View source for S/2015 (136472) 1

{{Short description|Moon of Makemake}}
{{Use dmy dates|date=July 2024}}
{{Infobox planet
| name                   = S/2015 (136472) 1
| image                  = File:Makemake moon Hubble image with legend (cropped).jpg
| caption                = [[Makemake]] and its moon S/2015 (136472) 1 (arrow)
| background             = <!-- #FFFFC0 -->
| discovery_ref          = <ref name="Parker2016"/>
| discoverer             = 
 {{plainlist |
* [[Hubble Space Telescope|HST]]/[[Wide Field Camera 3]]
* Alex H. Parker
* [[Marc William Buie|Marc W. Buie]]
* William M. Grundy
* Keith S. Noll
 }}
| discovered             = 27 April 2015
| mpc_name               =
| pronounced             = <!--{{IPAc-en||}}-->
| named_after            = 
| alt_names              = MK2 (unofficial)<ref name="hubblesite"/>
| adjectives             = 
| orbit_ref              = <ref name="Parker2016"/>{{rp|page=3}}
| epoch                  = 
| semimajor              = {{val|21000|u=km|p=>}}
| eccentricity           = ''unknown''
| period                 = {{val|12.4|p=>}} days
| mean_anomaly           = 
| inclination            = {{val|63|-|87|u=°}} wrt [[ecliptic]] ([[retrograde and prograde motion|prograde]])<ref name="Parker2016"/>{{rp|page=3}}
| asc_node               = 
| arg_peri               = 
| satellite_of           = [[Makemake]]
| mean_diameter          = ~175 km (4% albedo; best fit)<ref name="Parker2016"/>{{rp|page=4}}<br/>{{val|175|-|250|u=km}} (2–4% albedo){{efn|name=diameterrange}}
| mass                   = 
| density                = 
| albedo                 = 0.04 (best fit)<ref name="Parker2016"/>{{rp|page=4}}<br/>0.02–0.04<ref name="Parker2016"/>{{rp|page=4}}
| spectral_type          = 
| magnitude              = 25.0<ref name="Grundy-Makemake"/>
| abs_magnitude          = {{val|7.89|0.04}}<ref name="Parker2016"/>{{rp|page=3}}
}}

'''S/2015 (136472) 1''', unofficially nicknamed '''MK2''' by the discovery team,<ref name="hubblesite"/> is the only known [[natural satellite|moon]] of the [[trans-Neptunian object|trans-Neptunian]] [[dwarf planet]] [[Makemake]].<ref name="Parker2016"/><ref name="PlanetarySociety"/> It is estimated to be {{convert|175|km|4=-1|abbr=on}} in diameter and has a [[semi-major axis]] of at least {{convert|21000|km|4=-2|abbr=on}} from Makemake.<ref name="Parker2016"/> Its orbital period is at least 12 days if it has a circular orbit.<ref name="Parker2016"/><ref name="CBET4275"/><ref name="PlanetarySociety"/> Observations leading to its discovery occurred in April 2015, using the [[Hubble Space Telescope]]'s [[Wide Field Camera 3]], and its discovery was announced on 26 April 2016.<ref name="hubblesite"/>

== Physical characteristics ==
S/2015 (136472) 1 is extremely faint, with an [[apparent magnitude]] of 25 in [[visible light]].<ref name="Grundy-Makemake"/> The satellite is 1,300 times fainter than Makemake, which corresponds to a [[magnitude (astronomy)|magnitude]] difference of 7.80 between it and Makemake.<ref name="Spacecom-20160429"/><ref name="Parker2016"/>{{rp|page=3}}

Prior to the discovery S/2015 (136472) 1, measurements of Makemake's [[far-infrared]] [[thermal radiation|thermal emission]] by the ''[[Spitzer (spacecraft)|Spitzer]]'' and ''[[Herschel Space Observatory|Herschel]]'' space telescopes showed that the dwarf planet emits more thermal radiation than expected for its size and brightness in visible light.<ref name="PlanetarySociety"/> This led astronomers to suspect that Makemake must have extra dark surface area that is contributing to this excess thermal emission.<ref name="Parker2016"/>{{rp|page=3}} Makemake does not exhibit significant variations in brightness as it rotates, which leaves the possibilities that some of this dark surface area may either be uniformly distributed on Makemake's surface or is located on satellites orbiting Makemake.<ref name="PlanetarySociety"/><ref name="Parker2016"/>{{rp|page=3}}<ref name="Hromakina2019"/>{{rp|page=6}} The discovery of S/2015 (136472) 1 lends credibility to the hypothesis that Makemake's excess thermal emission largely comes from satellites with dark surfaces.<ref name="Hromakina2019"/>{{rp|page=6}}

