced      =
 | named_after     =
 | mp_category     = {{nowrap|[[Astronomy:Retrograde and prograde motion|retrograde]] Jupiter co-orbital&thinsp;<ref name="Wiegert-2017" /><ref name="BadAstronomy" /><ref name="Wiegert-WesternUniversity" />}}<br />[[Astronomy:Asteroid|asteroid]]&thinsp;<ref name="jpldata" />{{·}}main-belt&thinsp;<ref name="MPC-object" />
 | orbit_ref       = &thinsp;<ref name="jpldata" />
 | epoch           = 23 March 2018 ([[Astronomy:Julian day|JD]] 2458200.5)
 | uncertainty     = 2
 | observation_arc = 2.81 [[Astronomy:Julian year|yr]] (1,026 d)
 | aphelion        = 7.0925 [[Astronomy:Astronomical unit|AU]]
 | perihelion      = 3.1824 AU
 | semimajor       = 5.1375 AU
 | eccentricity    = 0.3805
 | period          = 11.64 yr (4,253 d)
 | mean_anomaly    = 66.375[[Degree (angle)|°]]
 | mean_motion     = {{Deg2DMS|0.0846|sup=ms}} / day
 | inclination     = 163.00°
 | asc_node        = 307.38°
 | arg_peri        = 257.38°
 | jupiter_moid    = 0.2272 AU
 | tisserand       = −0.7450
 | mean_diameter   = {{val|3|ul=km}} {{small|(approx.)}}<ref name="CNRS" />
 | rotation        =
 | albedo          =
 | spectral_type   =
 | abs_magnitude   = 16.0<ref name="jpldata" />
}}

'''{{mp|(514107) 2015 BZ|509}}''', provisional designation {{mp|2015 BZ|509}}, also called '''Bee-Zed''',<ref name=Phys.org/> is a small [[Astronomy:Asteroid|asteroid]], approximately 3km in diameter,<ref name="CNRS" /> in a resonant, co-orbital motion with [[Astronomy:Jupiter|Jupiter]].<ref name="Wiegert-2017" /> Its orbit is [[Astronomy:Retrograde and prograde motion|retrograde]], which is opposite to the direction of most other bodies in the [[Astronomy:Solar System|Solar System]].<ref name="BadAstronomy" /> It was discovered on 26 November 2014, by astronomers of the [[Astronomy:Pan-STARRS|Pan-STARRS]] survey at [[Astronomy:Haleakala Observatory|Haleakala Observatory]] on the island of Maui, United States.<ref name="MPC-object" /> It is the first example of an asteroid in a 1:−1 resonance with any of the planets.<ref name="Wiegert-WesternUniversity" /> A study has suggested it may be an interstellar asteroid captured 4.5 billion years ago into an orbit around the Sun.

== Orbit ==
[[File:JupiterRetroAstroLookingDow.jpg|thumb|left|200px|Orbital diagram]]
[[File:JupiterRetroAsterSideView.jpg|thumb|left|200px|Orbit (side-view) compared to Jupiter]]

As of February 2017 the asteroid's orbital period was 11.65 years, and its orbit had an eccentricity of 0.38 and an inclination of 163[[Degree (angle)|°]].<ref name="jpldata" /> Its period is close to the 11.86-year period of Jupiter. During one Jovian year, Jupiter moves 360° around the sun whereas {{mp|2015 BZ|509}} moves 366.3° in the opposite direction. The eccentricity of its orbit allows it to alternately pass inside and outside of Jupiter's orbit at its closest approaches of 176 million kilometers. Each time it passes near Jupiter its orbital elements, including its period, are slightly altered. Over thousands of years the angle between the position of the asteroid and its perihelion minus the angle between Jupiter and the asteroid's perihelion tends to oscillate around zero with a period of about 660 years and an amplitude of about 125°, although sometimes this difference slips by a whole 360°.{{NoteTag|See Figure 2 of {{harvnb|Wiegert|Connors|Veillet|2017}}.}}

The adjunct diagram shows one complete orbit of asteroid {{mp|2015 BZ|509}} in a frame of reference rotating with Jupiter. The view is from the north looking south onto the Solar System. The dot in the middle is the Sun and the green circle is the orbit of Earth. The black circle shows the size of the orbit of Jupiter but in this frame of reference Jupiter (the red dot) stays almost stationary at the point on the circle directly to the right of the sun. The orbit of this asteroid is shown in blue when it is above the plane of the orbit of Jupiter, and in magenta when it is below the plane of the orbit of Jupiter.<ref name="Wiegert-2017" />