Assuming S/2015 (136472) 1 has a uniformly dark surface, the satellite has a [[geometric albedo]] or visible light [[Reflectance|reflectivity]] of 2–4%, which makes it as dark as [[charcoal]].<ref name="Parker2016"/>{{rp|page=3–4}}<ref name="Spacecom-20160429"/> The satellite is exceptionally dark compared to Makemake's geometric albedo of 82%; this may be because the satellite's gravity is too weak to hold on to bright, [[volatile (astrogeology)|volatile ices]] as they sublimate off the satellite's surface into space.<ref name="Parker2016"/>{{rp|page=4}}<ref name="Spacecom-20160429"/> S/2015 (136472) 1 is estimated to have a diameter between {{cvt|175-250|km|mi}}, based on its geometric albedo and brightness in visible light.{{efn|name=diameterrange|For a nominal [[absolute magnitude#Small Solar System bodies (H)|absolute magnitude]] of 7.8, a geometric albedo of 0.02 gives a diameter of {{cvt|250|km|mi}}<ref name="Parker2016"/>{{rp|page=3}} while a geometric albedo of 0.04 gives a diameter of {{cvt|175|km|mi}}.<ref name="Parker2016"/>{{rp|page=4}}}} Within this range, S/2015 (136472) 1's diameter is most likely {{cvt|175|km|mi}} for a geometric albedo of 4%.<ref name="Parker2016"/>{{rp|page=4}} If S/2015 (136472) 1 has the same density as Makemake, then it would contribute less than 0.2% of the total system mass.<ref name="Parker2016"/>{{rp|page=4}}

=== Additional satellites of Makemake ===
S/2015 (136472) 1 alone cannot be responsible for all of Makemake's excess thermal emission because its diameter and surface area only accounts for 20–30% of the total dark surface area.<ref name="Parker2016"/>{{rp|page=3}}{{efn|Given S/2015 (136472) 1's diameter of <math>D_{MK2} = 175 \text{ km}</math> (radius <math>R_{MK2} = 87.5 \text{ km}</math>) and Makemake's dark terrain area-equivalent diameter of <math>D_{dark} = 310 \text{ to } 380 \text{ km}</math> (radius <math>R_{dark} = 155 \text{ to } 190 \text{ km}</math>)),<ref name="Parker2016"/>{{rp|page=3}} the ratio of S/2015 (136472) 1's surface area over the dark terrain surface area is <math>\frac{4\pi R_{MK2}^2}{4\pi R_{dark}^2}</math>, which gives 21–31%. }} Even the maximum possible diameter of S/2015 (136472) 1 is too small to account for all of this dark surface area.<ref name="Parker2016"/>{{rp|page=3}} Furthermore, S/2015 (136472) 1 is too small to have [[tidal force|tidally]] slowed down Makemake to its current rotation period of 22.8 hours.<ref name="Hromakina2019"/>{{rp|page=6}} These details indicate that there may be another large, undiscovered satellite orbiting Makemake. A satellite that is responsible for Makemake's slow rotation would have to be 3–5% of Makemake's mass and {{cvt|400-550|km|mi}} in diameter, which would be large enough to account for the remaining dark surface area. This undiscovered satellite would have to be closely orbiting Makemake at a distance of {{cvt|3000-5000|km|mi}}, which would make it undetectable to current telescopes like Hubble.<ref name="Hromakina2019"/>{{rp|page=6}} It is possible that this undiscovered satellite has an irregular shape, which could account for most of Makemake's rotational brightness variability.<ref name="Hromakina2019"/>{{rp|page=6}}

== Orbit ==
Alex Parker, the leader of the team that performed the analysis of the discovery images at the [[Southwest Research Institute]], said that from the discovery images, S/2015 (136472) 1's orbit appears to be aligned edge-on to Earth-based observatories.<ref name="CBET4275"/> This would make it difficult to detect because it would be lost in Makemake's glare much of the time, which, along with its dark surface, would contribute to previous surveys failing to observe it.<ref name="Parker2016"/> Observations taken in 2018 and 2019 may be enough to determine whether the orbit is close to circular, which would suggest that S/2015 (136472) 1 was formed by an ancient impact event, or if it is significantly eccentric, which would suggest that it was captured.<ref name="Spacecom-20160429"/>

== Name ==
{{See also|Makemake (deity)}}
{{As of|2024}}, the satellite has no official name.<ref name="jpldatamakemake"/> The designation S/2015 (136472) 1 is the satellite's [[provisional designation in astronomy|provisional designation]], with "S/" indicating satellite, "2015" being the satellite's year of discovery, and "1" being the satellite's order of discovery in that year.<ref name="iaunaming"/> "(136472)" is Makemake's [[minor planet number|minor-planet number]].<ref name="IAU0806"/>

The nickname 'MK2' simply means ''object 2 in the Makemake system''. A permanent name may be chosen from an associated figure in the mythology of Easter Island.

{{Clear}}

== Notes==
{{notelist}}

== References ==
{{reflist|30em|refs=

<ref name="IAU0806">{{cite press release |publisher=International Astronomical Union (News Release – IAU0806) |title=Fourth dwarf planet named Makemake |author=International Astronomical Union |url=http://www.iau.org/public_press/news/release/iau0806/ |date=2008-07-19 |access-date=2008-07-20 |archive-date=2008-07-23 |archive-url=https://web.archive.org/web/20080723021818/http://www.iau.org/public_press/news/release/iau0806/ |url-status=live }}</ref>

<ref name="CBET4275">{{cite journal
 |title        = S/2015 (136472) 1
 |first        = Daniel W. E. |last = Green
 |journal      = Central Bureau Electronic Telegram
 |publisher    = Central Bureau for Astronomical Telegrams
 |date         = 26 April 2016
 |issue        = 4275
 |bibcode      = 2016CBET.4275....1P}}</ref>

<ref name="iaunaming">{{cite web |url=https://www.iau.org/public/themes/naming/ |access-date=8 July 2017 |publisher=International Astronomical Union |title=Naming of Astronomical Objects }}</ref>

<ref name="jpldatamakemake">{{cite web |type=2019-05-12 last obs |title=JPL Small-Body Database Browser: 136472 Makemake ({{mp|2005 FY|9}}) |work=NASA Jet Propulsion Laboratory |url=https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=136472 |access-date=2020-02-20 |archive-date=2019-06-16 |archive-url=https://web.archive.org/web/20190616154758/https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=136472 |url-status=live }}</ref>

<ref name="hubblesite">{{cite web |url=https://hubblesite.org/contents/news-releases/2016/news-2016-18.html |title=HubbleSite – NewsCenter – Hubble Discovers Moon Orbiting the Dwarf Planet Makemake (04/26/2016) – The Full Story |work=hubblesite.org |access-date=14 July 2022}}</ref>

<ref name="Parker2016">{{cite journal |last1=Parker |first1=A. H. |last2=Buie |first2=M. W. |last3=Grundy |first3=W. M. |last4=Noll |first4=K. S. |title=Discovery of a Makemakean Moon |date=2016-04-25 |arxiv=1604.07461 |doi=10.3847/2041-8205/825/1/L9 |volume=825 |issue=1 |journal=The Astrophysical Journal |page=L9 |bibcode=2016ApJ...825L...9P |s2cid=119270442 |doi-access=free }}</ref>

<ref name="PlanetarySociety">{{cite web |url=http://www.planetary.org/blogs/guest-blogs/2016/0502-a-moon-for-makemake.html |title=A Moon for Makemake |last=Parker |first=A. |date=2016-05-02 |website=Planetary Society blogs |publisher=[[Planetary Society]] |access-date=2016-05-02}}</ref>

<ref name="Spacecom-20160429">{{cite web |url=http://www.space.com/32702-dwarf-planet-makemake-moon-hubble-discovery.html |title=Distant Dwarf Planet Makemake Has Its Own Moon |date=26 April 2016 |author=Mike Wall |publisher=Space.com |access-date=26 April 2016}}</ref>

<ref name="Hromakina2019">{{cite journal |title=Long-term photometric monitoring of the dwarf planet (136472) Makemake |author1=T. A. Hromakina |author2=I. N. Belskaya |author3=Yu. N. Krugly |author4=V. G. Shevchenko |author5=J. L. Ortiz |author6=P. Santos-Sanz |author7=R. Duffard |author8=N. Morales |author9=A. Thirouin |author10=R. Ya. Inasaridze |author11=V. R. Ayvazian |author12=V. T. Zhuzhunadze |author13=D. Perna |author14=V. V. Rumyantsev |author15=I. V. Reva |author16=A. V. Serebryanskiy |author17=A. V. Sergeyev |author18=I. E. Molotov |author19=V. A. Voropaev |author20=S. F. Velichko |journal=Astronomy & Astrophysics |volume=625 |pages=A46 |doi=10.1051/0004-6361/201935274 |arxiv=1904.03679 |date=2019-04-09|bibcode=2019A&A...625A..46H |s2cid=102350991 }}</ref>

<ref name="Grundy-Makemake">{{cite web |url=http://www2.lowell.edu/~grundy/tnbs/136472_2005_FY9_Makemake.html |title=Makemake (136472 2005 FY9) |date=13 February 2020 |author=William M. Grundy |publisher=Lowell Observatory |access-date=20 February 2020}}</ref>

}}

== External links ==
* [https://minorplanetcenter.net//mpec/K16/K16H46.html MPEC 2016-H46 : S/2015 (136472) 1], [[Minor Planet Center]], 26 April 2016

{{Moons of dwarf planets}}
{{Solar System moons (compact)}}
{{Solar System}}

[[Category:Makemake]]
[[Category:Astronomical objects discovered in 2015]]
[[Category:Trans-Neptunian satellites]]
[[Category:Moons of dwarf planets]]
[[Category:Solar System]]