The second diagram shows one complete orbit of asteroid {{mp|2015 BZ|509}} in a frame of reference rotating with Jupiter. The view is from the side looking into the Solar System. The Sun is the yellow disk in the middle. The plane of the orbit of Jupiter is shown in black, but in this frame of reference Jupiter (the red dot) stays at the right end of the black line. The orbit of this asteroid is shown in blue when it is above (north of) the plane of the orbit of Jupiter, and it is shown in magenta when it is below (south of) the plane of the orbit of Jupiter.<ref name="Wiegert-2017" />

Perturbations from Jupiter maintain the stability of this orbit over millions of years. Simulations show that it has been in its co-orbital relation with Jupiter for at least a million years and will continue for at least another million years. It is somewhat of a mystery how this asteroid (or comet) got into this orbit, but it is thought that at some time in the distant past it was put into an orbit resembling its present orbit by an interaction with Saturn, and then its orbit was perturbed into the state it is in today.<ref name="Wiegert-2017" /> Likewise, in the far future it may eventually get close enough to Saturn to be expelled from its present co-orbital relation with Jupiter.
[[File:2015 BZ509-retrograde-near-sun.png|320px|thumb|''2015 BZ509'' shows [[Astronomy:Apparent retrograde motion|apparent retrograde motion]] in the sky while it is on the far side of the sun, rather than at opposition with the sun.]]

== Naming ==
This [[Astronomy:Minor planet|minor planet]] was numbered by the [[Organization:Minor Planet Center|Minor Planet Center]] on 2 March 2018 ({{small|M.P.C. 109159}}).<ref name="MPC-Circulars-Archive" /> As of 2018, it has not been formally [[Astronomy:List of named minor planets (alphabetical)|named]].<ref name="MPC-object" />

== Possible interstellar origin ==
A statistical search for stable orbits by Fathi Namouni and Helena Morais using one million objects with similar orbits to that of {{mp|2015 BZ|509}} identified 27 that were stable for 4.5 billion years, the lifetime of the Solar System. Using this result they concluded that {{mp|2015 BZ|509}} has been in its retrograde resonance with Jupiter since the origin of the Solar System instead of it being an object that is only briefly in this orbit that was observed by chance using the [[Astronomy:Copernican principle|Copernican principle]].<ref name="Scientific-American" /><ref name="Namouni-2018" /> Since its retrograde orbit is in the opposite direction as objects that formed in the early Solar System they posit that {{mp|2015 BZ|509}} has an interstellar origin.<ref name="BBC" /> If confirmed, this origin would have implications on current theories such as the detailed timing and mechanics of [[Astronomy:Nebular hypothesis|planet formation]], and the delivery of water and [[Chemistry:Organic compound|organic molecules]] to Earth.<ref name="Scientific-American" /> Others suggest that {{mp|2015 BZ|509}} originated in the [[Astronomy:Oort cloud|Oort cloud]] or that it acquired a retrograde orbit due to interactions with [[Astronomy:Planet Nine|Planet Nine]], and that it is a short term resident of its current resonance.<ref name="Scientific-American" />

== See also ==
* {{Section link|List of exceptional asteroids|Retrograde}}
* 'Oumuamua, an interstellar object

== Notes ==
{{NoteFoot}}

== References ==
{{reflist|refs=

<ref name="jpldata">{{cite web
  |type       = 2017-09-17 last obs.
  |title      = JPL Small-Body Database Browser: 514107 (2015 BZ509)
  |url        = https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2514107
  |publisher  = [[Organization:Jet Propulsion Laboratory|Jet Propulsion Laboratory]]
  |accessdate = 7 March 2018}}</ref>

<ref name="MPC-object">{{cite web
  |title      = 514107 (2015 BZ509)
  |work       = Minor Planet Center
  |url        = https://www.minorplanetcenter.net/db_search/show_object?object_id=514107
  |accessdate = 7 March 2018}}</ref>

<ref name="MPC-Circulars-Archive">{{cite web
  |title      = MPC/MPO/MPS Archive
  |work       = Minor Planet Center
  |url        = https://www.minorplanetcenter.net/iau/ECS/MPCArchive/MPCArchive_TBL.html
  |accessdate = 7 March 2018}}</ref>

<ref name="Wiegert-2017">{{Cite journal
  |first1     = Paul |last1 = Wiegert
  |first2     = Martin |last2 = Connors
  |first3     = Christian |last3 = Veillet
  |date       = March 2017
  |title      = A retrograde co-orbital asteroid of Jupiter
  |url        = http://www.nature.com/nature/journal/v543/n7647/full/nature22029.html#videos
  |journal    = Nature
  |volume     = 543
  |issue      = 7647
  |pages      = 687–689
  |bibcode    = 2017Natur.543..687W
  |doi        = 10.1038/nature22029
  |pmid = 28358083
  |ref        = harv
  |access-date= 7 March 2018}}</ref>

<ref name="Wiegert-WesternUniversity">{{cite web
  |last       = Wiegert | first = Paul
  |title      = The first retrograde co-orbital asteroid: 2015 BZ509 – a Trojan in retreat
  |date       = 30 March 2017
  |publisher  = University of Western Ontario
  |url        = http://www.astro.uwo.ca/~wiegert/2015BZ509/
  |accessdate = 7 March 2018}}</ref>

<ref name="BadAstronomy">{{cite web
  |last1      = Plait |first1 = Phil
  |title      = Meet Jupiter's backwards little friend: Asteroid 2015 BZ509
  |publisher  = SyFy Wire
  |date       = Mar 30, 2017
  |url        = http://www.syfy.com/syfywire/meet-jupiters-backwards-little-friend-asteroid-2015-bz509
  |accessdate = 30 March 2017}}</ref>

<ref name="CNRS">{{Cite press release
  |title      = Discovery of the first body in the Solar System with an extrasolar origin
  |date       = 22 May 2018
  |publisher  = CNRS
  |website    = www2.cnrs.fr
  |url        = http://www2.cnrs.fr/en/3117.htm
  |access-date= 31 May 2018}}</ref>

<ref name="Namouni-2018">{{Cite journal
  |first1     = Fathi |last1 = Namouni
  |first2     = Maria Helena Moreira |last2 = Morais
  |date       = 21 May 2018
  |title      = An interstellar origin for Jupiter's retrograde co-orbital asteroid
  |journal    = Monthly Notices of the Royal Astronomical Society: Letters
  |volume     = 477
  |issue      = 1
  |pages      = L117–L121
  |bibcode    = 2018MNRAS.477L.117N 
  |doi        = 10.1093/mnrasl/sly057
  |arxiv      = 1805.09013
  |issn       = 1745-3925
  }}</ref>

<ref name="BBC">{{Cite news
  |last       = Halton
  |first      = Mary
  |date       = 21 May 2018
  |title      = 'Permanent' interstellar visitor found
  |work       = BBC News
  |url        = https://www.bbc.com/news/science-environment-44173403
  |access-date= 1 June 2018}}</ref>

<ref name="Scientific-American">{{Cite web
  |last       = Billings
  |first      = Lee
  |date       = 21 May 2018
  |title      = Astronomers Spot Potential "Interstellar" Asteroid Orbiting Backward around the Sun
  |publisher  = Scientific American
  |url        = https://www.scientificamerican.com/article/astronomers-spot-potential-interstellar-asteroid-orbiting-backward-around-the-sun/
  |accessdate = 1 June 2018}}</ref>
  
<ref name=Phys.org>{{cite news
| author       =<!--Staff writer(s); no by-line.-->
| title        = The stable retrograde orbit of the Bee-Zed asteroid explained
| url          = https://phys.org/news/2017-06-stable-retrograde-orbit-bee-zed-asteroid.html 
| work         = Phys.org
| date         = June 28, 2017
}}</ref>
}}
== External links ==
* {{Youtube|id=7_QbYX4jTrI|title=The first retrograde co-orbital asteroid: 2015 BZ509}}, Scientias.nl (0:52 min)
* [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/NumberedMPs510001.html Discovery Circumstances: Numbered Minor Planets (510001)-(515000)] – Minor Planet Center
* {{JPL small body|id=3708942}}
* [https://www.newscientist.com/article/2126301-backwards-asteroid-shares-an-orbit-with-jupiter-without-crashing Backwards asteroid shares an orbit with Jupiter without crashing] 29 March 2017
* [http://astrobob.areavoices.com/2018/05/23/is-there-an-alien-asteroid-among-us/ Is There An Alien Asteroid Among Us?] Bob King, 23 May 2018
* [https://apod.nasa.gov/apod/ap180530.html Animation of orbital motion] at APOD (30 May 2018)

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